android activity 管理器AMS----概述
Posted DemanMath
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AMS & WMS，应该是app端打交道最多的2个framwork层的service。
ActivityManagerService 是android提供给用于管理Activity运行状态的系统进程。
本系列共分3个部分，概述，ActivityStatck & Activiy Task.
AMS 主要用于管理Activity之间的交互问题。
核心问题有以下几个：
1.activity 生命周期管理
2.intent是怎么传递数据的。（可能跨进程，以及双向传递）
3.launchmode是怎么使用的。（Task的概念）
一. AMS概述
首先AMS 是一个同我们开发的service非常相似的一个service，只不过它的作用是管理activity。
所以AMS是一个进程，并且当开机以后，它就常驻在系统里面，归ServiceManager调度。
而AMS启动后，它开始有一个线程监听处理客户的需求。
一下为android5.0 的代码：
\\frameworks\\base\\services\\java\\com\\android\\server\\SystemServera.java
private void startBootstrapServices() { // Wait for installd to finish starting up so that it has a chance to // create critical directories such as /data/user with the appropriate // permissions. We need this to complete before we initialize other services. mInstaller = mSystemServiceManager.startService(Installer.class); // Activity manager runs the show. mActivityManagerService = mSystemServiceManager.startService( ActivityManagerService.Lifecycle.class).getService(); mActivityManagerService.setSystemServiceManager(mSystemServiceManager); // Power manager needs to be started early because other services need it. // Native daemons may be watching for it to be registered so it must be ready // to handle incoming binder calls immediately (including being able to verify // the permissions for those calls). mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class); // Now that the power manager has been started, let the activity manager // initialize power management features. mActivityManagerService.initPowerManagement(); // Display manager is needed to provide display metrics before package manager // starts up. mDisplayManagerService = mSystemServiceManager.startService(DisplayManagerService.class); // We need the default display before we can initialize the package manager. mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY); // Only run "core" apps if we\'re encrypting the device. String cryptState = SystemProperties.get("vold.decrypt"); if (ENCRYPTING_STATE.equals(cryptState)) { Slog.w(TAG, "Detected encryption in progress - only parsing core apps"); mOnlyCore = true; } else if (ENCRYPTED_STATE.equals(cryptState)) { Slog.w(TAG, "Device encrypted - only parsing core apps"); mOnlyCore = true; } // Start the package manager. Slog.i(TAG, "Package Manager"); mPackageManagerService = PackageManagerService.main(mSystemContext, mInstaller, mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore); mFirstBoot = mPackageManagerService.isFirstBoot(); mPackageManager = mSystemContext.getPackageManager(); Slog.i(TAG, "User Service"); ServiceManager.addService(Context.USER_SERVICE, UserManagerService.getInstance()); // Initialize attribute cache used to cache resources from packages. AttributeCache.init(mSystemContext); // Set up the Application instance for the system process and get started. mActivityManagerService.setSystemProcess(); }
可以看到AMS在这里启动。而这个函数startBootstrapServices是在run方法中运行。
public ActivityManagerService(Context systemContext) { mContext = systemContext; mFactoryTest = FactoryTest.getMode(); mSystemThread = ActivityThread.currentActivityThread(); Slog.i(TAG, "Memory class: " + ActivityManager.staticGetMemoryClass()); mHandlerThread = new ServiceThread(TAG, android.os.Process.THREAD_PRIORITY_FOREGROUND, false /*allowIo*/); mHandlerThread.start(); mHandler = new MainHandler(mHandlerThread.getLooper()); mFgBroadcastQueue = new BroadcastQueue(this, mHandler, "foreground", BROADCAST_FG_TIMEOUT, false); mBgBroadcastQueue = new BroadcastQueue(this, mHandler, "background", BROADCAST_BG_TIMEOUT, true); mBroadcastQueues[0] = mFgBroadcastQueue; mBroadcastQueues[1] = mBgBroadcastQueue; mServices = new ActiveServices(this); mProviderMap = new ProviderMap(this); // TODO: Move creation of battery stats service outside of activity manager service. File dataDir = Environment.getDataDirectory(); File systemDir = new File(dataDir, "system"); systemDir.mkdirs(); mBatteryStatsService = new BatteryStatsService(systemDir, mHandler); mBatteryStatsService.getActiveStatistics().readLocked(); mBatteryStatsService.getActiveStatistics().writeAsyncLocked(); mOnBattery = DEBUG_POWER ? true : mBatteryStatsService.getActiveStatistics().getIsOnBattery(); mBatteryStatsService.getActiveStatistics().setCallback(this); mProcessStats = new ProcessStatsService(this, new File(systemDir, "procstats")); mAppOpsService = new AppOpsService(new File(systemDir, "appops.xml"), mHandler); mGrantFile = new AtomicFile(new File(systemDir, "urigrants.xml")); // User 0 is the first and only user that runs at boot. mStartedUsers.put(0, new UserStartedState(new UserHandle(0), true)); mUserLru.add(Integer.valueOf(0)); updateStartedUserArrayLocked(); GL_ES_VERSION = SystemProperties.getInt("ro.opengles.version", ConfigurationInfo.GL_ES_VERSION_UNDEFINED); mConfiguration.setToDefaults(); mConfiguration.setLocale(Locale.getDefault()); mConfigurationSeq = mConfiguration.seq = 1; mProcessCpuTracker.init(); mCompatModePackages = new CompatModePackages(this, systemDir, mHandler); mIntentFirewall = new IntentFirewall(new IntentFirewallInterface(), mHandler); mStackSupervisor = new ActivityStackSupervisor(this); mTaskPersister = new TaskPersister(systemDir, mStackSupervisor); mProcessCpuThread = new Thread("CpuTracker") { @Override public void run() { while (true) { try { try { synchronized(this) { final long now = SystemClock.uptimeMillis(); long nextCpuDelay = (mLastCpuTime.get()+MONITOR_CPU_MAX_TIME)-now; long nextWriteDelay = (mLastWriteTime+BATTERY_STATS_TIME)-now; //Slog.i(TAG, "Cpu delay=" + nextCpuDelay // + ", write delay=" + nextWriteDelay); if (nextWriteDelay < nextCpuDelay) { nextCpuDelay = nextWriteDelay; } if (nextCpuDelay > 0) { mProcessCpuMutexFree.set(true); this.wait(nextCpuDelay); } } } catch (InterruptedException e) { } updateCpuStatsNow(); } catch (Exception e) { Slog.e(TAG, "Unexpected exception collecting process stats", e); } } } }; mLockToAppRequest = new LockToAppRequestDialog(mContext, this); Watchdog.getInstance().addMonitor(this); Watchdog.getInstance().addThread(mHandler); }
mStackSupervisor = new ActivityStackSupervisor(this); mTaskPersister = new TaskPersister(systemDir, mStackSupervisor);
这两句是ActivityStack & ActivityTask设置的地方。
public void setSystemProcess()就比较简单了，它不仅注册了自己一个server， 还注册了其他的server。
ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true); ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats); ServiceManager.addService("meminfo", new MemBinder(this)); ServiceManager.addService("gfxinfo", new GraphicsBinder(this)); ServiceManager.addService("dbinfo", new DbBinder(this)); if (MONITOR_CPU_USAGE) { ServiceManager.addService("cpuinfo", new CpuBinder(this)); } ServiceManager.addService("permission", new PermissionController(this));
二.Activit状态管理---ActivityStack
1.ActivityState
定义了如下状态：
状态变化图。
三：startActivity
startActivity@ActivityManagerService.java
startActivityAsUser@ActivityManagerService.java
startActivityMayWait@ActivityStack.java
startActivityLocked@ActivityStack.java
sartActivityUncheckedLocked@ActivityStack.java
这5个函数先后关系，就是上面的顺序。
public final int startActivity(IApplicationThread caller, String callingPackage, Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo, Bundle options) { return startActivityAsUser(caller, callingPackage, intent, resolvedType, resultTo, resultWho, requestCode, startFlags, profilerInfo, options, UserHandle.getCallingUserId()); }
多了一个
UserHandle.getCallingUserId()
调用者的Userid值，通过bind机制获得的。
@Override public final int startActivityAsUser(IApplicationThread caller, String callingPackage, Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo, Bundle options, int userId) { enforceNotIsolatedCaller("startActivity"); userId = handleIncomingUser(Binder.getCallingPid(), Binder.getCallingUid(), userId, false, ALLOW_FULL_ONLY, "startActivity", null); // TODO: Switch to user app stacks here. return mStackSupervisor.startActivityMayWait(caller, -1, callingPackage, intent, resolvedType, null, null, resultTo, resultWho, requestCode, startFlags, profilerInfo, null, null, options, false, userId, null, null); }
enforceNotIsolatedCaller 的目的是确认当前用户是否属于被隔离的对象。
接下来是 startActivityMayWait
startActivityMayWait
ActivityStackSupervisor.startActivityMayWait
