和你一起终身学习，这里是程序员Android

经典好文推荐，通过阅读本文，您将收获以下知识点:

一、Crash 概述
二、Crash处理流程
三、handleApplicationCrash处理分析
四、handleApplicationCrashInner 处理分析
五、APP Error info分析
六、makeAppCrashingLocked处理分析
七、startAppProblemLocked处理分析
八、stopFreezingAllLocked处理分析

九、 AppErrors.handleAppCrashLocked()
十、UIHandler
十一、 killProcess
十二、小结

Android 9.0 Crash 机制调用链

/frameworks/base/core/java/com/android/internal/os/RuntimeInit.java
/frameworks/base/core/java/android/app/ActivityManagerNative.java (含内部类AMP)
/frameworks/base/core/java/android/app/ApplicationErrorReport.java/frameworks/base/services/core/java/com/android/server/- am/ActivityManagerService.java- am/ProcessRecord.java- am/ActivityRecord.java- am/ActivityStackSupervisor.java- am/ActivityStack.java- am/ActivityRecord.java- am/BroadcastQueue.java- wm/WindowManagerService.java/libcore/libart/src/main/java/java/lang/Thread.java

一、Crash 概述

App Crash (全称Application Crash), 对于Crash可分为Native Crash和 Framework Crash(包含app crash在内)，对于Crash相信很多app开发者都会遇到，那么上层什么时候会出现Crash呢，系统又是如何处理Crash的呢。例如，在app大家经常使用try...catch语句，那么如果没有有效catch exception，就是导致应用Crash，发生没有catch exception，系统便会来进行捕获，并进入Crash流程。如果你是从事Android系统开发或者架构相关工作，或者遇到需要解系统性的疑难杂症，那么很有必要了解系统Crash处理流程，知其然还需知其所以然；如果你仅仅是App初级开发，可能本文并非很适合阅读，整个系统流程错综复杂。

在Android系统启动系列文章，已讲述过上层应用都是由Zygote fork孵化而来，分为system_server系统进程和各种应用进程，在这些进程创建之初会设置未捕获异常的处理器，当系统抛出未捕获的异常时，最终都交给异常处理器。

• 对于system_server进程：system_server启动过程中由RuntimeInit.java的commonInit方法设置UncaughtHandler，用于处理未捕获异常；

• 对于普通应用进程：进程创建过程中，同样会调用RuntimeInit.java的commonInit方法设置UncaughtHandler。

1.1 crash调用链

crash流程的方法调用关系如下：

AMP.handleApplicationCrashAMS.handleApplicationCrashAMS.findAppProcessAMS.handleApplicationCrashInnerAMS.addErrorToDropBoxAMS.crashApplicationAMS.makeAppCrashingLockedAMS.startAppProblemLockedProcessRecord.stopFreezingAllLockedActivityRecord.stopFreezingScreenLockedWMS.stopFreezingScreenLockedWMS.stopFreezingDisplayLockedAMS.handleAppCrashLockedmUiHandler.sendMessage(SHOW_ERROR_MSG)Process.killProcess(Process.myPid());
System.exit(10);

二、Crash处理流程

RuntimeInit.java类的 main方法会调用commonInit()方法。

    public static final void main(String[] argv) {enableDdms();if (argv.length == 2 && argv[1].equals("application")) {if (DEBUG) Slog.d(TAG, "RuntimeInit: Starting application");redirectLogStreams();} else {if (DEBUG) Slog.d(TAG, "RuntimeInit: Starting tool");}// AP Crash 处理流程初始化commonInit();// Native Crash  处理流程初始化nativeFinishInit();if (DEBUG) Slog.d(TAG, "Leaving RuntimeInit!");}

那么接下来以commonInit()方法为起点来展开说明。

1. RuntimeInit.commonInit

RuntimeInit.java

    protected static final void commonInit() {/** set handlers; these apply to all threads in the VM. Apps can replace* the default handler, but not the pre handler.*/LoggingHandler loggingHandler = new LoggingHandler();// app不能 替换 setUncaughtExceptionPreHandlerThread.setUncaughtExceptionPreHandler(loggingHandler);// 将异常处理器handler对象赋给Thread成员变量,Thread.setDefaultUncaughtExceptionHandler(new KillApplicationHandler(loggingHandler));... ...}

接下来我们看看LoggingHandler的实现。LoggingHandler实现 Thread.UncaughtExceptionHandler 方法。

    private static class LoggingHandler implements Thread.UncaughtExceptionHandler {public volatile boolean mTriggered = false;@Overridepublic void uncaughtException(Thread t, Throwable e) {mTriggered = true;//保证crash处理过程不会重入if (mCrashing) return;//mApplicationObject等于null,一定不是普通的app进程. //但是除了system进程, 也有可能是shell进程, //即通过app_process + 命令参数 的方式创建的进程.if (mApplicationObject == null && (Process.SYSTEM_UID == Process.myUid())) {            //系统 进程Crash打印的Log 信息/**发生 系统Crash  时候可以搜索 关键字 FATAL EXCEPTION IN SYSTEM PROCESS**/Clog_e(TAG, "*** FATAL EXCEPTION IN SYSTEM PROCESS: " + t.getName(), e);} else {/**发生 APP Crash  时候可以搜索 关键字 FATAL EXCEPTION**/StringBuilder message = new StringBuilder();message.append("FATAL EXCEPTION: ").append(t.getName()).append("\n");final String processName = ActivityThread.currentProcessName();if (processName != null) {message.append("Process: ").append(processName).append(", ");}message.append("PID: ").append(Process.myPid());Clog_e(TAG, message.toString(), e);}}}

• 1.当System进程Crash的信息：

开头 FATAL EXCEPTION IN SYSTEM PROCESS [线程名],接着输出Crash时的调用栈信息；

• 2.当app进程Crash时的信息：

开头 FATAL EXCEPTION: [线程名],紧接着 Process: [进程名], PID: [进程id]；最后输出发生Crash时的调用栈信息。

看到这里，你就会发现要从log中搜索Crash信息，只需要搜索关键词 FATAL EXCEPTION,即可查看出是那种异常；如果需要进一步筛选只搜索系统crash信息，则可以搜索的关键词可以有多样，比如 FATAL EXCEPTION IN SYSTEM PROCESS。

当输出完Crash信息到logcat里面，这只是Crash流程的刚开始阶段，接下来弹出Crash对话框，ActivityManagerNative.getDefault()返回的是ActivityManagerProxy（简称AMP），AMP经过binder调用最终交给ActivityManagerService(简称AMS)中相应的方法去处理,然后调用的是AMS.handleApplicationCrash()。

分析完LoggingHandler后，我们继续看setDefaultUncaughtExceptionHandler()，它只是将异常处理器handler对象赋给Thread成员变量,即Thread.setDefaultUncaughtExceptionHandler(new KillApplicationHandler(loggingHandler));。接下来看看KillApplicationHandler对象实例化过程。

2. KillApplicationHandler

RuntimeInit.java

KillApplicationHandler 实现 Thread.UncaughtExceptionHandler方法,主要处理由于未捕获的异常Crash导致APP 崩溃,运行在Main Thread的Framework 代码会捕获这些异常。

KillApplicationHandler 方法需要传递一个LoggingHandler的参数，
既 LoggingHandler loggingHandler = new LoggingHandler();，LoggingHandler在上文已经分析过，接下来我们看看KillApplicationHandler方法.

