【Android】Android Framework系列--Launcher3桌面图标加载流程

Launcher3桌面加载流程

Android Launcher3(简称Launcher）启动后会加载桌面。基于Android12代码，分析一下桌面加载的流程。
一些相关的概念：

WorkSpace：桌面。在桌面上可以添加快捷方式、Hoseat或Dock（就是手机或者车机系统在桌面底部的图标栏）、Widet小组件（比如天气）等。
AllApp：App List，呈现所有App。点击任意App图标可以启动该App。
DeepShortcuts: 桌面上的应用快捷方式。
Widget：小组件，一般添加到桌面上，比如天气、闹钟、股票之类。

Launcher桌面加载

Launcher被Android AMS拉起后，进入自己的生命流程。Launcher.java 中的onCreate函数被调用，准备开始加载桌面。

//packages/apps/Launcher3/src/com/android/launcher3/Launcher.java
@Override
protected void onCreate(Bundle savedInstanceState) {Object traceToken = TraceHelper.INSTANCE.beginSection(ON_CREATE_EVT,TraceHelper.FLAG_UI_EVENT);LauncherAppState app = LauncherAppState.getInstance(this);mOldConfig = new Configuration(getResources().getConfiguration());mModel = app.getModel();if (!mModel.addCallbacksAndLoad(this)) {// 省略}
}

addCallbacksAndLoad在LauncherModel.java中实现，在这个函数中调用了startLoader函数，该函数中会创建LoaderResults对象。如果是首次启动情况下，调用函数startLoaderForResults，在startLoaderForResults函数中创建LoaderTask并利用之前创建的LoaderResults开始加载桌面。

//packages/apps/Launcher3/src/com/android/launcher3/LauncherModel.java
/*** Adds a callbacks to receive model updates* @return true if workspace load was performed synchronously*/
public boolean addCallbacksAndLoad(Callbacks callbacks) {synchronized (mLock) {addCallbacks(callbacks);return startLoader();}
}/*** Starts the loader. Tries to bind {@params synchronousBindPage} synchronously if possible.* @return true if the page could be bound synchronously.*/
public boolean startLoader() {ItemInstallQueue.INSTANCE.get(mApp.getContext()).pauseModelPush(ItemInstallQueue.FLAG_LOADER_RUNNING);synchronized (mLock) {final Callbacks[] callbacksList = getCallbacks();if (callbacksList.length > 0) {for (Callbacks cb : callbacksList) {MAIN_EXECUTOR.execute(cb::clearPendingBinds);}//  如果直接在加载了，请停止掉。// If there is already one running, tell it to stop.stopLoader();LoaderResults loaderResults = new LoaderResults(mApp, mBgDataModel, mBgAllAppsList, callbacksList);if (mModelLoaded && !mIsLoaderTaskRunning) {// 非首次启动。Launcher直接从数据库中同步加载。loaderResults.bindWorkspace();loaderResults.bindAllApps();loaderResults.bindDeepShortcuts();loaderResults.bindWidgets();return true;} else {// 首次启动走这里。startLoaderForResults(loaderResults);}}}return false;
}public void startLoaderForResults(LoaderResults results) {synchronized (mLock) {stopLoader();// 创建LoaderTask，通过loadTask加载桌面。mLoaderTask = new LoaderTask(mApp, mBgAllAppsList, mBgDataModel, mModelDelegate, results);MODEL_EXECUTOR.post(mLoaderTask);}}

从startLoader这个函数中，可以看出来。Launcher启动时加载的流程是：

Workspace
AllApps
DeepShortcuts
Widgets
因为Workspace（直观上就是用户看到的桌面）是第一个呈现给用户的，并且桌面也是快捷方式、Widget的容器，所以肯定会第一个加载。
接下来，LoaderTask被执行，调用其run函数。

