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布局结构

抓取布局后，可以看到每个图标是一个DoubleShadowBubbleTextView，父布局是CellLayout、workspace。

我们可以在CellLayout添加子view打印出调用堆栈信息，可以整体上看页面加载显示流程。

主要类

• Launcher.java：主界面，即MainActivity
• launcher.xml：主界面布局文件
• LauncherModel.java：管理Launcher状态，包括加载任务、状态回调等
• LoaderTask.java：加载任务，是一个Runnable
• LoaderResults.java：加载结果
• BgDataModel#Callbacks：数据回调接口，Launcher实现该接口，加载任务通过该接口回调给Launcher
• LauncherProvider：桌面数据提供者，采用db保存桌面图标数据（包括排列位置、类型等）
• LauncherSettings：封装访问LauncherProvider时的uri、column等一些常量，通过ContentResolver来访问LauncherProvider，不直接操作db
• LoaderCursor：封装cursor操作

流程图

创建Activity

主界面创建的时候，常规的setContentView和findView，创建LauncherModel并开始加载数据

// Launcher.java
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);// 1.创建LauncherAppState和LauncherModelLauncherAppState app = LauncherAppState.getInstance(this);mModel = app.getModel();// 2.infalte布局文件，找到viewsetupViews();// 3. 设置loader监听，开始加载数据，加载完成后回调给主界面if (!mModel.addCallbacksAndLoad(this)) {if (!internalStateHandled) {// If we are not binding synchronously, pause drawing until initial bind complete,// so that the system could continue to show the device loading promptmOnInitialBindListener = Boolean.FALSE::booleanValue;}}// 4. 设置view给ActivitysetContentView(getRootView());

加载数据

创建加载任务

mModel.addCallbacksAndLoad将Launcher设置给LauncherModel，然后创建了加载任务

// LauncherModel.java    
/*** Adds a callbacks to receive model updates* @return true if workspace load was performed synchronously*/
public boolean addCallbacksAndLoad(@NonNull final Callbacks callbacks) {synchronized (mLock) {addCallbacks(callbacks);return startLoader(new Callbacks[] { callbacks });}
}private boolean startLoader(@NonNull final Callbacks[] newCallbacks) {synchronized (mLock) {// 1.取消旧的加载任务boolean wasRunning = stopLoader(); // 之前没有loader任务，wasRunning为falseboolean bindDirectly = mModelLoaded && !mIsLoaderTaskRunning;// 之前没有加载过，bindDirectly为falseboolean bindAllCallbacks = wasRunning || !bindDirectly || newCallbacks.length == 0; // bindAllCallbacks为true, 上一步已经addCallbacks了,所以callbacksList里面包含从Launcher.java传进来的callbacksfinal Callbacks[] callbacksList = bindAllCallbacks ? getCallbacks() : newCallbacks;if (callbacksList.length > 0) {// 2.清空PendingBindfor (Callbacks cb : callbacksList) {MAIN_EXECUTOR.execute(cb::clearPendingBinds);}// 3.创建LoaderResults和LoaderTask，开始加载数据LoaderResults loaderResults = new LoaderResults(mApp, mBgDataModel, mBgAllAppsList, callbacksList);if (bindDirectly) {loaderResults.bindWorkspace(bindAllCallbacks);loaderResults.bindAllApps();loaderResults.bindDeepShortcuts();loaderResults.bindWidgets();return true;} else {stopLoader();mLoaderTask = new LoaderTask(mApp, mBgAllAppsList, mBgDataModel, mModelDelegate, loaderResults);MODEL_EXECUTOR.post(mLoaderTask);}}}
}

