启动服务

1、在ContextImpl.java中

@Override
public ComponentName startService(Intent service) {
    warnIfCallingFromSystemProcess();
    return startServiceCommon(service, false, mUser);
}

@Override
public ComponentName startService(Intent service) {
    ...
    ComponentName cn = ActivityManager.getService().startService(
                mMainThread.getApplicationThread(), service, service.resolveTypeIfNeeded(
                            getContentResolver()), requireForeground,
                            getOpPackageName(), user.getIdentifier());
   ...
              
}

2、来到ActivityManagerService.java中

@Override
public ComponentName startService(IApplicationThread caller, Intent service,
            ...
            res = mServices.startServiceLocked(caller, service,
                        resolvedType, callingPid, callingUid,
                        requireForeground, callingPackage, userId);
            ...
            return res;
        }
    }

3、来到ActivityServices.java中

ComponentName startServiceLocked(IApplicationThread caller, Intent service, String resolvedType,
            int callingPid, int callingUid, boolean fgRequired, String callingPackage, final int userId)
            throws TransactionTooLargeException {
   ....
   ComponentName cmp = startServiceInnerLocked(smap, service, r, callerFg, addToStarting);
        return cmp;
}

ComponentName startServiceInnerLocked(ServiceMap smap, Intent service, ServiceRecord r,
            boolean callerFg, boolean addToStarting) throws TransactionTooLargeException {
       ...
       String error = bringUpServiceLocked(r, service.getFlags(), callerFg, false, false);
   
        ...
}

private String bringUpServiceLocked(ServiceRecord r, int intentFlags, boolean execInFg,
            boolean whileRestarting, boolean permissionsReviewRequired)
            throws TransactionTooLargeException {
        ...

        if (r.app != null && r.app.thread != null) {
            sendServiceArgsLocked(r, execInFg, false);
            return null;
        }
        ... 
        创建service
        realStartServiceLocked(r, app, execInFg);
        ... 
        开始一个进程
        if ((app=mAm.startProcessLocked(procName, r.appInfo, true, intentFlags,
                    hostingType, r.name, false, isolated, false)) == null) {
                String msg = "Unable to launch app "
                        + r.appInfo.packageName + "/"
                        + r.appInfo.uid + " for service "
                        + r.intent.getIntent() + ": process is bad";
                Slog.w(TAG, msg);
                bringDownServiceLocked(r);
                return msg;
            }
     ...
}

private final void realStartServiceLocked(ServiceRecord r,
            ProcessRecord app, boolean execInFg) throws RemoteException {
    ...
    bumpServiceExecutingLocked(r, execInFg, "create");
    app.thread.scheduleCreateService(r, r.serviceInfo,
                    mAm.compatibilityInfoForPackageLocked(r.serviceInfo.applicationInfo),
                    app.repProcState);
     ...
}

4、来到ActivityThread.java类

public final void scheduleCreateService(IBinder token,
                ServiceInfo info, CompatibilityInfo compatInfo, int processState) {
            updateProcessState(processState, false);
            CreateServiceData s = new CreateServiceData();
            s.token = token;
            s.info = info;
            s.compatInfo = compatInfo;

            sendMessage(H.CREATE_SERVICE, s);
        }
 public void handleMessage(Message msg) {
            if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + codeToString(msg.what));
            switch (msg.what) {
                case CREATE_SERVICE:
                    Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, ("serviceCreate: " + String.valueOf(msg.obj)));
                    handleCreateService((CreateServiceData)msg.obj);
                    Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                    break;
}

创建上下文
回调onCreate
private void handleCreateService(CreateServiceData data) {
    ...
    ContextImpl context = ContextImpl.createAppContext(this, packageInfo);
            context.setOuterContext(service);

            Application app = packageInfo.makeApplication(false, mInstrumentation);
            service.attach(context, this, data.info.name, data.token, app,
                    ActivityManager.getService());
            service.onCreate();
    ...
}

