android framework - startActivity

这里写自定义目录标题

前言

很长时间没写博客了,俗话说,好记性不如烂笔头,如今又忍不住想要小小记录一下。

相信应用开发对startActivity这个调用接口都不陌生,知道其能够跳转页面,然而,其具体是怎么跳转的,以及跳转关联的页面生命周期又是如何变化的,之前一直是知其然而不知其所以然,如今有机会静下心来,必须要好好的探索一番。

源码

源码探索是一个漫长而又枯燥的过程,只有静下心来,一步步梳理,理解其上下文关联,进而了然其相关流程,方能体会到其中的丰收乐趣。

java 复制代码
package android.app;
...
@UiContext
public class Activity extends ContextThemeWrapper
        implements LayoutInflater.Factory2,
        Window.Callback, KeyEvent.Callback,
        OnCreateContextMenuListener, ComponentCallbacks2,
        Window.OnWindowDismissedCallback,
        AutofillManager.AutofillClient, ContentCaptureManager.ContentCaptureClient {
	...
    public void startActivityForResult(@RequiresPermission Intent intent, int requestCode) {
        startActivityForResult(intent, requestCode, null);
    }

    public void startActivityForResult(@RequiresPermission Intent intent, int requestCode,
                                       @Nullable Bundle options) {
        if (mParent == null) {
            options = transferSpringboardActivityOptions(options);
            Instrumentation.ActivityResult ar =
                    mInstrumentation.execStartActivity(
                            this, mMainThread.getApplicationThread(), mToken, this,
                            intent, requestCode, options);
            if (ar != null) {
                mMainThread.sendActivityResult(
                        mToken, mEmbeddedID, requestCode, ar.getResultCode(),
                        ar.getResultData());
            }
            if (requestCode >= 0) {
                // If this start is requesting a result, we can avoid making
                // the activity visible until the result is received.  Setting
                // this code during onCreate(Bundle savedInstanceState) or onResume() will keep the
                // activity hidden during this time, to avoid flickering.
                // This can only be done when a result is requested because
                // that guarantees we will get information back when the
                // activity is finished, no matter what happens to it.
                mStartedActivity = true;
            }

            cancelInputsAndStartExitTransition(options);
            // TODO Consider clearing/flushing other event sources and events for child windows.
        } else {
            if (options != null) {
                mParent.startActivityFromChild(this, intent, requestCode, options);
            } else {
                // Note we want to go through this method for compatibility with
                // existing applications that may have overridden it.
                mParent.startActivityFromChild(this, intent, requestCode);
            }
        }
    }

    @Override
    public void startActivity(Intent intent) {
        this.startActivity(intent, null);
    }

    @Override
    public void startActivity(Intent intent, @Nullable Bundle options) {
        if (mIntent != null && mIntent.hasExtra(AutofillManager.EXTRA_RESTORE_SESSION_TOKEN)
                && mIntent.hasExtra(AutofillManager.EXTRA_RESTORE_CROSS_ACTIVITY)) {
            if (TextUtils.equals(getPackageName(),
                    intent.resolveActivity(getPackageManager()).getPackageName())) {
                // Apply Autofill restore mechanism on the started activity by startActivity()
                final IBinder token =
                        mIntent.getIBinderExtra(AutofillManager.EXTRA_RESTORE_SESSION_TOKEN);
                // Remove restore ability from current activity
                mIntent.removeExtra(AutofillManager.EXTRA_RESTORE_SESSION_TOKEN);
                mIntent.removeExtra(AutofillManager.EXTRA_RESTORE_CROSS_ACTIVITY);
                // Put restore token
                intent.putExtra(AutofillManager.EXTRA_RESTORE_SESSION_TOKEN, token);
                intent.putExtra(AutofillManager.EXTRA_RESTORE_CROSS_ACTIVITY, true);
            }
        }
        if (options != null) {
            startActivityForResult(intent, -1, options);
        } else {
            // Note we want to go through this call for compatibility with
            // applications that may have overridden the method.
            startActivityForResult(intent, -1);
        }
    }
    ...
}

根据源码不难看出,startActivity(Intent) > startActivity(Intent, Bundle) > startActivityForResult(Intent, int) > startActivityForResult(Intent, int, Bundle),好,到了这里就比较明确了,要跳转至mInstrumentation.execStartActivity

java 复制代码
package android.app;
...
public class Instrumentation {
	...
    public ActivityResult execStartActivity(
            Context who, IBinder contextThread, IBinder token, Activity target,
            Intent intent, int requestCode, Bundle options) {
        IApplicationThread whoThread = (IApplicationThread) contextThread;
        Uri referrer = target != null ? target.onProvideReferrer() : null;
        if (referrer != null) {
            intent.putExtra(Intent.EXTRA_REFERRER, referrer);
        }
        if (mActivityMonitors != null) {
            synchronized (mSync) {
                final int N = mActivityMonitors.size();
                for (int i = 0; i < N; i++) {
                    final ActivityMonitor am = mActivityMonitors.get(i);
                    ActivityResult result = null;
                    if (am.ignoreMatchingSpecificIntents()) {
                        if (options == null) {
                            options = ActivityOptions.makeBasic().toBundle();
                        }
                        result = am.onStartActivity(who, intent, options);
                    }
                    if (result != null) {
                        am.mHits++;
                        return result;
                    } else if (am.match(who, null, intent)) {
                        am.mHits++;
                        if (am.isBlocking()) {
                            return requestCode >= 0 ? am.getResult() : null;
                        }
                        break;
                    }
                }
            }
        }
        try {
            intent.migrateExtraStreamToClipData(who);
            intent.prepareToLeaveProcess(who);
            int result = ActivityTaskManager.getService().startActivity(whoThread,
                    who.getOpPackageName(), who.getAttributionTag(), intent,
                    intent.resolveTypeIfNeeded(who.getContentResolver()), token,
                    target != null ? target.mEmbeddedID : null, requestCode, 0, null, options);
            checkStartActivityResult(result, intent);
        } catch (RemoteException e) {
            throw new RuntimeException("Failure from system", e);
        }
        return null;
    }
    ...
}

