startService 的啟動流程
阿新 • • 發佈：2018-12-19
1. 在 Activity 啟動 Service 開始階段 都是 走 startService方法 ，裡面的mBase 是 在Activity 建立 過程中 利用 attach 傳入的 ContextImpl
@Override
public ComponentName startService(Intent service) {
return mBase.startService(service);
}2. ContextImpl 最終 呼叫 startServiceCommon 在內部主要 程式碼 ActivityManagerNative.getDefault().startService（），利用Bindle遠端呼叫 ActivityManagerService 得 startService 方法 。
@Override public ComponentName startService(Intent service) { warnIfCallingFromSystemProcess(); return startServiceCommon(service, mUser); } private ComponentName startServiceCommon(Intent service, UserHandle user) { try { validateServiceIntent(service); service.prepareToLeaveProcess(); ComponentName cn = ActivityManagerNative.getDefault().startService( mMainThread.getApplicationThread(), service, service.resolveTypeIfNeeded(getContentResolver()), user.getIdentifier()); if (cn != null) { if (cn.getPackageName().equals("!")) { throw new SecurityException( "Not allowed to start service " + service + " without permission " + cn.getClassName()); } else if (cn.getPackageName().equals("!!")) { throw new SecurityException( "Unable to start service " + service + ": " + cn.getClassName()); } } return cn; } catch (RemoteException e) { return null; } }
3. ActivityManagerService.startService
- enforceNotIsolatedCaller 校驗當前android 版本 。如果 當前版本大於 21等於 （android 5.0）則不能 隱式開啟否則會報錯。
- mServices.startServiceLocked 呼叫 ActivityService 開啟 Service。ActivityService是管理開啟Service的類。
@Override public ComponentName startService(IApplicationThread caller, Intent service, String resolvedType, int userId) { //開啟校驗 android 5.0及以上不能隱式 開啟 Service enforceNotIsolatedCaller("startService"); // Refuse possible leaked file descriptors if (service != null && service.hasFileDescriptors() == true) { throw new IllegalArgumentException("File descriptors passed in Intent"); } if (DEBUG_SERVICE) Slog.v(TAG, "startService: " + service + " type=" + resolvedType); synchronized(this) { final int callingPid = Binder.getCallingPid(); final int callingUid = Binder.getCallingUid(); final long origId = Binder.clearCallingIdentity(); ComponentName res = mServices.startServiceLocked(caller, service, resolvedType, callingPid, callingUid, userId); Binder.restoreCallingIdentity(origId); return res; } } private void validateServiceIntent(Intent service) { if (service.getComponent() == null && service.getPackage() == null) { if (getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.LOLLIPOP) { IllegalArgumentException ex = new IllegalArgumentException( "Service Intent must be explicit: " + service); throw ex; } else { Log.w(TAG, "Implicit intents with startService are not safe: " + service + " " + Debug.getCallers(2, 3)); } } }
4. ActiveServices .startServiceLocked
ComponentName startServiceLocked(IApplicationThread caller,
Intent service, String resolvedType,
int callingPid, int callingUid, int userId) {
if (DEBUG_DELAYED_STARTS) Slog.v(TAG, "startService: " + service
+ " type=" + resolvedType + " args=" + service.getExtras());
final boolean callerFg;
if (caller != null) {
//獲取程序記錄物件
final ProcessRecord callerApp = mAm.getRecordForAppLocked(caller);
if (callerApp == null) {
throw new SecurityException(
"Unable to find app for caller " + caller
+ " (pid=" + Binder.getCallingPid()
+ ") when starting service " + service);
}
callerFg = callerApp.setSchedGroup != Process.THREAD_GROUP_BG_NONINTERACTIVE;
