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Android Activity??????

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???????????????????????????????????????????????????????????Activity??????????????????????????????????Android??????????????

??????

?????Launcher Activity????????????????????Launcher?????startActivitySafely??????????Activity?????????????????AMS?ActivityManagerService??Zygote?????????????????????????????

?????????????????

1. Launcher?AMS??????

Launcher???????????????????????????????????????????????Launcher???startActivitySafely????????startActivity(Intent intent)?????????

public boolean startActivitySafely(View v, Intent intent, ItemInfo item) {  
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);  
    startActivity(intent, optsBundle);  
    return true;  
}  
public void startActivity(Intent intent, @Nullable Bundle options) {  
    if (options != null) {  
        startActivityForResult(intent, -1, options);  
    } else {  
        startActivityForResult(intent, -1);  
    }  
}  
public void startActivityForResult(@RequiresPermission Intent intent, int requestCode, @Nullable Bundle options) {  
    Instrumentation.ActivityResult ar = mInstrumentation.execStartActivity(  
        this, mMainThread.getApplicationThread(), mToken,  
        intent, requestCode, options);  
    // ????  
}

???????????startActivity??????Instrumentation?execStartActivity??????????AMS??????????????????Activity?????Instrumentation????Instrumentation??Binder?AMS???

2. AMS??Activity???Launcher??Paused??

AMS????????????Binder?Zygote??????????????????????????

public int startActivity(IApplicationThread caller, String callingPackage, String callingFeatureId,  
    Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,  
    int startFlags, ProfilerInfo profilerInfo, Bundle bOptions, int userId) {  
    return startActivityAsUser(caller, callingPackage, callingFeatureId, intent, resolvedType,  
        resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions, userId);  
}  
public int startActivityAsUser(IApplicationThread caller, String callingPackage, String callingFeatureId,  
    Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,  
    int startFlags, ProfilerInfo profilerInfo, Bundle bOptions, int userId, boolean validateIncomingUser) {  
    // ????  
    userId = getActivityStartController().checkTargetUser(userId, validateIncomingUser,  
        Binder.getCallingPid(), Binder.getCallingUid(), "startActivityAsUser");  
    return getActivityStartController().obtainStarter(intent, "startActivityAsUser")  
        .setCaller(caller)  
        .setCallingPackage(callingPackage)  
        .setCallingFeatureId(callingFeatureId)  
        .setResolvedType(resolvedType)  
        .setResultTo(resultTo)  
        .setResultWho(resultWho)  
        .setRequestCode(requestCode)  
        .setStartFlags(startFlags)  
        .setProfilerInfo(profilerInfo)  
        .setActivityOptions(bOptions)  
        .setUserId(userId)  
        .execute();  
}  
ActivityStarter.java  
int execute() {  
    // ??ActivityStack.java??startActivity??  
}  
ActivityStack.java  
private boolean resumeTopActivityInnerLocked(ActivityRecord prev, ActivityOptions options) {  
    // ??Launcher??Paused??  
}  
ActivityStackSupervisor.java  
void startSpecificActivity(ActivityRecord r, boolean andResume, boolean checkConfig) {  
    // ???????  
    final WindowProcessController wpc = mService.getProcessController(r.processName, r.info.applicationInfo.uid);  
    if (wpc != null && wpc.hasThread()) {  
        try {  
            realStartActivityLocked(r, wpc, andResume, checkConfig);  
        } catch (RemoteException e) {  
            // ????  
        }  
    }  
    // ??????  
    r.notifyUnknownVisibilityLaunchedForKeyguardTransition();  
    final boolean isTop = andResume && r.isTopRunningActivity();  
    mService.startProcessAsync(r, knownToBeDead, isTop, isTop ? "top-activity" : "activity");  
}

???????????AMS??ActivityTaskManagerService?Zygote?????????Zygote???????????????????ActivityThread?main???

3. ???????ActivityThread?main????

Zygote???????????????????????ActivityThread?main???ActivityThread?main???????Looper?ActivityThread????????????AMS??

public static void main(String[] args) {  
    // ???Looper  
    Looper.prepareMainLooper();  
    // ??ActivityThread?attach  
    ActivityThread thread = new ActivityThread();  
    thread.attach(false, startSeq);  
    // ????  
    Looper.loop();  
}  
ActivityThread.java  
private void attach(boolean system, long startSeq) {  
    final IActivityManager mgr = ActivityManager.getService();  
    try {  
        mgr.attachApplication(mAppThread, startSeq);  
    } catch (RemoteException ex) {  
        ex.rethrowFromSystemServer();  
    }  
    // ??Application  
    bindApplication();  
}  
ActivityManagerService.java  
private boolean attachApplicationLocked(IApplicationThread thread, int pid, int callingUid, long startSeq) {  
    // ??Application  
    thread.bindApplication(processName, appInfo, providerList, instr2.mClass, profilerInfo, instr2.mArguments, instr2.mWatcher, instr2.mUiAutomationConnection, testMode, enableTrackAllocation, isRestrictedBackupMode, app.isPersistent(), config, compatInfo, services, coreSettings, buildSerial, autofillOptions, contentCaptureOptions, disabledCompatChanges);  
    // ??onCreate  
    didSomething = mAtmInternal.attachApplication(app.getWindowProcessController());  
}

???????????ActivityThread?main??????????????????????AMS???????????????

4. ??Activity

??????????????????????????Activity?ActivityStackSupervisor?????????????????Activity???

public final void bindApplication(String processName, ApplicationInfo appInfo, ProviderInfoList providerList, ComponentName instrumentationName, ProfilerInfo profilerInfo, Bundle instrumentationArgs, IInstrumentationWatcher instrumentationWatcher, IUiAutomationConnection instrumentationUiConnection, int debugMode, boolean enableBinderTracking, boolean trackAllocation, boolean isRestrictedBackupMode, boolean persistent, Configuration config, CompatibilityInfo compatInfo, Map services, Bundle coreSettings, String buildSerial, AutofillOptions autofillOptions, ContentCaptureOptions contentCaptureOptions, long[] disabledCompatChanges) {  
    // ??BIND_APPLICATION??  
    sendMessage(H.BIND_APPLICATION, data);  
}  
public void handleMessage(Message msg) {  
    switch (msg.what) {  
        case BIND_APPLICATION:  
            AppBindData data = (AppBindData) msg.obj;  
            handleBindApplication(data);  
            Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
            break;  
        // ??case  
    }  
}  
private void handleBindApplication(AppBindData data) {  
    // ??Application?onCreate??  
    mInstrumentation.callApplicationOnCreate(app);  
}

???????????ActivityStackSupervisor??????????????????Activity??????????

??

????????????????Android????????????????????????????Activity????????????????????Launcher?AMS?Zygote??ActivityThread??????????????Android????????????

???????????????????Android??????????????????Activity??????????????Android??????????

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