KillApplicationHandler方法如下:

    private static class KillApplicationHandler implements Thread.UncaughtExceptionHandler {private final LoggingHandler mLoggingHandler;public KillApplicationHandler(LoggingHandler loggingHandler) {// 构造方法，初始化 loggingHandler this.mLoggingHandler = Objects.requireNonNull(loggingHandler);}@Overridepublic void uncaughtException(Thread t, Throwable e) {try {ensureLogging(t, e);// 保证crash处理过程不会重入if (mCrashing) return;mCrashing = true;... ...//启动crash对话框，等待处理完成 【见小节2.1和3】ActivityManager.getService().handleApplicationCrash(mApplicationObject, new ApplicationErrorReport.ParcelableCrashInfo(e));} catch (Throwable t2) {... ... } finally {//确保当前进程彻底杀掉【见小节11】Process.killProcess(Process.myPid());System.exit(10);}}... ...
}

接下来我们看看启动Crash弹窗的处理。new ApplicationErrorReport.ParcelableCrashInfo(e)方法。

2.1 ApplicationErrorReport.ParcelableCrashInfo

ApplicationErrorReport 主要用来描述 APP Error信息。
APP ERROR 信息分类如下：

• TYPE_CRASH：APP Crash 信息

• TYPE_ANR：APP ANR 信息

• TYPE_BATTERY：Battery 使用信息

• TYPE_RUNNING_SERVICE：正在运行的Service 相关信息

// 主要处理 APP Error 信息
public class ApplicationErrorReport implements Parcelable {... ...public static class ParcelableCrashInfo extends CrashInfo implements Parcelable {//创建 CrashInfo 实例，初始化异常信息public ParcelableCrashInfo(Throwable tr) {super(tr);}...  ... public static final Parcelable.Creator<ParcelableCrashInfo> CREATOR =new Parcelable.Creator<ParcelableCrashInfo>() {@Overridepublic ParcelableCrashInfo createFromParcel(Parcel in) {return new ParcelableCrashInfo(in);}@Overridepublic ParcelableCrashInfo[] newArray(int size) {return new ParcelableCrashInfo[size];}};}... ...
}

ParcelableCrashInfo 继承 CrashInfo,接下来我们看看 CrashInfo的实现。

CrashInfo

**CrashInfo ** 主要是将Crash信息文件名，类名，方法名，对应行号以及异常信息都封装到CrashInfo对象。

   // 描述 Crash 信息public static class CrashInfo {...  ...public CrashInfo() {}//CrashInfo 初始化实例 public CrashInfo(Throwable tr) {StringWriter sw = new StringWriter();PrintWriter pw = new FastPrintWriter(sw, false, 256);//输出栈tracetr.printStackTrace(pw);pw.flush();stackTrace = sanitizeString(sw.toString());exceptionMessage = tr.getMessage();// 显示异常的根本原因Throwable rootTr = tr;while (tr.getCause() != null) {tr = tr.getCause();if (tr.getStackTrace() != null && tr.getStackTrace().length > 0) {rootTr = tr;}String msg = tr.getMessage();if (msg != null && msg.length() > 0) {exceptionMessage = msg;}}// Crash 异常类名称 exceptionClassName = rootTr.getClass().getName();if (rootTr.getStackTrace().length > 0) {StackTraceElement trace = rootTr.getStackTrace()[0];// 获取 trace 文件名、类名、方法名、Crash 行号throwFileName = trace.getFileName();throwClassName = trace.getClassName();throwMethodName = trace.getMethodName();throwLineNumber = trace.getLineNumber();} else {throwFileName = "unknown";... ... }exceptionMessage = sanitizeString(exceptionMessage);}

三、handleApplicationCrash处理分析

handleApplicationCrash 会通过 JNI接口调用AMS中的方法。

               //发送 Crash 弹窗handler，直到Dialog  dismissActivityManager.getService().handleApplicationCrash(mApplicationObject, new ApplicationErrorReport.ParcelableCrashInfo(e));

ActivityManagerService.java
handleApplicationCrash 通过JNI 回调用 AMS中的handleApplicationCrash方法，进而调用AMS 中的内部方法handleApplicationCrashInner。
handleApplicationCrash

• 1.当远程IBinder对象为空Null时，则进程名为system_server；

• 2.当远程IBinder对象不为空，且ProcessRecord为空时，则进程名为unknown;

• 3.当远程IBinder对象不为空，且ProcessRecord不为空时，则进程名为ProcessRecord对象中相应进程名。

    //  当app Crash 时候，会调用此方法。//调用结束后 ，app 进程就会推出public void handleApplicationCrash(IBinder app,ApplicationErrorReport.ParcelableCrashInfo crashInfo) {// findAppProcess 详见 3.1 分析ProcessRecord r = findAppProcess(app, "Crash");// system_server 进程 为Null final String processName = app == null ? "system_server": (r == null ? "unknown" : r.processName);//handleApplicationCrashInner 详见 4 分析handleApplicationCrashInner("crash", r, processName, crashInfo);}

handleApplicationCrashInner主要是调用 AppErrors类中的crashApplication 方法处理。

    void handleApplicationCrashInner(String eventType, ProcessRecord r, String processName,ApplicationErrorReport.CrashInfo crashInfo) {... ... //调用APP Error 类方法中的 crashApplicationmAppErrors.crashApplication(r, crashInfo);}

3.1 findAppProcess

ActivityManagerService.java
findAppProcess主要是通过for循环遍历查找出IBinder对应的Process.

    private ProcessRecord findAppProcess(IBinder app, String reason) {... ...synchronized (this) {final int NP = mProcessNames.getMap().size();for (int ip=0; ip<NP; ip++) {SparseArray<ProcessRecord> apps = mProcessNames.getMap().valueAt(ip);final int NA = apps.size();for (int ia=0; ia<NA; ia++) {ProcessRecord p = apps.valueAt(ia);//当找到目标进程则返回if (p.thread != null && p.thread.asBinder() == app) {return p;}}}//如果代码执行到这里，表明无法找到应用所在的进程return null;}}

