**摘要:**本文将详细介绍Android系统中APK的安装流程，从PackageInstallerActivity的bindUi方法到PackageManagerService类的installStage方法，经过权限检查，安装参数设置，APK复制，安装处理，直至最终安装完成。
1. 安装apk的方式：
1.将APK放在手机内存卡手动安装
2.通过ADB安装
3.通过应用商店安装
这三种安装方式到PackageManagerService之后安装流程都是相同的
2. apk的安装过程
/frameworks/base/packages/PackageInstaller/src/com/android/packageinstaller/PackageInstallerActivity.java
private void bindUi() {
mAlert.setIcon(mAppSnippet.icon);
mAlert.setTitle(mAppSnippet.label);
mAlert.setView(R.layout.install_content_view);
mAlert.setButton(DialogInterface.BUTTON_POSITIVE, getString(R.string.install),
(ignored, ignored2) -> {
if (mOk.isEnabled()) {
if (mSessionId != -1) {
mInstaller.setPermissionsResult(mSessionId, true);
finish();
} else {
// 进行APK安装
startInstall();
}
}
}, null);
mAlert.setButton(DialogInterface.BUTTON_NEGATIVE, getString(R.string.cancel),
(ignored, ignored2) -> {
// Cancel and finish
setResult(RESULT_CANCELED);
if (mSessionId != -1) {
mInstaller.setPermissionsResult(mSessionId, false);
}
finish();
}, null);
setupAlert();
mOk = mAlert.getButton(DialogInterface.BUTTON_POSITIVE);
mOk.setEnabled(false);
}点击一个未安装的apk后，会弹出安装界面，点击确定按钮后会进入PackageInstallerActivity类的bindUi()方法中，点击安装后调用startInstall方法进行安装
private void startInstall() {
// Start subactivity to actually install the application
Intent newIntent = new Intent();
newIntent.putExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO,
mPkgInfo.applicationInfo);
newIntent.setData(mPackageURI);
newIntent.setClass(this, InstallInstalling.class);
String installerPackageName = getIntent().getStringExtra(
Intent.EXTRA_INSTALLER_PACKAGE_NAME);
if (mOriginatingURI != null) {
newIntent.putExtra(Intent.EXTRA_ORIGINATING_URI, mOriginatingURI);
}
if (mReferrerURI != null) {
newIntent.putExtra(Intent.EXTRA_REFERRER, mReferrerURI);
}
if (mOriginatingUid != PackageInstaller.SessionParams.UID_UNKNOWN) {
newIntent.putExtra(Intent.EXTRA_ORIGINATING_UID, mOriginatingUid);
}
if (installerPackageName != null) {
newIntent.putExtra(Intent.EXTRA_INSTALLER_PACKAGE_NAME,
installerPackageName);
}
if (getIntent().getBooleanExtra(Intent.EXTRA_RETURN_RESULT, false)) {
newIntent.putExtra(Intent.EXTRA_RETURN_RESULT, true);
}
newIntent.addFlags(Intent.FLAG_ACTIVITY_FORWARD_RESULT);
if(localLOGV) Log.i(TAG, "downloaded app uri="+mPackageURI);
startActivity(newIntent);
finish();
}跳转到InstallInstalling类
xref: /frameworks/base/packages/PackageInstaller/src/com/android/packageinstaller/InstallInstalling.java
protected void onResume() {
super.onResume();
if (mInstallingTask == null) {
PackageInstaller installer = getPackageManager().getPackageInstaller();
PackageInstaller.SessionInfo sessionInfo = installer.getSessionInfo(mSessionId);
if (sessionInfo != null && !sessionInfo.isActive()) {
//创建InstallingAsyncTask
mInstallingTask = new InstallingAsyncTask();
mInstallingTask.execute();
} else {
// we will receive a broadcast when the install is finished
mCancelButton.setEnabled(false);
setFinishOnTouchOutside(false);
}
}
}创建InstallingAsyncTask
private final class InstallingAsyncTask extends AsyncTask<Void, Void,
PackageInstaller.Session> {
volatile boolean isDone;
@Override
protected PackageInstaller.Session doInBackground(Void... params) {
PackageInstaller.Session session;
try {
//获取session
session = getPackageManager().getPackageInstaller().openSession(mSessionId);
} catch (IOException e) {
return null;
}
session.setStagingProgress(0);
try {
File file = new File(mPackageURI.getPath());
try (InputStream in = new FileInputStream(file)) {
long sizeBytes = file.length();
try (OutputStream out = session
.openWrite("PackageInstaller", 0, sizeBytes)) {
byte[] buffer = new byte[1024 * 1024];
while (true) {
int numRead = in.read(buffer);
if (numRead == -1) {
session.fsync(out);
break;
}
if (isCancelled()) {
session.close();
break;
}
// 将apk的信息写入session中