//packages/apps/Launcher3/src/com/android/launcher3/model/LoaderTask.java
public void run() {synchronized (this) {// 退出阶段，直接返回// Skip fast if we are already stopped.if (mStopped) {return;}}try (LauncherModel.LoaderTransaction transaction = mApp.getModel().beginLoader(this)) {//顺序也是先加载 workspace，然后AllApp，然后DeepShortcuts，然后WidgetsList<ShortcutInfo> allShortcuts = new ArrayList<>();// 加载WorkSpace数据loadWorkspace(allShortcuts);logASplit(logger, "loadWorkspace");verifyNotStopped();// 绑定WorkSpace数据（绑定图标之类的数据，桌面及其上内容开始呈现）mResults.bindWorkspace();logASplit(logger, "bindWorkspace");mModelDelegate.workspaceLoadComplete();// Notify the installer packages of packages with active installs on the first screen.// 发送第一个Screen（开机后默认显示的第一个Screen，如果图标多的话，会被分成多个Screen，通过左右滑动显示其他的）sendFirstScreenActiveInstallsBroadcast();logASplit(logger, "sendFirstScreenActiveInstallsBroadcast");// Take a breakwaitForIdle();logASplit(logger, "step 1 complete");verifyNotStopped();// second stepList<LauncherActivityInfo> allActivityList = loadAllApps();logASplit(logger, "loadAllApps");verifyNotStopped();mResults.bindAllApps();logASplit(logger, "bindAllApps");// 省略// Take a breakwaitForIdle();logASplit(logger, "step 2 complete");verifyNotStopped();// third stepList<ShortcutInfo> allDeepShortcuts = loadDeepShortcuts();logASplit(logger, "loadDeepShortcuts");verifyNotStopped();mResults.bindDeepShortcuts();logASplit(logger, "bindDeepShortcuts");// Take a breakwaitForIdle();logASplit(logger, "step 3 complete");verifyNotStopped();// fourth stepList<ComponentWithLabelAndIcon> allWidgetsList =mBgDataModel.widgetsModel.update(mApp, null);logASplit(logger, "load widgets");verifyNotStopped();mResults.bindWidgets();logASplit(logger, "bindWidgets");verifyNotStopped();mModelDelegate.modelLoadComplete();transaction.commit();} 
}

上面的代码中，开始加载Launcher中的workspace、allapp、deepshortcut、Widget。先加载其数据，然后一步步绑定这些数据（桌面上就开始呈现出内容）。因为代码比较多且流程相似，这里主要关注WorkSpace的加载。

//packages/apps/Launcher3/src/com/android/launcher3/model/LoaderTask.java
private void loadWorkspace(List<ShortcutInfo> allDeepShortcuts) {loadWorkspace(allDeepShortcuts, LauncherSettings.Favorites.CONTENT_URI,null /* selection */);
}protected void loadWorkspace(List<ShortcutInfo> allDeepShortcuts, Uri contentUri,String selection) {boolean clearDb = false;// 省略if (clearDb) {Log.d(TAG, "loadWorkspace: resetting launcher database");LauncherSettings.Settings.call(contentResolver,LauncherSettings.Settings.METHOD_CREATE_EMPTY_DB);}Log.d(TAG, "loadWorkspace: loading default favorites");LauncherSettings.Settings.call(contentResolver,LauncherSettings.Settings.METHOD_LOAD_DEFAULT_FAVORITES);synchronized (mBgDataModel) {final HashMap<PackageUserKey, SessionInfo> installingPkgs =mSessionHelper.getActiveSessions();installingPkgs.forEach(mApp.getIconCache()::updateSessionCache);mFirstScreenBroadcast = new FirstScreenBroadcast(installingPkgs);final LoaderCursor c = new LoaderCursor(contentResolver.query(contentUri, null, selection, null, null), contentUri,mApp, mUserManagerState);final Bundle extras = c.getExtras();mDbName = extras == null? null : extras.getString(LauncherSettings.Settings.EXTRA_DB_NAME);try {// 省略while (!mStopped && c.moveToNext()) {// 循环刚刚创建的DB文件。读取DB中的信息（呈现哪些应用图标之类）try {if (c.user == null) {// User has been deleted, remove the item.c.markDeleted("User has been deleted");continue;}boolean allowMissingTarget = false;switch (c.itemType) {case LauncherSettings.Favorites.ITEM_TYPE_SHORTCUT:case LauncherSettings.Favorites.ITEM_TYPE_APPLICATION:case LauncherSettings.Favorites.ITEM_TYPE_DEEP_SHORTCUT:// 获取对应的Intent（比如快捷方式对应的intent）intent = c.parseIntent();// If it's a deep shortcut, we'll use pinned shortcuts to restore itif (cn != null && validTarget && c.itemType!= LauncherSettings.Favorites.ITEM_TYPE_DEEP_SHORTCUT) {// If the component is already present// 如果应用没有被Disable掉，那就么会显示它（通过pm可以disable应用）if (mLauncherApps.isActivityEnabled(cn, c.user)) {// no special handling necessary for this itemc.markRestored();} else {//否则不会显示这个应用。// Gracefully try to find a fallback activity.intent = pmHelper.getAppLaunchIntent(targetPkg, c.user);if (intent != null) {c.restoreFlag = 0;c.updater().put(LauncherSettings.Favorites.INTENT,intent.toUri(0)).commit();cn = intent.getComponent();} else {c.markDeleted("Unable to find a launch target");continue;}}}// 省略，后面就是从数据库遍历出数据，缓存到各个对象中了（内存中）break;// 省略}} catch (Exception e) {Log.e(TAG, "Desktop items loading interrupted", e);}}// Load delegate itemsmModelDelegate.loadItems(mUserManagerState, shortcutKeyToPinnedShortcuts);// Break early if we've stopped loadingif (mStopped) {mBgDataModel.clear();return;}// Remove dead itemsmItemsDeleted = c.commitDeleted();}
}