整体加载步骤

LoaderTask#run中根据类型加载步骤分为了5步，图标的加载主要看第一步

// LoaderTask.java
public void run() {try (LauncherModel.LoaderTransaction transaction = mApp.getModel().beginLoader(this)) {// first stepList<ShortcutInfo> allShortcuts = new ArrayList<>();loadWorkspace(allShortcuts, memoryLogger);// Sanitize data re-syncs widgets/shortcuts based on the workspace loaded from db.// sanitizeData should not be invoked if the workspace is loaded from a db different// from the main db as defined in the invariant device profile.// (e.g. both grid preview and minimal device mode uses a different db)if (mApp.getInvariantDeviceProfile().dbFile.equals(mDbName)) {sanitizeData();}mResults.bindWorkspace(true /* incrementBindId */);mModelDelegate.workspaceLoadComplete();// Notify the installer packages of packages with active installs on the first screen.sendFirstScreenActiveInstallsBroadcast();// Take a breakwaitForIdle();// second stepList<LauncherActivityInfo> allActivityList;allActivityList = loadAllApps();mResults.bindAllApps();IconCacheUpdateHandler updateHandler = mIconCache.getUpdateHandler();setIgnorePackages(updateHandler);updateHandler.updateIcons(allActivityList,LauncherActivityCachingLogic.newInstance(mApp.getContext()),mApp.getModel()::onPackageIconsUpdated);updateHandler.updateIcons(allShortcuts, new ShortcutCachingLogic(),mApp.getModel()::onPackageIconsUpdated);waitForIdle();// third stepList<ShortcutInfo> allDeepShortcuts = loadDeepShortcuts();mResults.bindDeepShortcuts();updateHandler.updateIcons(allDeepShortcuts,new ShortcutCachingLogic(), (pkgs, user) -> { });waitForIdle();// fourth stepList<ComponentWithLabelAndIcon> allWidgetsList =mBgDataModel.widgetsModel.update(mApp, null);mResults.bindWidgets();updateHandler.updateIcons(allWidgetsList,new ComponentWithIconCachingLogic(mApp.getContext(), true),mApp.getModel()::onWidgetLabelsUpdated);// fifth steploadFolderNames();updateHandler.finish();mModelDelegate.modelLoadComplete();transaction.commit();} catch (CancellationException e) {...}
}

图标解析

loadWorkspace()代码比较多，主要作用是通过ContentResolver查询LauncherProvider中保存的桌面图标信息，然后遍历cursor来解析数据。

在分析代码的时候，抓到数据流向，可以结合真实的db数据进行分析，其中一些判断容错处理可以跳过

主要流程如下：

• 加载默认的数据（Provider会有判断，只有第一次才会加载）
• 通过ContentResolver查询所有数据
• 遍历cursor，根据不同图标类型进行解析，如ITEM_TYPE_APPLICATION代表普通的图标，ITEM_TYPE_FOLDER代表文件夹
• 对数据进行一些校验，校验通过后将数据添加到mBgDataModel

数据流向：

Db(LauncherProvider) --> Cursor(LoaderCursor) --> List(BgDataModel)

protected void loadWorkspace(List<ShortcutInfo> allDeepShortcuts,Uri contentUri,String selection,@Nullable LoaderMemoryLogger logger) {final Context context = mApp.getContext();final ContentResolver contentResolver = context.getContentResolver();// 1. 加载默认的数据（Provider会有判断，只有第一次才会加载）LauncherSettings.Settings.call(contentResolver,LauncherSettings.Settings.METHOD_LOAD_DEFAULT_FAVORITES);synchronized (mBgDataModel) {mBgDataModel.clear();mPendingPackages.clear();// 2. 查询所有数据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 {// 2.1 遍历cursorfinal int appWidgetIdIndex = c.getColumnIndexOrThrow(LauncherSettings.Favorites.APPWIDGET_ID);final int appWidgetProviderIndex = c.getColumnIndexOrThrow(LauncherSettings.Favorites.APPWIDGET_PROVIDER);final int spanXIndex = c.getColumnIndexOrThrow(LauncherSettings.Favorites.SPANX);final int spanYIndex = c.getColumnIndexOrThrow(LauncherSettings.Favorites.SPANY);final int rankIndex = c.getColumnIndexOrThrow(LauncherSettings.Favorites.RANK);final int optionsIndex = c.getColumnIndexOrThrow(LauncherSettings.Favorites.OPTIONS);final int sourceContainerIndex = c.getColumnIndexOrThrow(LauncherSettings.Favorites.APPWIDGET_SOURCE);WorkspaceItemInfo info;LauncherAppWidgetInfo appWidgetInfo;LauncherAppWidgetProviderInfo widgetProviderInfo;Intent intent;String targetPkg;List<IconRequestInfo<WorkspaceItemInfo>> iconRequestInfos = new ArrayList<>();while (!mStopped && c.moveToNext()) {try {// 2.2 根据不同图标类型进行解析，ITEM_TYPE_APPLICATION代表普通的图标，ITEM_TYPE_FOLDER代表文件夹switch (c.itemType) {case LauncherSettings.Favorites.ITEM_TYPE_SHORTCUT:case LauncherSettings.Favorites.ITEM_TYPE_APPLICATION:case LauncherSettings.Favorites.ITEM_TYPE_DEEP_SHORTCUT:intent = c.parseIntent();// 2.3 解析数据，进行一些校验判断if (info != null) {if (info.itemType!= LauncherSettings.Favorites.ITEM_TYPE_DEEP_SHORTCUT) {// Skip deep shortcuts; their title and icons have already been// loaded above.iconRequestInfos.add(c.createIconRequestInfo(info, useLowResIcon));}c.applyCommonProperties(info);info.intent = intent;info.rank = c.getInt(rankIndex);info.spanX = 1;info.spanY = 1;info.runtimeStatusFlags |= disabledState;if (isSafeMode && !isSystemApp(context, intent)) {info.runtimeStatusFlags |= FLAG_DISABLED_SAFEMODE;}LauncherActivityInfo activityInfo = c.getLauncherActivityInfo();if (activityInfo != null) {info.setProgressLevel(PackageManagerHelper.getLoadingProgress(activityInfo),PackageInstallInfo.STATUS_INSTALLED_DOWNLOADING);}if (c.restoreFlag != 0 && !TextUtils.isEmpty(targetPkg)) {tempPackageKey.update(targetPkg, c.user);SessionInfo si = installingPkgs.get(tempPackageKey);if (si == null) {info.runtimeStatusFlags &=~ItemInfoWithIcon.FLAG_INSTALL_SESSION_ACTIVE;} else if (activityInfo == null) {int installProgress = (int) (si.getProgress() * 100);info.setProgressLevel(installProgress,PackageInstallInfo.STATUS_INSTALLING);}}// 3.将数据添加到mBgDataModelc.checkAndAddItem(info, mBgDataModel, logger);} else {throw new RuntimeException("Unexpected null WorkspaceItemInfo");}break;case LauncherSettings.Favorites.ITEM_TYPE_FOLDER:FolderInfo folderInfo = mBgDataModel.findOrMakeFolder(c.id);c.applyCommonProperties(folderInfo);// Do not trim the folder label, as is was set by the user.folderInfo.title = c.getString(c.titleIndex);folderInfo.spanX = 1;folderInfo.spanY = 1;folderInfo.options = c.getInt(optionsIndex);// no special handling required for restored foldersc.markRestored();c.checkAndAddItem(folderInfo, mBgDataModel, logger);break;}} catch (Exception e) {Log.e(TAG, "Desktop items loading interrupted", e);}}} finally {IOUtils.closeSilently(c);}// Load delegate itemsmModelDelegate.loadItems(mUserManagerState, shortcutKeyToPinnedShortcuts);// Load string cachemModelDelegate.loadStringCache(mBgDataModel.stringCache);// Remove dead itemsmItemsDeleted = c.commitDeleted();// Sort the folder items, update ranks, and make sure all preview items are high res.FolderGridOrganizer verifier =new FolderGridOrganizer(mApp.getInvariantDeviceProfile());for (FolderInfo folder : mBgDataModel.folders) {Collections.sort(folder.contents, Folder.ITEM_POS_COMPARATOR);verifier.setFolderInfo(folder);int size = folder.contents.size();// Update ranks here to ensure there are no gaps caused by removed folder items.// Ranks are the source of truth for folder items, so cellX and cellY can be ignored// for now. Database will be updated once user manually modifies folder.for (int rank = 0; rank < size; ++rank) {WorkspaceItemInfo info = folder.contents.get(rank);info.rank = rank;if (info.usingLowResIcon()&& info.itemType == LauncherSettings.Favorites.ITEM_TYPE_APPLICATION&& verifier.isItemInPreview(info.rank)) {mIconCache.getTitleAndIcon(info, false);}}}c.commitRestoredItems();}
}

可以结合db数据进行分析：

• container: 表示显示的布局，像普通、文件夹、dock栏等
• screen: 表示现在第几屏
• itemType：表示类型，像应用图标、文件夹、快捷方式等
• 

图标显示

到这里，我们已经获取到桌面数据了，下面就是要设置到view显示出来。在上面LoaderTask#run()中，loadWorkspace()获取到了数据，而ui显示的触发在mResults.bindWorkspace(true)

bindWorkspace()先是将数据复制一份，然后遍历callback进行bind。上一步mBgDataModel保存了数据库中数据，mBgDataModel是LauncherModel的一个成员变量，在activity#onCreate时创建的，而activity就是Callbacks，所以到这里都关联了起来。
Launcher (Callbacks)—> LoaderTask —> LoaderResults --> BgDataModel --> Callbacks

// LoaderResults.java
/*** Binds all loaded data to actual views on the main thread.*/
public void bindWorkspace(boolean incrementBindId) {// 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);orderedScreenIds.addAll(mBgDataModel.collectWorkspaceScreens());mBgDataModel.extraItems.forEach(extraItems::add);if (incrementBindId) {mBgDataModel.lastBindId++;}mMyBindingId = mBgDataModel.lastBindId;}for (Callbacks cb : mCallbacksList) {new WorkspaceBinder(cb, mUiExecutor, mApp, mBgDataModel, mMyBindingId,workspaceItems, appWidgets, extraItems, orderedScreenIds).bind();}
}

WorkspaceBinder中bind方法会执行callback回调，回调到activity后，创建BubbleTextView添加到CellLayout。