Android?Service啟動(dòng)綁定流程詳解
更新時(shí)間：2023年03月08日 14:50:41 作者：新小夢
這篇文章主要為大家介紹了Android?Service啟動(dòng)綁定流程詳解，有需要的朋友可以借鑒參考下，希望能夠有所幫助，祝大家多多進(jìn)步，早日升職加薪
前言
本文基于Android 11，參考《Android進(jìn)階解密》一書資料。了解Service的啟動(dòng)和綁定流程，以及Service的Context創(chuàng)建過程。
由于基于分析流程，忽略很多細(xì)節(jié)分支。各位在看源碼的時(shí)候，要盡可能忽略細(xì)節(jié)，分析整體流程之后，還有精力的話再去看細(xì)節(jié)。例如有些屬性是在后面賦值的，如果在前面追究，難哦。
另：閱讀這種流程需要很大的耐心和毅力。建議在心情愉悅想要學(xué)習(xí)的時(shí)候搭配源碼一起食用。
一、Service 的啟動(dòng)流程
1、ContextImpl.startService
啟動(dòng)一個(gè)Service，通常在Activity調(diào)用startService來啟動(dòng)。
@Override
public ComponentName startService(Intent service) {
return startServiceCommon(service, false, mUser);
}
2、ContextImpl.startServiceCommon
startServiceCommon檢查intent內(nèi)容是否合法，然后做一些離開當(dāng)前進(jìn)程的準(zhǔn)備操作。調(diào)用 ActivityManager.getService()獲得AMS的本地引用，并調(diào)用其startService函數(shù)。
也就是說通過Binder機(jī)制跨進(jìn)程通信調(diào)用了AMS的startService函數(shù)。
private ComponentName startServiceCommon(Intent service, boolean requireForeground,
UserHandle user) {
try {
//檢查intent 的compant和package是否合法
validateServiceIntent(service);
...
ComponentName cn = ActivityManager.getService().startService(
mMainThread.getApplicationThread(), service,
service.resolveTypeIfNeeded(getContentResolver()), requireForeground,
getOpPackageName(), getAttributionTag(), user.getIdentifier());
...
return cn;
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
通過 ActivityManager.getService()的實(shí)現(xiàn)。
@UnsupportedAppUsage
public static IActivityManager getService() {
return IActivityManagerSingleton.get();
}
@UnsupportedAppUsage
private static final Singleton<IActivityManager> IActivityManagerSingleton =
new Singleton<IActivityManager>() {
@Override
protected IActivityManager create() {
final IBinder b = ServiceManager.getService(Context.ACTIVITY_SERVICE);
final IActivityManager am = IActivityManager.Stub.asInterface(b);
return am;
}
};
3、AMS.startService
AMS.startService函數(shù)獲取調(diào)用Pid和Uid,然后調(diào)用ActiveService的startServiceLocked函數(shù)。
@Override
public ComponentName startService(IApplicationThread caller, Intent service,
String resolvedType, boolean requireForeground, String callingPackage,
String callingFeatureId, int userId)
throws TransactionTooLargeException {
...
synchronized(this) {
final int callingPid = Binder.getCallingPid();
final int callingUid = Binder.getCallingUid();
final long origId = Binder.clearCallingIdentity();
ComponentName res;
try {
res = mServices.startServiceLocked(caller, service,
resolvedType, callingPid, callingUid,
requireForeground, callingPackage, callingFeatureId, userId);
} finally {
Binder.restoreCallingIdentity(origId);
}
return res;
}
}
4、ActiveService.startServiceLock
ActiveService.startServiceLock函數(shù)，對一些合法性的檢查，例如前臺(tái)Service的權(quán)限、限制性后臺(tái)Service進(jìn)行延遲運(yùn)行（standby）。并將要啟動(dòng)的信息封裝成ServiceRecord。然后調(diào)用了startServiceInnerLocked函數(shù)。
ComponentName startServiceLocked(IApplicationThread caller, Intent service, String resolvedType,
int callingPid, int callingUid, boolean fgRequired, String callingPackage,
@Nullable String callingFeatureId, final int userId)
throws TransactionTooLargeException {
return startServiceLocked(caller, service, resolvedType, callingPid, callingUid, fgRequired,
callingPackage, callingFeatureId, userId, false);
}
ComponentName startServiceLocked(IApplicationThread caller, Intent service, String resolvedType,
int callingPid, int callingUid, boolean fgRequired, String callingPackage,
@Nullable String callingFeatureId, final int userId,
boolean allowBackgroundActivityStarts) throws TransactionTooLargeException {
final boolean callerFg;
if (caller != null) {
//獲取調(diào)用Service的應(yīng)用程序進(jìn)程描述
final ProcessRecord callerApp = mAm.getRecordForAppLocked(caller);
if (callerApp == null) {
...