out.write(buffer, 0, numRead);
if (sizeBytes > 0) {
float fraction = ((float) numRead / (float) sizeBytes);
session.addProgress(fraction);
}
}
}
}
return session;
} catch (IOException | SecurityException e) {
Log.e(LOG_TAG, "Could not write package", e);
session.close();
return null;
} finally {
synchronized (this) {
isDone = true;
notifyAll();
}
}
}
@Override
protected void onPostExecute(PackageInstaller.Session session) {
if (session != null) {
Intent broadcastIntent = new Intent(BROADCAST_ACTION);
broadcastIntent.setFlags(Intent.FLAG_RECEIVER_FOREGROUND);
broadcastIntent.setPackage(getPackageName());
broadcastIntent.putExtra(EventResultPersister.EXTRA_ID, mInstallId);
PendingIntent pendingIntent = PendingIntent.getBroadcast(
InstallInstalling.this,
mInstallId,
broadcastIntent,
PendingIntent.FLAG_UPDATE_CURRENT);
// 调用PackageInstaller.Session进行安装
session.commit(pendingIntent.getIntentSender());
mCancelButton.setEnabled(false);
setFinishOnTouchOutside(false);
} else {
getPackageManager().getPackageInstaller().abandonSession(mSessionId);
if (!isCancelled()) {
launchFailure(PackageManager.INSTALL_FAILED_INVALID_APK, null);
}
}
}
}1.在doInBackground方法中根据apk的路径将apk的信息写入到session中
2.在onPostExecute方法中调用session的commit方法进行安装
xref: /frameworks/base/core/java/android/content/pm/PackageInstaller.java
public void commit(@NonNull IntentSender statusReceiver) {
try {
mSession.commit(statusReceiver, false);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}mSession的类型为IPackageInstallerSession，最终会调用到PackageInstallerSession的commit方法
xref: /frameworks/base/services/core/java/com/android/server/pm/PackageInstallerSession.java
public void commit(@NonNull IntentSender statusReceiver, boolean forTransfer) {
..................................................
mHandler.obtainMessage(MSG_COMMIT).sendToTarget();
}想handler发送了一个类型为MSG_COMMIT的消息，最终会调用commitNonStagedLocked方法
private void commitNonStagedLocked(List<PackageInstallerSession> childSessions)
throws PackageManagerException {
...........................................................
if (isMultiPackage()) {
...........................................................
if (!success) {
try {
mRemoteObserver.onPackageInstalled(
null, failure.error, failure.getLocalizedMessage(), null);
} catch (RemoteException ignored) {
}
return;
}
mPm.installStage(activeChildSessions);
} else {
mPm.installStage(committingSession);
}
}调用PackageManagerService的installStage方法
/frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java
void installStage(ActiveInstallSession activeInstallSession) {
if (DEBUG_INSTANT) {
if ((activeInstallSession.getSessionParams().installFlags
& PackageManager.INSTALL_INSTANT_APP) != 0) {
Slog.d(TAG, "Ephemeral install of " + activeInstallSession.getPackageName());
}
}
final Message msg = mHandler.obtainMessage(INIT_COPY);
// 创建InstallParams，设置安装包的安装数据
final InstallParams params = new InstallParams(activeInstallSession);
params.setTraceMethod("installStage").setTraceCookie(System.identityHashCode(params));
msg.obj = params;
Trace.asyncTraceBegin(TRACE_TAG_PACKAGE_MANAGER, "installStage",
System.identityHashCode(msg.obj));
Trace.asyncTraceBegin(TRACE_TAG_PACKAGE_MANAGER, "queueInstall",
System.identityHashCode(msg.obj));
mHandler.sendMessage(msg);
}创建InstallParams对象设置安装包的数据，让通过Handler发送INIT_COPY类型的消息
private abstract class HandlerParams {
.....................................................................
final void startCopy() {
if (DEBUG_INSTALL) Slog.i(TAG, "startCopy " + mUser + ": " + this);
handleStartCopy();
handleReturnCode();
}
abstract void handleStartCopy();
abstract void handleReturnCode();
}事件最终会调用到内部类HandlerParams里面的startCopy方法 ， 在startCopy方法里面先后调用了handleStartCopy和handleReturnCode方法。
public void handleStartCopy() {
...................................................................
