分析至如何与zygote至启动一个新的进程
//通过注释，主要是去判断是否需要将要启动activity放到顶部，还是说从活动栈里恢复
int startActivityInner(final ActivityRecord r, ActivityRecord sourceRecord,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
int startFlags, boolean doResume, ActivityOptions options, Task inTask,
boolean restrictedBgActivity, NeededUriGrants intentGrants) {
setInitialState(r, options, inTask, doResume, startFlags, sourceRecord, voiceSession,
voiceInteractor, restrictedBgActivity);
computeLaunchingTaskFlags();
computeSourceStack();
mIntent.setFlags(mLaunchFlags);
final Task reusedTask = getReusableTask();
//查找是否栈中已有可复用的activity：如果没有，并且没有对应合适的栈，那么就要将newTask置true，到时候创建新的栈
//第一次启动，所以reusedTask==null,newTask=true
final Task targetTask = reusedTask != null ? reusedTask : computeTargetTask();
final boolean newTask = targetTask == null;
mTargetTask = targetTask;
computeLaunchParams(r, sourceRecord, targetTask);
//检查是否允许启动该任务
int startResult = isAllowedToStart(r, newTask, targetTask);
if (startResult != START_SUCCESS) {
return startResult;
}
final ActivityRecord targetTaskTop = newTask
? null : targetTask.getTopNonFinishingActivity();
if (targetTaskTop != null) {
// Recycle the target task for this launch.
startResult = recycleTask(targetTask, targetTaskTop, reusedTask, intentGrants);
if (startResult != START_SUCCESS) {
return startResult;
}
} else {
mAddingToTask = true;
}
//判断是否栈顶已经是当前要启动的activity了，是否需要继续启动:即singletop启动模式
final ActivityStack topStack = mRootWindowContainer.getTopDisplayFocusedStack();
if (topStack != null) {
startResult = deliverToCurrentTopIfNeeded(topStack, intentGrants);
if (startResult != START_SUCCESS) {
return startResult;
}
}
if (mTargetStack == null) {
//ActivityStack:Activity的栈管理类
mTargetStack = getLaunchStack(mStartActivity, mLaunchFlags, targetTask, mOptions);
}
//这里是判断到底是加入新的栈还是说直接加入已有的栈
if (newTask) {
final Task taskToAffiliate = (mLaunchTaskBehind && mSourceRecord != null)
? mSourceRecord.getTask() : null;
setNewTask(taskToAffiliate);
if (mService.getLockTaskController().isLockTaskModeViolation(
mStartActivity.getTask())) {
Slog.e(TAG, "Attempted Lock Task Mode violation mStartActivity=" + mStartActivity);
return START_RETURN_LOCK_TASK_MODE_VIOLATION;
}
} else if (mAddingToTask) {
addOrReparentStartingActivity(targetTask, "adding to task");
}
if (!mAvoidMoveToFront && mDoResume) {
//移动到栈顶
mTargetStack.getStack().moveToFront("reuseOrNewTask", targetTask);
if (mOptions != null) {
if (mOptions.getTaskAlwaysOnTop()) {
mTargetStack.setAlwaysOnTop(true);
}
}
}
//mService:ActivityTaskManagerService 权限检查
mService.mUgmInternal.grantUriPermissionUncheckedFromIntent(intentGrants,
mStartActivity.getUriPermissionsLocked());
if (mStartActivity.resultTo != null && mStartActivity.resultTo.info != null) {
// we need to resolve resultTo to a uid as grantImplicitAccess deals explicitly in UIDs
final PackageManagerInternal pmInternal =
mService.getPackageManagerInternalLocked();
final int resultToUid = pmInternal.getPackageUidInternal(
mStartActivity.resultTo.info.packageName, 0, mStartActivity.mUserId);
pmInternal.grantImplicitAccess(mStartActivity.mUserId, mIntent,
UserHandle.getAppId(mStartActivity.info.applicationInfo.uid) /*recipient*/,
resultToUid /*visible*/, true /*direct*/);
}
mTargetStack.mLastPausedActivity = null;
//ActivityStack