} else {
callerFg = true;
}
//獲取 Service 的資訊
ServiceLookupResult res =
retrieveServiceLocked(service, resolvedType,
callingPid, callingUid, userId, true, callerFg);
if (res == null) {
return null;
}
if (res.record == null) {
return new ComponentName("!", res.permission != null
? res.permission : "private to package");
}
ServiceRecord r = res.record;
if (!mAm.getUserManagerLocked().exists(r.userId)) {
Slog.d(TAG, "Trying to start service with non-existent user! " + r.userId);
return null;
}
NeededUriGrants neededGrants = mAm.checkGrantUriPermissionFromIntentLocked(
callingUid, r.packageName, service, service.getFlags(), null, r.userId);
if (unscheduleServiceRestartLocked(r, callingUid, false)) {
if (DEBUG_SERVICE) Slog.v(TAG, "START SERVICE WHILE RESTART PENDING: " + r);
}
r.lastActivity = SystemClock.uptimeMillis();
// r.startRequested = true; 標記 此次開啟 是StratService 。bindService如果是會記//錄在 mServiceConnections 集合內部
r.startRequested = true;
r.delayedStop = false;
r.pendingStarts.add(new ServiceRecord.StartItem(r, false, r.makeNextStartId(),
service, neededGrants));
final ServiceMap smap = getServiceMap(r.userId);
boolean addToStarting = false;
............更多程式碼
return startServiceInnerLocked(smap, service, r, callerFg, addToStarting);
}5. startServiceInnerLocked
- bringUpServiceLocked 真正開啟流程，返回結果 error
- 如果 error 不是 null 代表失敗了
ComponentName startServiceInnerLocked(ServiceMap smap, Intent service,
ServiceRecord r, boolean callerFg, boolean addToStarting) {
ProcessStats.ServiceState stracker = r.getTracker();
if (stracker != null) {
stracker.setStarted(true, mAm.mProcessStats.getMemFactorLocked(), r.lastActivity);
}
r.callStart = false;
synchronized (r.stats.getBatteryStats()) {
r.stats.startRunningLocked();
}
String error = bringUpServiceLocked(r, service.getFlags(), callerFg, false);
if (error != null) {
return new ComponentName("!!", error);
}
if (r.startRequested && addToStarting) {
boolean first = smap.mStartingBackground.size() == 0;
smap.mStartingBackground.add(r);
r.startingBgTimeout = SystemClock.uptimeMillis() + BG_START_TIMEOUT;
if (DEBUG_DELAYED_SERVICE) {
RuntimeException here = new RuntimeException("here");
here.fillInStackTrace();
Slog.v(TAG, "Starting background (first=" + first + "): " + r, here);
} else if (DEBUG_DELAYED_STARTS) {
Slog.v(TAG, "Starting background (first=" + first + "): " + r);
}
if (first) {
smap.rescheduleDelayedStarts();
}
} else if (callerFg) {
smap.ensureNotStartingBackground(r);
}
return r.name;
}
6 bringUpServiceLocked
- 判斷Service是否已經建立，如已建立 則呼叫 sendServiceArgsLocked 去呼叫Service的
onStartCommand。避免一個程序重複建立開啟同一個Service
- 將 ServiceRecord 從 啟動計劃內移除
- realStartServiceLocked進入 建立Service的流程
- 7如果沒有相對應的程序，則將要記錄的操作記錄起來。先建立程序等建立完程序再執行啟動Service的操作
private final String bringUpServiceLocked(ServiceRecord r,
int intentFlags, boolean execInFg, boolean whileRestarting) {
//Slog.i(TAG, "Bring up service:");
//r.dump(" ");
如果 ServiceRecord 內包含 ActivityThread資訊，IapplicationInfo證明Service 已經開啟過了就不需要建立了，直接根據情況呼叫onStartCommand
if (r.app != null && r.app.thread != null) {
sendServiceArgsLocked(r, execInFg, false);
return null;
}
if (!whileRestarting && r.restartDelay > 0) {
// If waiting for a restart, then do nothing.
return null;
}
if (DEBUG_SERVICE) Slog.v(TAG, "Bringing up " + r + " " + r.intent);
// We are now bringing the service up, so no longer in the
// restarting state.
