startActivity
Am
void run() throws RemoteException {
try {
printMessageForState();
mAm.setActivityController(this);
mState = STATE_NORMAL;
InputStreamReader converter = new InputStreamReader(System.in);
BufferedReader in = new BufferedReader(converter);
String line;
while ((line = in.readLine()) != null) {
boolean addNewline = true;
if (line.length() <= 0) {
addNewline = false;
} else if ("q".equals(line) || "quit".equals(line)) {
resumeController(RESULT_DEFAULT);
break;
} else if (mState == STATE_CRASHED) {
if ("c".equals(line) || "continue".equals(line)) {
resumeController(RESULT_CRASH_DIALOG);
} else if ("k".equals(line) || "kill".equals(line)) {
resumeController(RESULT_CRASH_KILL);
} else {
System.out.println("Invalid command: " + line);
}
} else if (mState == STATE_ANR) {
if ("c".equals(line) || "continue".equals(line)) {
resumeController(RESULT_ANR_DIALOG);
} else if ("k".equals(line) || "kill".equals(line)) {
resumeController(RESULT_ANR_KILL);
} else if ("w".equals(line) || "wait".equals(line)) {
resumeController(RESULT_ANR_WAIT);
} else {
System.out.println("Invalid command: " + line);
}
} else if (mState == STATE_EARLY_ANR) {
if ("c".equals(line) || "continue".equals(line)) {
resumeController(RESULT_EARLY_ANR_CONTINUE);
} else if ("k".equals(line) || "kill".equals(line)) {
resumeController(RESULT_EARLY_ANR_KILL);
} else {
System.out.println("Invalid command: " + line);
}
} else {
System.out.println("Invalid command: " + line);
}
synchronized (this) {
if (addNewline) {
System.out.println("");
}
printMessageForState();
}
}
} catch (IOException e) {
e.printStackTrace();
} finally {
mAm.setActivityController(null);
}
} private void runStart() throws Exception {
Intent intent = makeIntent(UserHandle.USER_CURRENT);
if (mUserId == UserHandle.USER_ALL) {
System.err.println("Error: Can't start service with user 'all'");
return;
}
String mimeType = intent.getType();
if (mimeType == null && intent.getData() != null
&& "content".equals(intent.getData().getScheme())) {
mimeType = mAm.getProviderMimeType(intent.getData(), mUserId);
}
do {
if (mStopOption) {
String packageName;
if (intent.getComponent() != null) {
packageName = intent.getComponent().getPackageName();
} else {
IPackageManager pm = IPackageManager.Stub.asInterface(
ServiceManager.getService("package"));
if (pm == null) {
System.err.println("Error: Package manager not running; aborting");
return;
}
List<ResolveInfo> activities = pm.queryIntentActivities(intent, mimeType, 0,
mUserId);
if (activities == null || activities.size() <= 0) {
System.err.println("Error: Intent does not match any activities: "
+ intent);
return;
} else if (activities.size() > 1) {
System.err.println("Error: Intent matches multiple activities; can't stop: "
+ intent);
return;
}
packageName = activities.get(0).activityInfo.packageName;
}
System.out.println("Stopping: " + packageName);
mAm.forceStopPackage(packageName, mUserId);
Thread.sleep(250);
}
System.out.println("Starting: " + intent);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
ParcelFileDescriptor fd = null;
ProfilerInfo profilerInfo = null;
if (mProfileFile != null) {
try {
fd = openForSystemServer(
new File(mProfileFile),
ParcelFileDescriptor.MODE_CREATE |
ParcelFileDescriptor.MODE_TRUNCATE |
ParcelFileDescriptor.MODE_READ_WRITE);
} catch (FileNotFoundException e) {
System.err.println("Error: Unable to open file: " + mProfileFile);
System.err.println("Consider using a file under /data/local/tmp/");
return;
}
profilerInfo = new ProfilerInfo(mProfileFile, fd, mSamplingInterval, mAutoStop);
}
IActivityManager.WaitResult result = null;
int res;
final long startTime = SystemClock.uptimeMillis();
if (mWaitOption) {
result = mAm.startActivityAndWait(null, null, intent, mimeType,
null, null, 0, mStartFlags, profilerInfo, null, mUserId);
res = result.result;
} else {
res = mAm.startActivityAsUser(null, null, intent, mimeType,
null, null, 0, mStartFlags, profilerInfo, null, mUserId);
}
final long endTime = SystemClock.uptimeMillis();
PrintStream out = mWaitOption ? System.out : System.err;
boolean launched = false;
switch (res) {
case ActivityManager.START_SUCCESS:
launched = true;
break;
case ActivityManager.START_SWITCHES_CANCELED:
launched = true;
out.println(
"Warning: Activity not started because the "
+ " current activity is being kept for the user.");
break;
case ActivityManager.START_DELIVERED_TO_TOP:
launched = true;
out.println(
"Warning: Activity not started, intent has "
+ "been delivered to currently running "
+ "top-most instance.");
break;
case ActivityManager.START_RETURN_INTENT_TO_CALLER:
launched = true;
out.println(
"Warning: Activity not started because intent "
+ "should be handled by the caller");
break;
case ActivityManager.START_TASK_TO_FRONT:
launched = true;
out.println(
"Warning: Activity not started, its current "
+ "task has been brought to the front");
break;
case ActivityManager.START_INTENT_NOT_RESOLVED:
out.println(
"Error: Activity not started, unable to "
+ "resolve " + intent.toString());
break;
case ActivityManager.START_CLASS_NOT_FOUND:
out.println(NO_CLASS_ERROR_CODE);
out.println("Error: Activity class " +
intent.getComponent().toShortString()
+ " does not exist.");
break;
case ActivityManager.START_FORWARD_AND_REQUEST_CONFLICT:
out.println(
"Error: Activity not started, you requested to "
+ "both forward and receive its result");
break;
case ActivityManager.START_PERMISSION_DENIED:
out.println(
"Error: Activity not started, you do not "
+ "have permission to access it.");
break;
case ActivityManager.START_NOT_VOICE_COMPATIBLE:
out.println(
"Error: Activity not started, voice control not allowed for: "
+ intent);
break;
case ActivityManager.START_NOT_CURRENT_USER_ACTIVITY:
out.println(
"Error: Not allowed to start background user activity"
+ " that shouldn't be displayed for all users.");
break;
default:
out.println(
"Error: Activity not started, unknown error code " + res);
break;
}
if (mWaitOption && launched) {
if (result == null) {
result = new IActivityManager.WaitResult();
result.who = intent.getComponent();
}
System.out.println("Status: " + (result.timeout ? "timeout" : "ok"));
if (result.who != null) {
System.out.println("Activity: " + result.who.flattenToShortString());
}
if (result.thisTime >= 0) {
System.out.println("ThisTime: " + result.thisTime);
}
if (result.totalTime >= 0) {
System.out.println("TotalTime: " + result.totalTime);
}
System.out.println("WaitTime: " + (endTime-startTime));
System.out.println("Complete");
}
mRepeat--;
if (mRepeat > 1) {
mAm.unhandledBack();
}
} while (mRepeat > 1);
} am最終将調用AMS的startActivityAndWait函數來處理這次啟動請求。
@Override
public final WaitResult startActivityAndWait(IApplicationThread caller, String callingPackage,
Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
int startFlags, ProfilerInfo profilerInfo, Bundle options, int userId) {
enforceNotIsolatedCaller("startActivityAndWait");
userId = handleIncomingUser(Binder.getCallingPid(), Binder.getCallingUid(), userId,
false, ALLOW_FULL_ONLY, "startActivityAndWait", null);
WaitResult res = new WaitResult();
// TODO: Switch to user app stacks here.
mStackSupervisor.startActivityMayWait(caller, -1, callingPackage, intent, resolvedType,
null, null, resultTo, resultWho, requestCode, startFlags, profilerInfo, res, null,
options, false, userId, null, null);
return res;
} final void startActivityLocked(ActivityRecord r, boolean newTask,
boolean doResume, boolean keepCurTransition, Bundle options) {
TaskRecord rTask = r.task;
final int taskId = rTask.taskId;
// mLaunchTaskBehind tasks get placed at the back of the task stack.
if (!r.mLaunchTaskBehind && (taskForIdLocked(taskId) == null || newTask)) {
// Last activity in task had been removed or ActivityManagerService is reusing task.
// Insert or replace.