毫不意外最终又指向ActivityTaskManager.getService().startActivity,也就是要移步到ActivityTaskManagerService

出于梳理顺畅考虑,这里就没有赘述怎么到了ActivityTaskManagerService

java 复制代码
package com.android.server.wm;

public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
	...
    @Override
    public final int startActivity(IApplicationThread caller, String callingPackage,
                                   String callingFeatureId, Intent intent, String resolvedType, IBinder resultTo,
                                   String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo,
                                   Bundle bOptions) {
        return startActivityAsUser(caller, callingPackage, callingFeatureId, intent, resolvedType,
                resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions,
                UserHandle.getCallingUserId());
    }

    @Override
    public int startActivityAsUser(IApplicationThread caller, String callingPackage,
                                   String callingFeatureId, Intent intent, String resolvedType, IBinder resultTo,
                                   String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo,
                                   Bundle bOptions, int userId) {
        return startActivityAsUser(caller, callingPackage, callingFeatureId, intent, resolvedType,
                resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions, userId,
                true /*validateIncomingUser*/);
    }

    private int startActivityAsUser(IApplicationThread caller, String callingPackage,
                                    @Nullable String callingFeatureId, Intent intent, String resolvedType,
                                    IBinder resultTo, String resultWho, int requestCode, int startFlags,
                                    ProfilerInfo profilerInfo, Bundle bOptions, int userId, boolean validateIncomingUser) {
        assertPackageMatchesCallingUid(callingPackage);
        enforceNotIsolatedCaller("startActivityAsUser");

        userId = getActivityStartController().checkTargetUser(userId, validateIncomingUser,
                Binder.getCallingPid(), Binder.getCallingUid(), "startActivityAsUser");

        // TODO: Switch to user app stacks here.
        return getActivityStartController().obtainStarter(intent, "startActivityAsUser")
                .setCaller(caller)
                .setCallingPackage(callingPackage)
                .setCallingFeatureId(callingFeatureId)
                .setResolvedType(resolvedType)
                .setResultTo(resultTo)
                .setResultWho(resultWho)
                .setRequestCode(requestCode)
                .setStartFlags(startFlags)
                .setProfilerInfo(profilerInfo)
                .setActivityOptions(bOptions)
                .setUserId(userId)
                .execute();

    }
    ...
}

这里显然是继续走到最后getActivityStartController().obtainStarterexecute入口,也就是接下来移步到ActivityStarter

出于梳理顺畅考虑,这里就没有赘述怎么到了ActivityStarter

java 复制代码
package com.android.server.wm;
...
class ActivityStarter {
	...
    int execute() {
        try {
            // Refuse possible leaked file descriptors
            if (mRequest.intent != null && mRequest.intent.hasFileDescriptors()) {
                throw new IllegalArgumentException("File descriptors passed in Intent");
            }

            final LaunchingState launchingState;
            synchronized (mService.mGlobalLock) {
                final ActivityRecord caller = ActivityRecord.forTokenLocked(mRequest.resultTo);
                final int callingUid = mRequest.realCallingUid == Request.DEFAULT_REAL_CALLING_UID
                        ? Binder.getCallingUid() : mRequest.realCallingUid;
                launchingState = mSupervisor.getActivityMetricsLogger().notifyActivityLaunching(
                        mRequest.intent, caller, callingUid);
            }

            // If the caller hasn't already resolved the activity, we're willing
            // to do so here. If the caller is already holding the WM lock here,
            // and we need to check dynamic Uri permissions, then we're forced
            // to assume those permissions are denied to avoid deadlocking.
            if (mRequest.activityInfo == null) {
                mRequest.resolveActivity(mSupervisor);
            }

            // Add checkpoint for this shutdown or reboot attempt, so we can record the original
            // intent action and package name.
            if (mRequest.intent != null) {
                String intentAction = mRequest.intent.getAction();
                String callingPackage = mRequest.callingPackage;
                if (intentAction != null && callingPackage != null
                        && (Intent.ACTION_REQUEST_SHUTDOWN.equals(intentAction)
                        || Intent.ACTION_SHUTDOWN.equals(intentAction)
                        || Intent.ACTION_REBOOT.equals(intentAction))) {
                    ShutdownCheckPoints.recordCheckPoint(intentAction, callingPackage, null);
                }
            }

            int res;
            synchronized (mService.mGlobalLock) {
                final boolean globalConfigWillChange = mRequest.globalConfig != null
                        && mService.getGlobalConfiguration().diff(mRequest.globalConfig) != 0;
                final Task rootTask = mRootWindowContainer.getTopDisplayFocusedRootTask();
                if (rootTask != null) {
                    rootTask.mConfigWillChange = globalConfigWillChange;
                }
                ProtoLog.v(WM_DEBUG_CONFIGURATION, "Starting activity when config "
                        + "will change = %b", globalConfigWillChange);

                final long origId = Binder.clearCallingIdentity();

                res = resolveToHeavyWeightSwitcherIfNeeded();
                if (res != START_SUCCESS) {
                    return res;
                }
                res = executeRequest(mRequest);