// 從 計劃在崩潰後重新啟動的服務列表內移除
if (mRestartingServices.remove(r)) {
clearRestartingIfNeededLocked(r);
}
// Make sure this service is no longer considered delayed, we are starting it now.
//從延時陣列內移除
if (r.delayed) {
if (DEBUG_DELAYED_STARTS) Slog.v(TAG, "REM FR DELAY LIST (bring up): " + r);
getServiceMap(r.userId).mDelayedStartList.remove(r);
r.delayed = false;
}
// Make sure that the user who owns this service is started. If not,
// we don't want to allow it to run.
//
if (mAm.mStartedUsers.get(r.userId) == null) {
String msg = "Unable to launch app "
+ r.appInfo.packageName + "/"
+ r.appInfo.uid + " for service "
+ r.intent.getIntent() + ": user " + r.userId + " is stopped";
Slog.w(TAG, msg);
bringDownServiceLocked(r);
return msg;
}
// Service is now being launched, its package can't be stopped.
try {
AppGlobals.getPackageManager().setPackageStoppedState(
r.packageName, false, r.userId);
} catch (RemoteException e) {
} catch (IllegalArgumentException e) {
Slog.w(TAG, "Failed trying to unstop package "
+ r.packageName + ": " + e);
}
final boolean isolated = (r.serviceInfo.flags&ServiceInfo.FLAG_ISOLATED_PROCESS) != 0;
final String procName = r.processName;
ProcessRecord app;
if (!isolated) {
app = mAm.getProcessRecordLocked(procName, r.appInfo.uid, false);
if (DEBUG_MU) Slog.v(TAG_MU, "bringUpServiceLocked: appInfo.uid=" + r.appInfo.uid
+ " app=" + app);
if (app != null && app.thread != null) {
try {
app.addPackage(r.appInfo.packageName, r.appInfo.versionCode, mAm.mProcessStats);
realStartServiceLocked(r, app, execInFg);
return null;
} catch (RemoteException e) {
Slog.w(TAG, "Exception when starting service " + r.shortName, e);
}
// If a dead object exception was thrown -- fall through to
// restart the application.
}
} else {
// If this service runs in an isolated process, then each time
// we call startProcessLocked() we will get a new isolated
// process, starting another process if we are currently waiting
// for a previous process to come up. To deal with this, we store
// in the service any current isolated process it is running in or
// waiting to have come up.
app = r.isolatedProc;
}
// Not running -- get it started, and enqueue this service record
// to be executed when the app comes up.
//沒有相對應的程序 則記錄要執行的Service 等待再次開啟程序是執行
if (app == null) {
if ((app=mAm.startProcessLocked(procName, r.appInfo, true, intentFlags,
"service", 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;
}
if (isolated) {
r.isolatedProc = app;
}
}
//記錄 要等待的執行的Service 服務
if (!mPendingServices.contains(r)) {
mPendingServices.add(r);
}
if (r.delayedStop) {
// Oh and hey we've already been asked to stop!
r.delayedStop = false;
if (r.startRequested) {
if (DEBUG_DELAYED_STARTS) Slog.v(TAG, "Applying delayed stop (in bring up): " + r);
stopServiceLocked(r);
}
}
return null;
}7. realStartServiceLocked
- 利用bind跨程序呼叫AppicationThread 的 scheduleCreateService 穿件Service
- 利用bind跨程序呼叫AppicationThread 進行 onbind 和
onStartCommand操作
private final void realStartServiceLocked(ServiceRecord r,
ProcessRecord app, boolean execInFg) throws RemoteException {
......