至此服务就启动了

ANR

1、在ActivityServices.java中，调用了

private final void realStartServiceLocked(ServiceRecord r,
            ProcessRecord app, boolean execInFg) throws RemoteException {
    ...
    发了一个延迟消息
    bumpServiceExecutingLocked(r, execInFg, "create");
    app.thread.scheduleCreateService(r, r.serviceInfo,
                    mAm.compatibilityInfoForPackageLocked(r.serviceInfo.applicationInfo),
                    app.repProcState);
     ...
}

 private final void bumpServiceExecutingLocked(ServiceRecord r, boolean fg, String why) {
        ...
        long now = SystemClock.uptimeMillis();
        if (r.executeNesting == 0) {
            r.executeFg = fg;
            ServiceState stracker = r.getTracker();
            ...
            if (r.app != null) {
                r.app.executingServices.add(r);
                r.app.execServicesFg |= fg;
                if (r.app.executingServices.size() == 1) {
                    scheduleServiceTimeoutLocked(r.app);
                }
            }
        } else if (r.app != null && fg && !r.app.execServicesFg) {
            r.app.execServicesFg = true;
            scheduleServiceTimeoutLocked(r.app);
        }
         ...
    }

2、给AMS发了一个SERVICE_TIMEOUT延迟消息

 void scheduleServiceTimeoutLocked(ProcessRecord proc) {
        if (proc.executingServices.size() == 0 || proc.thread == null) {
            return;
        }
        Message msg = mAm.mHandler.obtainMessage(
                ActivityManagerService.SERVICE_TIMEOUT_MSG);
        msg.obj = proc;
       mAm是ActivityManagerService类型
        mAm.mHandler.sendMessageDelayed(msg,
                proc.execServicesFg ? SERVICE_TIMEOUT : SERVICE_BACKGROUND_TIMEOUT);
    }

3、在ActivityManagerService类中处理消息

public void handleMessage(Message msg) {
            switch (msg.what) {
            ...
            case SERVICE_TIMEOUT_MSG: {
               mServices是ActiveServices类型
                mServices.serviceTimeout((ProcessRecord)msg.obj);
            } break;
}

4、我们回到ActiveServices类

void serviceTimeout(ProcessRecord proc) {
   ...
   if (anrMessage != null) {
            mAm.mAppErrors.appNotResponding(proc, null, null, false, anrMessage);
        }
}

5、来到了AppErrors类

final void appNotResponding(ProcessRecord app, ActivityRecord activity,
            ActivityRecord parent, boolean aboveSystem, final String annotation) {
     dump anr信息
      File tracesFile = ActivityManagerService.dumpStackTraces(
                true, firstPids,
                (isSilentANR) ? null : processCpuTracker,
                (isSilentANR) ? null : lastPids,
                nativePids);
      展示anr信息
     makeAppNotRespondingLocked(app,
                    activity != null ? activity.shortComponentName : null,
                    annotation != null ? "ANR " + annotation : "ANR",
                    info.toString());

            // Bring up the infamous App Not Responding dialog
            Message msg = Message.obtain();
            HashMap<String, Object> map = new HashMap<String, Object>();
            msg.what = ActivityManagerService.SHOW_NOT_RESPONDING_UI_MSG;
            msg.obj = map;
            msg.arg1 = aboveSystem ? 1 : 0;
            map.put("app", app);
            if (activity != null) {
                map.put("activity", activity);
            }

            mService.mUiHandler.sendMessage(msg);
}

6、回到ActivityManagerService类的UiHandler

final class UiHandler extends Handler {
        public UiHandler() {
            super(com.android.server.UiThread.get().getLooper(), null, true);
        }

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
           ...
            case SHOW_NOT_RESPONDING_UI_MSG: {
                mAppErrors.handleShowAnrUi(msg);
                ensureBootCompleted();
            }
}

7、最后在AppErrors类生成一个Dialog显示anr信息

void handleShowAnrUi(Message msg) {
        Dialog d = null;
      
        ...
        if (mService.canShowErrorDialogs() || showBackground) {
                d = new AppNotRespondingDialog(mService,
                        mContext, proc, (ActivityRecord)data.get("activity"),
                        msg.arg1 != 0);
                proc.anrDialog = d;
            ...
        }
        // If we've created a crash dialog, show it without the lock held
        if (d != null) {
            d.show();
        }
    }