}
callerFg = callerApp.setSchedGroup != ProcessList.SCHED_GROUP_BACKGROUND;
} else {
callerFg = true;
}
//檢索ServiceRecord,包括同應(yīng)用和其他應(yīng)用
ServiceLookupResult res =
retrieveServiceLocked(service, null, resolvedType, callingPackage,
callingPid, callingUid, userId, true, callerFg, false, false);
...
//要啟動(dòng)的ServiceRecord
ServiceRecord r = res.record;
...
r.lastActivity = SystemClock.uptimeMillis();
r.startRequested = true;
r.delayedStop = false;
r.fgRequired = fgRequired;
r.pendingStarts.add(new ServiceRecord.StartItem(r, false, r.makeNextStartId(),
service, neededGrants, callingUid));
ComponentName cmp = startServiceInnerLocked(smap, service, r, callerFg, addToStarting);
...
return cmp;
}
5、ActiveServices.startServiceInnerLocker
調(diào)用了bringUpServiceLocked函數(shù),會(huì)將ServiceRecord添加到ServiceMap類型的smap集合，進(jìn)行緩存。
ComponentName startServiceInnerLocked(ServiceMap smap, Intent service, ServiceRecord r,
boolean callerFg, boolean addToStarting) throws TransactionTooLargeException {
r.callStart = false;
...
String error = bringUpServiceLocked(r, service.getFlags(), callerFg, false, false);
...
return r.name;
}
6、 ActiveService.bringUpServiceLocked
分析一：首次啟動(dòng)Service時(shí)，在執(zhí)行bringUpServiceLocked函數(shù)，ServiceRecord是屬于新創(chuàng)建的,而非從AMS的緩存mServices中檢索而來，所以此時(shí)的ServiceRecord的ProcessRecord類型app和IApplicationThread類型thread都是null。只有啟動(dòng)過后的ServiceRecord才有值，才會(huì)執(zhí)行sendServiceArgsLocked函數(shù)，重復(fù)調(diào)用Service的生命周期onStartCommand,而不調(diào)用onCreate函數(shù)。
private String bringUpServiceLocked(ServiceRecord r, int intentFlags, boolean execInFg,
boolean whileRestarting, boolean permissionsReviewRequired)
throws TransactionTooLargeException {
//分析一：未啟動(dòng)過的ServiceRecord兩者都是null，重復(fù)啟動(dòng)會(huì)執(zhí)行該函數(shù)，
//會(huì)重復(fù)調(diào)用service的onStartCommand函數(shù)。
if (r.app != null && r.app.thread != null) {
sendServiceArgsLocked(r, execInFg, false);
return null;
}
...