mTargetStack.startActivityLocked(mStartActivity,
topStack != null ? topStack.getTopNonFinishingActivity() : null, newTask,
mKeepCurTransition, mOptions);
//
if (mDoResume) {
final ActivityRecord topTaskActivity =
mStartActivity.getTask().topRunningActivityLocked();
if (!mTargetStack.isTopActivityFocusable()
|| (topTaskActivity != null && topTaskActivity.isTaskOverlay()
&& mStartActivity != topTaskActivity)) {
mTargetStack.ensureActivitiesVisible(null /* starting */,
0 /* configChanges */, !PRESERVE_WINDOWS);
mTargetStack.getDisplay().mDisplayContent.executeAppTransition();
} else {
if (mTargetStack.isTopActivityFocusable()
&& !mRootWindowContainer.isTopDisplayFocusedStack(mTargetStack)) {
mTargetStack.moveToFront("startActivityInner");
}
//具体见此处，后续启动
mRootWindowContainer.resumeFocusedStacksTopActivities(
mTargetStack, mStartActivity, mOptions);
}
}
mRootWindowContainer.updateUserStack(mStartActivity.mUserId, mTargetStack);
mSupervisor.mRecentTasks.add(mStartActivity.getTask());
mSupervisor.handleNonResizableTaskIfNeeded(mStartActivity.getTask(),
mPreferredWindowingMode, mPreferredTaskDisplayArea, mTargetStack);
return START_SUCCESS;
}
//frameworks/base/services/core/java/com/android/server/wm/RootWindowContainer.java
boolean resumeFocusedStacksTopActivities(
ActivityStack targetStack, ActivityRecord target, ActivityOptions targetOptions) {
if (!mStackSupervisor.readyToResume()) {
return false;
}
boolean result = false;
if (targetStack != null && (targetStack.isTopStackInDisplayArea()
|| getTopDisplayFocusedStack() == targetStack)) {
//如果当前的activitystack正好处于屏幕的顶部，那么直接调用将target设置到顶部显示
result = targetStack.resumeTopActivityUncheckedLocked(target, targetOptions);
}
for (int displayNdx = getChildCount() - 1; displayNdx >= 0; --displayNdx) {
final DisplayContent display = getChildAt(displayNdx);
//标记是否已经显示在屏幕上
boolean resumedOnDisplay = false;
for (int tdaNdx = display.getTaskDisplayAreaCount() - 1; tdaNdx >= 0; --tdaNdx) {
final TaskDisplayArea taskDisplayArea = display.getTaskDisplayAreaAt(tdaNdx);
for (int sNdx = taskDisplayArea.getStackCount() - 1; sNdx >= 0; --sNdx) {
final ActivityStack stack = taskDisplayArea.getStackAt(sNdx);
//获取到当前ActivityStack顶部正在运行的Activity
final ActivityRecord topRunningActivity = stack.topRunningActivity();
if (!stack.isFocusableAndVisible() || topRunningActivity == null) {
continue;
}
if (stack == targetStack) {
resumedOnDisplay |= result;
continue;
}
if (taskDisplayArea.isTopStack(stack) && topRunningActivity.isState(RESUMED)) {
stack.executeAppTransition(targetOptions);
} else {
resumedOnDisplay |= topRunningActivity.makeActiveIfNeeded(target);
}
}
}
//如果仍然没有显示在屏幕上，那么就获取到屏幕当前持有焦点的ActivityStack，然后将activity显示在上面
if (!resumedOnDisplay) {
final ActivityStack focusedStack = display.getFocusedStack();
if (focusedStack != null) {
//接着继续进行启动
result |= focusedStack.resumeTopActivityUncheckedLocked(target, targetOptions);
} else if (targetStack == null) {
result |= resumeHomeActivity(null /* prev */, "no-focusable-task",
display.getDefaultTaskDisplayArea());
}
}
}
return result;
}
//frameworks/base/services/core/java/com/android/server/wm/ActivityStack.java
boolean resumeTopActivityUncheckedLocked(ActivityRecord prev, ActivityOptions options) {
if (mInResumeTopActivity) {
// Don't even start recursing.