其中 mProcessNames = new ProcessMap<ProcessRecord>();对于代码mProcessNames.getMap()返回的是mMap，而mMap= new ArrayMap<String, SparseArray<ProcessRecord>>();

知识延伸：SparseArray和ArrayMap是Android专门针对内存优化而设计的取代Java API中的HashMap的数据结构。

对于key是int类型则使用SparseArray，可避免自动装箱过程；
对于key为其他类型则使用ArrayMap。
HashMap的查找和插入时间复杂度为O(1)的代价是牺牲大量的内存来实现的，而SparseArray和ArrayMap性能略逊于HashMap，但更节省内存。

再回到mMap，这是以进程name为key，再以(uid为key，以ProcessRecord为Value的)结构体作为value。下面看看其get()和put()方法

    public E get(String name, int uid) {SparseArray<E> uids = mMap.get(name);if (uids == null) return null;return uids.get(uid);}public E put(String name, int uid, E value) {SparseArray<E> uids = mMap.get(name);if (uids == null) {uids = new SparseArray<E>(2);mMap.put(name, uids);}uids.put(uid, value);return value;}

findAppProcess()根据app(IBinder类型)来查询相应的目标对象ProcessRecord。

有了进程记录对象ProcessRecord和进程名processName，则进入执行Crash处理方法 AppErrors.java，继续往下看。

四、handleApplicationCrashInner 处理分析

ActivityManagerService.java

    void handleApplicationCrashInner(String eventType, ProcessRecord r, String processName,ApplicationErrorReport.CrashInfo crashInfo) {... ...//将错误信息追加到DropBoxaddErrorToDropBox(eventType, r, processName, null, null, null, null, null, crashInfo);//【见小节5】mAppErrors.crashApplication(r, crashInfo);}

其中addErrorToDropBox是将Crash的信息输出到目录/data/system/dropbox。例如system_server的dropbox文件名为system_server_crash@xxx.txt (xxx代表的是时间戳)

五、APP Error info分析

AppErrors.java
AppErrors 主要是 控制APP Crash的场景条件。

    void crashApplication(ProcessRecord r, ApplicationErrorReport.CrashInfo crashInfo) {... ...try {// 调用内部 crashApplicationInner方法crashApplicationInner(r, crashInfo, callingPid, callingUid);} finally {Binder.restoreCallingIdentity(origId);}}

crashApplicationInner内部方法

 void crashApplicationInner(ProcessRecord r, ApplicationErrorReport.CrashInfo crashInfo,int callingPid, int callingUid) {... ... AppErrorResult result = new AppErrorResult();TaskRecord task;synchronized (mService) {// 如果是通过IActivityController 实例导致的Crash ，则不显示弹窗// 详见5.1 if (handleAppCrashInActivityController(r, crashInfo, shortMsg, longMsg, stackTrace,timeMillis, callingPid, callingUid)) {return;}... ...AppErrorDialog.Data data = new AppErrorDialog.Data();data.result = result;data.proc = r;// 无法势必的进程 也不显示Crash 弹窗【见小节6】if (r == null || !makeAppCrashingLocked(r, shortMsg, longMsg, stackTrace, data)) {return;}final Message msg = Message.obtain();msg.what = ActivityManagerService.SHOW_ERROR_UI_MSG;task = data.task;msg.obj = data;//发送消息SHOW_ERROR_MSG，弹出提示crash的对话框，等待用户选择【见小节10】mService.mUiHandler.sendMessage(msg);}//进入阻塞等待，直到用户选择crash对话框"退出"或者"退出并报告"int res = result.get();Intent appErrorIntent = null;MetricsLogger.action(mContext, MetricsProto.MetricsEvent.ACTION_APP_CRASH, res);if (res == AppErrorDialog.TIMEOUT || res == AppErrorDialog.CANCEL) {res = AppErrorDialog.FORCE_QUIT;}... ...
}

5.1 handleAppCrashInActivityController

handleAppCrashInActivityController,通过IActivityController 实例导致的Crash ，则不显示弹窗.
AppError.java

 private boolean handleAppCrashInActivityController(ProcessRecord r,ApplicationErrorReport.CrashInfo crashInfo,String shortMsg, String longMsg,String stackTrace, long timeMillis,int callingPid, int callingUid) {... ... // 当存在ActivityController的情况,比如monkeytry {String name = r != null ? r.processName : null;int pid = r != null ? r.pid : callingPid;int uid = r != null ? r.info.uid : callingUid;//调用monkey的 appCrashedif (!mService.mController.appCrashed(name, pid,shortMsg, longMsg, timeMillis, crashInfo.stackTrace)) {if ("1".equals(SystemProperties.get(SYSTEM_DEBUGGABLE, "0"))&& "Native crash".equals(crashInfo.exceptionClassName)) {Slog.w(TAG, "Skip killing native crashed app " + name+ "(" + pid + ") during testing");} else {Slog.w(TAG, "Force-killing crashed app " + name+ " at watcher's request");if (r != null) {//调用`makeAppCrashingLocked`，继续处理crash流程// 详见 小结 6 if (!makeAppCrashingLocked(r, shortMsg, longMsg, stackTrace, null)){r.kill("crash", true);}} else {// Huh.Process.killProcess(pid);ActivityManagerService.killProcessGroup(uid, pid);}}return true;}} catch (RemoteException e) {mService.mController = null;Watchdog.getInstance().setActivityController(null);}return false;}

该方法主要做的两件事：

• 调用makeAppCrashingLocked，继续处理Crash流程；

• 发送消息SHOW_ERROR_MSG，弹出提示Crash的对话框，等待用户选择；
  接下来我们看makeAppCrashingLocked实现。

六、makeAppCrashingLocked处理分析

AppError.java

   private boolean makeAppCrashingLocked(ProcessRecord app,String shortMsg, String longMsg, String stackTrace, AppErrorDialog.Data data) {app.crashing = true;//封装crash信息到crashingReport对象app.crashingReport = generateProcessError(app,ActivityManager.ProcessErrorStateInfo.CRASHED, null, shortMsg, longMsg, stackTrace);//【见小节7】startAppProblemLocked(app);//停止屏幕冻结【见小节8】app.stopFreezingAllLocked();//【见小节9】return handleAppCrashLocked(app, "force-crash" /*reason*/, shortMsg, longMsg, stackTrace,data);}

七、startAppProblemLocked处理分析

AppError.java
startAppProblemLocked 该方法主要功能：

• 获取当前用户下的crash应用的error receiver；

• 忽略当前App的广播接收；

    void startAppProblemLocked(ProcessRecord app) {// 如果不是当前user正在运行 app，这置为空app.errorReportReceiver = null;for (int userId : mService.mUserController.getCurrentProfileIds()) {if (app.userId == userId) {//获取当前用户下的crash应用的error receiver【见小节7.1】app.errorReportReceiver = ApplicationErrorReport.getErrorReportReceiver(mContext, app.info.packageName, app.info.flags);}}//忽略当前app的广播接收【见小节7.2】mService.skipCurrentReceiverLocked(app);}