final boolean isolated = (r.serviceInfo.flags&ServiceInfo.FLAG_ISOLATED_PROCESS) != 0;
final String procName = r.processName;
HostingRecord hostingRecord = new HostingRecord("service", r.instanceName);
ProcessRecord app;
if (!isolated) {
////通過AMS獲取service所在進(jìn)程的ProcessRecord。ProcessList=>MyProcessMap=》會(huì)緩存已創(chuàng)建過進(jìn)程的ProcessRecord
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);
//啟動(dòng)服務(wù)
realStartServiceLocked(r, app, execInFg);
return null;
} catch (TransactionTooLargeException e) {
throw e;
} catch (RemoteException e) {
Slog.w(TAG, "Exception when starting service " + r.shortInstanceName, e);
}
}
}
//如果service所在的進(jìn)程未啟動(dòng)，通過AMS啟動(dòng)該進(jìn)程，可以參考應(yīng)用進(jìn)程的啟動(dòng)流程
if (app == null && !permissionsReviewRequired) {
if ((app=mAm.startProcessLocked(procName, r.appInfo, true, intentFlags,
hostingRecord, ZYGOTE_POLICY_FLAG_EMPTY, false, isolated, false)) == null) {;
bringDownServiceLocked(r);
return msg;
}
if (isolated) {
r.isolatedProc = app;
}
}
//等待進(jìn)程啟動(dòng)完畢重啟啟動(dòng)
if (!mPendingServices.contains(r)) {
mPendingServices.add(r);
}
...
return null;
}
7、ActiveService.realStartServiceLocked
private final void realStartServiceLocked(ServiceRecord r,
ProcessRecord app, boolean execInFg) throws RemoteException {
//將ProcessRecord設(shè)置給ServiceRecord
r.setProcess(app);
//登記當(dāng)ServiceRecord到ProcessRecordd的數(shù)組mServices，表示Service已經(jīng)啟動(dòng)（實(shí)際未啟動(dòng)）
final boolean newService = app.startService(r);
boolean created = false;
try {
...
app.thread.scheduleCreateService(r, r.serviceInfo,
mAm.compatibilityInfoForPackage(r.serviceInfo.applicationInfo),
app.getReportedProcState());
...
} catch (DeadObjectException e) {
Slog.w(TAG, "Application dead when creating service " + r);
mAm.appDiedLocked(app, "Died when creating service");
throw e;
}
//會(huì)調(diào)用Service的onStartCommand函數(shù)
sendServiceArgsLocked(r, execInFg, true);
...
}
通過ProcessRecord對象的IApplicationThread引用，通過Binder機(jī)制調(diào)用了應(yīng)用程序的ApplicationThread的scheduleCreateService函數(shù)。
8、ApplicationThread.scheduleCreateService
將ServiceInfo等相關(guān)信息封裝到CreateServiceData中，并發(fā)送給ActivityThread的H類型的mH對象。
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);
}
9、H.handleMesssage
調(diào)用了ActivityThread的handleCreateService函數(shù)。
case CREATE_SERVICE:
handleCreateService((CreateServiceData)msg.obj);
break;
10、ActivityThread.handleCreateService
private void handleCreateService(CreateServiceData data) {
...
//獲取當(dāng)前應(yīng)用的描述信息LoadedApk
LoadedApk packageInfo = getPackageInfoNoCheck(
data.info.applicationInfo, data.compatInfo);
Service service = null;
try {
//創(chuàng)建Service的上下問文
ContextImpl context = ContextImpl.createAppContext(this, packageInfo);
//獲取當(dāng)前應(yīng)用Applcation對象
Application app = packageInfo.makeApplication(false, mInstrumentation);
//通過反射創(chuàng)建Service對象
java.lang.ClassLoader cl = packageInfo.getClassLoader();
service = packageInfo.getAppFactory()
.instantiateService(cl, data.info.name, data.intent);
//初始化資源
context.getResources().addLoaders(
app.getResources().getLoaders().toArray(new ResourcesLoader[0]));
//context 與service相互綁定
context.setOuterContext(service);
service.attach(context, this, data.info.name, data.token, app,
ActivityManager.getService());
//調(diào)用Service的生命周期onCreate函數(shù)，意味Service創(chuàng)建完畢
service.onCreate();
//緩存Service
mServices.put(data.token, service);
