【Android】恢复出厂后静态壁纸加载流程

Android静态壁纸功能实现参与的类

/frameworks/base/core/java/android/app/WallpaperManager.java
给开发者提供方法调用。例：setBitmap()/getBitmap()

/frameworks/base/services/core/java/com/android/server/wallpaper/WallpaperManagerService.java
系统服务，管理壁纸的运行和切换，由SystemServer启动

/frameworks/base/core/java/android/service/wallpaper/WallpaperService.java
Android壁纸服务，ImageWallpaper的父类

/frameworks/base/packages/SystemUI/src/com/android/systemui/ImageWallpaper.java
Android设定的壁纸服务，如果default_wallpaper_component没指定，则使用image_wallpaper_component指定的ImageWallpaper

开机壁纸加载流程

1.SystemServer.java -> startOtherServices()内通过config_enableWallpaperService该布尔值判断是否启动壁纸服务:

 if (context.getResources().getBoolean(R.bool.config_enableWallpaperService)) {traceBeginAndSlog("StartWallpaperManagerService");mSystemServiceManager.startService(WALLPAPER_SERVICE_CLASS);traceEnd();
}

服务准备就绪后进行初始化操作，WallpaperManagerService.java->initialize()

void initialize() {mMonitor.register(mContext, null, UserHandle.ALL, true);getWallpaperDir(UserHandle.USER_SYSTEM).mkdirs();// Initialize state from the persistent store, then guarantee that the// WallpaperData for the system imagery is instantiated & active, creating// it from defaults if necessary.loadSettingsLocked(UserHandle.USER_SYSTEM, false);getWallpaperSafeLocked(UserHandle.USER_SYSTEM, FLAG_SYSTEM);}

2.WallpaperManagerService.java->getWallpaperDir()

getWallpaperDir(UserHandle.USER_SYSTEM).mkdirs();

创建系统用户目录/data/system/users/0/，其目录下在壁纸显示后会生成wallpaper_info.xml文件，用于存放壁纸的宽度、高度、壁纸存放位置等信息。

3.WallpaperManagerService.java->loadSettingsLocked()
该方法内开头包括了wallpaper_info文件的创建(JounrnaledFile类)、壁纸文件wallpaper(WallpaperData)的生成、wallpaper_info文件的解析(XmlPullParser)。

loadSettingsLocked(){```if (!success) {wallpaper.width = -1;wallpaper.height = -1;wallpaper.cropHint.set(0, 0, 0, 0);wallpaper.padding.set(0, 0, 0, 0);wallpaper.name = "";//  wallpaper.name = "res:com.desaysv.dsvsettings:drawable/wallpaper_bg_dark_normal_1";mLockWallpaperMap.remove(userId);} else {if (wallpaper.wallpaperId <= 0) {wallpaper.wallpaperId = makeWallpaperIdLocked();if (DEBUG) {Slog.w(TAG, "Didn't set wallpaper id in loadSettingsLocked(" + userId+ "); now " + wallpaper.wallpaperId);}}}ensureSaneWallpaperData(wallpaper);```
}

由于首次启动时不存在wallpaper_info.xml，所以success为false，开始初始化wallpaperData属性，并调用ensureSaneWallpaperData()方法通过WindowManager.getDefaultDisplay.getMaximumSizeDimension()获取屏幕最大尺寸作为壁纸宽高。

4.WallpaperManagerService.java->switchUser()
开启WallpaperObserver和ThemeSettingsObserver监听，观测切换壁纸和主题操作

5.WallpaperManagerService.java->bindWallpaperComponentLocked()
拉起壁纸服务,默认为ImageWallpaper。并向WMS申请用于添加壁纸窗口的窗口令牌。后续这一部分主要由WallpaperConnection.onServiceConnected()回调中处理。

6.WallpaperManagerService.java->attachServiceLocked()
在方法内调用IWallpaperServiceWrapper的attach方法，将创建壁纸窗体需要的信息给到WallpaperService。

void attachServiceLocked(WallpaperConnection conn, WallpaperData wallpaper) {try {conn.mService.attach(conn, conn.mToken,TYPE_WALLPAPER, false,wallpaper.width, wallpaper.height, wallpaper.padding);} catch (RemoteException e) {Slog.w(TAG, "Failed attaching wallpaper; clearing", e);if (!wallpaper.wallpaperUpdating) {bindWallpaperComponentLocked(null, false, false, wallpaper, null);}}}

7.WallpaperService-IWallpaperServiceWrapper.attach()
构造IWallpaperEngineWrapperService实例，并在方法内发送DO_ATTACH信息。

8.WallpaperService.java->executeMessage()

public void executeMessage(Message message) {switch (message.what) {case DO_ATTACH: {try {mConnection.attachEngine(this);} catch (RemoteException e) {Log.w(TAG, "Wallpaper host disappeared", e);return;}Engine engine = onCreateEngine();mEngine = engine;mActiveEngines.add(engine);engine.attach(this);return;}....

WallpaperConnection保存IWallpaperEngineWrapper实例，无需担心被回收，而且WallpaperManagerService还可以通过它与实际Engine进行通信。之后再创建Engine对象，Engine是真正的壁纸实现。
engine.attach()方法内也进行壁纸绘制。

9.updataSurfaceSize()->loadWallpaper()->mWallpaperManager.getBitmap()
通过getBitmap()方法获取。

10.WallpaperManager.java->openDefaultWallpaper()

public static InputStream openDefaultWallpaper(Context context, @SetWallpaperFlags int which) {final String whichProp;final int defaultResId;if (which == FLAG_LOCK) {/* Factory-default lock wallpapers are not yet supportedwhichProp = PROP_LOCK_WALLPAPER;defaultResId = com.android.internal.R.drawable.default_lock_wallpaper;*/return null;} else {whichProp = PROP_WALLPAPER;defaultResId = com.android.internal.R.drawable.default_wallpaper;}//不走buildinfo.sh文件读取默认属性值，且该文件的ro.config.wallpaper属性已经丢失final String path = SystemProperties.get(whichProp);if (!TextUtils.isEmpty(path)) {final File file = new File(path);if (file.exists()) {try {return new FileInputStream(file);} catch (IOException e) {//Ignored, fall back to platform default below}}}try {return context.getResources().openRawResource(defaultResId);} catch (NotFoundException e) {// no default defined for this device; this is not a failure}return null;}

在此有frameworks/base/core/res/res/drawable 下提供壁纸资源，通过context.gerResource().openRawResource()返回，在getDefaultWallpaper()中转成bitmap交由ImageWallpaper的drawFrame()进行绘制