7.1 getErrorReportReceiver

ApplicationErrorReport.java
获取当前用户下的Crash应用的error receiver

 public static ComponentName getErrorReportReceiver(Context context,String packageName, int appFlags) {//检查Settings中的"send_action_app_error"是否使能错误报告的功能int enabled = Settings.Global.getInt(context.getContentResolver(),Settings.Global.SEND_ACTION_APP_ERROR, 0);if (enabled == 0) {//1.当未使能时，则直接返回return null;}PackageManager pm = context.getPackageManager();// look for receiver in the installer packageString candidate = null;ComponentName result = null;try {//获取该crash应用的安装器的包名candidate = pm.getInstallerPackageName(packageName);} catch (IllegalArgumentException e) {// the package could already removed}if (candidate != null) {result = getErrorReportReceiver(pm, packageName, candidate);if (result != null) {//2.当找到该crash应用的安装器，则返回；return result;}}//该系统属性名为"ro.error.receiver.system.apps"if ((appFlags&ApplicationInfo.FLAG_SYSTEM) != 0) {candidate = SystemProperties.get(SYSTEM_APPS_ERROR_RECEIVER_PROPERTY);// 通过上下文对象传参，调用类内部方法result = getErrorReportReceiver(pm, packageName, candidate);if (result != null) {//3.当crash应用是系统应用时，且系统属性指定error receiver时，则返回；return result;}}//该默认属性名为"ro.error.receiver.default"candidate = SystemProperties.get(DEFAULT_ERROR_RECEIVER_PROPERTY);//4.当默认属性值指定error receiver时，则返回；return getErrorReportReceiver(pm, packageName, candidate);}

getErrorReportReceiver：这是同名不同输入参数的另一个方法：

    static ComponentName getErrorReportReceiver(PackageManager pm, String errorPackage,String receiverPackage) {if (receiverPackage == null || receiverPackage.length() == 0) {return null;}//当安装应用程序的安装器Crash，则直接返回if (receiverPackage.equals(errorPackage)) {return null;}//ACTION_APP_ERROR值为"android.intent.action.APP_ERROR"Intent intent = new Intent(Intent.ACTION_APP_ERROR);intent.setPackage(receiverPackage);ResolveInfo info = pm.resolveActivity(intent, 0);if (info == null || info.activityInfo == null) {return null;}//创建包名为receiverPackage的组件return new ComponentName(receiverPackage, info.activityInfo.name);}

7.2 skipCurrentReceiverLocked

ActivityManagerService.java
忽略当前app的广播接收

    void skipCurrentReceiverLocked(ProcessRecord app) {for (BroadcastQueue queue : mBroadcastQueues) {// 会调用BroadcastQueue 中的方法【见小节7.2.1】queue.skipCurrentReceiverLocked(app);}}

7.2.1 skipCurrentReceiverLocked

BroadcastQueue.java skipCurrentReceiverLocked忽略当前app的广播接收.

    public void skipCurrentReceiverLocked(ProcessRecord app) {BroadcastRecord r = null;//查看app进程中的广播if (mOrderedBroadcasts.size() > 0) {BroadcastRecord br = mOrderedBroadcasts.get(0);// 判断是否一致if (br.curApp == app) {r = br;}}... ...if (r != null) {// 见7.2.2skipReceiverLocked(r);}}

7.2.2 skipReceiverLocked

BroadcastQueue.java

    private void skipReceiverLocked(BroadcastRecord r) {logBroadcastReceiverDiscardLocked(r);//结束app进程的广播结束finishReceiverLocked(r, r.resultCode, r.resultData,r.resultExtras, r.resultAbort, false);//执行广播调度scheduleBroadcastsLocked();}

八、stopFreezingAllLocked处理分析

AppError.java中的 makeAppCrashingLocked方法（第6步），会调用stopFreezingAllLocked 方法

ProcessRecord.java

    public void stopFreezingAllLocked() {int i = activities.size();while (i > 0) {i--;// 停止进程里所有的`Activity`. 详见8.1 activities.get(i).stopFreezingScreenLocked(true);}}

其中activities类型为ArrayList<ActivityRecord>，停止进程里所有的Activity.

8.1 AR.stopFreezingScreenLocked

ActivityRecord.java,stopFreezingScreenLocked停止进程里所有的Activity.

    public void stopFreezingScreenLocked(boolean force) {if (force || frozenBeforeDestroy) {frozenBeforeDestroy = false;// mWindowContainerController 见【8.1.1】mWindowContainerController.stopFreezingScreen(force);}}

8.1.1mWindowContainerController.stopFreezingScreen

stopFreezingScreen.java

    public void stopFreezingScreen(boolean force) {synchronized(mWindowMap) {if (mContainer == null) {return;}if (DEBUG_ORIENTATION) Slog.v(TAG_WM, "Clear freezing of " + mToken + ": hidden="+ mContainer.isHidden() + " freezing=" + mContainer.isFreezingScreen());mContainer.stopFreezingScreen(true, force);}}

8.1.1.1 WMS.stopFreezingScreenLocked

WindowManagerService.java

    @Overridepublic void stopFreezingScreen() {... ...synchronized(mWindowMap) {if (mClientFreezingScreen) {mClientFreezingScreen = false;mLastFinishedFreezeSource = "client";final long origId = Binder.clearCallingIdentity();try {// 详见 8.1.1.2stopFreezingDisplayLocked();} finally {Binder.restoreCallingIdentity(origId);}}}}

8.1.1.2 stopFreezingDisplayLocked();

WindowManagerService.java
该方法主要功能：

处理屏幕旋转相关逻辑；
移除冻屏的超时消息；
屏幕旋转动画的相关操作;
使能输入事件分发功能；
display冻结时，执行gc操作；
更新当前的屏幕方向；
向mH发送configuraion改变的消息