loadWorkspace函数中通过LauncherSettings创建了Launcher中的数据。并加载了默认的布局数据到创建的DB中。然后遍历DB，将数据赋给对应的对象。初次启动时，加载默认布局数据，会按如下顺序进行：

找launcher3.layout.provider这个key对应的value（contentprovider），然后通过这个value值读取到配置的launcher_layout的信息。
如果第一步没找到。那么找系统中包含“android.autoinstalls.config.action.PLAY_AUTO_INSTALL”的应用，通过它获取launcher_layout信息。
如果第二步没找到。找系统中com.android.launcher3.action.PARTNER_CUSTOMIZATION对应的应用，通过它获取launcher_layout信息。
如果第三步没找到。加载Launcher中默认的workspace布局（ /packages/apps/Launcher3/res/xml/这个目录下的default_workspace_*.xml文件）

关于查找默认布局的实现，可以参考LauncherProvider中的loadDefaultFavoritesIfNecessary函数。
在这里插入图片描述
到此，Launcher桌面需要的数据加载完成。下面将数据绑定（显示出来）

Launcher桌面数据绑定

回到LauncherTask的run函数中loadWorkspace函数执行完成后，调用LoaderResults的bindWorkspace函数完成WorkSpace的数据绑定。绑定数据后，后面Activity渲染时就会用这些数据呈现出桌面上的元素。

//packages/apps/Launcher3/src/com/android/launcher3/model/LoaderTask.java
public void run() {synchronized (this) {// Skip fast if we are already stopped.if (mStopped) {return;}}Object traceToken = TraceHelper.INSTANCE.beginSection(TAG);TimingLogger logger = new TimingLogger(TAG, "run");try (LauncherModel.LoaderTransaction transaction = mApp.getModel().beginLoader(this)) {List<ShortcutInfo> allShortcuts = new ArrayList<>();loadWorkspace(allShortcuts);logASplit(logger, "loadWorkspace");verifyNotStopped();// 绑定WorkSpace中的数据mResults.bindWorkspace();logASplit(logger, "bindWorkspace");
}

LoaderResults的bindWorkspace函数，在其父类BaseLoaderResults中定义。该函数中，创建workspaceItems、appWidgets、orderedScreenIds （屏幕数）等信息的数组。然后创建WorkspaceBinder，调用其bind函数开始绑定。

//packages/apps/Launcher3/src/com/android/launcher3/model/BaseLoaderResults.java
public void bindWorkspace() {// Save a copy of all the bg-thread collectionsArrayList<ItemInfo> workspaceItems = new ArrayList<>();ArrayList<LauncherAppWidgetInfo> appWidgets = new ArrayList<>();final IntArray orderedScreenIds = new IntArray();ArrayList<FixedContainerItems> extraItems = new ArrayList<>();synchronized (mBgDataModel) {workspaceItems.addAll(mBgDataModel.workspaceItems);appWidgets.addAll(mBgDataModel.appWidgets);//可能有多个屏幕（比如图标很多，一个屏幕放不下的情况）orderedScreenIds.addAll(mBgDataModel.collectWorkspaceScreens());mBgDataModel.extraItems.forEach(extraItems::add);mBgDataModel.lastBindId++;mMyBindingId = mBgDataModel.lastBindId;}for (Callbacks cb : mCallbacksList) {// callback对象是Launcher这个类new WorkspaceBinder(cb, mUiExecutor, mApp, mBgDataModel, mMyBindingId,workspaceItems, appWidgets, extraItems, orderedScreenIds).bind();}
}