                Binder.restoreCallingIdentity(origId);

                if (globalConfigWillChange) {
                    // If the caller also wants to switch to a new configuration, do so now.
                    // This allows a clean switch, as we are waiting for the current activity
                    // to pause (so we will not destroy it), and have not yet started the
                    // next activity.
                    mService.mAmInternal.enforceCallingPermission(
                            android.Manifest.permission.CHANGE_CONFIGURATION,
                            "updateConfiguration()");
                    if (rootTask != null) {
                        rootTask.mConfigWillChange = false;
                    }
                    ProtoLog.v(WM_DEBUG_CONFIGURATION,
                            "Updating to new configuration after starting activity.");

                    mService.updateConfigurationLocked(mRequest.globalConfig, null, false);
                }

                // The original options may have additional info about metrics. The mOptions is not
                // used here because it may be cleared in setTargetRootTaskIfNeeded.
                final ActivityOptions originalOptions = mRequest.activityOptions != null
                        ? mRequest.activityOptions.getOriginalOptions() : null;
                // If the new record is the one that started, a new activity has created.
                final boolean newActivityCreated = mStartActivity == mLastStartActivityRecord;
                // Notify ActivityMetricsLogger that the activity has launched.
                // ActivityMetricsLogger will then wait for the windows to be drawn and populate
                // WaitResult.
                mSupervisor.getActivityMetricsLogger().notifyActivityLaunched(launchingState, res,
                        newActivityCreated, mLastStartActivityRecord, originalOptions);
                if (mRequest.waitResult != null) {
                    mRequest.waitResult.result = res;
                    res = waitResultIfNeeded(mRequest.waitResult, mLastStartActivityRecord,
                            launchingState);
                }
                return getExternalResult(res);
            }
        } finally {
            onExecutionComplete();
        }
    }
	...
}

很显然,一大堆,重点还是在res = executeRequest(mRequest);,继续跟踪

java 复制代码
    private int executeRequest(Request request) {
        if (TextUtils.isEmpty(request.reason)) {
            throw new IllegalArgumentException("Need to specify a reason.");
        }
        mLastStartReason = request.reason;
        mLastStartActivityTimeMs = System.currentTimeMillis();
        mLastStartActivityRecord = null;

        final IApplicationThread caller = request.caller;
        Intent intent = request.intent;
        NeededUriGrants intentGrants = request.intentGrants;
        String resolvedType = request.resolvedType;
        ActivityInfo aInfo = request.activityInfo;
        ResolveInfo rInfo = request.resolveInfo;
        final IVoiceInteractionSession voiceSession = request.voiceSession;
        final IBinder resultTo = request.resultTo;
        String resultWho = request.resultWho;
        int requestCode = request.requestCode;
        int callingPid = request.callingPid;
        int callingUid = request.callingUid;
        String callingPackage = request.callingPackage;
        String callingFeatureId = request.callingFeatureId;
        final int realCallingPid = request.realCallingPid;
        final int realCallingUid = request.realCallingUid;
        final int startFlags = request.startFlags;
        final SafeActivityOptions options = request.activityOptions;
        Task inTask = request.inTask;
        TaskFragment inTaskFragment = request.inTaskFragment;

        int err = ActivityManager.START_SUCCESS;
        // Pull the optional Ephemeral Installer-only bundle out of the options early.
        final Bundle verificationBundle =
                options != null ? options.popAppVerificationBundle() : null;

        WindowProcessController callerApp = null;
        if (caller != null) {
            callerApp = mService.getProcessController(caller);
            if (callerApp != null) {
                callingPid = callerApp.getPid();
                callingUid = callerApp.mInfo.uid;
            } else {
                Slog.w(TAG, "Unable to find app for caller " + caller + " (pid=" + callingPid
                        + ") when starting: " + intent.toString());
                err = START_PERMISSION_DENIED;
            }
        }

        final int userId = aInfo != null && aInfo.applicationInfo != null
                ? UserHandle.getUserId(aInfo.applicationInfo.uid) : 0;
        if (err == ActivityManager.START_SUCCESS) {
            Slog.i(TAG, "START u" + userId + " {" + intent.toShortString(true, true, true, false)
                    + "} from uid " + callingUid);
        }

        ActivityRecord sourceRecord = null;
        ActivityRecord resultRecord = null;
        if (resultTo != null) {
            sourceRecord = ActivityRecord.isInAnyTask(resultTo);
            if (DEBUG_RESULTS) {
                Slog.v(TAG_RESULTS, "Will send result to " + resultTo + " " + sourceRecord);
            }
            if (sourceRecord != null) {
                if (requestCode >= 0 && !sourceRecord.finishing) {
                    resultRecord = sourceRecord;
                }
            }
        }

