Android 8.0系統啓動流程_Launcher（四）

時間 2019-12-01

標籤 android 8.0 系統啓動流程 launcher 欄目 Android 简体版

原文原文鏈接

本系列主要介紹Android8.0系統啓動過程當中涉及到的init、Zygote、SystemServer和Launcher。在以前的三篇文章中，講解了以下的過程：java

初始化化：電源上電，加載BootLoader程序；啓動init.cpp，解析init.rc配置文件；
啓動Zygote進程：啓動虛擬機和註冊JNI方法；註冊Socket服務端，預加載資源；執行runSelectLoop(）方法等待其餘進程的註冊；
啓動SystemServer進程：經過Zygote啓動，建立Binder線程池、執行main方法；開啓三個系統服務（引導、核心和其餘）。

在完成以上三個過程後，咱們的系統就開始加載Launcher應用，查看源碼能夠發現Launcher是做爲一個APP應用執行的，其通常位於系統的packages/apps目錄下，能夠經過該應用啓動系統中其餘應用程序，提供快捷訪問圖標。android

1、Launcher的啓動

1.1啓動準備

在SystemServer啓動時，會先啓動引導服務，其中包括PMS（PackageManagerService）和AMS(ActivityManagerService)，其中PMS主要做用是系統中的APK的解析和安裝；AMS主要用於四大組件的啓動和管理，所以LauncherActivity經過AMS啓動。完成引導服務的啓動後，開啓啓動其餘服務。啓動Launcher的入口爲AMS的systemReady方法，promise

frameworks\base\services\java\com\android\server\SystemServer.java
 private void startOtherServices() {
 ...
 //在此以前會作大量的準備工做，包括AMS、PMS 和NetworkScoreService等各類服務，完成以上操做後，表示activity manager能夠運行
 mActivityManagerService.systemReady(() -> {
            Slog.i(TAG, "Making services ready");
            traceBeginAndSlog("StartActivityManagerReadyPhase");
            mSystemServiceManager.startBootPhase(
                    SystemService.PHASE_ACTIVITY_MANAGER_READY);
                    ...
                    }
                    ...
 ...
}
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frameworks\base\services\core\java\com\android\server\am\ActivityManagerService.java
 public void systemReady(final Runnable goingCallback, TimingsTraceLog traceLog) {
        traceLog.traceBegin("PhaseActivityManagerReady");
        synchronized(this) {
...
             mStackSupervisor.resumeFocusedStackTopActivityLocked();
            mUserController.sendUserSwitchBroadcastsLocked(-1, currentUserId);
...
	}	
}
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1.2找到Launcher 的Activity

AMS經過調用ActivityStack實現對堆棧中Activity對象的管理，咱們的最終目的是查找到Launcher應用所在的Activity是如何被調用起來的？其流程以下： ActivityStackSuperior#resumeFocusedStackTopActivityLocked() ->ActivityStack#resumeTopActivityUncheckedLocked()->resumeTopActivityInnerLocked() 在resumeTopActivityInnerLocked中，經過調用startHomeActivityLocked方法，開啓啓動Launcher的Activty。緩存

frameworks\base\services\core\java\com\android\server\am\ActivityStackSupervisor.java
 boolean resumeFocusedStackTopActivityLocked(
            ActivityStack targetStack, ActivityRecord target, ActivityOptions targetOptions) {
            
 if (targetStack != null && isFocusedStack(targetStack)) {
            return targetStack.resumeTopActivityUncheckedLocked(target, targetOptions);
        }
        ...
        return false;
        
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frameworks\base\services\core\java\com\android\server\am\ActivityStack.java
boolean resumeTopActivityUncheckedLocked(ActivityRecord prev, ActivityOptions options) {
if (mStackSupervisor.inResumeTopActivity) {
            return false;
        }
         boolean result = false;
        try {
            mStackSupervisor.inResumeTopActivity = true;
            result = resumeTopActivityInnerLocked(prev, options);
        } finally {
            mStackSupervisor.inResumeTopActivity = false;
        }
        final ActivityRecord next = topRunningActivityLocked(true /* focusableOnly */);
        if (next == null || !next.canTurnScreenOn()) {
            checkReadyForSleep();
        }
        return result;
}
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frameworks\base\services\core\java\com\android\server\am\ActivityStackSupervisor.java
 private boolean resumeTopActivityInnerLocked(ActivityRecord prev, ActivityOptions options) {
 ...
return isOnHomeDisplay() &&
                mStackSupervisor.resumeHomeStackTask(prev, reason);
                ...
                 if (r != null && !r.finishing) {
            moveFocusableActivityStackToFrontLocked(r, myReason);
            return resumeFocusedStackTopActivityLocked(mHomeStack, prev, null);
        }
        return mService.startHomeActivityLocked(mCurrentUser, myReason);
...
}
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1.3 啓動Launcher

