Android 10第一次开机进Launcher闪白屏

标签：10 java 闪白屏 ... Launcher 开机 android com

一、背景说明

问题描述：软件第一次开机或恢复出厂设置后开机，进入原生Launcher前闪现白屏，由于显示时间较短（约500ms），白屏界面未显示完整（1/3~1/2屏幕大小）就消失了。
Android版本：Android 10
关键词：Android 10、开机、白屏

二、问题分析

所涉及的代码及其路径汇总如下：

packages\apps\Launcher3\src\com\android\launcher3\Launcher.java
packages\apps\Launcher3\AndroidManifest.xml
packages\apps\Settings\src\com\android\settings\FallbackHome.java
packages\apps\Provision\src\com\android\provision\DefaultActivity.java
frameworks\base\core\java\android\app\ApplicationPackageManager.java
frameworks\base\services\java\com\android\server\SystemServer.java
frameworks\base\services\core\java\com\android\server\am\ActivityManagerService.java
frameworks\base\services\core\java\com\android\server\wm\ActivityTaskManagerService.java
frameworks\base\services\core\java\com\android\server\wm\RootActivityContainer.java
frameworks\base\services\core\java\com\android\server\pm\PackageManagerService.java

从问题现象来看，可以有两种可能性

1.Launcher应用本身的问题，oncreate()前先显示了某个界面。
2.系统原因或者其他应用问题，在进入Launcher前先打开了某个应用或界面。

显然2的可能性更大，原因在于白屏仅在第一次和恢复出厂设置后才出现，而普通的开关机，recovery不会出现，这很容易联系到开机向导应用，我们知道开机向导主要用于对系统的语言，网络等配置进行设置，而且仅在系统第一次启动时出现，优先于Launcher显示，这些行为很符合问题的特征，但需要’证据‘支持。通常情况下，结合开机log分析开机启动顺序，比较容易定位到问题，但由于我的平台开机时跑完bootanimation会断开adb，并且没有UART串口，故没有办法抓取完整的开机log，和闪白屏log。

对于1情况，比较好容易验证，在Launcher的onCreate()；中添加打印及延时，确认白屏与Launcher显示的顺序。 packages\apps\Launcher3\src\com\android\launcher3\Launcher.java

@Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
        super.onCreate(savedInstanceState);
        try {
                Log.d(TAG,"delay 5 s");
                Thread.sleep(5000);
        } catch (InterruptedException e) {
                e.printStackTrace();
        }
        ...
        setContentView(mLauncherView);
        ...
    }

验证发现，任然会闪白屏。闪白屏后延迟了5s的黑屏进入了Launcher，因此可以断定闪白屏在前，进入Launcher在后。将上述延时移至FallbackHome packages\apps\Settings\src\com\android\settings\FallbackHome.java

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
		...
        try {
                Log.d(TAG,"delay 5 s");
                Thread.sleep(5000);//添加5s延时
        } catch (InterruptedException e) {
                e.printStackTrace();
        }
       ...
        mWallManager = getSystemService(WallpaperManager.class);
        if (mWallManager == null) {
            Log.w(TAG, "Wallpaper manager isn't ready, can't listen to color changes!");
        } else {
            loadWallpaperColors(flags);//加载壁纸
        }
        getWindow().getDecorView().setSystemUiVisibility(flags);
        registerReceiver(mReceiver, new IntentFilter(Intent.ACTION_USER_UNLOCKED));
        maybeFinish();//视情况Finish自身Activity
    }

而现象为开机动画播完后黑屏5s后闪白屏才进入Launcher，所以是先启动FallbackHome界面。那么问题来了：

为什么是先进入FallbackHome,而不是Launcher？
FallbackHome具体是怎么打开的，它起什么作用呢？
闪白屏由FallbackHome引起？对分析FallbackHome发现他使用的是系统壁纸，而系统使用定制的纯黑色背景，因此不会出现白屏，可以排除。那么'bug'到底藏在哪呢？前面说过还有一个可疑点——开机向导。于是乎，屏蔽平台的开机向导apk后恢复出厂设置进行验证。