rivate void stopFreezingDisplayLocked() {if (!mDisplayFrozen) {return; //显示没有冻结，则直接返回}//往往跟屏幕旋转相关...mDisplayFrozen = false;//从上次冻屏到现在的总时长mLastDisplayFreezeDuration = (int)(SystemClock.elapsedRealtime() - mDisplayFreezeTime);//移除冻屏的超时消息mH.removeMessages(H.APP_FREEZE_TIMEOUT);mH.removeMessages(H.CLIENT_FREEZE_TIMEOUT);boolean updateRotation = false;//获取默认的DisplayContentfinal DisplayContent displayContent = getDefaultDisplayContentLocked();final int displayId = displayContent.getDisplayId();ScreenRotationAnimation screenRotationAnimation =mAnimator.getScreenRotationAnimationLocked(displayId);//屏幕旋转动画的相关操作if (CUSTOM_SCREEN_ROTATION && screenRotationAnimation != null&& screenRotationAnimation.hasScreenshot()) {DisplayInfo displayInfo = displayContent.getDisplayInfo();boolean isDimming = displayContent.isDimming();if (!mPolicy.validateRotationAnimationLw(mExitAnimId, mEnterAnimId, isDimming)) {mExitAnimId = mEnterAnimId = 0;}//加载动画最大时长为10sif (screenRotationAnimation.dismiss(mFxSession, MAX_ANIMATION_DURATION,getTransitionAnimationScaleLocked(), displayInfo.logicalWidth,displayInfo.logicalHeight, mExitAnimId, mEnterAnimId)) {scheduleAnimationLocked();} else {screenRotationAnimation.kill();mAnimator.setScreenRotationAnimationLocked(displayId, null);updateRotation = true;}} else {if (screenRotationAnimation != null) {screenRotationAnimation.kill();mAnimator.setScreenRotationAnimationLocked(displayId, null);}updateRotation = true;}//经过层层调用到InputManagerService服务，IMS服务使能输入事件分发功能mInputMonitor.thawInputDispatchingLw();boolean configChanged;//当display被冻结时不再计算屏幕方向，以避免不连续的状态。configChanged = updateOrientationFromAppTokensLocked(false);//display冻结时，执行gc操作mH.removeMessages(H.FORCE_GC);mH.sendEmptyMessageDelayed(H.FORCE_GC, 2000);//mScreenFrozenLock的类型为PowerManager.WakeLock，即释放屏幕冻结的锁mScreenFrozenLock.release();if (updateRotation) {//更新当前的屏幕方向configChanged |= updateRotationUncheckedLocked(false);}if (configChanged) {//向mH发送configuraion改变的消息mH.sendEmptyMessage(H.SEND_NEW_CONFIGURATION);}
}

九、 AppErrors.handleAppCrashLocked()

AppErrors.java

1.当同一进程在时间间隔小于1分钟时连续两次Crash，则执行的情况下：

对于非persistent进程：

• [9.1] mStackSupervisor.handleAppCrashLocked(app);

• [9.2] removeProcessLocked(app, false, false, “crash”);

• [9.3] mStackSupervisor.resumeTopActivitiesLocked();

对于persistent进程，则只执行

• [9.3] mStackSupervisor.resumeTopActivitiesLocked();

2.否则执行

• [9.4] mStackSupervisor.finishTopCrashedActivitiesLocked(app, reason);

    boolean handleAppCrashLocked(ProcessRecord app, String reason,String shortMsg, String longMsg, String stackTrace, AppErrorDialog.Data data) {final long now = SystemClock.uptimeMillis();final boolean showBackground = Settings.Secure.getInt(mContext.getContentResolver(),Settings.Secure.ANR_SHOW_BACKGROUND, 0) != 0;final boolean procIsBoundForeground =(app.curProcState == ActivityManager.PROCESS_STATE_BOUND_FOREGROUND_SERVICE);Long crashTime;Long crashTimePersistent;boolean tryAgain = false;if (!app.isolated) {crashTime = mProcessCrashTimes.get(app.info.processName, app.uid);crashTimePersistent = mProcessCrashTimesPersistent.get(app.info.processName, app.uid);} else {crashTime = crashTimePersistent = null;}// Bump up the crash count of any services currently running in the proc.//运行在当前进程中的所有服务的crash次数操作for (int i = app.services.size() - 1; i >= 0; i--) {// list 所有的ServiceServiceRecord sr = app.services.valueAt(i);// Service 一会自动起来 重置count 为1，否则+1if (now > sr.restartTime + ProcessList.MIN_CRASH_INTERVAL) {sr.crashCount = 1;} else {sr.crashCount++;}// 允许重启正在Crash的服务以及 前台Service，wallpapers 等if (sr.crashCount < mService.mConstants.BOUND_SERVICE_MAX_CRASH_RETRY&& (sr.isForeground || procIsBoundForeground)) {tryAgain = true;}}//当同一个进程，连续两次crash的时间间隔小于1分钟时，则认为crash太过于频繁if (crashTime != null && now < crashTime + ProcessList.MIN_CRASH_INTERVAL) {Slog.w(TAG, "Process " + app.info.processName+ " has crashed too many times: killing!");EventLog.writeEvent(EventLogTags.AM_PROCESS_CRASHED_TOO_MUCH,app.userId, app.info.processName, app.uid);//【见小节9.1】mService.mStackSupervisor.handleAppCrashLocked(app);if (!app.persistent) {//不再重启非persistent进程，除非用户显式地调用EventLog.writeEvent(EventLogTags.AM_PROC_BAD, app.userId, app.uid,app.info.processName);if (!app.isolated) {//将当前app加入到mBadProcessesmBadProcesses.put(app.info.processName, app.uid,new BadProcessInfo(now, shortMsg, longMsg, stackTrace));mProcessCrashTimes.remove(app.info.processName, app.uid);}app.bad = true;app.removed = true;//移除非persistent 进程的所有服务，保证不再重启【见小节9.2】mService.removeProcessLocked(app, false, tryAgain, "crash");//恢复最顶部的Activity【见小节9.3】mService.mStackSupervisor.resumeFocusedStackTopActivityLocked();if (!showBackground) {return false;}}mService.mStackSupervisor.resumeFocusedStackTopActivityLocked();} else {//此处reason="force-crash"【见小节9.4】  final TaskRecord affectedTask =mService.mStackSupervisor.finishTopRunningActivityLockedfinishTopRunningActivityLocked(app, reason);if (data != null) {data.task = affectedTask;}if (data != null && crashTimePersistent != null&& now < crashTimePersistent + ProcessList.MIN_CRASH_INTERVAL) {data.repeating = true;}}if (data != null && tryAgain) {data.isRestartableForService = true;}//当桌面Home 进程 应用crash，并且被三方app所取代，那么需要清空桌面应用的偏爱选项。final ArrayList<ActivityRecord> activities = app.activities;if (app == mService.mHomeProcess && activities.size() > 0&& (mService.mHomeProcess.info.flags & ApplicationInfo.FLAG_SYSTEM) == 0) {for (int activityNdx = activities.size() - 1; activityNdx >= 0; --activityNdx) {final ActivityRecord r = activities.get(activityNdx);if (r.isActivityTypeHome()) {Log.i(TAG, "Clearing package preferred activities from " + r.packageName);try {//清空偏爱应用ActivityThread.getPackageManager().clearPackagePreferredActivities(r.packageName);} catch (RemoteException c) {// pm is in same process, this will never happen.}}}}if (!app.isolated) {//无法记录孤立进程的crash时间点，由于他们并没有一个固定身份.mProcessCrashTimes.put(app.info.processName, app.uid, now);mProcessCrashTimesPersistent.put(app.info.processName, app.uid, now);}//当app存在crash的handler，那么交给其处理if (app.crashHandler != null) mService.mHandler.post(app.crashHandler);return true;}

