Android應用程式啟動過程——Launcher源碼分析

標籤：android   應用程式啟動流程   

當我們在Launcher介面單擊一個應用程式圖示時就會啟動一個程式，那這一個過程究竟發生了些哪樣呢？讓我們跟蹤Launcher源碼來分析一下吧。

先上流程圖：

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step1、追蹤Launcher  從源碼中我們可以發現Launcher其實也是一個程式，它繼承於Activity。找到該檔案中的onCreate()方法，程式碼片段如下：

protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        LauncherApplication app = ((LauncherApplication)getApplication());        mModel = app.setLauncher(this);        mIconCache = app.getIconCache();        mDragController = new DragController(this);        mInflater = getLayoutInflater();        mAppWidgetManager = AppWidgetManager.getInstance(this);        mAppWidgetHost = new LauncherAppWidgetHost(this, APPWIDGET_HOST_ID);        mAppWidgetHost.startListening();        if (PROFILE_STARTUP) {            android.os.Debug.startMethodTracing("/sdcard/launcher");        }        loadHotseats();        checkForLocaleChange();        setWallpaperDimension();        setContentView(R.layout.launcher);        setupViews();        registerContentObservers();        lockAllApps();        mSavedState = savedInstanceState;        restoreState(mSavedState);        if (PROFILE_STARTUP) {            android.os.Debug.stopMethodTracing();        }        if (!mRestoring) {            mModel.startLoader(this, true);        }

找到關鍵區段，也就是上面被標註紅色代碼。mModel是LauncherModel類型對象，接下來我們跟蹤LauncerModel.java檔案。

step2、  `LauncherModel是一個BroadcastReceiver，在這裡我們先進入startLoader(Context context, boolean isLaunching) 方法。

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LoaderTask實現了Runnable介面，接著我們再找到該實作類別的run()方法，程式碼片段如下：

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讀取系統中各應用主Activity的資訊程式碼片段如下：

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step3、當我們單擊應用程式圖示時所執行的對應方法為Launcher.java裡的onClick()方法，其代碼如下：

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到此就對應用程式的啟動過程分析結束了，歡迎各位網友的指正和建議，以其共同進步。

本文出自 “嚴富坤-編程技術” 部落格，請務必保留此出處http://kinbos.blog.51cto.com/2092114/1408865