try {
ActivityManager.getService().serviceDoneExecuting(
data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
} catch (Exception e) {
if (!mInstrumentation.onException(service, e)) {
throw new RuntimeException(
"Unable to create service " + data.info.name
+ ": " + e.toString(), e);
}
}
}
通過ContextImpl.createAppContext創(chuàng)建Service的上下文context，通過packageInfo.getAppFactory().instantiateService反射獲得當(dāng)前Service對象service，將context與service相互綁定。然后調(diào)用service.onCreate。至此，Service創(chuàng)建完畢。
二、Service的綁定
1、 ContextImpl.bindService
public boolean bindService(Intent service, ServiceConnection conn, int flags) {
//系統(tǒng)進(jìn)程調(diào)用綁定服務(wù)或發(fā)送廣播都會(huì)發(fā)出警告
warnIfCallingFromSystemProcess();
return bindServiceCommon(service, conn, flags, null, mMainThread.getHandler(), null,
getUser());
}
2、ContextImpl.bindServiceCommon
在分析一，主要判斷入?yún)?code>Executor executor或UserHandle user哪個(gè)為null，總有一個(gè)為null，但最終都是調(diào)用了LoadedApk的getServiceDispatcherCommon函數(shù)來獲取ServiceDispathcer類型sd。影響只是回調(diào)代碼是在主線程執(zhí)行，還是線程池。這里傳入ActivityThread的H對象，意味著后續(xù)連接成功回調(diào)onServiceConnected是在主線程。
分析二：通過Binder機(jī)制調(diào)用AMS的bindIsolatedService函數(shù)。
private boolean bindServiceCommon(Intent service, ServiceConnection conn, int flags,
String instanceName, Handler handler, Executor executor, UserHandle user) {
// Keep this in sync with DevicePolicyManager.bindDeviceAdminServiceAsUser.
IServiceConnection sd;
if (conn == null) {
throw new IllegalArgumentException("connection is null");
}
if (handler != null && executor != null) {
throw new IllegalArgumentException("Handler and Executor both supplied");
}
if (mPackageInfo != null) {
if (executor != null) {//分析一：無論哪個(gè)分支，都是獲得ServiceConnect的本地引用sd,兩者最終都是
//調(diào)用LoadedApk的getServiceDispatcherCommon
sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), executor, flags);
} else {
//正常使用走這個(gè)分支
sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), handler, flags);
}
} else {
throw new RuntimeException("Not supported in system context");
}
//檢查compant and package is null ?
validateServiceIntent(service);
try {
IBinder token = getActivityToken();
if (token == null && (flags&BIND_AUTO_CREATE) == 0 && mPackageInfo != null
&& mPackageInfo.getApplicationInfo().targetSdkVersion
< android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
flags |= BIND_WAIVE_PRIORITY;
}
service.prepareToLeaveProcess(this);
//分析二：調(diào)用AMS.bindIsolatedService
int res = ActivityManager.getService().bindIsolatedService(
mMainThread.getApplicationThread(), getActivityToken(), service,
service.resolveTypeIfNeeded(getContentResolver()),
sd, flags, instanceName, getOpPackageName(), user.getIdentifier());
if (res < 0) {
throw new SecurityException(
"Not allowed to bind to service " + service);
}
return res != 0;
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
IServiceConnection連接的創(chuàng)建會(huì)先從緩存中獲取，避免每次都要新建。分析一：通過executor或handler創(chuàng)建ServiceDispatcher類型的sd,含有靜態(tài)內(nèi)部類InnerConnection的引用mIServiceConnection。繼承自IServiceConnection.Stub，也就是InnerConnection是實(shí)現(xiàn)者，遠(yuǎn)程調(diào)用代理在其他進(jìn)程，例如SystemServer進(jìn)程中的ActiveService。
private IServiceConnection getServiceDispatcherCommon(ServiceConnection c,
Context context, Handler handler, Executor executor, int flags) {
synchronized (mServices) {
LoadedApk.ServiceDispatcher sd = null;
//從緩存獲取
