service組件-bindService源碼分析
因為有前面分析startService的代碼實現過程，則對於bindService的代碼分析就不用那麼詳細介紹，在介紹流程的同時更關注一些細節上的部分。
首先，bindService也是通過 ContextWrapper.bindService，再到ContextImpl的bindService，然後是bindServiceCommon，需要注意的是，傳入的ServiceConnection被轉換成IServiceConnection類型，
private boolean bindServiceCommon(Intent service, ServiceConnection conn,
int flags,
UserHandle user)
{
IServiceConnection sd;
sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(),
mMainThread.getHandler(), flags);
int res = ActivityManagerNative.getDefault().bindService(
mMainThread.getApplicationThread(), getActivityToken(),
service, service.resolveTypeIfNeeded(getContentResolver()),
sd, flags, user.getIdentifier());
}
接下去是進入AMS的bindService，再調用ActiveServices.java 的bindServiceLocked，它會把IServiceConnection實例存放到ConnectionRecord裡面，並執行bringUpServiceLocked，
int bindServiceLocked(IApplicationThread caller, IBinder token,
Intent service, String resolvedType,
IServiceConnection connection, int flags, int userId)
{
ConnectionRecord c = new ConnectionRecord(b, activity,
connection, flags, clientLabel, clientIntent);
IBinder binder = connection.asBinder();
if ((flags & Context.BIND_AUTO_CREATE) != 0) {
s.lastActivity = SystemClock.uptimeMillis();
if (bringUpServiceLocked(s, service.getFlags(), callerFg, false) != null) {
return 0;
}
}
if (s.app != null && b.intent.received) {
// Service is already running, so we can immediately
// publish the connection.
try {
c.conn.connected(s.name, b.intent.binder);
} 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) {
requestServiceBindingLocked(s, b.intent, callerFg, false);
}
}
根據之前的分析ServiceLocked會調用realStartServiceLocked，而realStartServiceLocked則先調用scheduleCreateService，完成service的創建和Oncreate（）的執行，然後執行requestServiceBindingsLocked，這個是bind服務相關處理，最後是sendServiceArgsLocked，這個是Start服務的處理。
private final void realStartServiceLocked(ServiceRecord r,
ProcessRecord app, boolean execInFg) throws RemoteException {
app.thread.scheduleCreateService(r, r.serviceInfo, mAm.compatibilityInfoForPackageLocked(r.serviceInfo.applicationInfo), app.repProcState);
requestServiceBindingsLocked(r, execInFg);
sendServiceArgsLocked(r, execInFg, true);
}
requestServiceBindingsLocked再調用ActivityThread的方法scheduleBindService，在ActivityThread.java 中，它發出一個BIND_SERVICE事件，被handleBindService處理，
void publishServiceLocked(ServiceRecord r, Intent intent, IBinder service)
{
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);
try {
c.conn.connected(r.name, service);
}
serviceDoneExecutingLocked(r, mDestroyingServices.contains(r), false);
}
}
}
這裡主要調用到c.conn.connected，c就是ConnectionRecord，其成員conn是一個IServiceConnection類型實例，這在前面有提到，connected則是其實現類的方法。
對於IServiceConnection，它是一個接口，位置在(frameworks\base): core/java/android/app/IServiceConnection.aidl，aidl定義如下，它只有一個接口方法connected，
oneway interface IServiceConnection {
void connected(in ComponentName name, IBinder service);
}
其服務端的實現在LoadedApk.java，如下，InnerConnection類是在ServiceDispatcher的內部類，並在ServiceDispatcher的構造函數裡面實例化的，其方法connected也是調用的ServiceDispatcher的方法connected，
private static class InnerConnection extendsIServiceConnection.Stub
{
final WeakReference<LoadedApk.ServiceDispatcher> mDispatcher;
InnerConnection(LoadedApk.ServiceDispatcher sd)
{
mDispatcher = new WeakReference<LoadedApk.ServiceDispatcher>(sd);
}
public void connected(ComponentName name,
IBinder service) throws RemoteException {
LoadedApk.ServiceDispatcher sd = mDispatcher.get();
if (sd != null)
{
sd.connected(name, service);
}
}
}
ServiceDispatcher(ServiceConnection conn,
Context context, Handler activityThread, int flags)
{
mIServiceConnection = new InnerConnection(this);
mConnection = conn;
mContext = context;
mActivityThread = activityThread;
mLocation = new ServiceConnectionLeaked(null);
mLocation.fillInStackTrace();
mFlags = flags;
}
這裡就再回到我們前面的ContextImpl裡面bindServiceCommon方法裡面，這裡進行ServiceConnection轉化為IServiceConnection時，調用了mPackageInfo.getServiceDispatcher，mPackageInfo就是一個LoadedApk實例，
/*package*/ LoadedApk mPackageInfo;
private boolean bindServiceCommon(Intent service, ServiceConnection conn,
int flags,
UserHandle user)
{
IServiceConnection sd;
sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(),
mMainThread.getHandler(), flags);
}
所以，getServiceDispatcher會創建一個ServiceDispatcher實例，並將ServiceDispatcher實例和ServiceConnection實例形成KV對，並在ServiceDispatcher的構造函數裡將ServiceConnection實例c賦值給ServiceConnection的成員變量mConnection，
public final IServiceConnection getServiceDispatcher(ServiceConnection c,
Context context, Handler handler, int flags)
{
synchronized(mServices) {
LoadedApk.ServiceDispatcher sd = null;
ArrayMap<ServiceConnection, LoadedApk.ServiceDispatcher> map = mServices.get(
context);
if (map != null) {
sd = map.get(c);
}
if (sd == null) {
sd = new ServiceDispatcher(c, context, handler, flags);
if (map == null) {
map = new ArrayMap<ServiceConnection, LoadedApk.ServiceDispatcher>();
mServices.put(context, map);
}
map.put(c, sd);
}
}
}
這樣，在執行ServiceDispatcher的connected方法時，就會調用到ServiceConnection的 onServiceConnected，完成綁定ServiceConnection的觸發。
public void doConnected(ComponentName name, IBinder service)
{
if (old != null) {
mConnection.onServiceDisconnected(name);
}
// If there is a new service, it is now connected.
if (service != null) {
mConnection.onServiceConnected(name, service);
}
}
至此，就執行完了bindService的主要過程。
