安卓源码学习之【导航方式切换分析及实战】

分析

系统启动后通过过滤 SettingsActivity ，然后点击设置-系统-手势-系统导航，进入系统导航设置界面，通过日志可以看出，

SettingsActivity com.android.settings D Switching to fragment com.android.settings.gestures.SystemNavigationGestureSettings

当前界面就是：com.android.settings.gestures.SystemNavigationGestureSettings

后续需要自定义导航方式切换，代码就从这里复制过来。

SystemNavigationGestureSettings关键代码：

typescript 复制代码

    @VisibleForTesting
    static final String KEY_SYSTEM_NAV_3BUTTONS = "system_nav_3buttons";
    @VisibleForTesting
    static final String KEY_SYSTEM_NAV_2BUTTONS = "system_nav_2buttons";
    @VisibleForTesting
    static final String KEY_SYSTEM_NAV_GESTURAL = "system_nav_gestural";

    \...

        @VisibleForTesting
    static String getCurrentSystemNavigationMode(Context context) {
        if (SystemNavigationPreferenceController.isGestureNavigationEnabled(context)) {
            return KEY_SYSTEM_NAV_GESTURAL;
        } else if (SystemNavigationPreferenceController.is2ButtonNavigationEnabled(context)) {
            return KEY_SYSTEM_NAV_2BUTTONS;
        } else {
            return KEY_SYSTEM_NAV_3BUTTONS;
        }
    }

    @VisibleForTesting
    static void setCurrentSystemNavigationMode(IOverlayManager overlayManager, String key) {
        String overlayPackage = NAV_BAR_MODE_GESTURAL_OVERLAY;
        switch (key) {
            case KEY_SYSTEM_NAV_GESTURAL:
                overlayPackage = NAV_BAR_MODE_GESTURAL_OVERLAY;
                break;
            case KEY_SYSTEM_NAV_2BUTTONS:
                overlayPackage = NAV_BAR_MODE_2BUTTON_OVERLAY;
                break;
            case KEY_SYSTEM_NAV_3BUTTONS:
                overlayPackage = NAV_BAR_MODE_3BUTTON_OVERLAY;
                break;
        }

        try {
            overlayManager.setEnabledExclusiveInCategory(overlayPackage, USER_CURRENT);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }
    \...

getCurrentSystemNavigationMode：获取当前导航方式

setCurrentSystemNavigationMode：设置导航方式

在获取当前导航方式时，通过 SystemNavigationGestureSettings同级目录下的SystemNavigationPreferenceController中的两个方法去判断导航方式：

scss 复制代码

   static boolean is2ButtonNavigationEnabled(Context context) {
        return NAV_BAR_MODE_2BUTTON == context.getResources().getInteger(
                com.android.internal.R.integer.config_navBarInteractionMode);
    }

    static boolean isGestureNavigationEnabled(Context context) {
        return NAV_BAR_MODE_GESTURAL == context.getResources().getInteger(
                com.android.internal.R.integer.config_navBarInteractionMode);
    }

设置导航方式主要通过获取 IOverlayManager设置：

ini 复制代码

mOverlayManager = IOverlayManager.Stub.asInterface(
                ServiceManager.getService(Context.OVERLAY_SERVICE));

实战（自定义导航方式）

继续使用上篇文章的 OOBE 项目，新建一个 SystemNavActivity，当进入欢迎界面后点击进入该界面

布局如下：

点击该界面的 OK 按钮，则结束开机向导流程，需要将 WelcomeActivity 中的结束开机向导流程代码拷贝过来，选择导航方式调用setCurrentSystemNavigationMode() 代码即可，所以SystemNavActivity 完整代码如下：

typescript 复制代码

public class SystemNavActivity extends AppCompatActivity {
    private final String TAG = "SystemNavActivity";

    static final String KEY_SYSTEM_NAV_3BUTTONS = "system_nav_3buttons";
    static final String KEY_SYSTEM_NAV_2BUTTONS = "system_nav_2buttons";
    static final String KEY_SYSTEM_NAV_GESTURAL = "system_nav_gestural";

    private IOverlayManager mOverlayManager;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_navigation);

        mOverlayManager = IOverlayManager.Stub.asInterface(
                ServiceManager.getService(Context.OVERLAY_SERVICE));