9.1 ASS.handleAppCrashLocked

ActivityStackSupervisor.java

   void handleAppCrashLocked(ProcessRecord app) {for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {final ActivityDisplay display = mActivityDisplays.valueAt(displayNdx);for (int stackNdx = display.getChildCount() - 1; stackNdx >= 0; --stackNdx) {final ActivityStack stack = display.getChildAt(stackNdx);//调用ActivityStack【见小节9.1.1】stack.handleAppCrashLocked(app);}}}

9.1.1 AS.handleAppCrashLocked

ActivityStack.java

    void handleAppCrashLocked(ProcessRecord app) {for (int taskNdx = mTaskHistory.size() - 1; taskNdx >= 0; --taskNdx) {final ArrayList<ActivityRecord> activities = mTaskHistory.get(taskNdx).mActivities;for (int activityNdx = activities.size() - 1; activityNdx >= 0; --activityNdx) {final ActivityRecord r = activities.get(activityNdx);if (r.app == app) {Slog.w(TAG, "  Force finishing activity "+ r.intent.getComponent().flattenToShortString());// Force the destroy to skip right to removal.r.app = null;mWindowManager.prepareAppTransition(TRANSIT_CRASHING_ACTIVITY_CLOSE,false /* alwaysKeepCurrent */);//结束当前activityfinishCurrentActivityLocked(r, FINISH_IMMEDIATELY, false,"handleAppCrashedLocked");}}}}

这里的mTaskHistory数据类型为ArrayList，记录着所有先前的后台activities。遍历所有activities，找到位于该ProcessRecord的所有ActivityRecord，并结束该Acitivity。

9.2 AMS.removeProcessLocked

ActivityManagerService.java

@GuardedBy("this")boolean removeProcessLocked(ProcessRecord app,boolean callerWillRestart, boolean allowRestart, String reason) {final String name = app.processName;final int uid = app.uid;if (DEBUG_PROCESSES) Slog.d(TAG_PROCESSES,"Force removing proc " + app.toShortString() + " (" + name + "/" + uid + ")");ProcessRecord old = mProcessNames.get(name, uid);if (old != app) {// This process is no longer active, so nothing to do.Slog.w(TAG, "Ignoring remove of inactive process: " + app);return false;}//从mProcessNames移除该进程removeProcessNameLocked(name, uid);if (mHeavyWeightProcess == app) {mHandler.sendMessage(mHandler.obtainMessage(CANCEL_HEAVY_NOTIFICATION_MSG,mHeavyWeightProcess.userId, 0));mHeavyWeightProcess = null;}boolean needRestart = false;if ((app.pid > 0 && app.pid != MY_PID) || (app.pid == 0 && app.pendingStart)) {int pid = app.pid;if (pid > 0) {synchronized (mPidsSelfLocked) {mPidsSelfLocked.remove(pid);mHandler.removeMessages(PROC_START_TIMEOUT_MSG, app);}mBatteryStatsService.noteProcessFinish(app.processName, app.info.uid);if (app.isolated) {mBatteryStatsService.removeIsolatedUid(app.uid, app.info.uid);getPackageManagerInternalLocked().removeIsolatedUid(app.uid);}}boolean willRestart = false;//对于非孤立的persistent进程设置成可重启flagsif (app.persistent && !app.isolated) {if (!callerWillRestart) {willRestart = true;} else {needRestart = true;}}// 杀进程【9.2.1】app.kill(reason, true);//移除进程并清空该进程相关联的activity/service等组件 【9.2.2】handleAppDiedLocked(app, willRestart, allowRestart);if (willRestart) {//此处willRestart=false，不进入该分支removeLruProcessLocked(app);addAppLocked(app.info, null, false, null /* ABI override */);}} else {mRemovedProcesses.add(app);}return needRestart;}

• mProcessNames数据类型为ProcessMap，这是以进程名为key，记录着所有的ProcessRecord信息

• mPidsSelfLocked数据类型为SparseArray,这是以pid为key，记录着所有的ProcessRecord信息。该对象的同步保护是通过自身锁，而非全局ActivityManager锁。

9.2.1 app.kill

ProcessRecord.java]

void kill(String reason, boolean noisy) {//通过am 杀进程if (!killedByAm) {// 如果不想让am kill 当前进程，可以在这地方跳过if (!mService.mAmsExt.shouldKilledByAm(this.processName, reason)) {return;}Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "kill");if (mService != null && (noisy || info.uid == mService.mCurOomAdjUid)) {mService.reportUidInfoMessageLocked(TAG,"Killing " + toShortString() + " (adj " + setAdj + "): " + reason,info.uid);}if (pid > 0) {EventLog.writeEvent(EventLogTags.AM_KILL, userId, pid, processName, setAdj, reason);// pid > 0 杀进程以及所在的进程组Process.killProcessQuiet(pid);ActivityManagerService.killProcessGroup(uid, pid);} else {pendingStart = false;}if (!persistent) {killed = true;killedByAm = true;}Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);}}

此处reason为“crash”.

9.2.2 handleAppDiedLocked

ActivityManagerService.java

  // 通过AM 移除当前存在的进程，不存在，则清除当前进程包含的所有内容@GuardedBy("this")private final void handleAppDiedLocked(ProcessRecord app,boolean restarting, boolean allowRestart) {int pid = app.pid;final boolean clearLaunchStartTime = !restarting && app.removed && app.foregroundActivities;//清除应用中service/receiver/ContentProvider信息boolean kept = cleanUpApplicationRecordLocked(app, restarting, allowRestart, -1,false /*replacingPid*/);if (!kept && !restarting) {// 根据LRU 算法移除 app 进程removeLruProcessLocked(app);if (pid > 0) {//从list 移除对应的pid        ProcessList.remove(pid);}}if (mProfileProc == app) {clearProfilerLocked();}//清除应用中activity相关信息boolean hasVisibleActivities = mStackSupervisor.handleAppDiedLocked(app);app.clearRecentTasks();app.activities.clear();if (app.instr != null) {Slog.w(TAG, "Crash of app " + app.processName+ " running instrumentation " + app.instr.mClass);Bundle info = new Bundle();info.putString("shortMsg", "Process crashed.");finishInstrumentationLocked(app, Activity.RESULT_CANCELED, info);}mWindowManager.deferSurfaceLayout();try {if (!restarting && hasVisibleActivities&& !mStackSupervisor.resumeFocusedStackTopActivityLocked()) {// If there was nothing to resume, and we are not already restarting this process, but// there is a visible activity that is hosted by the process...  then make sure all// visible activities are running, taking care of restarting this process.mStackSupervisor.ensureActivitiesVisibleLocked(null, 0, !PRESERVE_WINDOWS);}} finally {mWindowManager.continueSurfaceLayout();}// TODO (b/67683350)// When an app process is removed, activities from the process may be relaunched. In the// case of forceStopPackageLocked the activities are finished before any window is drawn,// and the launch time is not cleared. This will be incorrectly used to calculate launch// time for the next launched activity launched in the same windowing mode.if (clearLaunchStartTime) {final LaunchTimeTracker.Entry entry = mStackSupervisor.getLaunchTimeTracker().getEntry(mStackSupervisor.getWindowingMode());if (entry != null) {entry.mLaunchStartTime = 0;}}}