frameworks\base\services\core\java\com\android\server\am\ActivityManagerService.java
 boolean startHomeActivityLocked(int userId, String reason) {
 //1 判斷工廠模式和topAction
if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL
                && mTopAction == null) {
            return false;
        }
        //2 建立啓動Launcher的Intent
        Intent intent = getHomeIntent();
        ActivityInfo aInfo = resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);
        if (aInfo != null) {
            intent.setComponent(new ComponentName(aInfo.applicationInfo.packageName, aInfo.name));
            aInfo = new ActivityInfo(aInfo);
            aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId);
            ProcessRecord app = getProcessRecordLocked(aInfo.processName,
                    aInfo.applicationInfo.uid, true);
            if (app == null || app.instr == null) {
                intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);
                final int resolvedUserId = UserHandle.getUserId(aInfo.applicationInfo.uid); 
                final String myReason = reason + ":" + userId + ":" + resolvedUserId;
                //3 啓動Launcdr
                mActivityStarter.startHomeActivityLocked(intent, aInfo, myReason);
            }
        } else {
            Slog.wtf(TAG, "No home screen found for " + intent, new Throwable());
        }
        return true;
}
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在註釋1處是對運行模式和Action的判斷，其中運行模式包括：非工廠模式、低級工廠模式和高級工廠模式。而Action的是是指啓動該Intent的Action，默認是Intent.ACTION_MAIN，表示是該應用的第一個啓動的Activity，通常在建立應用時，AndroidMainfest.xm中都會包含惟一個該標籤的Action。而對於桌面應用，會增長Intent.HOME的標籤，若是咱們想自定義桌面應用，可在該應用的AndroidMainfest中的啓動Activity的Action添加android.Intent.action.HOME，以下所示：bash

<application
       ...
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.HOME"/>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>
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啓動Launer是在ActivityStarter的startHomeActivityLocked方法中完成，經過ActivityStackSupervisor將該Intent移動至HomeStack(用於存儲Launcher的變量)的頂部，最終調用startActivityLocked方法啓動該Intnet，實現對Launcer的啓動。app

void startHomeActivityLocked(Intent intent, ActivityInfo aInfo, String reason) {
        mSupervisor.moveHomeStackTaskToTop(reason);
       ...
    }
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二、Launcher桌面圖標顯示

完成Launcer的啓動後，做爲一個獨立的APP，Launcher開始執行應用的加載和桌面圖標的顯示。 ide

2.1 加載APP

packages\apps\Launcher3\src\com\android\launcher3\Launcher.java
protected void onCreate(Bundle savedInstanceState) {
...
//加載桌面顏色信息和監聽主題變化
 WallpaperColorInfo wallpaperColorInfo = WallpaperColorInfo.getInstance(this);
  wallpaperColorInfo.setOnThemeChangeListener(this);
...
//加載桌面應用信息
 LauncherAppState app = LauncherAppState.getInstance(this);
 ...
 mModel = app.setLauncher(this);
 ...
 //加載和設置桌面view
 mLauncherView = LayoutInflater.from(this).inflate(R.layout.launcher, null);
  setupViews();
  ...
   if (!mModel.startLoader(currentScreen)) {
            mDragLayer.setAlpha(0);
        } else {
            mWorkspace.setCurrentPage(currentScreen);
            setWorkspaceLoading(true);
        }
}
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//設置launcher的監聽，初始化model
packages\apps\Launcher3\src\com\android\launcher3\LauncherAppState
 LauncherModel setLauncher(Launcher launcher) {
        getLocalProvider(mContext).setLauncherProviderChangeListener(launcher);
        mModel.initialize(launcher); //傳入Launcher對象
        return mModel;
    }
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在設置監聽時，傳入的Callbacks 對象時Launcher，是爲了在APP加載完成時，方便經過接口回調的形式返回值Launcher，下面開始加載App。oop