        final int launchFlags = intent.getFlags();
        if ((launchFlags & Intent.FLAG_ACTIVITY_FORWARD_RESULT) != 0 && sourceRecord != null) {
            // Transfer the result target from the source activity to the new one being started,
            // including any failures.
            if (requestCode >= 0) {
                SafeActivityOptions.abort(options);
                return ActivityManager.START_FORWARD_AND_REQUEST_CONFLICT;
            }
            resultRecord = sourceRecord.resultTo;
            if (resultRecord != null && !resultRecord.isInRootTaskLocked()) {
                resultRecord = null;
            }
            resultWho = sourceRecord.resultWho;
            requestCode = sourceRecord.requestCode;
            sourceRecord.resultTo = null;
            if (resultRecord != null) {
                resultRecord.removeResultsLocked(sourceRecord, resultWho, requestCode);
            }
            if (sourceRecord.launchedFromUid == callingUid) {
                // The new activity is being launched from the same uid as the previous activity
                // in the flow, and asking to forward its result back to the previous.  In this
                // case the activity is serving as a trampoline between the two, so we also want
                // to update its launchedFromPackage to be the same as the previous activity.
                // Note that this is safe, since we know these two packages come from the same
                // uid; the caller could just as well have supplied that same package name itself
                // . This specifially deals with the case of an intent picker/chooser being
                // launched in the app flow to redirect to an activity picked by the user, where
                // we want the final activity to consider it to have been launched by the
                // previous app activity.
                callingPackage = sourceRecord.launchedFromPackage;
                callingFeatureId = sourceRecord.launchedFromFeatureId;
            }
        }

        if (err == ActivityManager.START_SUCCESS && intent.getComponent() == null) {
            // We couldn't find a class that can handle the given Intent.
            // That's the end of that!
            err = ActivityManager.START_INTENT_NOT_RESOLVED;
        }

        if (err == ActivityManager.START_SUCCESS && aInfo == null) {
            // We couldn't find the specific class specified in the Intent.
            // Also the end of the line.
            err = ActivityManager.START_CLASS_NOT_FOUND;
        }

        if (err == ActivityManager.START_SUCCESS && sourceRecord != null
                && sourceRecord.getTask().voiceSession != null) {
            // If this activity is being launched as part of a voice session, we need to ensure
            // that it is safe to do so.  If the upcoming activity will also be part of the voice
            // session, we can only launch it if it has explicitly said it supports the VOICE
            // category, or it is a part of the calling app.
            if ((launchFlags & FLAG_ACTIVITY_NEW_TASK) == 0
                    && sourceRecord.info.applicationInfo.uid != aInfo.applicationInfo.uid) {
                try {
                    intent.addCategory(Intent.CATEGORY_VOICE);
                    if (!mService.getPackageManager().activitySupportsIntent(
                            intent.getComponent(), intent, resolvedType)) {
                        Slog.w(TAG, "Activity being started in current voice task does not support "
                                + "voice: " + intent);
                        err = ActivityManager.START_NOT_VOICE_COMPATIBLE;
                    }
                } catch (RemoteException e) {
                    Slog.w(TAG, "Failure checking voice capabilities", e);
                    err = ActivityManager.START_NOT_VOICE_COMPATIBLE;
                }
            }
        }

        if (err == ActivityManager.START_SUCCESS && voiceSession != null) {
            // If the caller is starting a new voice session, just make sure the target
            // is actually allowing it to run this way.
            try {
                if (!mService.getPackageManager().activitySupportsIntent(intent.getComponent(),
                        intent, resolvedType)) {
                    Slog.w(TAG,
                            "Activity being started in new voice task does not support: " + intent);
                    err = ActivityManager.START_NOT_VOICE_COMPATIBLE;
                }
            } catch (RemoteException e) {
                Slog.w(TAG, "Failure checking voice capabilities", e);
                err = ActivityManager.START_NOT_VOICE_COMPATIBLE;
            }
        }

        final Task resultRootTask = resultRecord == null
                ? null : resultRecord.getRootTask();

        if (err != START_SUCCESS) {
            if (resultRecord != null) {
                resultRecord.sendResult(INVALID_UID, resultWho, requestCode, RESULT_CANCELED,
                        null /* data */, null /* dataGrants */);
            }
            SafeActivityOptions.abort(options);
            return err;
        }

        boolean abort = !mSupervisor.checkStartAnyActivityPermission(intent, aInfo, resultWho,
                requestCode, callingPid, callingUid, callingPackage, callingFeatureId,
                request.ignoreTargetSecurity, inTask != null, callerApp, resultRecord,
                resultRootTask);
        abort |= !mService.mIntentFirewall.checkStartActivity(intent, callingUid,
                callingPid, resolvedType, aInfo.applicationInfo);
        abort |= !mService.getPermissionPolicyInternal().checkStartActivity(intent, callingUid,
                callingPackage);

        boolean restrictedBgActivity = false;
        if (!abort) {
            try {
                Trace.traceBegin(Trace.TRACE_TAG_WINDOW_MANAGER,
                        "shouldAbortBackgroundActivityStart");
                restrictedBgActivity = shouldAbortBackgroundActivityStart(callingUid,
                        callingPid, callingPackage, realCallingUid, realCallingPid, callerApp,
                        request.originatingPendingIntent, request.allowBackgroundActivityStart,
                        intent);
            } finally {
                Trace.traceEnd(Trace.TRACE_TAG_WINDOW_MANAGER);
            }
        }

