一、startService源码启动流程
（1）启动流程是从ContextWraper的startService方法开始的
- ActivityManager.getService()是IActivityManager的代理对象，调用代理对象的startService方法，会向系统服务ActivityManagerService发起请求，基于Binder机制，调用ActivityManagerService的startService方法。
@Override
public ComponentName startService(Intent service) {
return mBase.startService(service);
}
//ContextImpl.java
@Override
public ComponentName startService(Intent service) {
warnIfCallingFromSystemProcess();
return startServiceCommon(service, false, mUser);
}
private ComponentName startServiceCommon(Intent service, boolean requireForeground, UserHandle user) {
try {
validateServiceIntent(service);
service.prepareToLeaveProcess(this);
//注释
ComponentName cn = ActivityManager.getService().startService(
mMainThread.getApplicationThread(), service, service.resolveTypeIfNeeded(
getContentResolver()), requireForeground,
getOpPackageName(), user.getIdentifier());
//code...
return cn;
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
（2）查看ActivityManagerService.startService源码
- mServices的类型是ActiveServices，管理Service类的启动、绑定和销毁等。调用ActiveServices.startServiceLocked()执行启动操作。
@Override
public ComponentName startService(IApplicationThread caller, Intent service,
String resolvedType, boolean requireForeground, String callingPackage, int userId)
throws TransactionTooLargeException {
enforceNotIsolatedCaller("startService");
//code...
synchronized(this) {
final int callingPid = Binder.getCallingPid();
final int callingUid = Binder.getCallingUid();
final long origId = Binder.clearCallingIdentity();
ComponentName res;
try {
//注释
res = mServices.startServiceLocked(caller, service,
resolvedType, callingPid, callingUid,
requireForeground, callingPackage, userId);
} finally {
Binder.restoreCallingIdentity(origId);
}
return res;
}
}
- 查看ActiveServices.startServiceLocked源码
ComponentName startServiceLocked(IApplicationThread caller, Intent service, String resolvedType,
int callingPid, int callingUid, boolean fgRequired, String callingPackage, final int userId)
throws TransactionTooLargeException {
//coed...
ComponentName cmp = startServiceInnerLocked(smap, service, r, callerFg, addToStarting);
return cmp;
}
ComponentName startServiceInnerLocked(ServiceMap smap, Intent service, ServiceRecord r,
boolean callerFg, boolean addToStarting) throws TransactionTooLargeException {
//code...
String error = bringUpServiceLocked(r, service.getFlags(), callerFg, false, false);
//code...
return r.name;
}
- 查看bringUpServiceLocked源码
- 如果service所在进程已经存在，则通过realStartServiceLocked方法启动Service。
- 如果service所在进程未启动，则通过startProcessLocked创建。
private String bringUpServiceLocked(ServiceRecord r, int intentFlags, boolean execInFg,
boolean whileRestarting, boolean permissionsReviewRequired)
throws TransactionTooLargeException {
//code...
if (!isolated) {
app = mAm.getProcessRecordLocked(procName, r.appInfo.uid, false);
if (app != null && app.thread != null) {
try {
app.addPackage(r.appInfo.packageName, r.appInfo.longVersionCode, mAm.mProcessStats);
//注释
realStartServiceLocked(r, app, execInFg);
return null;
} catch (TransactionTooLargeException e) {
throw e;
} catch (RemoteException e) {
}
}
} else {
app = r.isolatedProc;
if (WebViewZygote.isMultiprocessEnabled()
&& r.serviceInfo.packageName.equals(WebViewZygote.getPackageName())) {
hostingType = "webview_service";
}
}
//注释
if (app == null && !permissionsReviewRequired) {
if ((app=mAm.startProcessLocked(procName, r.appInfo, true, intentFlags,
hostingType, r.name, false, isolated, false)) == null) {
bringDownServiceLocked(r);
return msg;
}
if (isolated) {
r.isolatedProc = app;
}
}
//code...
return null;
}
- 查看realStartServiceLocked源码
- 通过aidl的调用调用ApplicationThread中scheduleCreateService创建service
- 如果设置更新通知栏，进行通知栏的更新
private final void realStartServiceLocked(ServiceRecord r,
ProcessRecord app, boolean execInFg) throws RemoteException {
//code...
//注释
app.thread.scheduleCreateService(r, r.serviceInfo,
mAm.compatibilityInfoForPackageLocked(r.serviceInfo.applicationInfo),
app.repProcState);
//注释
r.postNotification();
//code..
}
（3）查看ApplicationThread.scheduleCreateService源码
- 发送消息到ActivityThread内部类H中
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;
//注释
sendMessage(H.CREATE_SERVICE, s);
}
- 查看H中handleMessage方法
- 在handleMessage中接收消息并调用handleCreateService方法启动服务
- 启动Service回调attach和onCreate方法
public void handleMessage(Message msg) {
switch (msg.what) {
//code...
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;
}
Object obj = msg.obj;
if (obj instanceof SomeArgs) {
((SomeArgs) obj).recycle();
}
}
}
private void handleCreateService(CreateServiceData data) {
unscheduleGcIdler();
//code...
try {
ContextImpl context = ContextImpl.createAppContext(this, packageInfo);
context.setOuterContext(service);
Application app = packageInfo.makeApplication(false, mInstrumentation);
//注释
service.attach(context, this, data.info.name, data.token, app,
ActivityManager.getService());
service.onCreate();
mServices.put(data.token, service);
try {
ActivityManager.getService().serviceDoneExecuting(
data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
//code...
}
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