9.3 ASS.resumeFocusedStackTopActivityLocked

ActivityStackSupervisor.java

boolean resumeFocusedStackTopActivityLocked() {return resumeFocusedStackTopActivityLocked(null, null, null);}boolean resumeFocusedStackTopActivityLocked(ActivityStack targetStack, ActivityRecord target, ActivityOptions targetOptions) {if (!readyToResume()) {return false;}if (targetStack != null && isFocusedStack(targetStack)) {//【见小节9.3.1】return targetStack.resumeTopActivityUncheckedLocked(target, targetOptions);}final ActivityRecord r = mFocusedStack.topRunningActivityLocked();if (r == null || !r.isState(RESUMED)) {mFocusedStack.resumeTopActivityUncheckedLocked(null, null);} else if (r.isState(RESUMED)) {// Kick off any lingering app transitions form the MoveTaskToFront operation.mFocusedStack.executeAppTransition(targetOptions);}return false;}

9.3.1 AS.resumeTopActivityLocked

ActivityStack.java

  //确保 top Activity 在resumed 状态// 最好使用ActivityStackSupervisor#ActivityStackSupervisor#resumeFocusedStackTopActivityLockedActivityStackSupervisor#resumeFocusedStackTopActivityLocked 待替此方法boolean resumeTopActivityUncheckedLocked(ActivityRecord prev, ActivityOptions options) {if (mStackSupervisor.inResumeTopActivity) {// Don't even start recursing.return false;}boolean result = false;try {// Protect against recursion.mStackSupervisor.inResumeTopActivity = true;result = resumeTopActivityInnerLocked(prev, options);// When resuming the top activity, it may be necessary to pause the top activity (for// example, returning to the lock screen. We suppress the normal pause logic in// {@link #resumeTopActivityUncheckedLocked}, since the top activity is resumed at the// end. We call the {@link ActivityStackSupervisor#checkReadyForSleepLocked} again here// to ensure any necessary pause logic occurs. In the case where the Activity will be// shown regardless of the lock screen, the call to// {@link ActivityStackSupervisor#checkReadyForSleepLocked} is skipped.final ActivityRecord next = topRunningActivityLocked(true /* focusableOnly */);if (next == null || !next.canTurnScreenOn()) {checkReadyForSleep();}} finally {mStackSupervisor.inResumeTopActivity = false;}return result;}

9.4 finishTopCrashedActivitiesLocked

ActivityStackSupervisor.java

     //Finish the topmost activities in all stacks that belong to the crashed appTaskRecord finishTopCrashedActivitiesLocked(ProcessRecord app, String reason) {TaskRecord finishedTask = null;ActivityStack focusedStack = getFocusedStack();for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {final ActivityDisplay display = mActivityDisplays.valueAt(displayNdx);// It is possible that request to finish activity might also remove its task and stack,// so we need to be careful with indexes in the loop and check child count every time.for (int stackNdx = 0; stackNdx < display.getChildCount(); ++stackNdx) {final ActivityStack stack = display.getChildAt(stackNdx);此处reason= "force-crash" 见小节9.4.1final TaskRecord t = stack.finishTopCrashedActivityLocked(app, reason);if (stack == focusedStack || finishedTask == null) {finishedTask = t;}}}return finishedTask;}

9.4.1AS.finishTopCrashedActivityLocked

ActivityStack.java

   /*** Finish the topmost activity that belongs to the crashed app. We may also finish the activity* that requested launch of the crashed one to prevent launch-crash loop.*/ final TaskRecord finishTopCrashedActivityLocked(ProcessRecord app, String reason) {ActivityRecord r = topRunningActivityLocked();TaskRecord finishedTask = null;if (r == null || r.app != app) {return null;}Slog.w(TAG, "  Force finishing activity "+ r.intent.getComponent().flattenToShortString());finishedTask = r.getTask();int taskNdx = mTaskHistory.indexOf(finishedTask);final TaskRecord task = finishedTask;int activityNdx = task.mActivities.indexOf(r);mWindowManager.prepareAppTransition(TRANSIT_CRASHING_ACTIVITY_CLOSE,false /* alwaysKeepCurrent */);// 见小结 9.4.2finishActivityLocked(r, Activity.RESULT_CANCELED, null, reason, false);finishedTask = task;// Also terminate any activities below it that aren't yet// stopped, to avoid a situation where one will get// re-start our crashing activity once it gets resumed again.--activityNdx;if (activityNdx < 0) {do {--taskNdx;if (taskNdx < 0) {break;}activityNdx = mTaskHistory.get(taskNdx).mActivities.size() - 1;} while (activityNdx < 0);}if (activityNdx >= 0) {r = mTaskHistory.get(taskNdx).mActivities.get(activityNdx);if (r.isState(RESUMED, PAUSING, PAUSED)) {if (!r.isActivityTypeHome() || mService.mHomeProcess != r.app) {Slog.w(TAG, "  Force finishing activity "+ r.intent.getComponent().flattenToShortString());finishActivityLocked(r, Activity.RESULT_CANCELED, null, reason, false);}}}return finishedTask;}

