Android 8.0系统启动流程_Launcher(四)

本系列主要介绍Android8.0系统启动过程中涉及到的init、Zygote、SystemServer和Launcher。
在之前的三篇文章中,讲解了如下的过程:

  • 初始化化:电源上电,加载BootLoader程序; 启动init.cpp,解析init.rc配置文件;
  • 启动Zygote进程:启动虚拟机和注册JNI方法;注册Socket服务端,预加载资源;执行runSelectLoop()方法等待其他进程的注册;
  • 启动SystemServer进程:通过Zygote启动,创建Binder线程池、执行main方法;开启 三个系统服务(引导、核心和其他)。

在完成以上三个过程后,我们的系统就开始加载Launcher应用,查看源码可以发现Launcher是作为一个APP应用执行的,其一般位于系统的packages/apps目录下,可以通过该应用启动系统中其他应用程序,提供快捷访问图标。

一、Launcher的启动

Android 8.0系统启动流程_Launcher(四)_第1张图片

1.1启动准备

在SystemServer启动时,会先启动引导服务,其中包括PMS(PackageManagerService)和AMS(ActivityManagerService),其中PMS主要作用是系统中的APK的解析和安装;AMS主要用于四大组件的启动 和管理,因此LauncherActivity通过AMS启动。
完成引导服务的启动后,开启启动其他服务。启动Launcher的入口为AMS的systemReady方法,

frameworks\base\services\java\com\android\server\SystemServer.java
 private void startOtherServices() {
 ...
 //在此之前会做大量的准备工作,包括AMS、PMS 和NetworkScoreService等各种服务,完成以上操作后,表示activity manager可以运行
 mActivityManagerService.systemReady(() -> {
            Slog.i(TAG, "Making services ready");
            traceBeginAndSlog("StartActivityManagerReadyPhase");
            mSystemServiceManager.startBootPhase(
                    SystemService.PHASE_ACTIVITY_MANAGER_READY);
                    ...
                    }
                    ...
 ...
}
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);
...
	}	
}

1.2找到Launcher 的Activity

AMS通过调用ActivityStack实现对堆栈中Activity对象的管理,我们的最终目的是查找到Launcher应用所在的Activity是如何被调用起来的?
其流程如下:
ActivityStackSuperior#resumeFocusedStackTopActivityLocked() ->ActivityStack#resumeTopActivityUncheckedLocked()->resumeTopActivityInnerLocked()
在resumeTopActivityInnerLocked中,通过调用startHomeActivityLocked方法,开启启动Launcher的Activty。

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;
        
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;
}
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);
...
}

1.3 启动Launcher

frameworks\base\services\core\java\com\android\server\am\ActivityManagerService.java
 boolean startHomeActivityLocked(int userId, String reason) {
 //1 判断工厂模式和topAction
if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL
                && mTopAction == null) {
            return false;
        }
        //2 创建启动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 启动Launcdr
                mActivityStarter.startHomeActivityLocked(intent, aInfo, myReason);
            }
        } else {
            Slog.wtf(TAG, "No home screen found for " + intent, new Throwable());
        }
        return true;
}

在注释1处是对运行模式和Action的判断,其中运行模式包括:非工厂模式、低级工厂模式和高级工厂模式。而Action的是是指启动该Intent的Action,默认是Intent.ACTION_MAIN,表示是该应用的第一个启动的Activity,一般在创建应用时,AndroidMainfest.xm中都会包含唯一个该标签的Action。
而对于桌面应用,会增加Intent.HOME的标签,如果我们想自定义桌面应用,可在该应用的AndroidMainfest中的启动Activity的Action添加android.Intent.action.HOME,如下所示:

 
            
                
                
                
            
        
    

启动Launer是在ActivityStarter的startHomeActivityLocked方法中完成,通过ActivityStackSupervisor将该Intent移动至HomeStack(用于存储Launcher的变量)的顶部,最终调用startActivityLocked方法启动该Intnet,实现对Launcer的启动。

 void startHomeActivityLocked(Intent intent, ActivityInfo aInfo, String reason) {
        mSupervisor.moveHomeStackTaskToTop(reason);
       ...
    }

二 、Launcher桌面图标显示

完成Launcer的启动后,作为一个独立的APP,Launcher开始执行应用的加载和桌面图标的显示。
Android 8.0系统启动流程_Launcher(四)_第2张图片

2.1 加载APP

packages\apps\Launcher3\src\com\android\launcher3\Launcher.java
protected void onCreate(Bundle savedInstanceState) {
...
//加载桌面颜色信息和监听主题变化
 WallpaperColorInfo wallpaperColorInfo = WallpaperColorInfo.getInstance(this);
  wallpaperColorInfo.setOnThemeChangeListener(this);
...
//加载桌面应用信息
 LauncherAppState app = LauncherAppState.getInstance(this);
 ...
 mModel = app.setLauncher(this);
 ...
 //加载和设置桌面view
 mLauncherView = LayoutInflater.from(this).inflate(R.layout.launcher, null);
  setupViews();
  ...
   if (!mModel.startLoader(currentScreen)) {
            mDragLayer.setAlpha(0);
        } else {
            mWorkspace.setCurrentPage(currentScreen);
            setWorkspaceLoading(true);
        }
}
//设置launcher的监听,初始化model
packages\apps\Launcher3\src\com\android\launcher3\LauncherAppState
 LauncherModel setLauncher(Launcher launcher) {
        getLocalProvider(mContext).setLauncherProviderChangeListener(launcher);
        mModel.initialize(launcher); //传入Launcher对象
        return mModel;
    }

在设置监听时,传入的Callbacks 对象时Launcher,是为了在APP加载完成时,方便通过接口回调的形式返回值Launcher,
下面开始加载App。

packages\apps\Launcher3\src\com\android\launcher3\LauncherModel
  public void initialize(Callbacks callbacks) {
        synchronized (mLock) {
            Preconditions.assertUIThread();
            mCallbacks = new WeakReference<>(callbacks);
        }
    }
    //Callbacks 接口包含的内容如下,主要用到bindAllApplications
public interface Callbacks extends LauncherAppWidgetHost.ProviderChangedListener {
      ...
        public void bindAllApplications(ArrayList apps);
        public void bindAppsAddedOrUpdated(ArrayList apps);
        public void bindAppsAdded(ArrayList newScreens,
                                  ArrayList addNotAnimated,
                                  ArrayList addAnimated);
        public void bindPromiseAppProgressUpdated(PromiseAppInfo app);
        public void bindShortcutsChanged(ArrayList updated, UserHandle user);
        public void bindWidgetsRestored(ArrayList widgets);
        public void bindRestoreItemsChange(HashSet updates);
        public void bindWorkspaceComponentsRemoved(ItemInfoMatcher matcher);
        public void bindAppInfosRemoved(ArrayList appInfos);
        public void bindAllWidgets(MultiHashMap widgets);
      ...
    }

加载的Task分析如下

...
packages\apps\Launcher3\src\com\android\launcher3\LauncherModel
//开始加载
public boolean startLoader(int synchronousBindPage) {
       ...
        synchronized (mLock) {
        //清除之前的回调缓存
            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对象
                if (mModelLoaded && !mIsLoaderTaskRunning) {    //已经加载完成且没有正在加载
                   //加载完成后,开始将结果回调至Launcher
                    loaderResults.bindWorkspace();
                    loaderResults.bindAllApps(); //加载的回调
                    loaderResults.bindDeepShortcuts();
                    loaderResults.bindWidgets();
                    return true;
                } else {
               //开始不断的加载 工作区间、所有的APP、快捷图标和抽屉控件
                    startLoaderForResults(loaderResults);
                }
            }
        }
        return false;
    }

packages\apps\Launcher3\src\com\android\launcher3\LauncherModel
public void startLoaderForResults(LoaderResults results) {
        synchronized (mLock) {
             //停止加载
            stopLoader();
            //创建新的加载task
            mLoaderTask = new LoaderTask(mApp, mBgAllAppsList, sBgDataModel, results);
            //在WorkerThread中执行该task
            runOnWorkerThread(mLoaderTask);
        }
    }
   //加载中涉及的线程初始化
 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());