WorkspaceBinder的bind函数中，首先拿到当前屏幕（就是呈现给用户的第一个屏幕）ID，然后优先往第一个屏幕上绑定内容。之后再绑定其他屏幕的内容。

private void bind() {final int currentScreen;{// Create an anonymous scope to calculate currentScreen as it has to be a// final variable.int currScreen = mCallbacks.getPageToBindSynchronously();if (currScreen >= mOrderedScreenIds.size()) {// There may be no workspace screens (just hotseat items and an empty page).currScreen = PagedView.INVALID_PAGE;}currentScreen = currScreen;}final boolean validFirstPage = currentScreen >= 0;// 拿到当前的屏幕IDfinal int currentScreenId =validFirstPage ? mOrderedScreenIds.get(currentScreen) : INVALID_SCREEN_ID;// Separate the items that are on the current screen, and all the other remaining itemsArrayList<ItemInfo> currentWorkspaceItems = new ArrayList<>();ArrayList<ItemInfo> otherWorkspaceItems = new ArrayList<>();ArrayList<LauncherAppWidgetInfo> currentAppWidgets = new ArrayList<>();ArrayList<LauncherAppWidgetInfo> otherAppWidgets = new ArrayList<>();filterCurrentWorkspaceItems(currentScreenId, mWorkspaceItems, currentWorkspaceItems,otherWorkspaceItems);filterCurrentWorkspaceItems(currentScreenId, mAppWidgets, currentAppWidgets,otherAppWidgets);final InvariantDeviceProfile idp = mApp.getInvariantDeviceProfile();sortWorkspaceItemsSpatially(idp, currentWorkspaceItems);sortWorkspaceItemsSpatially(idp, otherWorkspaceItems);// Tell the workspace that we're about to start binding itemsexecuteCallbacksTask(c -> {c.clearPendingBinds();c.startBinding();}, mUiExecutor);// Bind workspace screens// 先绑定屏幕executeCallbacksTask(c -> c.bindScreens(mOrderedScreenIds), mUiExecutor);Executor mainExecutor = mUiExecutor;// Load items on the current page.// 往当前的屏幕上绑定数据内容bindWorkspaceItems(currentWorkspaceItems, mainExecutor);bindAppWidgets(currentAppWidgets, mainExecutor);mExtraItems.forEach(item ->executeCallbacksTask(c -> c.bindExtraContainerItems(item), mainExecutor));// In case of validFirstPage, only bind the first screen, and defer binding the// remaining screens after first onDraw (and an optional the fade animation whichever// happens later).// This ensures that the first screen is immediately visible (eg. during rotation)// In case of !validFirstPage, bind all pages one after other.final Executor deferredExecutor =validFirstPage ? new ViewOnDrawExecutor() : mainExecutor;executeCallbacksTask(c -> c.finishFirstPageBind(validFirstPage ? (ViewOnDrawExecutor) deferredExecutor : null), mainExecutor);// 绑定非当前屏幕上的内容bindWorkspaceItems(otherWorkspaceItems, deferredExecutor);bindAppWidgets(otherAppWidgets, deferredExecutor);// Tell the workspace that we're done binding itemsexecuteCallbacksTask(c -> c.finishBindingItems(currentScreen), deferredExecutor);if (validFirstPage) {executeCallbacksTask(c -> {// We are loading synchronously, which means, some of the pages will be// bound after first draw. Inform the mCallbacks that page binding is// not complete, and schedule the remaining pages.c.onPageBoundSynchronously(currentScreen);c.executeOnNextDraw((ViewOnDrawExecutor) deferredExecutor);}, mUiExecutor);}
}

通过调用Launcher类的bindScreens函数，绑定屏幕（添加屏幕）后，调用bindWorkspaceItems和bindAppWidgets等函数往屏幕上绑定数据。实际上这些函数，最终会调用Launcher类中的bindItems，根据图标信息创建View并addView，并且给各个View设置其TouchListener。感兴趣的可以顺着这些函数继续看下。
另外Launcher中的数据库（就是上面首次启动时创建的空数据库，并加载了布局数据。一般名称为Launcher.db）用于保存桌面相关数据信息，其创建在LauncherProvider中实现。
在这里插入图片描述