// Might not even be in.
insertTaskAtTop(rTask, r);
mWindowManager.moveTaskToTop(taskId);
}
TaskRecord task = null;
if (!newTask) {
// If starting in an existing task, find where that is...
boolean startIt = true;
for (int taskNdx = mTaskHistory.size() - 1; taskNdx >= 0; --taskNdx) {
task = mTaskHistory.get(taskNdx);
if (task.getTopActivity() == null) {
// All activities in task are finishing.
continue;
}
if (task == r.task) {
// Here it is! Now, if this is not yet visible to the
// user, then just add it without starting; it will
// get started when the user navigates back to it.
if (!startIt) {
if (DEBUG_ADD_REMOVE) Slog.i(TAG, "Adding activity " + r + " to task "
+ task, new RuntimeException("here").fillInStackTrace());
task.addActivityToTop(r);
r.putInHistory();
mWindowManager.addAppToken(task.mActivities.indexOf(r), r.appToken,
r.task.taskId, mStackId, r.info.screenOrientation, r.fullscreen,
(r.info.flags & ActivityInfo.FLAG_SHOW_FOR_ALL_USERS) != 0,
r.userId, r.info.configChanges, task.voiceSession != null,
r.mLaunchTaskBehind);
if (VALIDATE_TOKENS) {
validateAppTokensLocked();
}
ActivityOptions.abort(options);
return;
}
break;
} else if (task.numFullscreen > 0) {
startIt = false;
}
}
}
// Place a new activity at top of stack, so it is next to interact
// with the user.
// If we are not placing the new activity frontmost, we do not want
// to deliver the onUserLeaving callback to the actual frontmost
// activity
if (task == r.task && mTaskHistory.indexOf(task) != (mTaskHistory.size() - 1)) {
mStackSupervisor.mUserLeaving = false;
if (DEBUG_USER_LEAVING) Slog.v(TAG_USER_LEAVING,
"startActivity() behind front, mUserLeaving=false");
}
task = r.task;
// Slot the activity into the history stack and proceed
if (DEBUG_ADD_REMOVE) Slog.i(TAG, "Adding activity " + r + " to stack to task " + task,
new RuntimeException("here").fillInStackTrace());
task.addActivityToTop(r);
task.setFrontOfTask();
r.putInHistory();
if (!isHomeStack() || numActivities() > 0) {
// We want to show the starting preview window if we are
// switching to a new task, or the next activity's process is
// not currently running.
boolean showStartingIcon = newTask;
ProcessRecord proc = r.app;
if (proc == null) {
proc = mService.mProcessNames.get(r.processName, r.info.applicationInfo.uid);
}
if (proc == null || proc.thread == null) {
showStartingIcon = true;
}
if (DEBUG_TRANSITION) Slog.v(TAG_TRANSITION,
"Prepare open transition: starting " + r);
if ((r.intent.getFlags() & Intent.FLAG_ACTIVITY_NO_ANIMATION) != 0) {
mWindowManager.prepareAppTransition(AppTransition.TRANSIT_NONE, keepCurTransition);
mNoAnimActivities.add(r);
} else {
mWindowManager.prepareAppTransition(newTask
? r.mLaunchTaskBehind
? AppTransition.TRANSIT_TASK_OPEN_BEHIND
: AppTransition.TRANSIT_TASK_OPEN
: AppTransition.TRANSIT_ACTIVITY_OPEN, keepCurTransition);
mNoAnimActivities.remove(r);
}
mWindowManager.addAppToken(task.mActivities.indexOf(r),
r.appToken, r.task.taskId, mStackId, r.info.screenOrientation, r.fullscreen,
(r.info.flags & ActivityInfo.FLAG_SHOW_FOR_ALL_USERS) != 0, r.userId,
r.info.configChanges, task.voiceSession != null, r.mLaunchTaskBehind);
boolean doShow = true;
if (newTask) {
// Even though this activity is starting fresh, we still need
// to reset it to make sure we apply affinities to move any
// existing activities from other tasks in to it.
// If the caller has requested that the target task be
// reset, then do so.
if ((r.intent.getFlags() & Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) != 0) {
resetTaskIfNeededLocked(r, r);
doShow = topRunningNonDelayedActivityLocked(null) == r;
}
} else if (options != null && new ActivityOptions(options).getAnimationType()
== ActivityOptions.ANIM_SCENE_TRANSITION) {
doShow = false;
}
if (r.mLaunchTaskBehind) {
// Don't do a starting window for mLaunchTaskBehind. More importantly make sure we
// tell WindowManager that r is visible even though it is at the back of the stack.
mWindowManager.setAppVisibility(r.appToken, true);
ensureActivitiesVisibleLocked(null, 0);
} else if (SHOW_APP_STARTING_PREVIEW && doShow) {
// Figure out if we are transitioning from another activity that is
// "has the same starting icon" as the next one. This allows the
// window manager to keep the previous window it had previously
// created, if it still had one.