packages\apps\Launcher3\src\com\android\launcher3\LauncherModel
  public void initialize(Callbacks callbacks) {
        synchronized (mLock) {
            Preconditions.assertUIThread();
            mCallbacks = new WeakReference<>(callbacks);
        }
    }
    //Callbacks 接口包含的內容以下，主要用到bindAllApplications
public interface Callbacks extends LauncherAppWidgetHost.ProviderChangedListener {
      ...
        public void bindAllApplications(ArrayList<AppInfo> apps);
        public void bindAppsAddedOrUpdated(ArrayList<AppInfo> apps);
        public void bindAppsAdded(ArrayList<Long> newScreens,
                                  ArrayList<ItemInfo> addNotAnimated,
                                  ArrayList<ItemInfo> addAnimated);
        public void bindPromiseAppProgressUpdated(PromiseAppInfo app);
        public void bindShortcutsChanged(ArrayList<ShortcutInfo> updated, UserHandle user);
        public void bindWidgetsRestored(ArrayList<LauncherAppWidgetInfo> widgets);
        public void bindRestoreItemsChange(HashSet<ItemInfo> updates);
        public void bindWorkspaceComponentsRemoved(ItemInfoMatcher matcher);
        public void bindAppInfosRemoved(ArrayList<AppInfo> appInfos);
        public void bindAllWidgets(MultiHashMap<PackageItemInfo, WidgetItem> widgets);
      ...
    }
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加載的Task分析以下佈局

...
packages\apps\Launcher3\src\com\android\launcher3\LauncherModel
//開始加載
public boolean startLoader(int synchronousBindPage) {
       ...
        synchronized (mLock) {
        //清除以前的回調緩存
            if (mCallbacks != null && mCallbacks.get() != null) {
                final Callbacks oldCallbacks = mCallbacks.get();
                // Clear any pending bind-runnables from the synchronized load process.
                mUiExecutor.execute(new Runnable() {
                            public void run() {
                                oldCallbacks.clearPendingBinds();
                            }
                        });
                // If there is already one running, tell it to stop.
                stopLoader();
                LoaderResults loaderResults = new LoaderResults(mApp, sBgDataModel,
                        mBgAllAppsList, synchronousBindPage, mCallbacks);//包含Callbacks對象
                if (mModelLoaded && !mIsLoaderTaskRunning) {    //已經加載完成且沒有正在加載
                   //加載完成後，開始將結果回調至Launcher
                    loaderResults.bindWorkspace();
                    loaderResults.bindAllApps(); //加載的回調
                    loaderResults.bindDeepShortcuts();
                    loaderResults.bindWidgets();
                    return true;
                } else {
               //開始不斷的加載 工做區間、全部的APP、快捷圖標和抽屜控件
                    startLoaderForResults(loaderResults);
                }
            }
        }
        return false;
    }

packages\apps\Launcher3\src\com\android\launcher3\LauncherModel
public void startLoaderForResults(LoaderResults results) {
        synchronized (mLock) {
             //中止加載
            stopLoader();
            //建立新的加載task
            mLoaderTask = new LoaderTask(mApp, mBgAllAppsList, sBgDataModel, results);
            //在WorkerThread中執行該task
            runOnWorkerThread(mLoaderTask);
        }
    }
   //加載中涉及的線程初始化
 packages\apps\Launcher3\src\com\android\launcher3\LauncherModel
@Thunk static final HandlerThread sWorkerThread = new HandlerThread("launcher-loader");
    static {
        sWorkerThread.start();
    }
@Thunk static final Handler sWorker = new Handler(sWorkerThread.getLooper());
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2.2 加載回調處理

經過LauncherModel的加載線程，獲取到了系統中全部的apps的信息，同時經過其Callbacks的接口，很方便的將結果傳遞出去，post

packages\apps\Launcher3\src\com\android\launcher3\Launcher.java
public void bindAllApplications(final ArrayList<AppInfo> apps) {
        Runnable r = new RunnableWithId(RUNNABLE_ID_BIND_APPS) {
            public void run() {
                bindAllApplications(apps);
            }
        };
     ...
			//加載完成後AllAppsContainerView數據更新
            mAppsView.setApps(apps);
        }
        if (mLauncherCallbacks != null) {
            mLauncherCallbacks.bindAllApplications(apps);
        }
    }
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數據回調值Launcher的bindAllApplications，開始對AllAppsContainerView界面進行數據設置，其設置的控制控件爲AlphabeticalAppsList，經過調用AlphabeticalAppsList實現對數據的設置處理，其實現流程和Recycleview的設置比較相似。

packages\apps\Launcher3\src\com\android\launcher3\allapps\AllAppsContainerView.java
 public void setApps(List<AppInfo> apps) {
        mApps.setApps(apps);
    }