# mv system/product/priv-app/Provision/Provision.apk system/product/priv-app/Provision/Provision.apk.1
# sync

恢复出厂设置后开机发现不再闪白屏，反复对比验证可以确定就是Provosion导致的闪白屏，至于具体的原因，我们还得从Launcher的启动流程开始分析。

三、Launcher启动流程

Launcher启动整体流程如下：

Android 10第一次开机进Launcher闪白屏_java

系统开机时init进程启动systemserver，这里从systemserver进程开始分析，之前的启动过程不再赘述。 frameworks\base\services\java\com\android\server\SystemServer.java

private void run() {
        try {
        ...
        // Start services.
        try {
            traceBeginAndSlog("StartServices");
            startBootstrapServices();//启动引导服务，如AMS、PMS、PKMS、DMS等
            startCoreServices();//启动系统核心服务，如BatteryService、WebViewUpdateService等
            startOtherServices();//启动其他服务，如IMS,WMS,GpuService等
            SystemServerInitThreadPool.shutdown();
        } catch (Throwable ex) {
            Slog.e("System", "******************************************");
            Slog.e("System", "************ Failure starting system services", ex);
            throw ex;
        } finally {
            traceEnd();
        }
        ...
        }
	}

	private void startBootstrapServices() {
	    ...
	    // Activity manager runs the show.
        traceBeginAndSlog("StartActivityManager");
        // TODO: Might need to move after migration to WM.
        ActivityTaskManagerService atm = mSystemServiceManager.startService(
            ActivityTaskManagerService.Lifecycle.class).getService();//启动ATMS服务
        mActivityManagerService = ActivityManagerService.Lifecycle.startService(
            mSystemServiceManager, atm);//启动AMS服务
        mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
        mActivityManagerService.setInstaller(installer);
        mWindowManagerGlobalLock = atm.getGlobalLock();
        traceEnd();
	    ...
	}

	private void startOtherServices() {
	...
		mActivityManagerService.systemReady(() -> {
	...
	}

从Android 10（API29）开始，ActivityManagerService的工作被ActivityTaskManagerService接管，虽然AMS被接管，但为例保持不同版本系统的正常运行，AMS依然可用，原有接口依然有用。只是有些接口被注解为@Deprecated ,代码跳转至ATMS执行，例如startActiviy():

@Override
    public int startActivity(IApplicationThread caller, String callingPackage,
            Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
            int startFlags, ProfilerInfo profilerInfo, Bundle bOptions) {
        return mActivityTaskManager.startActivity(caller, callingPackage, intent, resolvedType,
                resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions);
    }

调用AMS的systemReady(),准备启动Launcher frameworks\base\services\core\java\com\android\server\am\ActivityManagerService.java

public void systemReady(final Runnable goingCallback, TimingsTraceLog traceLog) {
	...
	if (bootingSystemUser) {
        mAtmInternal.startHomeOnAllDisplays(currentUserId, "systemReady");
    }
	...
}

mAtmInternal 是ActivityTaskManagerInternal在ATMS的构造方法中初始化，是由ATMS对外提供的一个抽象类，真正的实现是在ATMS中的 LocalService，所以执行到了 LocalService 的 startHomeOnAllDisplays方法。 frameworks\base\services\core\java\com\android\server\wm\ActivityTaskManagerService.java

final class LocalService extends ActivityTaskManagerInternal {
	...
	@Override
    public boolean startHomeOnAllDisplays(int userId, String reason) {
        synchronized (mGlobalLock) {
            return mRootActivityContainer.startHomeOnAllDisplays(userId, reason);
        }
    }
	...
}

frameworks\base\services\core\java\com\android\server\wm\RootActivityContainer.java

boolean startHomeOnAllDisplays(int userId, String reason) {
        boolean homeStarted = false;
        for (int i = mActivityDisplays.size() - 1; i >= 0; i--) {
            final int displayId = mActivityDisplays.get(i).mDisplayId;
            homeStarted |= startHomeOnDisplay(userId, reason, displayId);
        }
        return homeStarted;
    }
    ...
    boolean startHomeOnDisplay(int userId, String reason, int displayId) {
        return startHomeOnDisplay(userId, reason, displayId, false /* allowInstrumenting */,
            false /* fromHomeKey */);
    }
    boolean startHomeOnDisplay(int userId, String reason, int displayId, boolean allowInstrumenting,
            boolean fromHomeKey) {
        ...
        if (displayId == DEFAULT_DISPLAY) {
            homeIntent = mService.getHomeIntent();//构建一个category为CATEGORY_HOME的Intent，表明是Home Activity
            aInfo = resolveHomeActivity(userId, homeIntent);//通过PKMS从系统所用已安装的应用中，找到一个符合HomeItent的Activity
        } 
        ...
        mService.getActivityStartController().startHomeActivity(homeIntent, aInfo, myReason,
                displayId);//启动Home Activity
        return true;
    }

frameworks\base\services\core\java\com\android\server\wm\ActivityTaskManagerService.java