        // Merge the two options bundles, while realCallerOptions takes precedence.
        ActivityOptions checkedOptions = options != null
                ? options.getOptions(intent, aInfo, callerApp, mSupervisor) : null;
        if (request.allowPendingRemoteAnimationRegistryLookup) {
            checkedOptions = mService.getActivityStartController()
                    .getPendingRemoteAnimationRegistry()
                    .overrideOptionsIfNeeded(callingPackage, checkedOptions);
        }
        if (mService.mController != null) {
            try {
                // The Intent we give to the watcher has the extra data stripped off, since it
                // can contain private information.
                Intent watchIntent = intent.cloneFilter();
                abort |= !mService.mController.activityStarting(watchIntent,
                        aInfo.applicationInfo.packageName);
            } catch (RemoteException e) {
                mService.mController = null;
            }
        }

        mInterceptor.setStates(userId, realCallingPid, realCallingUid, startFlags, callingPackage,
                callingFeatureId);
        if (mInterceptor.intercept(intent, rInfo, aInfo, resolvedType, inTask, callingPid,
                callingUid, checkedOptions)) {
            // activity start was intercepted, e.g. because the target user is currently in quiet
            // mode (turn off work) or the target application is suspended
            intent = mInterceptor.mIntent;
            rInfo = mInterceptor.mRInfo;
            aInfo = mInterceptor.mAInfo;
            resolvedType = mInterceptor.mResolvedType;
            inTask = mInterceptor.mInTask;
            callingPid = mInterceptor.mCallingPid;
            callingUid = mInterceptor.mCallingUid;
            checkedOptions = mInterceptor.mActivityOptions;

            // The interception target shouldn't get any permission grants
            // intended for the original destination
            intentGrants = null;
        }

        if (abort) {
            if (resultRecord != null) {
                resultRecord.sendResult(INVALID_UID, resultWho, requestCode, RESULT_CANCELED,
                        null /* data */, null /* dataGrants */);
            }
            // We pretend to the caller that it was really started, but they will just get a
            // cancel result.
            ActivityOptions.abort(checkedOptions);
            return START_ABORTED;
        }

        // If permissions need a review before any of the app components can run, we
        // launch the review activity and pass a pending intent to start the activity
        // we are to launching now after the review is completed.
        if (aInfo != null) {
            if (mService.getPackageManagerInternalLocked().isPermissionsReviewRequired(
                    aInfo.packageName, userId)) {
                final IIntentSender target = mService.getIntentSenderLocked(
                        ActivityManager.INTENT_SENDER_ACTIVITY, callingPackage, callingFeatureId,
                        callingUid, userId, null, null, 0, new Intent[]{intent},
                        new String[]{resolvedType}, PendingIntent.FLAG_CANCEL_CURRENT
                                | PendingIntent.FLAG_ONE_SHOT, null);

                Intent newIntent = new Intent(Intent.ACTION_REVIEW_PERMISSIONS);

                int flags = intent.getFlags();
                flags |= Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS;

                /*
                 * Prevent reuse of review activity: Each app needs their own review activity. By
                 * default activities launched with NEW_TASK or NEW_DOCUMENT try to reuse activities
                 * with the same launch parameters (extras are ignored). Hence to avoid possible
                 * reuse force a new activity via the MULTIPLE_TASK flag.
                 *
                 * Activities that are not launched with NEW_TASK or NEW_DOCUMENT are not re-used,
                 * hence no need to add the flag in this case.
                 */
                if ((flags & (FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_NEW_DOCUMENT)) != 0) {
                    flags |= Intent.FLAG_ACTIVITY_MULTIPLE_TASK;
                }
                newIntent.setFlags(flags);

                newIntent.putExtra(Intent.EXTRA_PACKAGE_NAME, aInfo.packageName);
                newIntent.putExtra(Intent.EXTRA_INTENT, new IntentSender(target));
                if (resultRecord != null) {
                    newIntent.putExtra(Intent.EXTRA_RESULT_NEEDED, true);
                }
                intent = newIntent;

                // The permissions review target shouldn't get any permission
                // grants intended for the original destination
                intentGrants = null;

                resolvedType = null;
                callingUid = realCallingUid;
                callingPid = realCallingPid;

                rInfo = mSupervisor.resolveIntent(intent, resolvedType, userId, 0,
                        computeResolveFilterUid(
                                callingUid, realCallingUid, request.filterCallingUid));
                aInfo = mSupervisor.resolveActivity(intent, rInfo, startFlags,
                        null /*profilerInfo*/);

                if (DEBUG_PERMISSIONS_REVIEW) {
                    final Task focusedRootTask =
                            mRootWindowContainer.getTopDisplayFocusedRootTask();
                    Slog.i(TAG, "START u" + userId + " {" + intent.toShortString(true, true,
                            true, false) + "} from uid " + callingUid + " on display "
                            + (focusedRootTask == null ? DEFAULT_DISPLAY
                            : focusedRootTask.getDisplayId()));
                }
            }
        }

        // If we have an ephemeral app, abort the process of launching the resolved intent.
        // Instead, launch the ephemeral installer. Once the installer is finished, it
        // starts either the intent we resolved here [on install error] or the ephemeral
        // app [on install success].
        if (rInfo != null && rInfo.auxiliaryInfo != null) {
            intent = createLaunchIntent(rInfo.auxiliaryInfo, request.ephemeralIntent,
                    callingPackage, callingFeatureId, verificationBundle, resolvedType, userId);
            resolvedType = null;
            callingUid = realCallingUid;
            callingPid = realCallingPid;