final int startActivityMayWait(IApplicationThread caller, int callingUid, String callingPackage, Intent intent, String resolvedType, IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor, IBinder resultTo, String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo, WaitResult outResult, Configuration config, Bundle options, boolean ignoreTargetSecurity, int userId, IActivityContainer iContainer, TaskRecord inTask) { // Refuse possible leaked file descriptors if (intent != null && intent.hasFileDescriptors()) { throw new IllegalArgumentException("File descriptors passed in Intent"); } boolean componentSpecified = intent.getComponent() != null; // Don\'t modify the client\'s object! intent = new Intent(intent); // Collect information about the target of the Intent. ActivityInfo aInfo = resolveActivity(intent, resolvedType, startFlags, profilerInfo, userId); ActivityContainer container = (ActivityContainer)iContainer; synchronized (mService) { if (container != null && container.mParentActivity != null && container.mParentActivity.state != RESUMED) { // Cannot start a child activity if the parent is not resumed. return ActivityManager.START_CANCELED; } final int realCallingPid = Binder.getCallingPid(); final int realCallingUid = Binder.getCallingUid(); int callingPid; if (callingUid >= 0) { callingPid = -1; } else if (caller == null) { callingPid = realCallingPid; callingUid = realCallingUid; } else { callingPid = callingUid = -1; } final ActivityStack stack; if (container == null || container.mStack.isOnHomeDisplay()) { stack = mFocusedStack; } else { stack = container.mStack; } stack.mConfigWillChange = config != null && mService.mConfiguration.diff(config) != 0; if (DEBUG_CONFIGURATION) Slog.v(TAG_CONFIGURATION, "Starting activity when config will change = " + stack.mConfigWillChange); final long origId = Binder.clearCallingIdentity(); if (aInfo != null && (aInfo.applicationInfo.privateFlags &ApplicationInfo.PRIVATE_FLAG_CANT_SAVE_STATE) != 0) { // This may be a heavy-weight process! Check to see if we already // have another, different heavy-weight process running. if (aInfo.processName.equals(aInfo.applicationInfo.packageName)) { if (mService.mHeavyWeightProcess != null && (mService.mHeavyWeightProcess.info.uid != aInfo.applicationInfo.uid || !mService.mHeavyWeightProcess.processName.equals(aInfo.processName))) { int appCallingUid = callingUid; if (caller != null) { ProcessRecord callerApp = mService.getRecordForAppLocked(caller); if (callerApp != null) { appCallingUid = callerApp.info.uid; } else { Slog.w(TAG, "Unable to find app for caller " + caller + " (pid=" + callingPid + ") when starting: " + intent.toString()); ActivityOptions.abort(options); return ActivityManager.START_PERMISSION_DENIED; } } IIntentSender target = mService.getIntentSenderLocked( ActivityManager.INTENT_SENDER_ACTIVITY, "android", appCallingUid, userId, null, null, 0, new Intent[] { intent }, new String[] { resolvedType }, PendingIntent.FLAG_CANCEL_CURRENT | PendingIntent.FLAG_ONE_SHOT, null); Intent newIntent = new Intent(); if (requestCode >= 0) { // Caller is requesting a result. newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_HAS_RESULT, true); } newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_INTENT, new IntentSender(target)); if (mService.mHeavyWeightProcess.activities.size() > 0) { ActivityRecord hist = mService.mHeavyWeightProcess.activities.get(0); newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_CUR_APP, hist.packageName); newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_CUR_TASK, hist.task.taskId); } newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_NEW_APP, aInfo.packageName); newIntent.setFlags(intent.getFlags()); newIntent.setClassName("android", HeavyWeightSwitcherActivity.class.getName()); intent = newIntent; resolvedType = null; caller = null; callingUid = Binder.getCallingUid(); callingPid = Binder.getCallingPid(); componentSpecified = true; try { ResolveInfo rInfo = AppGlobals.getPackageManager().resolveIntent( intent, null, PackageManager.MATCH_DEFAULT_ONLY | ActivityManagerService.STOCK_PM_FLAGS, userId); aInfo = rInfo != null ? rInfo.activityInfo : null; aInfo = mService.getActivityInfoForUser(aInfo, userId); } catch (RemoteException e) { aInfo = null; } } } } int res = startActivityLocked(caller, intent, resolvedType, aInfo, voiceSession, voiceInteractor, resultTo, resultWho, requestCode, callingPid, callingUid, callingPackage, realCallingPid, realCallingUid, startFlags, options, ignoreTargetSecurity, componentSpecified, null, container, inTask); Binder.restoreCallingIdentity(origId); if (stack.mConfigWillChange) { // If the caller also wants to switch to a new configuration, // do so now. This allows a clean switch, as we are waiting // for the current activity to pause (so we will not destroy // it), and have not yet started the next activity. mService.enforceCallingPermission(android.Manifest.permission.CHANGE_CONFIGURATION, "updateConfiguration()"); stack.mConfigWillChange = false; if (DEBUG_CONFIGURATION) Slog.v(TAG_CONFIGURATION, "Updating to new configuration after starting activity."); mService.updateConfigurationLocked(config, null, false, false); } if (outResult != null) { outResult.result = res; if (res == ActivityManager.START_SUCCESS) { mWaitingActivityLaunched.add(outResult); do { try { mService.wait(); } catch (InterruptedException e) { } } while (!outResult.timeout && outResult.who == null); } else if (res == ActivityManager.START_TASK_TO_FRONT) { ActivityRecord r = stack.topRunningActivityLocked(null); if (r.nowVisible && r.state == RESUMED) { outResult.timeout = false; outResult.who = new ComponentName(r.info.packageName, r.info.name); outResult.totalTime = 0; outResult.thisTime = 0; } else { outResult.thisTime = SystemClock.uptimeMillis(); mWaitingActivityVisible.add(outResult); do { try { mService.wait(); } catch (InterruptedException e) { } } while (!outResult.timeout && outResult.who == null); } } } return res; } }
首先判断是不是显示intent，
调用resolveActivity来进行查找。这里有一段注释：
// Store the found target back into the intent, because now that // we have it we never want to do this again. For example, if the // user navigates back to this point in the history, we should // always restart the exact same activity.
为了确保在history里面的intent统一，只查找一次，获取ActivityInfo。
判断当前目标进程是不是重量级进程。
最后调用startActivityLocked来进一部启动。
如果onResult不为空，还需要将函数的结果写入这个变量中。在onResult的处理上，有可能会wait，所以这个函数叫startActivityMayWait。
StartActivityLocked
顾名思义，它是线程安全的。
final int startActivityLocked(IApplicationThread caller, Intent intent, String resolvedType, ActivityInfo aInfo, IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor, IBinder resultTo, String resultWho, int requestCode, int callingPid, int callingUid, String callingPackage, int realCallingPid, int realCallingUid, int startFlags, Bundle options, boolean ignoreTargetSecurity, boolean componentSpecified, ActivityRecord[] outActivity, ActivityContainer container, TaskRecord inTask) { int err = ActivityManager.START_SUCCESS; ProcessRecord callerApp = null; if (caller != null) { callerApp = mService.getRecordForAppLocked(caller); if (callerApp != null) { callingPid = callerApp.pid; callingUid = callerApp.info.uid; } else { Slog.w(TAG, "Unable to find app for caller " + caller + " (pid=" + callingPid + ") when starting: " + intent.toString()); err = ActivityManager.START_PERMISSION_DENIED; } } final int userId = aInfo != null ? UserHandle.getUserId(aInfo.applicationInfo.uid) : 0; if (err == ActivityManager.START_SUCCESS) { Slog.i(TAG, "START u" + userId + " {" + intent.toShortString(true, true, true, false) + "} from uid " + callingUid + " on display " + (container == null ? (mFocusedStack == null ? Display.DEFAULT_DISPLAY : mFocusedStack.mDisplayId) : (container.mActivityDisplay == null ? Display.DEFAULT_DISPLAY : container.mActivityDisplay.mDisplayId))); } ActivityRecord sourceRecord = null; ActivityRecord resultRecord = null; if (resultTo != null) { sourceRecord = isInAnyStackLocked(resultTo); if (DEBUG_RESULTS) Slog.v(TAG_RESULTS, "Will send result to " + resultTo + " " + sourceRecord); if (sourceRecord != null) { if (requestCode >= 0 && !sourceRecord.finishing) { resultRecord = sourceRecord; } } } final int launchFlags = intent.getFlags(); if ((launchFlags & Intent.FLAG_ACTIVITY_FORWARD_RESULT) != 0 && sourceRecord != null) { // Transfer the result target from the source activity to the new // one being started, including any failures. if (requestCode >= 0) { ActivityOptions.abort(options); return ActivityManager.START_FORWARD_AND_REQUEST_CONFLICT; } resultRecord = sourceRecord.resultTo; if (resultRecord != null && !resultRecord.isInStackLocked()) { resultRecord = null; } resultWho = sourceRecord.resultWho; requestCode = sourceRecord.requestCode; sourceRecord.resultTo = null; if (resultRecord != null) { resultRecord.removeResultsLocked(sourceRecord, resultWho, requestCode); } if (sourceRecord.launchedFromUid == callingUid) { // The new activity is being launched from the same uid as the previous // activity in the flow, and asking to forward its result back to the // previous. In this case the activity is serving as a trampoline between // the two, so we also want to update its launchedFromPackage to be the // same as the previous activity. Note that this is safe, since we know // these two packages come from the same uid; the caller could just as // well have supplied that same package name itself. This specifially // deals with the case of an intent picker/chooser being launched in the app // flow to redirect to an activity picked by the user, where we want the final // activity to consider it to have been launched by the previous app activity. callingPackage = sourceRecord.launchedFromPackage; } } if (err == ActivityManager.START_SUCCESS && intent.getComponent() == null) { // We couldn\'t find a class that can handle the given Intent. // That\'s the end of that! err = ActivityManager.START_INTENT_NOT_RESOLVED; } if (err == ActivityManager.START_SUCCESS && aInfo == null) { // We couldn\'t find the specific class specified in the Intent. // Also the end of the line. err = ActivityManager.START_CLASS_NOT_FOUND; } if (err == ActivityManager.START_SUCCESS && !isCurrentProfileLocked(userId) && (aInfo.flags & FLAG_SHOW_FOR_ALL_USERS) == 0) { // Trying to launch a background activity that doesn\'t show for all users. err = ActivityManager.START_NOT_CURRENT_USER_ACTIVITY; } if (err == ActivityManager.START_SUCCESS && sourceRecord != null && sourceRecord.task.voiceSession != null) { // If this activity is being launched as part of a voice session, we need // to ensure that it is safe to do so. If the upcoming activity will also // be part of the voice session, we can only launch it if it has explicitly // said it supports the VOICE category, or it is a part of the calling app. if ((launchFlags & Intent.FLAG_ACTIVITY_NEW_TASK) == 0 && sourceRecord.info.applicationInfo.uid != aInfo.applicationInfo.uid) { try { intent.addCategory(Intent.CATEGORY_VOICE); if (!AppGlobals.getPackageManager().activitySupportsIntent( intent.getComponent(), intent, resolvedType)) { Slog.w(TAG, "Activity being started in current voice task does not support voice: " + intent); err = ActivityManager.START_NOT_VOICE_COMPATIBLE; } } catch (RemoteException e) { Slog.w(TAG, "Failure checking voice capabilities", e); err = ActivityManager.START_NOT_VOICE_COMPATIBLE; } } } if (err == ActivityManager.START_SUCCESS && voiceSession != null) { // If the caller is starting a new voice session, just make sure the target // is actually allowing it to run this way. try { if (!AppGlobals.getPackageManager().activitySupportsIntent(intent.getComponent(), intent, resolvedType)) { Slog.w(TAG, "Activity being started in new voice task does not support: " + intent); err = ActivityManager.START_NOT_VOICE_COMPATIBLE; } } catch (RemoteException e) { Slog.w(TAG, "Failure checking voice capabilities", e); err = ActivityManager.START_NOT_VOICE_COMPATIBLE; } } final ActivityStack resultStack = resultRecord == null ? null : resultRecord.task.stack; if (err != ActivityManager.START_SUCCESS) { if (resultRecord != null) { resultStack.sendActivityResultLocked(-1, resultRecord, resultWho, requestCode, Activity.RESULT_CANCELED, null); } ActivityOptions.abort(options); return err; } boolean abort = false; final int startAnyPerm = mService.checkPermission( START_ANY_ACTIVITY, callingPid, callingUid); if (startAnyPerm != PERMISSION_GRANTED) { final int componentRestriction = getComponentRestrictionForCallingPackage( aInfo, callingPackage, callingPid, callingUid, ignoreTargetSecurity); final int actionRestriction = getActionRestrictionForCallingPackage( intent.getAction(), callingPackage, callingPid, callingUid); if (componentRestriction == ACTIVITY_RESTRICTION_PERMISSION || actionRestriction == ACTIVITY_RESTRICTION_PERMISSION) { if (resultRecord != null) { resultStack.sendActivityResultLocked(-1, resultRecord, resultWho, requestCode, Activity.RESULT_CANCELED, null); } String msg; if (actionRestriction == ACTIVITY_RESTRICTION_PERMISSION) { msg = "以上是关于android activity 管理器AMS----概述的主要内容，如果未能解决你的问题，请参考以下文章
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