Intent getHomeIntent() {
        Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null);
        intent.setComponent(mTopComponent);
        intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING);
        if (mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL) {
            intent.addCategory(Intent.CATEGORY_HOME);
        }
        return intent;
    }

从上面代码分析可知，通过构建category为CATEGORY_HOME的Intent，与PKMS已安装的应用中找到一个匹配的aInfo，并准备启动。讲道理aInfo应当为Launcher。 packages\apps\Launcher3\AndroidManifest.xml

<activity
            android:name="com.android.launcher3.Launcher"
            ...
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.HOME" />
                ...
        </activity>

但事实上通过打印aInfo，发现有限启动的是FallbackHome，原来在安装的apk中，除了Launcher，还有以下应用有配置android.intent.category.HOME packages/apps/Provision/AndroidManifest.xml

<application>
        <activity android:name="DefaultActivity"
                android:excludeFromRecents="true">
            <intent-filter android:priority="1">
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.HOME" />
                ...
    </application>

packages/apps/Settings/AndroidManifest.xml

<activity android:name=".CryptKeeper"
                  ...
            <intent-filter android:priority="10">
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.HOME" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

        <!-- Triggered when user-selected home app isn't encryption aware -->
        <activity android:name=".FallbackHome"
                  ...
            <intent-filter android:priority="-1000">
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.HOME" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

奇怪的是，从android:priority属性来看，优先级顺序应该是CryptKeeper>DefaultActivity>Launcher>FallbackHome,但事实上启动的顺序是FallbackHome>DefaultActivity>Launcher。 CryptKeeper负责锁屏相关，系统第一次开机并未进行锁屏，故不会启动。至于为什么FallbackHome优先启动呢？顺着resolveHomeActivity()往下看... frameworks\base\services\core\java\com\android\server\wm\RootActivityContainer.java

@VisibleForTesting
    ActivityInfo resolveHomeActivity(int userId, Intent homeIntent) {
        final int flags = ActivityManagerService.STOCK_PM_FLAGS;
        final ComponentName comp = homeIntent.getComponent();
        ActivityInfo aInfo = null;
        try {
            if (comp != null) {
                // Factory test.
                aInfo = AppGlobals.getPackageManager().getActivityInfo(comp, flags, userId);
            } else {
                final String resolvedType =
                        homeIntent.resolveTypeIfNeeded(mService.mContext.getContentResolver());
                final ResolveInfo info = AppGlobals.getPackageManager()
                        .resolveIntent(homeIntent, resolvedType, flags, userId);
                if (info != null) {
                    aInfo = info.activityInfo;
                }
            }
        } 
        ...
        aInfo = new ActivityInfo(aInfo);
        aInfo.applicationInfo = mService.getAppInfoForUser(aInfo.applicationInfo, userId);
        return aInfo;
    }

frameworks\base\services\core\java\com\android\server\pm\PackageManagerService.java

@Override
    public ResolveInfo resolveIntent(Intent intent, String resolvedType,
            int flags, int userId) {
        return resolveIntentInternal(intent, resolvedType, flags, userId, false,
                Binder.getCallingUid());
    }

	private ResolveInfo resolveIntentInternal(Intent intent, String resolvedType,
            int flags, int userId, boolean resolveForStart, int filterCallingUid) {
        try {
            Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "resolveIntent");
            ...
            //查询所有符合条件的activities
            Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "queryIntentActivities");
            final List<ResolveInfo> query = queryIntentActivitiesInternal(intent, resolvedType,
                    flags, filterCallingUid, userId, resolveForStart, true /*allowDynamicSplits*/);
            Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
            final ResolveInfo bestChoice =
                    chooseBestActivity(intent, resolvedType, flags, query, userId);//从query 中选择最适的启动Activity
            return bestChoice;
        } finally {
            Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
        }
    }

