最近在看同一个程序中Service的两种驱动方式时，起以Bind启动然后可以进行Service和Activity之间的相互通信。一直没看明白，在翻看SDK时发现一个例子，特别摘抄如下：
这个时BindingService继承自Activity，然后通过点击按钮来启动Service
public class BindingService extends Activity {
private static final String TAG = "BindingService";
// mService负责接收Service传过来的对象
LocalService mService;
boolean mBound = false;
Button bindBtn;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
bindBtn = (Button) findViewById(R.id.bindBtn);
bindBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Log.i(TAG, "OnClick....");
if(mBound) {
int num = mService.getRandomNumber();
Toast.makeText(BindingService.this, num+"", