谈谈Activity如何启动的
调用栈如下
ActivityManagerService.java
public void systemReady(final Runnable goingCallback) 传入goingCallback = null，
ActivityStack.java
final boolean resumeTopActivityLocked(ActivityRecord prev) 传入 null
ActivityRecord next = topRunningActivityLocked(null); //判断有没有Activity在运行。
if (next == null) {
// There are no more activities! Let's just start up the
// Launcher...
if (mMainStack) {
return mService.startHomeActivityLocked();
}
}
mMainStack.startActivityLocked(null, intent, null, null, 0, aInfo,
null, null, 0, 0, 0, false, false, null);
然后是
ActivityStack.java 中的
final int startActivityLocked(IApplicationThread caller,
Intent intent, String resolvedType,
Uri[] grantedUriPermissions,
int grantedMode, ActivityInfo aInfo, IBinder resultTo,
String resultWho, int requestCode,
int callingPid, int callingUid, boolean onlyIfNeeded,
boolean componentSpecified, ActivityRecord[] outActivity)
if (mMainStack) {
if (mResumedActivity == null
|| mResumedActivity.info.applicationInfo.uid != callingUid) {
if (!mService.checkAppSwitchAllowedLocked(callingPid, callingUid, "Activity start")) {
PendingActivityLaunch pal = new PendingActivityLaunch();
pal.r = r;
pal.sourceRecord = sourceRecord;
pal.grantedUriPermissions = grantedUriPermissions;
pal.grantedMode = grantedMode;
pal.onlyIfNeeded = onlyIfNeeded;
mService.mPendingActivityLaunches.add(pal);
mDismissKeyguardOnNextActivity = false;
return START_SWITCHES_CANCELED;
}
}
if (mService.mDidAppSwitch) {
// This is the second allowed switch since we stopped switches,
// so now just generally allow switches. Use case: user presses
// home (switches disabled, switch to home, mDidAppSwitch now true);
// user taps a home icon (coming from home so allowed, we hit here
// and now allow anyone to switch again).
mService.mAppSwitchesAllowedTime = 0;
} else {
mService.mDidAppSwitch = true;
}
mService.doPendingActivityLaunchesLocked(false);
}
err = startActivityUncheckedLocked(r, sourceRecord,
grantedUriPermissions, grantedMode, onlyIfNeeded, true);
if (mDismissKeyguardOnNextActivity && mPausingActivity == null) {
// Someone asked to have the keyguard dismissed on the next
// activity start, but we are not actually doing an activity
// switch... just dismiss the keyguard now, because we
// probably want to see whatever is behind it.
mDismissKeyguardOnNextActivity = false;
mService.mWindowManager.dismissKeyguard();
}
进程启动的方法
private final void startProcessLocked(ProcessRecord app,
String hostingType, String hostingNameStr) {
if (app.pid > 0 && app.pid != MY_PID) {
synchronized (mPidsSelfLocked) {
mPidsSelfLocked.remove(app.pid);
mHandler.removeMessages(PROC_START_TIMEOUT_MSG, app);
}
app.pid = 0;
}
if (DEBUG_PROCESSES && mProcessesOnHold.contains(app)) Slog.v(TAG,
"startProcessLocked removing on hold: " + app);
mProcessesOnHold.remove(app);
updateCpuStats();
System.arraycopy(mProcDeaths, 0, mProcDeaths, 1, mProcDeaths.length-1);
mProcDeaths[0] = 0;
try {
int uid = app.info.uid;
int[] gids = null;
try {
gids = mContext.getPackageManager().getPackageGids(
app.info.packageName);
} catch (PackageManager.NameNotFoundException e) {
Slog.w(TAG, "Unable to retrieve gids", e);
}
if (mFactoryTest != SystemServer.FACTORY_TEST_OFF) {
if (mFactoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL
&& mTopComponent != null
&& app.processName.equals(mTopComponent.getPackageName())) {
uid = 0;
}
if (mFactoryTest == SystemServer.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 ||
Zygote.systemInSafeMode == true) {
debugFlags |= Zygote.DEBUG_ENABLE_SAFEMODE;
}
if ("1".equals(SystemProperties.get("debug.checkjni"))) {
debugFlags |= Zygote.DEBUG_ENABLE_CHECKJNI;
}
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;
}
// Start the process. It will either succeed and return a result containing
// the PID of the new process, or else throw a RuntimeException.
Process.ProcessStartResult startResult = Process.start("android.app.ActivityThread",
app.processName, uid, uid, gids, debugFlags,
app.info.targetSdkVersion, null);
BatteryStatsImpl bs = app.batteryStats.getBatteryStats();
synchronized (bs) {
if (bs.isOnBattery()) {
app.batteryStats.incStartsLocked();
}
}
EventLog.writeEvent(EventLogTags.AM_PROC_START, startResult.pid, uid,
app.processName, hostingType,
hostingNameStr != null ? hostingNameStr : "");
if (app.persistent) {
Watchdog.getInstance().processStarted(app.processName, startResult.pid);
}
StringBuilder buf = mStringBuilder;
buf.setLength(0);
buf.append("Start proc ");
buf.append(app.processName);
buf.append(" for ");
buf.append(hostingType);
if (hostingNameStr != null) {
buf.append(" ");
buf.append(hostingNameStr);
}
buf.append(": pid=");
buf.append(startResult.pid);
buf.append(" uid=");
buf.append(uid);
buf.append(" gids={");
if (gids != null) {
for (int gi=0; gi<gids.length; gi++) {
if (gi != 0) buf.append(", ");
buf.append(gids[gi]);
}
}
buf.append("}");
Slog.i(TAG, buf.toString());
app.pid = startResult.pid;
app.usingWrapper = startResult.usingWrapper;
app.removed = false;
synchronized (mPidsSelfLocked) {
this.mPidsSelfLocked.put(startResult.pid, app);
Message msg = mHandler.obtainMessage(PROC_START_TIMEOUT_MSG);
msg.obj = app;
mHandler.sendMessageDelayed(msg, startResult.usingWrapper
? PROC_START_TIMEOUT_WITH_WRAPPER : PROC_START_TIMEOUT);
}
} catch (RuntimeException e) {
// XXX do better error recovery.
app.pid = 0;
Slog.e(TAG, "Failure starting process " + app.processName, e);
}
}
Process.java
public static final ProcessStartResult start(final String processClass,
final String niceName,
int uid, int gid, int[] gids,
int debugFlags, int targetSdkVersion,
String[] zygoteArgs) {
try {
return startViaZygote(processClass, niceName, uid, gid, gids,
debugFlags, targetSdkVersion, zygoteArgs);
} catch (ZygoteStartFailedEx ex) {
Log.e(LOG_TAG,
"Starting VM process through Zygote failed");
throw new RuntimeException(
"Starting VM process through Zygote failed", ex);
}
}