继上一篇大概介绍了startService的流程之后，下面来看看bindService流程。
public boolean bindService(Intent service, ServiceConnection conn, int flags) {
warnIfCallingFromSystemProcess();
return bindServiceCommon(service, conn, flags, null, mMainThread.getHandler(), null,
getUser());
}
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;
//有上面可知，handler不为null,所以走else
if (mPackageInfo != null) {
if (executor != null) {
sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), executor, flags);
} else {
// handler不为null，将 ServiceConnection 封装成 IServiceConnection
// IServiceConnection 就是 LoadedApk.ServiceDispatcher.InnerConnection 类
// 将 conn 保持到InnerConnection中，handler 为主线程Handler，也就是 ActivityThread的内部类 H 对象
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);
//跨进程调用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();
}
}
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");
}
//AMS中同样直接交给了ActiveService处理。
synchronized(this) {
return mServices.bindServiceLocked(caller, token, service,
resolvedType, connection, flags, callingPackage, userId);
}
}
int bindServiceLocked(IApplicationThread caller, IBinder token, Intent service,
String resolvedType, final IServiceConnection connection, int flags,
String callingPackage, final int userId) throws TransactionTooLargeException {
.....
// 从ServiceMap中查找ServiceRecord，在这里进行了exported属性、权限等校验。
ServiceLookupResult res =
retrieveServiceLocked(service, resolvedType, callingPackage, Binder.getCallingPid(),
Binder.getCallingUid(), userId, true, callerFg, isBindExternal, allowInstant);
if (res == null) {
return 0;
}
if (res.record == null) {
return -1;
}
ServiceRecord s = res.record;
boolean permissionsReviewRequired = false;
}
try {
// 将Service调用方和被调用方的信息保存到AMS中
mAm.startAssociationLocked(callerApp.uid, callerApp.processName, callerApp.curProcState,
s.appInfo.uid, s.name, s.processName);
mAm.grantEphemeralAccessLocked(callerApp.userId, service,
s.appInfo.uid, UserHandle.getAppId(callerApp.uid));
// 创建连接信息
AppBindRecord b = s.retrieveAppBindingLocked(service, callerApp);
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);
//将连接信息保存到mServiceConnections中
if (clist == null) {
clist = new ArrayList<ConnectionRecord>();
mServiceConnections.put(binder, clist);
}
clist.add(c);
//如flag包含BIND_AUTO_CREATE，先启动Service
if ((flags&Context.BIND_AUTO_CREATE) != 0) {
s.lastActivity = SystemClock.uptimeMillis();
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) {
try {
// 6.如Service已启动或者此intent未被连接过，立即发布连接，回调onServiceConnected
c.conn.connected(s.name, b.intent.binder, false);
} catch (Exception e) {
}
if (b.intent.apps.size() == 1 && b.intent.doRebind) {
requestServiceBindingLocked(s, b.intent, callerFg, true);
}
} else if (!b.intent.requested) {
// 7.Service未被bind过，先调用onBind，再回调onServiceConnected
requestServiceBindingLocked(s, b.intent, callerFg, false);
}
getServiceMapLocked(s.userId).ensureNotStartingBackgroundLocked(s);
} finally {
Binder.restoreCallingIdentity(origId);
}
return 1;
}
然后调用requestServiceBindingLocked（）进行绑定工作。
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);
//跨进程调用scheduleBindService
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) {
}
}
return true;
}
private void handleBindService(BindServiceData data) {
Service s = mServices.get(data.token);
if (DEBUG_SERVICE)
Slog.v(TAG, "handleBindService s=" + s + " rebind=" + data.rebind);
if (s != null) {
try {
data.intent.setExtrasClassLoader(s.getClassLoader());
data.intent.prepareToEnterProcess();
try {
if (!data.rebind) {
// 调用 Service 的 onBind() 方法
IBinder binder = s.onBind(data.intent);
// 这里调用 ActivityManagerService 的 publishService() 方法
ActivityManager.getService().publishService(
data.token, data.intent, binder);
} else {
// 如果是重新绑定，就调用 Service 的 onRebind() 方法
s.onRebind(data.intent);
ActivityManager.getService().serviceDoneExecuting(
data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
}
} 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);
}
}
}
}
调用 ActivityManagerService 的 publishService()方法
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) {
// 将IntentBindRecord.binder赋值为onBinder返回的Binder对象
b.binder = service;
b.requested = true;
//将IntentBindRecord.binder置为true，表示已调用onBind
b.received = true;
//遍历此Service的所有连接记录
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 {
// 找到匹配的intent进行连接
c.conn.connected(r.name, service, false);
} catch (Exception e) {
}
}
}
}
serviceDoneExecutingLocked(r, mDestroyingServices.contains(r), false);
}
} finally {
Binder.restoreCallingIdentity(origId);
}
}
c.conn 为 IServiceConnection 对象，实际就是 LoadedApk.ServiceDispatcher.InnerConnection 类。
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);
}
}
}
最后会调用ServiceDispatcher的connected（）；
public void connected(ComponentName name, IBinder service, boolean dead) {
if (mActivityExecutor != null) {
mActivityExecutor.execute(new RunConnection(name, service, 0, dead));
} else if (mActivityThread != null) {
// 由 ContextImpl#bindServiceCommon() 方法中可知，mActivityThread 就是 ActivityThread 的 H对象（主线程的Handler），不为null
// RunConnection 的 run方法中调用 doConnected() 方法
// 因为是通过主线程的Handler调用的方法，所以客户端的ServiceConnection#onServiceConnected()运行在主线程
mActivityThread.post(new RunConnection(name, service, 0, dead));
} else {
doConnected(name, service, dead);
}
}
private final class RunConnection implements Runnable {
RunConnection(ComponentName name, IBinder service, int command, boolean dead) {
mName = name;
mService = service;
mCommand = command;
mDead = dead;
}
public void run() {
if (mCommand == 0) {
//表示连接成功，在这里面会调用onServiceConnected回调
doConnected(mName, mService, mDead);
} else if (mCommand == 1) {
//表示失去连接，在这会调用onServiceDisconnected回调。
doDeath(mName, mService);
}
}
}
}
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