return false;
}
boolean result = false;
try {
// Protect against recursion.
mInResumeTopActivity = true;
//继续activity的后续启动
result = resumeTopActivityInnerLocked(prev, options);
final ActivityRecord next = topRunningActivity(true /* focusableOnly */);
if (next == null || !next.canTurnScreenOn()) {
checkReadyForSleep();
}
} finally {
mInResumeTopActivity = false;
}
return result;
}
private boolean resumeTopActivityInnerLocked(ActivityRecord prev, ActivityOptions options) {
if (mResumedActivity != null) {
if (DEBUG_STATES) Slog.d(TAG_STATES,
"resumeTopActivityLocked: Pausing " + mResumedActivity);
//重点一，将activity onPause
pausing |= startPausingLocked(userLeaving, false /* uiSleeping */, next);
}
//...省略部分代码
if (pausing) {
//接着继续启动
mStackSupervisor.startSpecificActivity(next, true, false);
return true;
}
return true;
}
//frameworks/base/services/core/java/com/android/server/wm/ActivityStackSupervisor.java
void startSpecificActivity(ActivityRecord r, boolean andResume, boolean checkConfig) {
//根据uid和pid，获取activity对应的进行和线程信息
final WindowProcessController wpc =
mService.getProcessController(r.processName, r.info.applicationInfo.uid);
boolean knownToBeDead = false;
if (wpc != null && wpc.hasThread()) {
//如果进程和线程都存在，那么执行下面代码
try {
realStartActivityLocked(r, wpc, andResume, checkConfig);
return;
} catch (RemoteException e) {
Slog.w(TAG, "Exception when starting activity "
+ r.intent.getComponent().flattenToShortString(), e);
}
knownToBeDead = true;
}
r.notifyUnknownVisibilityLaunchedForKeyguardTransition();
final boolean isTop = andResume && r.isTopRunningActivity();
//进程不存在，通过ActivityTaskManagerService创建进程
mService.startProcessAsync(r, knownToBeDead, isTop, isTop ? "top-activity" : "activity");
}
//frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
void startProcessAsync(ActivityRecord activity, boolean knownToBeDead, boolean isTop,
String hostingType) {
try {
final Message m = PooledLambda.obtainMessage(ActivityManagerInternal::startProcess,
mAmInternal, activity.processName, activity.info.applicationInfo, knownToBeDead,
isTop, hostingType, activity.intent.getComponent());
mH.sendMessage(m);
} finally {
Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
}
}
//frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
// 内部类 LocalService extends ActivityManagerInternal
@Override
public void startProcess(String processName, ApplicationInfo info, boolean knownToBeDead,
boolean isTop, String hostingType, ComponentName hostingName) {
synchronized (ActivityManagerService.this) {
startProcessLocked(processName, info, knownToBeDead, 0 /* intentFlags */,
new HostingRecord(hostingType, hostingName, isTop),
ZYGOTE_POLICY_FLAG_LATENCY_SENSITIVE, false /* allowWhileBooting */,
false /* isolated */, true /* keepIfLarge */);
}
}
final ProcessRecord startProcessLocked(String processName,
ApplicationInfo info, boolean knownToBeDead, int intentFlags,
HostingRecord hostingRecord, int zygotePolicyFlags, boolean allowWhileBooting,
boolean isolated, boolean keepIfLarge) {
//ProcessList:将以前放在AMS中的进程启动相关逻辑，单独抽到了ProcessList中，使之逻辑分离
return mProcessList.startProcessLocked(processName, info, knownToBeDead, intentFlags,
hostingRecord, zygotePolicyFlags, allowWhileBooting, isolated, 0 /* isolatedUid */,
keepIfLarge, null /* ABI override */, null /* entryPoint */,
null /* entryPointArgs */, null /* crashHandler */);
}
//frameworks/base/services/core/java/com/android/server/am/ProcessList.java
//进过一系列startProcessLocked的重载调用，最终走到此处
boolean startProcessLocked(HostingRecord hostingRecord, String entryPoint, ProcessRecord app,
int uid, int[] gids, int runtimeFlags, int zygotePolicyFlags, int mountExternal,
String seInfo, String requiredAbi, String instructionSet, String invokeWith,
long startTime) {
app.pendingStart = true;
app.killedByAm = false;
app.removed = false;
app.killed = false;
app.mDisabledCompatChanges = null;
if (mPlatformCompat != null) {
app.mDisabledCompatChanges = mPlatformCompat.getDisabledChanges(app.info);
}
final long startSeq = app.startSeq = ++mProcStartSeqCounter;
app.setStartParams(uid, hostingRecord, seInfo, startTime);
app.setUsingWrapper(invokeWith != null
|| Zygote.getWrapProperty(app.processName) != null);
mPendingStarts.put(startSeq, app);
if (mService.mConstants.FLAG_PROCESS_START_ASYNC) {
if (DEBUG_PROCESSES) Slog.i(TAG_PROCESSES,
"Posting procStart msg for " + app.toShortString());
//异步其实最终也是调用的startProcess
mService.mProcStartHandler.post(() -> handleProcessStart(
app, entryPoint, gids, runtimeFlags, zygotePolicyFlags, mountExternal,
requiredAbi, instructionSet, invokeWith, startSeq));
return true;
} else {
try {
final Process.ProcessStartResult startResult = startProcess(hostingRecord,
entryPoint, app,
uid, gids, runtimeFlags, zygotePolicyFlags, mountExternal, seInfo,
requiredAbi, instructionSet, invokeWith, startTime);
handleProcessStartedLocked(app, startResult.pid, startResult.usingWrapper,
startSeq, false);
} catch (RuntimeException e) {
Slog.e(ActivityManagerService.TAG, "Failure starting process "
+ app.processName, e);
app.pendingStart = false;
mService.forceStopPackageLocked(app.info.packageName, UserHandle.getAppId(app.uid),
false, false, true, false, false, app.userId, "start failure");
}
return app.pid > 0;
}
}
//frameworks/base/core/java/android/os/Process.java
public static ProcessStartResult start(@NonNull final String processClass,
@Nullable final String niceName,
int uid, int gid, @Nullable int[] gids,
int runtimeFlags,
int mountExternal,
int targetSdkVersion,
@Nullable String seInfo,
@NonNull String abi,
@Nullable String instructionSet,
@Nullable String appDataDir,
@Nullable String invokeWith,
@Nullable String packageName,
int zygotePolicyFlags,
boolean isTopApp,
@Nullable long[] disabledCompatChanges,
@Nullable Map>
pkgDataInfoMap,
@Nullable Map>
whitelistedDataInfoMap,
boolean bindMountAppsData,
boolean bindMountAppStorageDirs,
@Nullable String[] zygoteArgs) {
return ZYGOTE_PROCESS.start(processClass, niceName, uid, gid, gids,
runtimeFlags, mountExternal, targetSdkVersion, seInfo,
abi, instructionSet, appDataDir, invokeWith, packageName,
zygotePolicyFlags, isTopApp, disabledCompatChanges,
pkgDataInfoMap, whitelistedDataInfoMap, bindMountAppsData,
bindMountAppStorageDirs, zygoteArgs);
}
//frameworks/base/core/java/android/os/ZygoteProcess.java
public final Process.ProcessStartResult start(@NonNull final String processClass,
final String niceName,
int uid, int gid, @Nullable int[] gids,
int runtimeFlags, int mountExternal,