9.4.2 AS.finishActivityLocked

ActivityStack.java

 /*** See {@link #finishActivityLocked(ActivityRecord, int, Intent, String, boolean, boolean)}*/final boolean finishActivityLocked(ActivityRecord r, int resultCode, Intent resultData,String reason, boolean oomAdj) {return finishActivityLocked(r, resultCode, resultData, reason, oomAdj, !PAUSE_IMMEDIATELY);}/*** @return Returns true if this activity has been removed from the history* list, or false if it is still in the list and will be removed later.*/final boolean finishActivityLocked(ActivityRecord r, int resultCode, Intent resultData,String reason, boolean oomAdj, boolean pauseImmediately) {if (r.finishing) {Slog.w(TAG, "Duplicate finish request for " + r);return false;}mWindowManager.deferSurfaceLayout();try {//设置finish状态的activity不可见r.makeFinishingLocked();final TaskRecord task = r.getTask();EventLog.writeEvent(EventLogTags.AM_FINISH_ACTIVITY,r.userId, System.identityHashCode(r),task.taskId, r.shortComponentName, reason);final ArrayList<ActivityRecord> activities = task.mActivities;final int index = activities.indexOf(r);if (index < (activities.size() - 1)) {task.setFrontOfTask();if ((r.intent.getFlags() & Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET) != 0) {// If the caller asked that this activity (and all above it)// be cleared when the task is reset, don't lose that information,// but propagate it up to the next activity.ActivityRecord next = activities.get(index+1);next.intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);}}//暂停key的分发事件r.pauseKeyDispatchingLocked();adjustFocusedActivityStack(r, "finishActivity");finishActivityResultsLocked(r, resultCode, resultData);final boolean endTask = index <= 0 && !task.isClearingToReuseTask();final int transit = endTask ? TRANSIT_TASK_CLOSE : TRANSIT_ACTIVITY_CLOSE;if (mResumedActivity == r) {if (DEBUG_VISIBILITY || DEBUG_TRANSITION) Slog.v(TAG_TRANSITION,"Prepare close transition: finishing " + r);if (endTask) {mService.mTaskChangeNotificationController.notifyTaskRemovalStarted(task.taskId);}mWindowManager.prepareAppTransition(transit, false);// Tell window manager to prepare for this one to be removed.r.setVisibility(false);if (mPausingActivity == null) {if (DEBUG_PAUSE) Slog.v(TAG_PAUSE, "Finish needs to pause: " + r);if (DEBUG_USER_LEAVING) Slog.v(TAG_USER_LEAVING,"finish() => pause with userLeaving=false");//回调activity的onPause方法startPausingLocked(false, false, null, pauseImmediately);/// M: onBeforeActivitySwitch @{ActivityRecord nextResumedActivity =mStackSupervisor.getFocusedStack().topRunningActivityLocked();if (nextResumedActivity != null) {mService.mAmsExt.onBeforeActivitySwitch(mService.mLastResumedActivity,nextResumedActivity, true, nextResumedActivity.getActivityType());}/// M: onBeforeActivitySwitch @}}if (endTask) {mService.getLockTaskController().clearLockedTask(task);}} else if (!r.isState(PAUSING)) {// If the activity is PAUSING, we will complete the finish once// it is done pausing; else we can just directly finish it here.if (DEBUG_PAUSE) Slog.v(TAG_PAUSE, "Finish not pausing: " + r);if (r.visible) {prepareActivityHideTransitionAnimation(r, transit);}final int finishMode = (r.visible || r.nowVisible) ? FINISH_AFTER_VISIBLE: FINISH_AFTER_PAUSE;final boolean removedActivity = finishCurrentActivityLocked(r, finishMode, oomAdj,"finishActivityLocked") == null;// The following code is an optimization. When the last non-task overlay activity// is removed from the task, we remove the entire task from the stack. However,// since that is done after the scheduled destroy callback from the activity, that// call to change the visibility of the task overlay activities would be out of// sync with the activitiy visibility being set for this finishing activity above.// In this case, we can set the visibility of all the task overlay activities when// we detect the last one is finishing to keep them in sync.if (task.onlyHasTaskOverlayActivities(true /* excludeFinishing */)) {for (ActivityRecord taskOverlay : task.mActivities) {if (!taskOverlay.mTaskOverlay) {continue;}prepareActivityHideTransitionAnimation(taskOverlay, transit);}}return removedActivity;} else {if (DEBUG_PAUSE) Slog.v(TAG_PAUSE, "Finish waiting for pause of: " + r);}return false;} finally {mWindowManager.continueSurfaceLayout();}}

十、UIHandler

通过mUiHandler发送message，且消息的msg.waht=SHOW_ERROR_MSG，接下来进入UiHandler来看看handleMessage的处理过程。

ActivityManagerService.java

final class UiHandler extends Handler {public void handleMessage(Message msg) {switch (msg.what) {case SHOW_ERROR_MSG: {HashMap<String, Object> data = (HashMap<String, Object>) msg.obj;synchronized (ActivityManagerService.this) {ProcessRecord proc = (ProcessRecord)data.get("app");AppErrorResult res = (AppErrorResult) data.get("result");、boolean isBackground = (UserHandle.getAppId(proc.uid)>= Process.FIRST_APPLICATION_UID&& proc.pid != MY_PID);...if (mShowDialogs && !mSleeping && !mShuttingDown) {//创建提示crash对话框，等待用户选择，5分钟操作等待。Dialog d = new AppErrorDialog(mContext,ActivityManagerService.this, res, proc);d.show();proc.crashDialog = d;} else {//当处于sleep状态，则默认选择退出。if (res != null) {res.set(0);}}}} break;...}
}

在发生Crash时，默认系统会弹出提示crash的对话框，并阻塞等待用户选择是“退出”或 “退出并报告”，当用户不做任何选择时5min超时后，默认选择“退出”，当手机休眠时也默认选择“退出”。到这里也并没有真正结束，在小节2.uncaughtException中在finnally语句块还有一个杀进程的动作。

十一 、 killProcess

Process.killProcess(Process.myPid());
System.exit(10);

通过finnally语句块保证能执行并彻底杀掉Crash进程。当Crash进程被杀后，并没有完全结束，还有Binder死亡通知的流程还没有处理完成

十二、小结

当进程抛出未捕获异常时，则系统会处理该异常并进入Crash处理流程。

Crash处理流程

其中最为核心的工作图中红色部分AMS.handleAppCrashLocked的主要功能：

1. 当同一进程1分钟之内连续两次Crash，则执行的情况下：

对于非persistent进程：

-ASS.handleAppCrashLocked, 直接结束该应用所有activity

• AMS.removeProcessLocked，杀死该进程以及同一个进程组下的所有进
  -ASS.resumeTopActivitiesLocked，恢复栈顶第一个非finishing状态的activity

对于persistent进程，则只执行

ASS.resumeTopActivitiesLocked，恢复栈顶第一个非finishing状态的activity
2.否则，当进程没连续频繁crash

• ASS.finishTopRunningActivityLocked，执行结束栈顶正在运行activity
  另外，AMS.handleAppCrashLocked，该方法内部主要调用链，如下：

AMS.handleAppCrashLockedASS.handleAppCrashLockedAS.handleAppCrashLockedAS.finishCurrentActivityLockedAMS.removeProcessLockedProcessRecord.killAMS.handleAppDiedLockedASS.handleAppDiedLockedAMS.cleanUpApplicationRecordLockedAS.handleAppDiedLockedAS.removeHistoryRecordsForAppLockedASS.resumeTopActivitiesLockedAS.resumeTopActivityLockedAS.resumeTopActivityInnerLockedASS.finishTopRunningActivityLockedAS.finishTopRunningActivityLockedAS.finishActivityLocked

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