ArrayMap<ServiceConnection, LoadedApk.ServiceDispatcher> map = mServices.get(context);
if (map != null) {
sd = map.get(c);
}
if (sd == null) {
//分析一：通過executor或handler創(chuàng)建ServiceDispatcher
if (executor != null) {
sd = new ServiceDispatcher(c, context, executor, flags);
} else {
sd = new ServiceDispatcher(c, context, handler, flags);
}
if (DEBUG) Slog.d(TAG, "Creating new dispatcher " + sd + " for conn " + c);
if (map == null) {
map = new ArrayMap<>();
mServices.put(context, map);
}
map.put(c, sd);
} else {
sd.validate(context, handler, executor);
}
return sd.getIServiceConnection();
}
}
3、AMS.bindIsolatedService
AMS經(jīng)過兩次重載函數(shù)bindIsolatedService調(diào)用，簡單檢查相關(guān)合法性。然后調(diào)用ActiveService類型的mService的bindServiceLocked函數(shù)。
4、ActiveService.bindServiceLocked
int bindServiceLocked(IApplicationThread caller, IBinder token, Intent service,
String resolvedType, final IServiceConnection connection, int flags,
String instanceName, String callingPackage, final int userId)
throws TransactionTooLargeException {
//發(fā)起綁定service的app進(jìn)程描述
final ProcessRecord callerApp = mAm.getRecordForAppLocked(caller);
...
ServiceLookupResult res =
retrieveServiceLocked(service, instanceName, resolvedType, callingPackage,
Binder.getCallingPid(), Binder.getCallingUid(), userId, true,
callerFg, isBindExternal, allowInstant);
...
ServiceRecord s = res.record;
...
//描述Service和應(yīng)用程序進(jìn)程之間的關(guān)聯(lián)，內(nèi)部維護(hù)Service、進(jìn)程、IntentFilter以及所有綁定信息。
AppBindRecord b = s.retrieveAppBindingLocked(service, callerApp);
//描述應(yīng)用程序與service建立的一次通信（綁定）
ConnectionRecord c = new ConnectionRecord(b, activity,
connection, flags, clientLabel, clientIntent,
callerApp.uid, callerApp.processName, callingPackage);
IBinder binder = connection.asBinder();
s.addConnection(binder, c);
b.connections.add(c);
if (activity != null) {
activity.addConnection(c);
}
b.client.connections.add(c);
c.startAssociationIfNeeded();
...
//啟動(dòng)Service，可以參考Service的啟動(dòng)
if ((flags&Context.BIND_AUTO_CREATE) != 0) {
s.lastActivity = SystemClock.uptimeMillis();
if (bringUpServiceLocked(s, service.getFlags(), callerFg, false,
permissionsReviewRequired) != null) {
return 0;
}
}
...
//表示Service已啟動(dòng)，且已返回binder,可以通過binder訪問接口
if (s.app != null && b.intent.received) {
// Service is already running, so we can immediately
// publish the connection.
try {
//建立連接
c.conn.connected(s.name, b.intent.binder, false);
} catch (Exception e) {
Slog.w(TAG, "Failure sending service " + s.shortInstanceName
+ " to connection " + c.conn.asBinder()
+ " (in " + c.binding.client.processName + ")", e);
}
//第一個(gè)綁定該Service的進(jìn)程，且要重綁
if (b.intent.apps.size() == 1 && b.intent.doRebind) {
requestServiceBindingLocked(s, b.intent, callerFg, true);
}
} else if (!b.intent.requested) {//首次綁定，執(zhí)行此次
requestServiceBindingLocked(s, b.intent, callerFg, false);
}
...
}
AppBindRecord 描述應(yīng)用程序進(jìn)程和Service的關(guān)聯(lián)，包括誰綁定了Service的ProcessRecord，綁定信息IntentBindRecord，當(dāng)前服務(wù)ServiceRecord，當(dāng)前應(yīng)用進(jìn)程的所有連接記錄connections。
5、requestServiceBindingLocked
調(diào)用了ApplicationThread的scheduleBindService函數(shù)。
private final boolean requestServiceBindingLocked(ServiceRecord r, IntentBindRecord i,
boolean execInFg, boolean rebind) throws TransactionTooLargeException {
...
r.app.thread.scheduleBindService(r, i.intent.getIntent(), rebind, r.app.getReportedProcState());
...
