在上一篇文章中分析了【startService()的启动过程】；今天从源码去分析bindService()。
bindService()流程.png
Intent intent = new Intent(this, mService.class);
bindService(intent, serviceConnection,BIND_AUTO_CREATE);
在调用上面两行代码对Service进行绑定，实际调用的是ContextImpl的bindService()。
@Override
public boolean bindService(Intent service, ServiceConnection conn,
int flags) {
warnIfCallingFromSystemProcess();
return bindServiceCommon(service, conn, flags, mMainThread.getHandler(),
Process.myUserHandle());
}
private boolean bindServiceCommon(Intent service, ServiceConnection conn, int flags, Handler
handler, UserHandle user) {
// Keep this in sync with DevicePolicyManager.bindDeviceAdminServiceAsUser.
IServiceConnection sd;
if (conn == null) {
throw new IllegalArgumentException("connection is null");
}
//1
if (mPackageInfo != null) {
sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), handler, flags);
} else {
throw new RuntimeException("Not supported in system context");
}
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);
//2
int res = ActivityManager.getService().bindService(
mMainThread.getApplicationThread(), getActivityToken(), service,
service.resolveTypeIfNeeded(getContentResolver()),
sd, flags, 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();
}
}
从上面代码可以发现：bindService()内部调用了bindServiceCommon()，在注释1处，mPackageInfo是一个LoadedApk实例对象，getServiceDispatcher()返回的是一个LoadedApk的静态内部类ServiceDispatcher中的InnerConnection对象，InnerConnection是ServiceDispatcher中的静态内部类，继承 了IServiceConnection.Stub。
private static class InnerConnection extends IServiceConnection.Stub {
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);
}
}
}
在上面代码中调用ServiceDispatcher内的connected()方法，connected()内部又调用了ServiceDispatcher内的doConnected()方法。
public void doConnected(ComponentName name, IBinder service, boolean dead) {
ServiceDispatcher.ConnectionInfo old;
ServiceDispatcher.ConnectionInfo info;
//省略代码...............
// If there was an old service, it is now disconnected.
if (old != null) {
mConnection.onServiceDisconnected(name);
}
if (dead) {
mConnection.onBindingDied(name);
}
// If there is a new service, it is now connected.
if (service != null) {
mConnection.onServiceConnected(name, service);
}
}
到这里可以发现，回调了我们在绑定服务时定义的ServiceConnection对象的两个实现方法。那么InnerConnection类中的connected()方式是在哪里调用的呢？回到bindServiceCommon()方法的注释2处，下面是缩略的bindServiceCommon()。
private boolean bindServiceCommon(Intent service, ServiceConnection conn, int flags, Handler
handler, UserHandle user) {
//省略代码.........
int res = ActivityManager.getService().bindService(
mMainThread.getApplicationThread(), getActivityToken(), service,
service.resolveTypeIfNeeded(getContentResolver()),
sd, flags, getOpPackageName(), user.getIdentifier());
//省略代码.........
}
这里又是以进程间通信的方式建立关联，关于ActivityManager.getService()就不再多介绍了，不了解的可以看下【从源码探索Activity的启动过程】这篇文章对ActivityManager.getService()的阐述。那么这里就把绑定的任务切换到了服务端ActivityManagerService的bindService()方法，并且传入客户端ApplicationThread对象和sd，这个sd是在开始处通过mPackageInfo.getServiceDispatcher()返回的InnerConnection 对象。下面进入到ActivityManagerService的bindService()中。
public int bindService(IApplicationThread caller, IBinder token, Intent service,
String resolvedType, IServiceConnection connection, int flags, String callingPackage,
int userId) throws TransactionTooLargeException {
enforceNotIsolatedCaller("bindService");
// Refuse possible leaked file descriptors
if (service != null && service.hasFileDescriptors() == true) {
throw new IllegalArgumentException("File descriptors passed in Intent");
}
if (callingPackage == null) {
throw new IllegalArgumentException("callingPackage cannot be null");
}
synchronized(this) {
return mServices.bindServiceLocked(caller, token, service,
resolvedType, connection, flags, callingPackage, userId);
}
}
从上面的代码发现，调用了 mServices.bindServiceLocked()，mServices是一个ActiveServices对象实例，进入ActiveServices的bindServiceLocked()方法。
int bindServiceLocked(IApplicationThread caller, IBinder token, Intent service,
String resolvedType, final IServiceConnection connection, int flags,
String callingPackage, final int userId) throws TransactionTooLargeException {
//通过ApplicationThread对象caller获取ActivityManagerService中的ProcessRecord 对象。
final ProcessRecord callerApp = mAm.getRecordForAppLocked(caller);