        ((RadioGroup) findViewById(R.id.rg_navigation)).setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {
                if (checkedId == R.id.rb_ges) {
                    setCurrentSystemNavigationMode(KEY_SYSTEM_NAV_GESTURAL);
                } else if (checkedId == R.id.rb_two) {
                    setCurrentSystemNavigationMode(KEY_SYSTEM_NAV_2BUTTONS);
                } else {
                    setCurrentSystemNavigationMode(KEY_SYSTEM_NAV_3BUTTONS);
                }
            }
        });

        findViewById(R.id.btn_ok).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                finishSetup();
            }
        });
    }

    String getCurrentSystemNavigationMode(Context context) {
        if (isGestureNavigationEnabled(context)) {
            return KEY_SYSTEM_NAV_GESTURAL;
        } else if (is2ButtonNavigationEnabled(context)) {
            return KEY_SYSTEM_NAV_2BUTTONS;
        } else {
            return KEY_SYSTEM_NAV_3BUTTONS;
        }
    }

    void setCurrentSystemNavigationMode(String key) {
        if (key.equals(getCurrentSystemNavigationMode(this))) {
            return;
        }
        String overlayPackage = NAV_BAR_MODE_GESTURAL_OVERLAY;
        switch (key) {
            case KEY_SYSTEM_NAV_GESTURAL:
                overlayPackage = NAV_BAR_MODE_GESTURAL_OVERLAY;
                break;
            case KEY_SYSTEM_NAV_2BUTTONS:
                overlayPackage = NAV_BAR_MODE_2BUTTON_OVERLAY;
                break;
            case KEY_SYSTEM_NAV_3BUTTONS:
                overlayPackage = NAV_BAR_MODE_3BUTTON_OVERLAY;
                break;
        }

        try {
            mOverlayManager.setEnabledExclusiveInCategory(overlayPackage, USER_CURRENT);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    static boolean is2ButtonNavigationEnabled(Context context) {
        return NAV_BAR_MODE_2BUTTON == context.getResources().getInteger(
                com.android.internal.R.integer.config_navBarInteractionMode);
    }

    static boolean isGestureNavigationEnabled(Context context) {
        return NAV_BAR_MODE_GESTURAL == context.getResources().getInteger(
                com.android.internal.R.integer.config_navBarInteractionMode);
    }

    private void finishSetup() {
        setProvisioningState();
        disableSelfAndFinish();
    }

    private void setProvisioningState() {
        Log.i(TAG, "Setting provisioning state");
        // Add a persistent setting to allow other apps to know the device has been provisioned.
        Settings.Global.putInt(getContentResolver(), Settings.Global.DEVICE_PROVISIONED, 1);
        Settings.Secure.putInt(getContentResolver(), Settings.Secure.USER_SETUP_COMPLETE, 1);
    }

    private void disableSelfAndFinish() {
        // remove this activity from the package manager.
        PackageManager pm = getPackageManager();
        ComponentName name = new ComponentName(this, WelcomeActivity.class);
        Log.i(TAG, "Disabling itself (" + name + ")");
        pm.setComponentEnabledSetting(name, PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
                PackageManager.DONT_KILL_APP);
        // terminate the activity.
        finish();
    }
}

接下来无脑导包就行了，注意，个别的系统级别的变量仍会爆红，但我们在上篇导入了 framework.jar在编译时不会报错，所以不必理会。

为了防止 SystemNavActivity finish() 后回到 WelcomeActivity ，需要在WelcomeActivity onCreate方法中添加如下判断，防止逻辑跳转错误：

scss 复制代码

if (Settings.Secure.getInt(getContentResolver(),Settings.Secure.USER_SETUP_COMPLETE,0) == 1) {
        finish();
}

代码作用就是判断开机向导是否结束，结束了，就自然不会进到该界面了，因为我们常见的开机向导功能都包含上一步操作，用户可能还会返回上一个界面进行操作，所以不能简单的 finish()！

到这里界面功能就完成了！

因为设置导航方式，涉及到了跨用户通信，这里需要在清单文件中添加如下系统级别权限：

ini 复制代码

<uses-permission android:name="android.permission.INTERACT_ACROSS_USERS_FULL"/>

并且这个权限只能由系统级别的应用才能调用！所以仿照着 Settings 的清单文件，还需在清单文件头部添加以下代码：

ini 复制代码

coreApp="true"
android:sharedUserId="android.uid.system"

至此，自定义开机向导设置导航应用配置完成！接下来就是放到源码中编译验证即可。