// 快速、轻量级地解析一个APK文件，提取其最基本的安装信息，用于后续的安装位置决策和空间检查
pkgLite = PackageManagerServiceUtils.getMinimalPackageInfo(mContext,
origin.resolvedPath, installFlags, packageAbiOverride);
...................................................................
if (!origin.staged && pkgLite.recommendedInstallLocation
== PackageHelper.RECOMMEND_FAILED_INSUFFICIENT_STORAGE) {
// TODO: focus freeing disk space on the target device
final StorageManager storage = StorageManager.from(mContext);
final long lowThreshold = storage.getStorageLowBytes(
Environment.getDataDirectory());
// 计算一个APK（或拆分APK集合）在安装完成后，在设备上实际占用的存储空间大小
final long sizeBytes = PackageManagerServiceUtils.calculateInstalledSize(
origin.resolvedPath, packageAbiOverride);
if (sizeBytes >= 0) {
try {
mInstaller.freeCache(null, sizeBytes + lowThreshold, 0, 0);
pkgLite = PackageManagerServiceUtils.getMinimalPackageInfo(mContext,
origin.resolvedPath, installFlags, packageAbiOverride);
} catch (InstallerException e) {
Slog.w(TAG, "Failed to free cache", e);
}
}
...................................................................
}
if (ret == PackageManager.INSTALL_SUCCEEDED) {
...................................................................
// 决定应用最终安装位置的核心策略方法
loc = installLocationPolicy(pkgLite);
if (loc == PackageHelper.RECOMMEND_FAILED_VERSION_DOWNGRADE) {
ret = PackageManager.INSTALL_FAILED_VERSION_DOWNGRADE;
} else if (loc == PackageHelper.RECOMMEND_FAILED_WRONG_INSTALLED_VERSION) {
ret = PackageManager.INSTALL_FAILED_WRONG_INSTALLED_VERSION;
} else if (!onInt) {
// Override install location with flags
if (loc == PackageHelper.RECOMMEND_INSTALL_EXTERNAL) {
// Set the flag to install on external media.
installFlags &= ~PackageManager.INSTALL_INTERNAL;
} else if (loc == PackageHelper.RECOMMEND_INSTALL_EPHEMERAL) {
if (DEBUG_INSTANT) {
Slog.v(TAG, "...setting INSTALL_EPHEMERAL install flag");
}
installFlags |= PackageManager.INSTALL_INSTANT_APP;
installFlags &= ~PackageManager.INSTALL_INTERNAL;
} else {
// Make sure the flag for installing on external
// media is unset
installFlags |= PackageManager.INSTALL_INTERNAL;
}
}
}
...................................................................
if (ret == PackageManager.INSTALL_SUCCEEDED) {
// TODO: http://b/22976637
// Apps installed for "all" users use the device owner to verify the app
UserHandle verifierUser = getUser();
if (verifierUser == UserHandle.ALL) {
verifierUser = UserHandle.SYSTEM;
}
/*
* Determine if we have any installed package verifiers. If we
* do, then we'll defer to them to verify the packages.
*/
final int requiredUid = mRequiredVerifierPackage == null ? -1
: getPackageUid(mRequiredVerifierPackage, MATCH_DEBUG_TRIAGED_MISSING,
verifierUser.getIdentifier());
final int installerUid =
verificationInfo == null ? -1 : verificationInfo.installerUid;
if (!origin.existing && requiredUid != -1
&& isVerificationEnabled(
verifierUser.getIdentifier(), installFlags, installerUid)) {
...................................................................
final PackageVerificationState verificationState = new PackageVerificationState(
requiredUid, this);
mPendingVerification.append(verificationId, verificationState);
// 将APK清单中声明的"可选验证器"与系统中实际存在的验证器进行匹配，并将匹配成功的验证器加入到验证状态管理中。
final List<ComponentName> sufficientVerifiers = matchVerifiers(pkgLite,
receivers, verificationState);
DeviceIdleController.LocalService idleController = getDeviceIdleController();
final long idleDuration = getVerificationTimeout();
/*
* If any sufficient verifiers were listed in the package
* manifest, attempt to ask them.
*/
if (sufficientVerifiers != null) {
final int N = sufficientVerifiers.size();
if (N == 0) {
Slog.i(TAG, "Additional verifiers required, but none installed.");
ret = PackageManager.INSTALL_FAILED_VERIFICATION_FAILURE;
} else {
for (int i = 0; i < N; i++) {
final ComponentName verifierComponent = sufficientVerifiers.get(i);
idleController.addPowerSaveTempWhitelistApp(Process.myUid(),
verifierComponent.getPackageName(), idleDuration,
verifierUser.getIdentifier(), false, "package verifier");
// 向每个验证器发送广播
final Intent sufficientIntent = new Intent(verification);
sufficientIntent.setComponent(verifierComponent);
mContext.sendBroadcastAsUser(sufficientIntent, verifierUser);
}
}
}
........................................................................
}
........................................................................