}
6、ApplicationThread.scheduleBindService
將數(shù)據(jù)封裝 BindServiceData，發(fā)送個(gè)ActivityThread的H類型的mH處理。
public final void scheduleBindService(IBinder token, Intent intent,
boolean rebind, int processState) {
updateProcessState(processState, false);
BindServiceData s = new BindServiceData();
s.token = token;
s.intent = intent;
s.rebind = rebind;
sendMessage(H.BIND_SERVICE, s);
}
7 、 H.handleMessage
case BIND_SERVICE:
handleBindService((BindServiceData)msg.obj);
8、ActivityThread.handleBindService
handleBindService函數(shù)有兩個(gè)分支，即是否重新綁定。
如果當(dāng)前進(jìn)程第一個(gè)與Service綁定，且調(diào)用過了onUbBinder方法，那么這里的data.rebind將為true,直接執(zhí)行Service的onRebind函數(shù)即可。另外一種就是沒有綁定過，那么需要執(zhí)行Service的onBind函數(shù)。然后還要執(zhí)行AMS的publishService函數(shù)。
private void handleBindService(BindServiceData data) {
Service s = mServices.get(data.token);
if (s != null) {
...
try {
if (!data.rebind) {
IBinder binder = s.onBind(data.intent);
ActivityManager.getService().publishService(
data.token, data.intent, binder);
} else {
s.onRebind(data.intent);
ActivityManager.getService().serviceDoneExecuting(
data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
}
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
...
}
}
9、AMS.publishService
public void publishService(IBinder token, Intent intent, IBinder service) {
// Refuse possible leaked file descriptors
if (intent != null && intent.hasFileDescriptors() == true) {
throw new IllegalArgumentException("File descriptors passed in Intent");
}
synchronized(this) {
if (!(token instanceof ServiceRecord)) {
throw new IllegalArgumentException("Invalid service token");
}
mServices.publishServiceLocked((ServiceRecord)token, intent, service);
}
}
10、ActiveService.publishServiceLocked
分析一：可見在第4步bindServiceLocked函數(shù)，IntentBindRecord對象的屬性binder、requested、received都是false。
在ServiceRecord的所有連接記錄connections中，通過intent查找對應(yīng)之前已經(jīng)保存的ConnectionRecord,并調(diào)用其IServiceConnection的connected函數(shù)。
在第2步的時(shí)候調(diào)用bindServiceCommon函數(shù)時(shí)，會(huì)創(chuàng)建ServiceDispatcher時(shí)，內(nèi)部持有InnerConnection實(shí)例，這里的IServiceConnection代理引用指向該InnerConnection實(shí)例,這里會(huì)調(diào)用其connected函數(shù)。
void publishServiceLocked(ServiceRecord r, Intent intent, IBinder service) {
final long origId = Binder.clearCallingIdentity();
try {
if (r != null) {
Intent.FilterComparison filter
= new Intent.FilterComparison(intent);
IntentBindRecord b = r.bindings.get(filter);
if (b != null && !b.received) {//分析1
b.binder = service;
b.requested = true;
b.received = true;
ArrayMap<IBinder, ArrayList<ConnectionRecord>> connections = r.getConnections();
for (int conni = connections.size() - 1; conni >= 0; conni--) {
ArrayList<ConnectionRecord> clist = connections.valueAt(conni);
for (int i=0; i<clist.size(); i++) {
ConnectionRecord c = clist.get(i);
if (!filter.equals(c.binding.intent.intent)) {
...
continue;
}
...