ActivityRecord prev = mResumedActivity;
if (prev != null) {
// We don't want to reuse the previous starting preview if:
// (1) The current activity is in a different task.
if (prev.task != r.task) {
prev = null;
}
// (2) The current activity is already displayed.
else if (prev.nowVisible) {
prev = null;
}
}
mWindowManager.setAppStartingWindow(
r.appToken, r.packageName, r.theme,
mService.compatibilityInfoForPackageLocked(
r.info.applicationInfo), r.nonLocalizedLabel,
r.labelRes, r.icon, r.logo, r.windowFlags,
prev != null ? prev.appToken : null, showStartingIcon);
r.mStartingWindowShown = true;
}
} else {
// If this is the first activity, don't do any fancy animations,
// because there is nothing for it to animate on top of.
mWindowManager.addAppToken(task.mActivities.indexOf(r), r.appToken,
r.task.taskId, mStackId, r.info.screenOrientation, r.fullscreen,
(r.info.flags & ActivityInfo.FLAG_SHOW_FOR_ALL_USERS) != 0, r.userId,
r.info.configChanges, task.voiceSession != null, r.mLaunchTaskBehind);
ActivityOptions.abort(options);
options = null;
}
if (VALIDATE_TOKENS) {
validateAppTokensLocked();
}
if (doResume) {
mStackSupervisor.resumeTopActivitiesLocked(this, r, options);
}
} startActivityLocked函數的主要工作包括
1.處理sourceRecord及resultRecord。其中，sourceRecord表示發起本次請求的Activity，resultRecord表示接收處理結果的Activity（啟動一個Activity肯定需要它完成某項事情，當目标Activity将事情成後，就需要告知請求者該事情的處理結果）。在一般情況下，sourceRecord和resultRecord應指向同一個Activity。
2.處理app switch。如果AMS目前禁止app switch，則隻能把本次啟動請求儲存起來，以待允許app switch時再處理。從代碼中可知，AMS在處理本次請求前，會先調用doPendingActivityLaunchesLocked函數，在該函數内部将啟動之前因系統禁止app switch而儲存的Pending請求
3.調用startActivityUncheckedLocked處理本次Activity啟動請求
@Override
public void stopAppSwitches() {
if (checkCallingPermission(android.Manifest.permission.STOP_APP_SWITCHES)
!= PackageManager.PERMISSION_GRANTED) {
throw new SecurityException("Requires permission "
+ android.Manifest.permission.STOP_APP_SWITCHES);
}
synchronized(this) {
mAppSwitchesAllowedTime = SystemClock.uptimeMillis()
+ APP_SWITCH_DELAY_TIME;
mDidAppSwitch = false;
mHandler.removeMessages(DO_PENDING_ACTIVITY_LAUNCHES_MSG);
Message msg = mHandler.obtainMessage(DO_PENDING_ACTIVITY_LAUNCHES_MSG);
mHandler.sendMessageDelayed(msg, APP_SWITCH_DELAY_TIME);
}
} public void resumeAppSwitches() {
if (checkCallingPermission(android.Manifest.permission.STOP_APP_SWITCHES)
!= PackageManager.PERMISSION_GRANTED) {
throw new SecurityException("Requires permission "
+ android.Manifest.permission.STOP_APP_SWITCHES);
}
synchronized(this) {
// Note that we don't execute any pending app switches... we will
// let those wait until either the timeout, or the next start
// activity request.
mAppSwitchesAllowedTime = 0;
}
} startActivityUncheckedLocked函數很長，但是目的比較簡單，即為新建立的ActivityRecord找到一個合适的Task。
ActivityStack
final boolean resumeTopActivityLocked(ActivityRecord prev, Bundle options) {
if (mStackSupervisor.inResumeTopActivity) {
// Don't even start recursing.
return false;
}
boolean result = false;
try {
// Protect against recursion.
