【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：

1. Workspace
2. AllApps
3. DeepShortcuts
4. 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Widgets
		List<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 break
		waitForIdle();
		logASplit(logger, "step 1 complete");
		verifyNotStopped();

		// second step
		List<LauncherActivityInfo> allActivityList = loadAllApps();
		logASplit(logger, "loadAllApps");

		verifyNotStopped();
		mResults.bindAllApps();
		logASplit(logger, "bindAllApps");
		// 省略

		// Take a break
		waitForIdle();
		logASplit(logger, "step 2 complete");
		verifyNotStopped();

		// third step
		List<ShortcutInfo> allDeepShortcuts = loadDeepShortcuts();
		logASplit(logger, "loadDeepShortcuts");

		verifyNotStopped();
		mResults.bindDeepShortcuts();
		logASplit(logger, "bindDeepShortcuts");

		// Take a break
		waitForIdle();
		logASplit(logger, "step 3 complete");
		verifyNotStopped();

		// fourth step
		List<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 &amp;& 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 it
						if (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 item
								c.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 items
		mModelDelegate.loadItems(mUserManagerState, shortcutKeyToPinnedShortcuts);

		// Break early if we've stopped loading
		if (mStopped) {
			mBgDataModel.clear();
			return;
		}

		// Remove dead items
		mItemsDeleted = 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：

1. 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。
2. 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。
3. 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。
4. 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。

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 collections
	ArrayList<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ID
	final int currentScreenId =
			validFirstPage ? mOrderedScreenIds.get(currentScreen) : INVALID_SCREEN_ID;

	// Separate the items that are on the current screen, and all the other remaining items
	ArrayList<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 items
	executeCallbacksTask(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 items
	executeCallbacksTask(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。

代码007普通

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