try {
c.conn.connected(r.name, service, false);
} catch (Exception e) {
Slog.w(TAG, "Failure sending service " + r.shortInstanceName
+ " to connection " + c.conn.asBinder()
+ " (in " + c.binding.client.processName + ")", e);
}
}
}
}
serviceDoneExecutingLocked(r, mDestroyingServices.contains(r), false);
}
} finally {
Binder.restoreCallingIdentity(origId);
}
}
11、InnerConnection.connected
private static class InnerConnection extends IServiceConnection.Stub {
@UnsupportedAppUsage
final WeakReference<LoadedApk.ServiceDispatcher> mDispatcher;
InnerConnection(LoadedApk.ServiceDispatcher sd) {
mDispatcher = new WeakReference<LoadedApk.ServiceDispatcher>(sd);
}
public void connected(ComponentName name, IBinder service, boolean dead)
throws RemoteException {
LoadedApk.ServiceDispatcher sd = mDispatcher.get();
if (sd != null) {
sd.connected(name, service, dead);
}
}
}
12、ServiceDispatcher.connected
這里調(diào)用了 mActivityThread.post(new RunConnection(name, service, 0, dead))，執(zhí)行RunConnection的run函數(shù)。這里的話run函數(shù)執(zhí)行代碼又回到了應(yīng)用進(jìn)程的主線程。
public void connected(ComponentName name, IBinder service, boolean dead) {
if (mActivityExecutor != null) {
mActivityExecutor.execute(new RunConnection(name, service, 0, dead));
} else if (mActivityThread != null) {
mActivityThread.post(new RunConnection(name, service, 0, dead));
} else {
doConnected(name, service, dead);
}
}
13、RunConnection.run
RunConnection是ServiceDispatcher的內(nèi)部類，這里執(zhí)行SD的doConnected函數(shù)。
public void run() {
if (mCommand == 0) {
doConnected(mName, mService, mDead);
} else if (mCommand == 1) {
doDeath(mName, mService);
}
}
14、ServiceDispatcher.doConnected
這里調(diào)用了ServiceConnection對象的onServiceConnected函數(shù)，也就是我們發(fā)起綁定，調(diào)用context.bindService的參數(shù)。
public void doConnected(ComponentName name, IBinder service, boolean dead) {
...
mConnection.onServiceConnected(name, service);
...
}
到此,Service的綁定流程分析完畢。
三、Service的Context
在第一節(jié)Service的啟動(dòng)流程最后函數(shù)調(diào)用了ActivityThread的handleCreateService函數(shù)。
private void handleCreateService(CreateServiceData data) {
unscheduleGcIdler();
//應(yīng)用的描述信息
LoadedApk packageInfo = getPackageInfoNoCheck(
data.info.applicationInfo, data.compatInfo);
Service service = null;
try {
//分析一
ContextImpl context = ContextImpl.createAppContext(this, packageInfo);
Application app = packageInfo.makeApplication(false, mInstrumentation);
java.lang.ClassLoader cl = packageInfo.getClassLoader();
service = packageInfo.getAppFactory()
.instantiateService(cl, data.info.name, data.intent);
context.getResources().addLoaders(
app.getResources().getLoaders().toArray(new ResourcesLoader[0]));
//分析二
context.setOuterContext(service);
//分析三
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();
}
} catch (Exception e) {
if (!mInstrumentation.onException(service, e)) {
throw new RuntimeException(
"Unable to create service " + data.info.name
+ ": " + e.toString(), e);
}
}
}