mStackSupervisor.inResumeTopActivity = true;
if (mService.mLockScreenShown == ActivityManagerService.LOCK_SCREEN_LEAVING) {
mService.mLockScreenShown = ActivityManagerService.LOCK_SCREEN_HIDDEN;
mService.updateSleepIfNeededLocked();
}
result = resumeTopActivityInnerLocked(prev, options);
} finally {
mStackSupervisor.inResumeTopActivity = false;
}
return result;
} resumeTopActivityLocked函數中有兩個非常重要的關鍵點
1.如果mResumedActivity不為空，則需要先暫停（pause）這個Activity。由代碼中的注釋可知，mResumedActivity代表上一次啟動的（即目前正顯示的）Activity。現在要啟動一個新的Activity，須先停止目前Activity，這部分工作由startPausingLocked函數完成
2.mResumeActivity什麼時候為空呢？當然是在啟動全系統第一個Activity時，即啟動Home界面的時候。除此之外，該值都不會為空
resumeTopActivityLocked最後将調用另外一個startSpecificActivityLocked，該函數将真正建立一個應用程序。
private final void startProcessLocked(ProcessRecord app, String hostingType,
String hostingNameStr, String abiOverride, String entryPoint, String[] entryPointArgs) {
long startTime = SystemClock.elapsedRealtime();
if (app.pid > 0 && app.pid != MY_PID) {
checkTime(startTime, "startProcess: removing from pids map");
synchronized (mPidsSelfLocked) {
mPidsSelfLocked.remove(app.pid);
mHandler.removeMessages(PROC_START_TIMEOUT_MSG, app);
}
checkTime(startTime, "startProcess: done removing from pids map");
app.setPid(0);
}
if (DEBUG_PROCESSES && mProcessesOnHold.contains(app)) Slog.v(TAG_PROCESSES,
"startProcessLocked removing on hold: " + app);
mProcessesOnHold.remove(app);
checkTime(startTime, "startProcess: starting to update cpu stats");
updateCpuStats();
checkTime(startTime, "startProcess: done updating cpu stats");
try {
try {
if (AppGlobals.getPackageManager().isPackageFrozen(app.info.packageName)) {
// This is caught below as if we had failed to fork zygote
throw new RuntimeException("Package " + app.info.packageName + " is frozen!");
}
} catch (RemoteException e) {
throw e.rethrowAsRuntimeException();
}
int uid = app.uid;
int[] gids = null;
int mountExternal = Zygote.MOUNT_EXTERNAL_NONE;
if (!app.isolated) {
int[] permGids = null;
try {
checkTime(startTime, "startProcess: getting gids from package manager");
final IPackageManager pm = AppGlobals.getPackageManager();
permGids = pm.getPackageGids(app.info.packageName, app.userId);
MountServiceInternal mountServiceInternal = LocalServices.getService(
MountServiceInternal.class);
mountExternal = mountServiceInternal.getExternalStorageMountMode(uid,
app.info.packageName);
} catch (RemoteException e) {
throw e.rethrowAsRuntimeException();
}
/*
* Add shared application and profile GIDs so applications can share some
* resources like shared libraries and access user-wide resources
*/
if (ArrayUtils.isEmpty(permGids)) {
gids = new int[2];
} else {
gids = new int[permGids.length + 2];
System.arraycopy(permGids, 0, gids, 2, permGids.length);
}
gids[0] = UserHandle.getSharedAppGid(UserHandle.getAppId(uid));
gids[1] = UserHandle.getUserGid(UserHandle.getUserId(uid));
}
checkTime(startTime, "startProcess: building args");
if (mFactoryTest != FactoryTest.FACTORY_TEST_OFF) {
if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL
&& mTopComponent != null
&& app.processName.equals(mTopComponent.getPackageName())) {
uid = 0;
}
if (mFactoryTest == FactoryTest.FACTORY_TEST_HIGH_LEVEL
&& (app.info.flags&ApplicationInfo.FLAG_FACTORY_TEST) != 0) {
uid = 0;
}
}
int debugFlags = 0;
if ((app.info.flags & ApplicationInfo.FLAG_DEBUGGABLE) != 0) {
debugFlags |= Zygote.DEBUG_ENABLE_DEBUGGER;
// Also turn on CheckJNI for debuggable apps. It's quite
// awkward to turn on otherwise.
debugFlags |= Zygote.DEBUG_ENABLE_CHECKJNI;
}
// Run the app in safe mode if its manifest requests so or the
// system is booted in safe mode.
if ((app.info.flags & ApplicationInfo.FLAG_VM_SAFE_MODE) != 0 ||
mSafeMode == true) {
debugFlags |= Zygote.DEBUG_ENABLE_SAFEMODE;
}
if ("1".equals(SystemProperties.get("debug.checkjni"))) {
debugFlags |= Zygote.DEBUG_ENABLE_CHECKJNI;
}
String jitDebugProperty = SystemProperties.get("debug.usejit");
if ("true".equals(jitDebugProperty)) {
debugFlags |= Zygote.DEBUG_ENABLE_JIT;
} else if (!"false".equals(jitDebugProperty)) {
// If we didn't force disable by setting false, defer to the dalvik vm options.