            // The ephemeral installer shouldn't get any permission grants
            // intended for the original destination
            intentGrants = null;

            aInfo = mSupervisor.resolveActivity(intent, rInfo, startFlags, null /*profilerInfo*/);
        }
        // TODO (b/187680964) Correcting the caller/pid/uid when start activity from shortcut
        // Pending intent launched from systemui also depends on caller app
        if (callerApp == null && realCallingPid > 0) {
            final WindowProcessController wpc = mService.mProcessMap.getProcess(realCallingPid);
            if (wpc != null) {
                callerApp = wpc;
            }
        }
        final ActivityRecord r = new ActivityRecord.Builder(mService)
                .setCaller(callerApp)
                .setLaunchedFromPid(callingPid)
                .setLaunchedFromUid(callingUid)
                .setLaunchedFromPackage(callingPackage)
                .setLaunchedFromFeature(callingFeatureId)
                .setIntent(intent)
                .setResolvedType(resolvedType)
                .setActivityInfo(aInfo)
                .setConfiguration(mService.getGlobalConfiguration())
                .setResultTo(resultRecord)
                .setResultWho(resultWho)
                .setRequestCode(requestCode)
                .setComponentSpecified(request.componentSpecified)
                .setRootVoiceInteraction(voiceSession != null)
                .setActivityOptions(checkedOptions)
                .setSourceRecord(sourceRecord)
                .build();

        mLastStartActivityRecord = r;

        if (r.appTimeTracker == null && sourceRecord != null) {
            // If the caller didn't specify an explicit time tracker, we want to continue
            // tracking under any it has.
            r.appTimeTracker = sourceRecord.appTimeTracker;
        }

        // Only allow app switching to be resumed if activity is not a restricted background
        // activity and target app is not home process, otherwise any background activity
        // started in background task can stop home button protection mode.
        // As the targeted app is not a home process and we don't need to wait for the 2nd
        // activity to be started to resume app switching, we can just enable app switching
        // directly.
        WindowProcessController homeProcess = mService.mHomeProcess;
        boolean isHomeProcess = homeProcess != null
                && aInfo.applicationInfo.uid == homeProcess.mUid;
        if (!restrictedBgActivity && !isHomeProcess) {
            mService.resumeAppSwitches();
        }

        mLastStartActivityResult = startActivityUnchecked(r, sourceRecord, voiceSession,
                request.voiceInteractor, startFlags, true /* doResume */, checkedOptions,
                inTask, inTaskFragment, restrictedBgActivity, intentGrants);

        if (request.outActivity != null) {
            request.outActivity[0] = mLastStartActivityRecord;
        }

        return mLastStartActivityResult;
    }

前面一大串都是为了后面startActivityUnchecked做铺垫,接着往下看

java 复制代码
    private int startActivityUnchecked(final ActivityRecord r, ActivityRecord sourceRecord,
                                       IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
                                       int startFlags, boolean doResume, ActivityOptions options, Task inTask,
                                       TaskFragment inTaskFragment, boolean restrictedBgActivity,
                                       NeededUriGrants intentGrants) {
        int result = START_CANCELED;
        boolean startResultSuccessful = false;
        final Task startedActivityRootTask;

        // Create a transition now to record the original intent of actions taken within
        // startActivityInner. Otherwise, logic in startActivityInner could start a different
        // transition based on a sub-action.
        // Only do the create here (and defer requestStart) since startActivityInner might abort.
        final TransitionController transitionController = r.mTransitionController;
        Transition newTransition = (!transitionController.isCollecting()
                && transitionController.getTransitionPlayer() != null)
                ? transitionController.createTransition(TRANSIT_OPEN) : null;
        RemoteTransition remoteTransition = r.takeRemoteTransition();
        if (newTransition != null && remoteTransition != null) {
            newTransition.setRemoteTransition(remoteTransition);
        }
        transitionController.collect(r);
        final boolean isTransient = r.getOptions() != null && r.getOptions().getTransientLaunch();
        try {
            mService.deferWindowLayout();
            Trace.traceBegin(Trace.TRACE_TAG_WINDOW_MANAGER, "startActivityInner");
            result = startActivityInner(r, sourceRecord, voiceSession, voiceInteractor,
                    startFlags, doResume, options, inTask, inTaskFragment, restrictedBgActivity,
                    intentGrants);
            startResultSuccessful = ActivityManager.isStartResultSuccessful(result);
            final boolean taskAlwaysOnTop = options != null && options.getTaskAlwaysOnTop();
            // Apply setAlwaysOnTop when starting an Activity is successful regardless of creating
            // a new Activity or recycling the existing Activity.
            if (taskAlwaysOnTop && startResultSuccessful) {
                final Task targetRootTask =
                        mTargetRootTask != null ? mTargetRootTask : mTargetTask.getRootTask();
                targetRootTask.setAlwaysOnTop(true);
            }
        } finally {
            Trace.traceEnd(Trace.TRACE_TAG_WINDOW_MANAGER);
            startedActivityRootTask = handleStartResult(r, result);
            mService.continueWindowLayout();
            mSupervisor.mUserLeaving = false;

            // Transition housekeeping
            if (!startResultSuccessful) {
                if (newTransition != null) {
                    newTransition.abort();
                }
            } else {
                if (!mAvoidMoveToFront && mDoResume
                        && mRootWindowContainer.hasVisibleWindowAboveButDoesNotOwnNotificationShade(
                        r.launchedFromUid)) {
                    // If the UID launching the activity has a visible window on top of the
                    // notification shade and it's launching an activity that's going to be at the
                    // front, we should move the shade out of the way so the user can see it.
                    // We want to avoid the case where the activity is launched on top of a
                    // background task which is not moved to the front.
                    StatusBarManagerInternal statusBar = mService.getStatusBarManagerInternal();
                    if (statusBar != null) {
                        // This results in a async call since the interface is one-way
                        statusBar.collapsePanels();
                    }
                }
                final boolean started = result == START_SUCCESS || result == START_TASK_TO_FRONT;
                if (started) {
                    // The activity is started new rather than just brought forward, so record
                    // it as an existence change.
                    transitionController.collectExistenceChange(r);
                } else if (result == START_DELIVERED_TO_TOP && newTransition != null) {
                    // We just delivered to top, so there isn't an actual transition here
                    newTransition.abort();
                    newTransition = null;
                }
                if (isTransient) {
                    // `r` isn't guaranteed to be the actual relevant activity, so we must wait
                    // until after we launched to identify the relevant activity.
                    transitionController.setTransientLaunch(mLastStartActivityRecord);
                }
                if (newTransition != null) {
                    transitionController.requestStartTransition(newTransition,
                            mTargetTask, remoteTransition);
                } else if (started) {
                    // Make the collecting transition wait until this request is ready.
                    transitionController.setReady(r, false);
                }
            }
        }