if (callerApp == null) {
throw new SecurityException(
"Unable to find app for caller " + caller
+ " (pid=" + Binder.getCallingPid()
+ ") when binding service " + service);
}
ActivityRecord activity = null;
if (token != null) {
//获取当前绑定服务的Activity对应的ActivityRecord对象
activity = ActivityRecord.isInStackLocked(token);
if (activity == null) {
Slog.w(TAG, "Binding with unknown activity: " + token);
return 0;
}
}
int clientLabel = 0;
PendingIntent clientIntent = null;
final boolean isCallerSystem = callerApp.info.uid == Process.SYSTEM_UID;
if (isCallerSystem) {
service.setDefusable(true);
clientIntent = service.getParcelableExtra(Intent.EXTRA_CLIENT_INTENT);
if (clientIntent != null) {
clientLabel = service.getIntExtra(Intent.EXTRA_CLIENT_LABEL, 0);
if (clientLabel != 0) {
service = service.cloneFilter();
}
}
}
if ((flags&Context.BIND_TREAT_LIKE_ACTIVITY) != 0) {
mAm.enforceCallingPermission(android.Manifest.permission.MANAGE_ACTIVITY_STACKS,
"BIND_TREAT_LIKE_ACTIVITY");
}
if ((flags & Context.BIND_ALLOW_WHITELIST_MANAGEMENT) != 0 && !isCallerSystem) {
throw new SecurityException(
"Non-system caller " + caller + " (pid=" + Binder.getCallingPid()
+ ") set BIND_ALLOW_WHITELIST_MANAGEMENT when binding service " + service);
}
final boolean callerFg = callerApp.setSchedGroup != ProcessList.SCHED_GROUP_BACKGROUND;
final boolean isBindExternal = (flags & Context.BIND_EXTERNAL_SERVICE) != 0;
//解析Service，并保存在ServiceRecord
ServiceLookupResult res =
retrieveServiceLocked(service, resolvedType, callingPackage, Binder.getCallingPid(),
Binder.getCallingUid(), userId, true, callerFg, isBindExternal);
if (res == null) {
return 0;
}
if (res.record == null) {
return -1;
}
ServiceRecord s = res.record;
//......................省略代码
try {
if (unscheduleServiceRestartLocked(s, callerApp.info.uid, false)) {
if (DEBUG_SERVICE) Slog.v(TAG_SERVICE, "BIND SERVICE WHILE RESTART PENDING: "
+ s);
}
if ((flags&Context.BIND_AUTO_CREATE) != 0) {
s.lastActivity = SystemClock.uptimeMillis();
if (!s.hasAutoCreateConnections()) {
// This is the first binding, let the tracker know.
ServiceState stracker = s.getTracker();
if (stracker != null) {
stracker.setBound(true, mAm.mProcessStats.getMemFactorLocked(),
s.lastActivity);
}
}
}
mAm.startAssociationLocked(callerApp.uid, callerApp.processName, callerApp.curProcState,
s.appInfo.uid, s.name, s.processName);
// Once the apps have become associated, if one of them is caller is ephemeral
// the target app should now be able to see the calling app
mAm.grantEphemeralAccessLocked(callerApp.userId, service,
s.appInfo.uid, UserHandle.getAppId(callerApp.uid));
AppBindRecord b = s.retrieveAppBindingLocked(service, callerApp);
//把参数封装在ConnectionRecord对象中，这里的connection就是最初从客户端传过来的
//也就是
ConnectionRecord c = new ConnectionRecord(b, activity,
connection, flags, clientLabel, clientIntent);
IBinder binder = connection.asBinder();
ArrayList<ConnectionRecord> clist = s.connections.get(binder);
if (clist == null) {
clist = new ArrayList<ConnectionRecord>();
s.connections.put(binder, clist);
}
clist.add(c);
b.connections.add(c);
if (activity != null) {
if (activity.connections == null) {
activity.connections = new HashSet<ConnectionRecord>();
}
activity.connections.add(c);
}
b.client.connections.add(c);
if ((c.flags&Context.BIND_ABOVE_CLIENT) != 0) {
b.client.hasAboveClient = true;
}
if ((c.flags&Context.BIND_ALLOW_WHITELIST_MANAGEMENT) != 0) {
s.whitelistManager = true;
}
if (s.app != null) {
updateServiceClientActivitiesLocked(s.app, c, true);
}
clist = mServiceConnections.get(binder);
if (clist == null) {
clist = new ArrayList<ConnectionRecord>();
mServiceConnections.put(binder, clist);
}
clist.add(c);
if ((flags&Context.BIND_AUTO_CREATE) != 0) {
s.lastActivity = SystemClock.uptimeMillis();
//当bindService()第三个参数为BIND_AUTO_CREATE，
//这里又回到了startService()流程中的bringUpServiceLocked()
if (bringUpServiceLocked(s, service.getFlags(), callerFg, false,
permissionsReviewRequired) != null) {
return 0;
}
}
if (s.app != null) {
if ((flags&Context.BIND_TREAT_LIKE_ACTIVITY) != 0) {
s.app.treatLikeActivity = true;
}
if (s.whitelistManager) {
s.app.whitelistManager = true;
}
// This could have made the service more important.