int targetSdkVersion,
@Nullable String seInfo,
@NonNull String abi,
@Nullable String instructionSet,
@Nullable String appDataDir,
@Nullable String invokeWith,
@Nullable String packageName,
int zygotePolicyFlags,
boolean isTopApp,
@Nullable long[] disabledCompatChanges,
@Nullable Map>
pkgDataInfoMap,
@Nullable Map>
whitelistedDataInfoMap,
boolean bindMountAppsData,
boolean bindMountAppStorageDirs,
@Nullable String[] zygoteArgs) {
if (fetchUsapPoolEnabledPropWithMinInterval()) {
informZygotesOfUsapPoolStatus();
}
try {
return startViaZygote(processClass, niceName, uid, gid, gids,
runtimeFlags, mountExternal, targetSdkVersion, seInfo,
abi, instructionSet, appDataDir, invokeWith, /*startChildZygote=*/ false,
packageName, zygotePolicyFlags, isTopApp, disabledCompatChanges,
pkgDataInfoMap, whitelistedDataInfoMap, bindMountAppsData,
bindMountAppStorageDirs, zygoteArgs);
} catch (ZygoteStartFailedEx ex) {
throw new RuntimeException(
"Starting VM process through Zygote failed", ex);
}
}
private Process.ProcessStartResult startViaZygote(@NonNull final String processClass,
@Nullable final String niceName,
final int uid, final int gid,
@Nullable final int[] gids,
int runtimeFlags, int mountExternal,
int targetSdkVersion,
@Nullable String seInfo,
@NonNull String abi,
@Nullable String instructionSet,
@Nullable String appDataDir,
@Nullable String invokeWith,
boolean startChildZygote,
@Nullable String packageName,
int zygotePolicyFlags,
boolean isTopApp,
@Nullable long[] disabledCompatChanges,
@Nullable Map>
pkgDataInfoMap,
@Nullable Map>
whitelistedDataInfoMap,
boolean bindMountAppsData,
boolean bindMountAppStorageDirs,
@Nullable String[] extraArgs)
throws ZygoteStartFailedEx {
ArrayList argsForZygote = new ArrayList<>();
//......省略部分通信参数的设置
synchronized(mLock) {
//直接关注这里就行
return zygoteSendArgsAndGetResult(openZygoteSocketIfNeeded(abi),
zygotePolicyFlags,
argsForZygote);
}
}
private Process.ProcessStartResult zygoteSendArgsAndGetResult(
ZygoteState zygoteState, int zygotePolicyFlags, @NonNull ArrayList args)
throws ZygoteStartFailedEx {
String msgStr = args.size() + "\n" + String.join("\n", args) + "\n";
if (shouldAttemptUsapLaunch(zygotePolicyFlags, args)) {
try {
return attemptUsapSendArgsAndGetResult(zygoteState, msgStr);
} catch (IOException ex) {
}
}
//此处继续进行
return attemptZygoteSendArgsAndGetResult(zygoteState, msgStr);
}
private Process.ProcessStartResult attemptZygoteSendArgsAndGetResult(
ZygoteState zygoteState, String msgStr) throws ZygoteStartFailedEx {
try {
//可以看到这里直接就用zygoteState进行数据读写通信了:而zygotestate其实就是对LocalSocket的封装
//这样zygote进程就会在循环中收到信息，开始创建新的进程
//具体见//frameworks/base/core/java/com/android/internal/os/ZygoteServer.java
final BufferedWriter zygoteWriter = zygoteState.mZygoteOutputWriter;
final DataInputStream zygoteInputStream = zygoteState.mZygoteInputStream;
zygoteWriter.write(msgStr);
zygoteWriter.flush();
//最后返回子进程启动的封装信息类
Process.ProcessStartResult result = new Process.ProcessStartResult();
result.pid = zygoteInputStream.readInt();
result.usingWrapper = zygoteInputStream.readBoolean();
if (result.pid < 0) {
throw new ZygoteStartFailedEx("fork() failed");
}
return result;
} catch (IOException ex) {
//关闭socket
zygoteState.close();
throw new ZygoteStartFailedEx(ex);
}
}