        postStartActivityProcessing(r, result, startedActivityRootTask);

        return result;
    }

这里不必多说,继续要转至startActivityInner

java 复制代码
    int startActivityInner(final ActivityRecord r, ActivityRecord sourceRecord,
                           IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
                           int startFlags, boolean doResume, ActivityOptions options, Task inTask,
                           TaskFragment inTaskFragment, boolean restrictedBgActivity,
                           NeededUriGrants intentGrants) {
        setInitialState(r, options, inTask, inTaskFragment, doResume, startFlags, sourceRecord,
                voiceSession, voiceInteractor, restrictedBgActivity);

        computeLaunchingTaskFlags();

        computeSourceRootTask();

        mIntent.setFlags(mLaunchFlags);

        // Get top task at beginning because the order may be changed when reusing existing task.
        final Task prevTopTask = mPreferredTaskDisplayArea.getFocusedRootTask();
        final Task reusedTask = getReusableTask();

        // If requested, freeze the task list
        if (mOptions != null && mOptions.freezeRecentTasksReordering()
                && mSupervisor.mRecentTasks.isCallerRecents(r.launchedFromUid)
                && !mSupervisor.mRecentTasks.isFreezeTaskListReorderingSet()) {
            mFrozeTaskList = true;
            mSupervisor.mRecentTasks.setFreezeTaskListReordering();
        }

        // Compute if there is an existing task that should be used for.
        final Task targetTask = reusedTask != null ? reusedTask : computeTargetTask();
        final boolean newTask = targetTask == null;
        mTargetTask = targetTask;

        computeLaunchParams(r, sourceRecord, targetTask);

        // Check if starting activity on given task or on a new task is allowed.
        int startResult = isAllowedToStart(r, newTask, targetTask);
        if (startResult != START_SUCCESS) {
            return startResult;
        }

        final ActivityRecord targetTaskTop = newTask
                ? null : targetTask.getTopNonFinishingActivity();
        if (targetTaskTop != null) {
            // Recycle the target task for this launch.
            startResult = recycleTask(targetTask, targetTaskTop, reusedTask, intentGrants); // 2
            if (startResult != START_SUCCESS) {
                return startResult;
            }
        } else {
            mAddingToTask = true;
        }

        // If the activity being launched is the same as the one currently at the top, then
        // we need to check if it should only be launched once.
        final Task topRootTask = mPreferredTaskDisplayArea.getFocusedRootTask();
        if (topRootTask != null) {
            startResult = deliverToCurrentTopIfNeeded(topRootTask, intentGrants);
            if (startResult != START_SUCCESS) {
                return startResult;
            }
        }

        if (mTargetRootTask == null) {
            mTargetRootTask = getLaunchRootTask(mStartActivity, mLaunchFlags, targetTask, mOptions);
        }
        if (newTask) {
            final Task taskToAffiliate = (mLaunchTaskBehind && mSourceRecord != null)
                    ? mSourceRecord.getTask() : null;
            setNewTask(taskToAffiliate);
        } else if (mAddingToTask) {
            addOrReparentStartingActivity(targetTask, "adding to task");
        }

        if (!mAvoidMoveToFront && mDoResume) {
            mTargetRootTask.getRootTask().moveToFront("reuseOrNewTask", targetTask);
            if (!mTargetRootTask.isTopRootTaskInDisplayArea() && mService.mInternal.isDreaming()) {
                // Launching underneath dream activity (fullscreen, always-on-top). Run the launch-
                // -behind transition so the Activity gets created and starts in visible state.
                mLaunchTaskBehind = true;
                r.mLaunchTaskBehind = true;
            }
        }

        mService.mUgmInternal.grantUriPermissionUncheckedFromIntent(intentGrants,
                mStartActivity.getUriPermissionsLocked());
        if (mStartActivity.resultTo != null && mStartActivity.resultTo.info != null) {
            // we need to resolve resultTo to a uid as grantImplicitAccess deals explicitly in UIDs
            final PackageManagerInternal pmInternal =
                    mService.getPackageManagerInternalLocked();
            final int resultToUid = pmInternal.getPackageUid(
                    mStartActivity.resultTo.info.packageName, 0 /* flags */,
                    mStartActivity.mUserId);
            pmInternal.grantImplicitAccess(mStartActivity.mUserId, mIntent,
                    UserHandle.getAppId(mStartActivity.info.applicationInfo.uid) /*recipient*/,
                    resultToUid /*visible*/, true /*direct*/);
        }
        final Task startedTask = mStartActivity.getTask();
        if (newTask) {
            EventLogTags.writeWmCreateTask(mStartActivity.mUserId, startedTask.mTaskId);
        }
        mStartActivity.logStartActivity(EventLogTags.WM_CREATE_ACTIVITY, startedTask);

        mStartActivity.getTaskFragment().clearLastPausedActivity();

        mRootWindowContainer.startPowerModeLaunchIfNeeded(
                false /* forceSend */, mStartActivity);

        final boolean isTaskSwitch = startedTask != prevTopTask && !startedTask.isEmbedded();
        mTargetRootTask.startActivityLocked(mStartActivity,
                topRootTask != null ? topRootTask.getTopNonFinishingActivity() : null, newTask,
                isTaskSwitch, mOptions, sourceRecord);
        if (mDoResume) {
            final ActivityRecord topTaskActivity = startedTask.topRunningActivityLocked();
            if (!mTargetRootTask.isTopActivityFocusable()
                    || (topTaskActivity != null && topTaskActivity.isTaskOverlay()
                    && mStartActivity != topTaskActivity)) {
                // If the activity is not focusable, we can't resume it, but still would like to
                // make sure it becomes visible as it starts (this will also trigger entry
                // animation). An example of this are PIP activities.
                // Also, we don't want to resume activities in a task that currently has an overlay
                // as the starting activity just needs to be in the visible paused state until the
                // over is removed.
                // Passing {@code null} as the start parameter ensures all activities are made
                // visible.
                mTargetRootTask.ensureActivitiesVisible(null /* starting */,
                        0 /* configChanges */, !PRESERVE_WINDOWS);
                Slog.d(TAG_CODE_1100, "execute app transition");
                // Go ahead and tell window manager to execute app transition for this activity
                // since the app transition will not be triggered through the resume channel.
                mTargetRootTask.mDisplayContent.executeAppTransition();
            } else {
                // If the target root-task was not previously focusable (previous top running
                // activity on that root-task was not visible) then any prior calls to move the
                // root-task to the will not update the focused root-task.  If starting the new
                // activity now allows the task root-task to be focusable, then ensure that we
                // now update the focused root-task accordingly.
                if (mTargetRootTask.isTopActivityFocusable()
                        && !mRootWindowContainer.isTopDisplayFocusedRootTask(mTargetRootTask)) {
                    mTargetRootTask.moveToFront("startActivityInner");
                }
                mRootWindowContainer.resumeFocusedTasksTopActivities(
                        mTargetRootTask, mStartActivity, mOptions, mTransientLaunch); // 1
            }
        }
        mRootWindowContainer.updateUserRootTask(mStartActivity.mUserId, mTargetRootTask);

        // Update the recent tasks list immediately when the activity starts
        mSupervisor.mRecentTasks.add(startedTask);
        mSupervisor.handleNonResizableTaskIfNeeded(startedTask,
                mPreferredWindowingMode, mPreferredTaskDisplayArea, mTargetRootTask);

        return START_SUCCESS;
    }

不出意外的话,就会走到mRootWindowContainer.resumeFocusedTasksTopActivities

java 复制代码
package com.android.server.wm;
...
class RootWindowContainer extends WindowContainer<DisplayContent>
        implements DisplayManager.DisplayListener {
    ...
    boolean resumeFocusedTasksTopActivities(
            Task targetRootTask, ActivityRecord target, ActivityOptions targetOptions,
            boolean deferPause) {
        if (!mTaskSupervisor.readyToResume()) {
            return false;
        }

        boolean result = false;
        if (targetRootTask != null && (targetRootTask.isTopRootTaskInDisplayArea()
                || getTopDisplayFocusedRootTask() == targetRootTask)) {
            result = targetRootTask.resumeTopActivityUncheckedLocked(target, targetOptions,
                    deferPause);
        }

        for (int displayNdx = getChildCount() - 1; displayNdx >= 0; --displayNdx) {
            final DisplayContent display = getChildAt(displayNdx);
            final boolean curResult = result;
            boolean[] resumedOnDisplay = new boolean[1];
            display.forAllRootTasks(rootTask -> {
                final ActivityRecord topRunningActivity = rootTask.topRunningActivity();
                if (!rootTask.isFocusableAndVisible() || topRunningActivity == null) {
                    return;
                }
                if (rootTask == targetRootTask) {
                    // Simply update the result for targetRootTask because the targetRootTask
                    // had already resumed in above. We don't want to resume it again,
                    // especially in some cases, it would cause a second launch failure
                    // if app process was dead.
                    resumedOnDisplay[0] |= curResult;
                    return;
                }
                if (rootTask.getDisplayArea().isTopRootTask(rootTask)
                        && topRunningActivity.isState(RESUMED)) {
                    // Kick off any lingering app transitions form the MoveTaskToFront
                    // operation, but only consider the top task and root-task on that
                    // display.
                    rootTask.executeAppTransition(targetOptions);
                } else {
                    resumedOnDisplay[0] |= topRunningActivity.makeActiveIfNeeded(target);
                }
            });
            result |= resumedOnDisplay[0];
            if (!resumedOnDisplay[0]) {
                // In cases when there are no valid activities (e.g. device just booted or launcher
                // crashed) it's possible that nothing was resumed on a display. Requesting resume
                // of top activity in focused root task explicitly will make sure that at least home
                // activity is started and resumed, and no recursion occurs.
                final Task focusedRoot = display.getFocusedRootTask();
                if (focusedRoot != null) {
                    result |= focusedRoot.resumeTopActivityUncheckedLocked(target, targetOptions);
                } else if (targetRootTask == null) {
                    result |= resumeHomeActivity(null /* prev */, "no-focusable-task",
                            display.getDefaultTaskDisplayArea());
                }
            }
        }

        return result;
    }
    ...
}
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