通过打印发现query 只有FallbackHome，因此FallbackHome最新启动。 packages\apps\Settings\src\com\android\settings\FallbackHome.java

@Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
        //注册用户解锁的广播
        registerReceiver(mReceiver, new IntentFilter(Intent.ACTION_USER_UNLOCKED));
        maybeFinish();
    }
	private BroadcastReceiver mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            maybeFinish();//接收到广播后执行maybeFinish()
        }
    };

	private void maybeFinish() {
        if (getSystemService(UserManager.class).isUserUnlocked()) {
            final Intent homeIntent = new Intent(Intent.ACTION_MAIN)
                    .addCategory(Intent.CATEGORY_HOME);
            //最终调用resolveIntent()再次获取合适的HomeActivity
            final ResolveInfo homeInfo = getPackageManager().resolveActivity(homeIntent, 0);
            if (Objects.equals(getPackageName(), homeInfo.activityInfo.packageName)) {
                if (UserManager.isSplitSystemUser()
                        && UserHandle.myUserId() == UserHandle.USER_SYSTEM) {
                    // This avoids the situation where the system user has no home activity after
                    // SUW and this activity continues to throw out warnings. See b/28870689.
                    return;
                }
                Log.d(TAG, "User unlocked but no home; let's hope someone enables one soon?");
                mHandler.sendEmptyMessageDelayed(0, 500);
            } else {
                Log.d(TAG, "User unlocked and real home found; let's go!");
                getSystemService(PowerManager.class).userActivity(
                        SystemClock.uptimeMillis(), false);
                finish();//finish()自身
            }
        }
    }

由于开机向导的优先级高于Launcher，故FallbackHome启动DefaultActivity packages\apps\Provision\src\com\android\provision\DefaultActivity.java

public class DefaultActivity extends Activity {

    @Override
    protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);

        // Add a persistent setting to allow other apps to know the device has been provisioned.
        Settings.Global.putInt(getContentResolver(), Settings.Global.DEVICE_PROVISIONED, 1);
        Settings.Secure.putInt(getContentResolver(), Settings.Secure.USER_SETUP_COMPLETE, 1);

        // remove this activity from the package manager.
        PackageManager pm = getPackageManager();
        ComponentName name = new ComponentName(this, DefaultActivity.class);
        pm.setComponentEnabledSetting(name, PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
                PackageManager.DONT_KILL_APP);
        // terminate the activity.
        finish();
    }
}

可以看到系统开机向导内容很简单，设置DEVICE_PROVISIONED和USER_SETUP_COMPLETE表示系统完成开机设置，通常用于拉起app。另外就是diable自身，后续开机不会启动，并finish()自身。后续则启动Launcher，走正常的应用启动流程了，后续过程不在赘述了。自此，从现象，结合log及系统启动流程，理清了白屏产生的机制，那么如何解决该问题呢？

方法一、修改如下： packages/apps/Provision/AndroidManifest.xml

<application>
        <activity android:name="DefaultActivity"
    +       	android:directBootAware="true"
                android:excludeFromRecents="true">
            <intent-filter android:priority="1">
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.HOME" />
                ...
    </application>

由于FallbackHome启动后需要接受到用户取消解锁广播后才finish自己，启动下一个homeActivity，这样就引起了白屏闪现。因此打开Provision 的directBootAware属性，使其可直接启动。

方案二、移除Provision开机向导，并将DefaultActivity中的DEVICE_PROVISIONED和USER_SETUP_COMPLETE移到Launcher中或者其他开机启动的apk。 device/qcom/common/base.mk

PRODUCT_PACKAGES := \
    AccountAndSyncSettings \
    DeskClock \
    ...
-   Provision \
    ...

总结

通过Launcher启动的代码流程分析，配合log验证，梳理了FallbackHome、Launcher、Provision三者之间的启动优先级，并锁定白屏所在应用，找到合适的规避方法。

标签：10,java,闪白屏,...,Launcher,开机,android,com
From： https://blog.51cto.com/u_12727059/7402040

Android 10第一次开机进Launcher闪白屏

一、背景说明

二、问题分析

三、Launcher启动流程

总结

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