if ("true".equals(SystemProperties.get("dalvik.vm.usejit"))) {
debugFlags |= Zygote.DEBUG_ENABLE_JIT;
}
}
String genDebugInfoProperty = SystemProperties.get("debug.generate-debug-info");
if ("true".equals(genDebugInfoProperty)) {
debugFlags |= Zygote.DEBUG_GENERATE_DEBUG_INFO;
}
if ("1".equals(SystemProperties.get("debug.jni.logging"))) {
debugFlags |= Zygote.DEBUG_ENABLE_JNI_LOGGING;
}
if ("1".equals(SystemProperties.get("debug.assert"))) {
debugFlags |= Zygote.DEBUG_ENABLE_ASSERT;
}
String requiredAbi = (abiOverride != null) ? abiOverride : app.info.primaryCpuAbi;
if (requiredAbi == null) {
requiredAbi = Build.SUPPORTED_ABIS[0];
}
String instructionSet = null;
if (app.info.primaryCpuAbi != null) {
instructionSet = VMRuntime.getInstructionSet(app.info.primaryCpuAbi);
}
app.gids = gids;
app.requiredAbi = requiredAbi;
app.instructionSet = instructionSet;
// Start the process. It will either succeed and return a result containing
// the PID of the new process, or else throw a RuntimeException.
boolean isActivityProcess = (entryPoint == null);
if (entryPoint == null) entryPoint = "android.app.ActivityThread";
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "Start proc: " +
app.processName);
checkTime(startTime, "startProcess: asking zygote to start proc");
Process.ProcessStartResult startResult = Process.start(entryPoint,
app.processName, uid, uid, gids, debugFlags, mountExternal,
app.info.targetSdkVersion, app.info.seinfo, requiredAbi, instructionSet,
app.info.dataDir, entryPointArgs);
checkTime(startTime, "startProcess: returned from zygote!");
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
if (app.isolated) {
mBatteryStatsService.addIsolatedUid(app.uid, app.info.uid);
}
mBatteryStatsService.noteProcessStart(app.processName, app.info.uid);
checkTime(startTime, "startProcess: done updating battery stats");
EventLog.writeEvent(EventLogTags.AM_PROC_START,
UserHandle.getUserId(uid), startResult.pid, uid,
app.processName, hostingType,
hostingNameStr != null ? hostingNameStr : "");
if (app.persistent) {
Watchdog.getInstance().processStarted(app.processName, startResult.pid);
}
checkTime(startTime, "startProcess: building log message");
StringBuilder buf = mStringBuilder;
buf.setLength(0);
buf.append("Start proc ");
buf.append(startResult.pid);
buf.append(':');
buf.append(app.processName);
buf.append('/');
UserHandle.formatUid(buf, uid);
if (!isActivityProcess) {
buf.append(" [");
buf.append(entryPoint);
buf.append("]");
}
buf.append(" for ");
buf.append(hostingType);
if (hostingNameStr != null) {
buf.append(" ");
buf.append(hostingNameStr);
}
Slog.i(TAG, buf.toString());
app.setPid(startResult.pid);
app.usingWrapper = startResult.usingWrapper;
app.removed = false;
app.killed = false;
app.killedByAm = false;
checkTime(startTime, "startProcess: starting to update pids map");
synchronized (mPidsSelfLocked) {
this.mPidsSelfLocked.put(startResult.pid, app);
if (isActivityProcess) {
Message msg = mHandler.obtainMessage(PROC_START_TIMEOUT_MSG);
msg.obj = app;
mHandler.sendMessageDelayed(msg, startResult.usingWrapper
? PROC_START_TIMEOUT_WITH_WRAPPER : PROC_START_TIMEOUT);
}
}
checkTime(startTime, "startProcess: done updating pids map");
} catch (RuntimeException e) {
// XXX do better error recovery.
app.setPid(0);
mBatteryStatsService.noteProcessFinish(app.processName, app.info.uid);
if (app.isolated) {
mBatteryStatsService.removeIsolatedUid(app.uid, app.info.uid);
}
Slog.e(TAG, "Failure starting process " + app.processName, e);
}
} 1.FLAG_FROM_BACKGROUND标志發起這次啟動的Task屬于背景任務。很顯然，手機中沒有界面供使用者操作位于背景Task中的Activity。如果沒有設定該标志，那麼這次啟動請求就是由前台Task因某種原因而觸發的（例如：使用者單擊某個按鈕）
2.如果一個應用程序在1分鐘内連續崩潰超過2次，則AMS會将其ProcessRecord加入所謂的mBadProcesses中。一個應用崩潰後，系統會彈出一個警告框以提醒使用者。
ActivityThread
public static void main(String[] args) {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain");
SamplingProfilerIntegration.start();
// CloseGuard defaults to true and can be quite spammy. We
// disable it here, but selectively enable it later (via
// StrictMode) on debug builds, but using DropBox, not logs.