try {
if (LOG_SERVICE_START_STOP) {
String nameTerm;
int lastPeriod = r.shortName.lastIndexOf('.');
nameTerm = lastPeriod >= 0 ? r.shortName.substring(lastPeriod) : r.shortName;
EventLogTags.writeAmCreateService(
r.userId, System.identityHashCode(r), nameTerm, r.app.uid, r.app.pid);
}
synchronized (r.stats.getBatteryStats()) {
r.stats.startLaunchedLocked();
}
mAm.ensurePackageDexOpt(r.serviceInfo.packageName);
app.forceProcessStateUpTo(ActivityManager.PROCESS_STATE_SERVICE);
//利用bind機制回撥ActivityThread 建立 Service
app.thread.scheduleCreateService(r, r.serviceInfo,
mAm.compatibilityInfoForPackageLocked(r.serviceInfo.applicationInfo),
app.repProcState);
r.postNotification();
created = true;
} catch (DeadObjectException e) {
Slog.w(TAG, "Application dead when creating service " + r);
mAm.appDiedLocked(app);
} finally {
if (!created) {
app.services.remove(r);
r.app = null;
scheduleServiceRestartLocked(r, false);
return;
}
}
//遠端進行bind操作
requestServiceBindingsLocked(r, execInFg);
updateServiceClientActivitiesLocked(app, null, true);
// If the service is in the started state, and there are no
// pending arguments, then fake up one so its onStartCommand() will
// be called.
if (r.startRequested && r.callStart && r.pendingStarts.size() == 0) {
r.pendingStarts.add(new ServiceRecord.StartItem(r, false, r.makeNextStartId(),
null, null));
}
//遠端呼叫onStartCommand
sendServiceArgsLocked(r, execInFg, true);
.......
}
8. app.thread.scheduleCreateService
其實是呼叫ActivityThread 內部類 AppicationThread 的 scheduleCreateService方法，最後呼叫 ActivityThread 的 handleCreateService方法 建立Service
private void handleCreateService(CreateServiceData data) {
// If we are getting ready to gc after going to the background, well
// we are back active so skip it.
unscheduleGcIdler();
LoadedApk packageInfo = getPackageInfoNoCheck(
data.info.applicationInfo, data.compatInfo);
Service service = null;
try {
//利用 PathClassLoad 反射獲取
java.lang.ClassLoader cl = packageInfo.getClassLoader();
service = (Service) cl.loadClass(data.info.name).newInstance();
} catch (Exception e) {
if (!mInstrumentation.onException(service, e)) {
throw new RuntimeException(
"Unable to instantiate service " + data.info.name
+ ": " + e.toString(), e);
}
}
try {
if (localLOGV) Slog.v(TAG, "Creating service " + data.info.name);
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,
ActivityManagerNative.getDefault());
service.onCreate();
mServices.put(data.token, service);
try {
ActivityManagerNative.getDefault().serviceDoneExecuting(
data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
} catch (RemoteException e) {
// nothing to do.
}
} catch (Exception e) {
if (!mInstrumentation.onException(service, e)) {
throw new RuntimeException(
"Unable to create service " + data.info.name
+ ": " + e.toString(), e);
}
}
}9. sendServiceArgsLocked
- 利用Bind遠端 呼叫ApplictionThread 的 scheduleServiceArgs
- 再通過Handler 呼叫到 ActivityThread handleServiceArgs方法內
- 呼叫Service 的 onStartCommand 方法
-
private void handleServiceArgs(ServiceArgsData data) { Service s = mServices.get(data.token); if (s != null) { try { if (data.args != null) { data.args.setExtrasClassLoader(s.getClassLoader()); data.args.prepareToEnterProcess(); } int res; if (!data.taskRemoved) { //呼叫 Service onStartCommand res = s.onStartCommand(data.args, data.flags, data.startId); } else { s.onTaskRemoved(data.args); res = Service.START_TASK_REMOVED_COMPLETE; } QueuedWork.waitToFinish(); try { ActivityManagerNative.getDefault().serviceDoneExecuting( data.token, SERVICE_DONE_EXECUTING_START, data.startId, res); } catch (RemoteException e) { // nothing to do. } ensureJitEnabled(); } catch (Exception e) { if (!mInstrumentation.onException(s, e)) { throw new RuntimeException( "Unable to start service " + s + " with " + data.args + ": " + e.toString(), e); } } } }