1、首先看两个例子
（1）进程内
Client端
public class CounterService extends Service implements ICounterService {
......
public class CounterBinder extends Binder {
public CounterService getService() {
return CounterService.this;
}
}
......
}
Server端
public class MainActivity extends Activity implements OnClickListener {
......
private ServiceConnection serviceConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
counterService = ((CounterService.CounterBinder)service).getService();
Log.i(LOG_TAG, "Counter Service Connected");
}
......
};
......
}
Client端
public class RemoteService extends Service {
private final static String TAG = "RemoteService";
@Override
public IBinder onBind(Intent intent) {
Log.i(TAG, "执行了OnBind");
return new MyBinder();
}
private class MyBinder extends RemoteWebPage.Stub{
@Override
public String getCurrentPageUrl() throws RemoteException{
return "http://www.cnblogs.com/hibraincol/";
}
}
}
Server端
private class MyServiceConnection implements ServiceConnection{
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Log.i(TAG, "建立连接...");
remoteWebPage = RemoteWebPage.Stub.asInterface(service);
try {
Log.d(TAG, remoteWebPage.getCurrentPageUrl());
} catch (RemoteException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void onServiceDisconnected(ComponentName name) {
Log.i(TAG, "onServiceDisconnected...");
}
}
为什么一个是
counterService = ((CounterService.CounterBinder)service).getService();另一个是
remoteWebPage = RemoteWebPage.Stub.asInterface(service);原因在于第一个service是CounterService对象，第二个Service是BinderProxy对象，指向MyBinder对象。
为什么进程内和进程间会有差别呢？请看下图：
就在于第6步，要传递的参数是BinderProxy对象。
进程内会执行如下代码：
case BINDER_TYPE_HANDLE:
case BINDER_TYPE_WEAK_HANDLE: {
struct binder_ref *ref = binder_get_ref(proc, fp->handle);
...........
if (ref->node->proc == target_proc) {//相同进程
if (fp->type == BINDER_TYPE_HANDLE)
fp->type = BINDER_TYPE_BINDER;
else
fp->type = BINDER_TYPE_WEAK_BINDER;
fp->binder = ref->node->ptr;
fp->cookie = ref->node->cookie;
binder_inc_node(ref->node, fp->type == BINDER_TYPE_BINDER, 0, NULL);
if (binder_debug_mask & BINDER_DEBUG_TRANSACTION)
printk(KERN_INFO " ref %d desc %d -> node %d u%p\n",
ref->debug_id, ref->desc, ref->node->debug_id, ref->node->ptr);
} else {
......
}
} 为转换成CounterService对象做准备。进程间会执行如下代码：
case BINDER_TYPE_HANDLE:
case BINDER_TYPE_WEAK_HANDLE: {
struct binder_ref *ref = binder_get_ref(proc, fp->handle);
.........
if (ref->node->proc == target_proc) {
.....
} else {//不同进程
struct binder_ref *new_ref;
new_ref = binder_get_ref_for_node(target_proc, ref->node);
if (new_ref == NULL) {
return_error = BR_FAILED_REPLY;
goto err_binder_get_ref_for_node_failed;
}
fp->handle = new_ref->desc;
binder_inc_ref(new_ref, fp->type == BINDER_TYPE_HANDLE, NULL);
if (binder_debug_mask & BINDER_DEBUG_TRANSACTION)
printk(KERN_INFO " ref %d desc %d -> ref %d desc %d (node %d)\n",
ref->debug_id, ref->desc, new_ref->debug_id, new_ref->desc, ref->node->debug_id);
}
} 为转换成BinderProxy对象做准备。此时BinderProxy对象是Counter进程的，MyBinder对象是CounterService进程的。它们通过进程间通信的方式传递数据。