CloseGuard.setEnabled(false);
Environment.initForCurrentUser();
// Set the reporter for event logging in libcore
EventLogger.setReporter(new EventLoggingReporter());
AndroidKeyStoreProvider.install();
// Make sure TrustedCertificateStore looks in the right place for CA certificates
final File configDir = Environment.getUserConfigDirectory(UserHandle.myUserId());
TrustedCertificateStore.setDefaultUserDirectory(configDir);
Process.setArgV0("<pre-initialized>");
Looper.prepareMainLooper();
ActivityThread thread = new ActivityThread();
thread.attach(false);
if (sMainThreadHandler == null) {
sMainThreadHandler = thread.getHandler();
}
if (false) {
Looper.myLooper().setMessageLogging(new
LogPrinter(Log.DEBUG, "ActivityThread"));
}
// End of event ActivityThreadMain.
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
Looper.loop();
throw new RuntimeException("Main thread loop unexpectedly exited");
} 在main函數内部将建立一個消息循環Loop，接着調用ActivityThread的attach函數，最終将主線程加入消息循環
private void attach(boolean system) {
sCurrentActivityThread = this;
mSystemThread = system;
if (!system) {
ViewRootImpl.addFirstDrawHandler(new Runnable() {
@Override
public void run() {
ensureJitEnabled();
}
});
android.ddm.DdmHandleAppName.setAppName("<pre-initialized>",
UserHandle.myUserId());
RuntimeInit.setApplicationObject(mAppThread.asBinder());
final IActivityManager mgr = ActivityManagerNative.getDefault();
try {
mgr.attachApplication(mAppThread);
} catch (RemoteException ex) {
// Ignore
}
// Watch for getting close to heap limit.
BinderInternal.addGcWatcher(new Runnable() {
@Override public void run() {
if (!mSomeActivitiesChanged) {
return;
}
Runtime runtime = Runtime.getRuntime();
long dalvikMax = runtime.maxMemory();
long dalvikUsed = runtime.totalMemory() - runtime.freeMemory();
if (dalvikUsed > ((3*dalvikMax)/4)) {
if (DEBUG_MEMORY_TRIM) Slog.d(TAG, "Dalvik max=" + (dalvikMax/1024)
+ " total=" + (runtime.totalMemory()/1024)
+ " used=" + (dalvikUsed/1024));
mSomeActivitiesChanged = false;
try {
mgr.releaseSomeActivities(mAppThread);
} catch (RemoteException e) {
}
}
}
});
} else {
// Don't set application object here -- if the system crashes,
// we can't display an alert, we just want to die die die.
android.ddm.DdmHandleAppName.setAppName("system_process",
UserHandle.myUserId());
try {
mInstrumentation = new Instrumentation();
ContextImpl context = ContextImpl.createAppContext(
this, getSystemContext().mPackageInfo);
mInitialApplication = context.mPackageInfo.makeApplication(true, null);
mInitialApplication.onCreate();
} catch (Exception e) {
throw new RuntimeException(
"Unable to instantiate Application():" + e.toString(), e);
}
}
// add dropbox logging to libcore
DropBox.setReporter(new DropBoxReporter());
ViewRootImpl.addConfigCallback(new ComponentCallbacks2() {
@Override
public void onConfigurationChanged(Configuration newConfig) {
synchronized (mResourcesManager) {
// We need to apply this change to the resources
// immediately, because upon returning the view
// hierarchy will be informed about it.
if (mResourcesManager.applyConfigurationToResourcesLocked(newConfig, null)) {
// This actually changed the resources! Tell
// everyone about it.