//數據傳遞控制控件中
packages\apps\Launcher3\src\com\android\launcher3\allapps\AlphabeticalAppsList.java
public void setApps(List<AppInfo> apps) {
        mComponentToAppMap.clear();
        addOrUpdateApps(apps);
    }

packages\apps\Launcher3\src\com\android\launcher3\allapps\AllAppsContainerView.java
 @Override
    protected void onFinishInflate() {
...
		 mAppsRecyclerView = findViewById(R.id.apps_list_view); //能夠看到桌面應用部分的界面爲RecyclerView
        mAppsRecyclerView.setApps(mApps);
        mAppsRecyclerView.setLayoutManager(mLayoutManager);
        mAppsRecyclerView.setAdapter(mAdapter);
        mAppsRecyclerView.setHasFixedSize(true);
...

}
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AllAppsContainerView會在XML佈局文件加載完成後，調用onFinishInflate方法，使加載的數據最終顯示在桌面上。造成咱們看到的桌面圖標。

2.3 點擊桌面圖標的跳轉至應用

在AllAppsContainerView設置adapter後，因爲RecyclerView不包含setOnItemClickListener方法，所以通常是在Adapter中自定義實現，可經過回調的形式將點擊事件傳遞出去，Launcher的執行流程以下：

//packages\apps\Launcher3\src\com\android\launcher3\allapps\AllAppsContainerView.java
 public AllAppsContainerView(Context context, AttributeSet attrs, int defStyleAttr) {
      ...
        //建立新的Adapter
        mAdapter = new AllAppsGridAdapter(mLauncher, mApps, mLauncher, this);
        mSpringAnimationHandler = mAdapter.getSpringAnimationHandler();
        mApps.setAdapter(mAdapter);
       ...
    }
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設置點擊的監聽回調

//packages\apps\Launcher3\src\com\android\launcher3\allapps\AllAppsGridAdapter.java
 public AllAppsGridAdapter(Launcher launcher, AlphabeticalAppsList apps, View.OnClickListener
            iconClickListener, View.OnLongClickListener iconLongClickListener) {
      ...
        mIconClickListener = iconClickListener;
      ...
    }
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點擊事件的處理

packages\apps\Launcher3\src\com\android\launcher3\Launcher.java
 public void onClick(View v) {
...
 Object tag = v.getTag();
        if (tag instanceof ShortcutInfo) {
            onClickAppShortcut(v);
        } else if (tag instanceof FolderInfo) {
            if (v instanceof FolderIcon) {
                onClickFolderIcon(v);
            }
        } else if ((v instanceof PageIndicator) ||
            (v == mAllAppsButton && mAllAppsButton != null)) {
            onClickAllAppsButton(v);
        } else if (tag instanceof AppInfo) {
            startAppShortcutOrInfoActivity(v);
        } else if (tag instanceof LauncherAppWidgetInfo) {
            if (v instanceof PendingAppWidgetHostView) {
                onClickPendingWidget((PendingAppWidgetHostView) v);
            }
        }
}

//點擊桌面應用的快捷圖標的處理
protected void onClickAppShortcut(final View v) {
...
 startAppShortcutOrInfoActivity(v);
...
}

 private void startAppShortcutOrInfoActivity(View v) {
        ItemInfo item = (ItemInfo) v.getTag();
        Intent intent;
        if (item instanceof PromiseAppInfo) {
            PromiseAppInfo promiseAppInfo = (PromiseAppInfo) item;
            intent = promiseAppInfo.getMarketIntent();
        } else {
            intent = item.getIntent();
        }
     ...
     //跳轉至相應的應用
        boolean success = startActivitySafely(v, intent, item);
...
    }
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至此Launcher的啓動過程便分析完，總結以下：

啓動：SystemServer啓動PMS和AMS，經過AMS的systemReady開始加載；
查找：查找流程以下ActivityStackSuperior#resumeFocusedStackTopActivityLocked() ->ActivityStack#resumeTopActivityUncheckedLocked()->resumeTopActivityInnerLocked()；
顯示：在resumeTopActivityInnerLocked中經過調用startHomeActivityLocked方法，啓動Launcher的Activty，經過LauncherModel的加載線程處理，獲取到全部的Apps信息，藉助Callbacks的接口回調的形式將數據返回值Launcher，而後將數據賦值給AllAppsContainerView，使Apps的桌面圖標顯示至桌面中。
跳轉：經過設置點擊事件的回調處理，點擊桌面圖標後，經過startActivitySafely跳轉至應用的Main界面。