分析一：通過ContextImpl的靜態(tài)函數(shù)createAppContext返回了一個(gè)ContextImpl類型的context。createAppContext又調(diào)用了重載函數(shù)createAppContext。直接新建了ContextImpl實(shí)例context，構(gòu)造函數(shù)傳遞了ActivityThread類型的mainThread和LoadedApk類型的packageInfo。并給context設(shè)置了資源環(huán)境和是否Syetem屬性。
static ContextImpl createAppContext(ActivityThread mainThread, LoadedApk packageInfo) {
return createAppContext(mainThread, packageInfo, null);
}
static ContextImpl createAppContext(ActivityThread mainThread, LoadedApk packageInfo,
String opPackageName) {
if (packageInfo == null) throw new IllegalArgumentException("packageInfo");
ContextImpl context = new ContextImpl(null, mainThread, packageInfo, null, null, null, null,
0, null, opPackageName);
context.setResources(packageInfo.getResources());
context.mIsSystemOrSystemUiContext = isSystemOrSystemUI(context);
return context;
}
ContextImpl類有一個(gè)Context類型的mOuterContext屬性，在構(gòu)造函數(shù)時(shí)指向了自己。
回到handleCreateService函數(shù)的分析二，在創(chuàng)建好Service對象service之后，將service作為參數(shù)傳遞給了context.setOuterContext函數(shù)。Service本身繼承自ContextWrapper,ContextWrapper又是Context的子類。這時(shí)候的setOuterContext函數(shù)將service設(shè)置給了context的mOuterContext屬性。意味著當(dāng)前上下文context持有當(dāng)前新建的service引用。
在分析三，調(diào)用了service.attach函數(shù)，context并作為第一個(gè)參數(shù)被傳入。attach函數(shù)又調(diào)用了attachBaseContext函數(shù)。
public final void attach(
Context context,
ActivityThread thread, String className, IBinder token,
Application application, Object activityManager) {
attachBaseContext(context);
mThread = thread;
mClassName = className;
mToken = token;
mApplication = application;
mActivityManager = (IActivityManager)activityManager;
mStartCompatibility = getApplicationInfo().targetSdkVersion
< Build.VERSION_CODES.ECLAIR;
setContentCaptureOptions(application.getContentCaptureOptions());
}
attachBaseContext調(diào)用了父類ContextWrapper的attachBaseContext函數(shù)
@Override
protected void attachBaseContext(Context newBase) {
super.attachBaseContext(newBase);
if (newBase != null) {
newBase.setContentCaptureOptions(getContentCaptureOptions());
}
}
ContextWrapper將一路傳遞過來的上下文base設(shè)置給你了mBase屬性。
protected void attachBaseContext(Context base) {
if (mBase != null) {
throw new IllegalStateException("Base context already set");
}
mBase = base;
}
也就是說，我們在啟動(dòng)Service時(shí)，會(huì)同時(shí)創(chuàng)建Service的上下文context，并將其存儲(chǔ)到Service的父類ContextWrapper的mBases屬性中，同時(shí)context也會(huì)有當(dāng)前Service引用，存儲(chǔ)在mOuterContext變量中。
總結(jié)
Service的啟動(dòng)和綁定從AMS轉(zhuǎn)移到ActiveServiceService的啟動(dòng)，會(huì)先判斷進(jìn)程是否創(chuàng)建，提前啟動(dòng)進(jìn)程，再啟動(dòng)自己。Service重復(fù)啟動(dòng)，會(huì)重復(fù)調(diào)用onStratCommand及后續(xù)生命周期函數(shù)。Service的綁定，會(huì)先走一趟Service的啟動(dòng)流程，再綁定。- 應(yīng)用進(jìn)程與
SytemServer進(jìn)程（AMS、ActiveService）的交互式通過Binder機(jī)制進(jìn)行，通過AIDL各持有雙方接口。應(yīng)用進(jìn)程通過H對象，將現(xiàn)成重新切回主線程（所有應(yīng)用夸進(jìn)程通信應(yīng)如此）。 Service在應(yīng)用和AMS兩邊都會(huì)做緩存，以便快速在找到使用。應(yīng)用程序存儲(chǔ)在ArrayMap<IBinder, Service>類型的mServices;ActiveService則是ArraySet<ServiceRecord>類型的mServices。
以上就是Service啟動(dòng)綁定流程詳解的詳細(xì)內(nèi)容，更多關(guān)于Service啟動(dòng)綁定流程的資料請關(guān)注腳本之家其它相關(guān)文章！
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