mAm.updateLruProcessLocked(s.app, s.app.hasClientActivities
|| s.app.treatLikeActivity, b.client);
mAm.updateOomAdjLocked(s.app, true);
}
if (s.app != null && b.intent.received) {
// Service is already running, so we can immediately
// publish the connection.
try {
//如果绑定的service已经运行，直接回调connected
c.conn.connected(s.name, b.intent.binder, false);
} catch (Exception e) {
Slog.w(TAG, "Failure sending service " + s.shortName
+ " to connection " + c.conn.asBinder()
+ " (in " + c.binding.client.processName + ")", e);
}
// If this is the first app connected back to this binding,
// and the service had previously asked to be told when
// rebound, then do so.
if (b.intent.apps.size() == 1 && b.intent.doRebind) {
requestServiceBindingLocked(s, b.intent, callerFg, true);
}
} else if (!b.intent.requested) {
//请求绑定Service
requestServiceBindingLocked(s, b.intent, callerFg, false);
}
getServiceMapLocked(s.userId).ensureNotStartingBackgroundLocked(s);
} finally {
Binder.restoreCallingIdentity(origId);
}
return 1;
}
在bindServiceLocked()方法中可以发现，最终会走到requestServiceBindingLocked()方法。
private final boolean requestServiceBindingLocked(ServiceRecord r, IntentBindRecord i,
boolean execInFg, boolean rebind) throws TransactionTooLargeException {
if (r.app == null || r.app.thread == null) {
// If service is not currently running, can't yet bind.
return false;
}
if ((!i.requested || rebind) && i.apps.size() > 0) {
try {
bumpServiceExecutingLocked(r, execInFg, "bind");
r.app.forceProcessStateUpTo(ActivityManager.PROCESS_STATE_SERVICE);
//1
r.app.thread.scheduleBindService(r, i.intent.getIntent(), rebind,
r.app.repProcState);
if (!rebind) {
i.requested = true;
}
i.hasBound = true;
i.doRebind = false;
} catch (TransactionTooLargeException e) {
// Keep the executeNesting count accurate.
if (DEBUG_SERVICE) Slog.v(TAG_SERVICE, "Crashed while binding " + r, e);
final boolean inDestroying = mDestroyingServices.contains(r);
serviceDoneExecutingLocked(r, inDestroying, inDestroying);
throw e;
} catch (RemoteException e) {
if (DEBUG_SERVICE) Slog.v(TAG_SERVICE, "Crashed while binding " + r);
// Keep the executeNesting count accurate.
final boolean inDestroying = mDestroyingServices.contains(r);
serviceDoneExecutingLocked(r, inDestroying, inDestroying);
return false;
}
}
return true;
}
上面注释1处，r.app.thread是客户端传递的ApplicationThread（ActivityTread的静态内部类）对象，切换到scheduleBindService()方法。
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;
//发送BIND_SERVICE，在H 的handleMessage中回调
//handleBindService()
sendMessage(H.BIND_SERVICE, s);
}
private void handleBindService(BindServiceData data) {
//在前面成功执行onCreate后，会通过mServices.put()保存service
//mServices是一个ArrayMap对象
Service s = mServices.get(data.token);
if (s != null) {
try {
data.intent.setExtrasClassLoader(s.getClassLoader());
data.intent.prepareToEnterProcess();
try {
if (!data.rebind) {
//执行onBind()
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);
}
ensureJitEnabled();
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
} catch (Exception e) {
if (!mInstrumentation.onException(s, e)) {
throw new RuntimeException(
"Unable to bind to service " + s
+ " with " + data.intent + ": " + e.toString(), e);
}
}
}
}
从上面代码可以知道，执行了onBind()后，又通过publishService()通知服务端ActivityManagerService已经完成绑定。
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);
}
}
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) {
b.binder = service;
b.requested = true;
b.received = true;
for (int conni=r.connections.size()-1; conni>=0; conni--) {
ArrayList<ConnectionRecord> clist = r.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 {
//1
c.conn.connected(r.name, service, false);
} catch (Exception e) {
Slog.w(TAG, "Failure sending service " + r.name +
" to connection " + c.conn.asBinder() +
" (in " + c.binding.client.processName + ")", e);
}
}
}
}
serviceDoneExecutingLocked(r, mDestroyingServices.contains(r), false);
}
} finally {
Binder.restoreCallingIdentity(origId);
}
}
从上面代码可以知道，ActivityManagerService接收到客户端的消息后，在publishService调用ActiveServices的publishServiceLocked()方法。最终会在注释1处调用connected()方法，并且传递Binder对象， 而这个connected()就是前面分析的InnerConnection的connected()方法，在其里面回调ServiceConnection接口的onServiceDisconnected()或者onServiceConnected()告知客户端绑定结果。
Service的绑定流程到这就结束了