if (mPendingConfiguration == null ||
mPendingConfiguration.isOtherSeqNewer(newConfig)) {
mPendingConfiguration = newConfig;
sendMessage(H.CONFIGURATION_CHANGED, newConfig);
}
}
}
}
@Override
public void onLowMemory() {
}
@Override
public void onTrimMemory(int level) {
}
});
} AMS建立一個應用程序後，會設定一個逾時時間（一般是10秒）。如果超過這個時間，應用程序還沒有和AMS互動，則斷定該程序建立失敗。是以，應用程序啟動後，需要盡快和AMS互動，即調用AMS的attachApplication函數。在該函數内部将調用attachApplicationLocked。
attachApplicationLocked第一階段的工作比較簡單：
1.設定代表該應用程序的ProcessRecord對象的一些成員變量，如用于和應用程序互動的thread對象、jincheng 排程優先級及oom_adj的值等
2.從消息隊列中撤銷PROC_START_TIMEOUT_MSG
應用程序的建立及初始化總結
1.在應用程序啟動後，需要盡快調用AMS的attachApplication函數，該函數是這個剛建立的應用程序第一次和AMS互動。此時的它還默默無名，連一個确定的程序名都沒有。不過沒關系，attachApplication函數将根據建立該應用程序之前所儲存的ProcessRecord為其準備一切手續
2.attachApplication準備好一切後，将調用應用程序的bindApplication函數，在該函數内部将發消息給主線程，最終該消息由handleBindApplication處理。handleBindApplication将為該程序設定程序名，初始化一些政策和參數資訊等。另外，它還建立一個Application對象。同時，如果該Application聲明了ContentProvider，還需要為該程序安裝ContentProvider。
AMS調用完bindApplication後，将通過realStartActivityLocked啟動Activity。在此之前，要建立完應用程序并初始化Android運作環境
private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent) {
// If we are getting ready to gc after going to the background, well
// we are back active so skip it.
unscheduleGcIdler();
mSomeActivitiesChanged = true;
if (r.profilerInfo != null) {
mProfiler.setProfiler(r.profilerInfo);
mProfiler.startProfiling();
}
// Make sure we are running with the most recent config.
handleConfigurationChanged(null, null);
if (localLOGV) Slog.v(
TAG, "Handling launch of " + r);
// Initialize before creating the activity
WindowManagerGlobal.initialize();
Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
Bundle oldState = r.state;
handleResumeActivity(r.token, false, r.isForward,
!r.activity.mFinished && !r.startsNotResumed);
if (!r.activity.mFinished && r.startsNotResumed) {
// The activity manager actually wants this one to start out
// paused, because it needs to be visible but isn't in the
// foreground. We accomplish this by going through the
// normal startup (because activities expect to go through
// onResume() the first time they run, before their window
// is displayed), and then pausing it. However, in this case
// we do -not- need to do the full pause cycle (of freezing
// and such) because the activity manager assumes it can just
// retain the current state it has.
try {
r.activity.mCalled = false;
mInstrumentation.callActivityOnPause(r.activity);
// We need to keep around the original state, in case
// we need to be created again. But we only do this
// for pre-Honeycomb apps, which always save their state
// when pausing, so we can not have them save their state
// when restarting from a paused state. For HC and later,
// we want to (and can) let the state be saved as the normal
// part of stopping the activity.
if (r.isPreHoneycomb()) {
r.state = oldState;
}
if (!r.activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString() +
" did not call through to super.onPause()");
}
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
if (!mInstrumentation.onException(r.activity, e)) {
throw new RuntimeException(
"Unable to pause activity "
+ r.intent.getComponent().toShortString()
+ ": " + e.toString(), e);
}
}
r.paused = true;
}
} else {
// If there was an error, for any reason, tell the activity
// manager to stop us.
try {
ActivityManagerNative.getDefault()
.finishActivity(r.token, Activity.RESULT_CANCELED, null, false);
} catch (RemoteException ex) {
// Ignore
}
}
} 1.首先調用performLaunchActivity，該在函數内部通過Java反射機制建立目标Activity，然後調用它的onCreate及onStart函數
2.調用handleResumeActivity，會在其内部調用目标Activity的onResume函數。
startActivity總結
1.起點是am。我們利用am start指令，發起本次目标Activity的啟動請求
2.接下來進入ActivityManagerService和ActivityStack這兩個核心類。對于啟動Activity來說，這段行程又可細分為兩個階段：第一階段就是根據啟動模式和啟動标志找到活建立ActivityRecord及對應的TaskRecord；第二階段就是處理Activity啟動或切換相關的工作
3.然後AMS直接建立目标程序并運作Activity的流程，其中涉及目标程序的建立，目标程序中Android運作環境的初始化，目标Activity的建立以及onCreate、onStart及onResume等生命周期中重要函數的調用等相關知識
4.AMS先暫停目前Activity，然後再建立目标程序并運作Activity的流程，其中兩個應用程序和AMS互動。
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