2.2 加载回调处理

通过LauncherModel的加载线程,获取到了系统中所有的apps的信息,同时通过其Callbacks的接口,很方便的将结果传递出去,

packages\apps\Launcher3\src\com\android\launcher3\Launcher.java
public void bindAllApplications(final ArrayList apps) {
        Runnable r = new RunnableWithId(RUNNABLE_ID_BIND_APPS) {
            public void run() {
                bindAllApplications(apps);
            }
        };
     ...
			//加载完成后AllAppsContainerView数据更新
            mAppsView.setApps(apps);
        }
        if (mLauncherCallbacks != null) {
            mLauncherCallbacks.bindAllApplications(apps);
        }
    }

数据回调值Launcher的bindAllApplications,开始对AllAppsContainerView界面进行数据设置,其设置的控制控件为AlphabeticalAppsList,通过调用AlphabeticalAppsList实现对数据的设置处理,其实现流程和Recycleview的设置比较类似。

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

//数据传递控制控件中
packages\apps\Launcher3\src\com\android\launcher3\allapps\AlphabeticalAppsList.java
public void setApps(List 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); //可以看到桌面应用部分的界面为RecyclerView
        mAppsRecyclerView.setApps(mApps);
        mAppsRecyclerView.setLayoutManager(mLayoutManager);
        mAppsRecyclerView.setAdapter(mAdapter);
        mAppsRecyclerView.setHasFixedSize(true);
...

}

AllAppsContainerView会在XML布局文件加载完成后,调用onFinishInflate方法,使加载的数据最终显示在桌面上。形成我们看到的桌面图标。

2.3 点击桌面图标的跳转至应用

在AllAppsContainerView设置adapter后,由于RecyclerView不包含setOnItemClickListener方法,因此一般是在Adapter中自定义实现,可通过回调的形式将点击事件传递出去,Launcher的执行流程如下:

//packages\apps\Launcher3\src\com\android\launcher3\allapps\AllAppsContainerView.java
 public AllAppsContainerView(Context context, AttributeSet attrs, int defStyleAttr) {
      ...
        //创建新的Adapter
        mAdapter = new AllAppsGridAdapter(mLauncher, mApps, mLauncher, this);
        mSpringAnimationHandler = mAdapter.getSpringAnimationHandler();
        mApps.setAdapter(mAdapter);
       ...
    }

设置点击的监听回调

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

点击事件的处理

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);
            }
        }
}

//点击桌面应用的快捷图标的处理
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();
        }
     ...
     //跳转至相应的应用
        boolean success = startActivitySafely(v, intent, item);
...
    }

至此Launcher的启动过程便分析完,总结如下:

  1. 启动:SystemServer启动PMS和AMS,通过AMS的systemReady开始加载;
  2. 查找:查找流程如下ActivityStackSuperior#resumeFocusedStackTopActivityLocked() ->ActivityStack#resumeTopActivityUncheckedLocked()->resumeTopActivityInnerLocked();
  3. 显示:在resumeTopActivityInnerLocked中通过调用startHomeActivityLocked方法,启动Launcher的Activty,通过LauncherModel的加载线程处理,获取到所有的Apps信息,借助Callbacks的接口回调的形式将数据返回值Launcher,然后将数据赋值给AllAppsContainerView,使Apps的桌面图标显示至桌面中。
  4. 跳转:通过设置点击事件的回调处理,点击桌面图标后,通过startActivitySafely跳转至应用的Main界面。

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