}
mRet = ret;
}在正式开始复制 APK 文件之前，进行一系列的前置检查、空间确认、安装位置决策以及安全验证的发起工作
void handleReturnCode() {
if (mVerificationCompleted && mEnableRollbackCompleted) {
if ((installFlags & PackageManager.INSTALL_DRY_RUN) != 0) {
String packageName = "";
try {
PackageLite packageInfo =
new PackageParser().parsePackageLite(origin.file, 0);
packageName = packageInfo.packageName;
} catch (PackageParserException e) {
Slog.e(TAG, "Can't parse package at " + origin.file.getAbsolutePath(), e);
}
try {
observer.onPackageInstalled(packageName, mRet, "Dry run", new Bundle());
} catch (RemoteException e) {
Slog.i(TAG, "Observer no longer exists.");
}
return;
}
if (mRet == PackageManager.INSTALL_SUCCEEDED) {
mRet = mArgs.copyApk();
}
processPendingInstall(mArgs, mRet);
}
}handleReturnCode方法扮演的就是"守门人"和"执行者"的角色。它的核心职责是等待所有必需的验证（如包验证、完整性验证）完成，一旦条件满足，就正式启动APK文件的拷贝和后续安装流程。
private void processPendingInstall(final InstallArgs args, final int currentStatus) {
if (args.mMultiPackageInstallParams != null) {
args.mMultiPackageInstallParams.tryProcessInstallRequest(args, currentStatus);
} else {
// 将当前的安装状态码封装成一个PackageInstalledInfo对象
PackageInstalledInfo res = createPackageInstalledInfo(currentStatus);
processInstallRequestsAsync(
res.returnCode == PackageManager.INSTALL_SUCCEEDED,
Collections.singletonList(new InstallRequest(args, res)));
}
}
private void processInstallRequestsAsync(boolean success,
List<InstallRequest> installRequests) {
mHandler.post(() -> {
if (success) {
for (InstallRequest request : installRequests) {
request.args.doPreInstall(request.installResult.returnCode);
}
synchronized (mInstallLock) {
installPackagesTracedLI(installRequests);
}
for (InstallRequest request : installRequests) {
request.args.doPostInstall(
request.installResult.returnCode, request.installResult.uid);
}
}
for (InstallRequest request : installRequests) {
restoreAndPostInstall(request.args.user.getIdentifier(), request.installResult,
new PostInstallData(request.args, request.installResult, null));
}
});
}installPackagesTracedLI是PMS中执行实际安装逻辑的关键方法。installPackagesTracedLI最终会调用installPackagesLI方法
private void installPackagesLI(List<InstallRequest> requests) {
....................................................................
boolean success = false;
try {
Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "installPackagesLI");
for (InstallRequest request : requests) {
final PrepareResult prepareResult;
try {
Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "preparePackage");
// 准备阶段，解析apk的AndroidManifest.xml文件，获取四大组件以及权限信息
prepareResult = preparePackageLI(request.args, request.installResult);
} catch (PrepareFailure prepareFailure) {
request.installResult.setError(prepareFailure.error,
prepareFailure.getMessage());
request.installResult.origPackage = prepareFailure.conflictingPackage;
request.installResult.origPermission = prepareFailure.conflictingPermission;
return;
} finally {
Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
}
....................................................................
try {
// 扫描阶段， 确定包名唯一性，校验包有效性，搜集apk信息
final List<ScanResult> scanResults = scanPackageTracedLI(
prepareResult.packageToScan, prepareResult.parseFlags,
prepareResult.scanFlags, System.currentTimeMillis(),
request.args.user);
....................................................................
} catch (PackageManagerException e) {
request.installResult.setError("Scanning Failed.", e);
return;
}
}
....................................................................
synchronized (mPackages) {
....................................................................
try {
Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "commitPackages");
commitRequest = new CommitRequest(reconciledPackages,
sUserManager.getUserIds());
// 将应用信息正式写入 PMS 的数据结构中，使应用对系统"可见"，唯一可以修改系统状态的地方，必须在此阶段之前确定所有可预测的错误。
commitPackagesLocked(commitRequest);
success = true;
} finally {
for (PrepareResult result : prepareResults.values()) {
if (result.freezer != null) {
result.freezer.close();
}
}
Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
}
}
// 安装后的清理、优化和通知工作
executePostCommitSteps(commitRequest);
} finally {
..............................................................
}
}1.准备阶段，解析apk的AndroidManifest.xml文件，获取四大组件以及权限信息
2.扫描阶段， 确定包名唯一性，校验包有效性，搜集apk信息
3.将应用信息正式写入 PMS 的数据结构中，使应用对系统"可见"，唯一可以修改系统状态的地方，必须在此阶段之前确定所有可预测的错误
4.安装后的清理、优化和通知工作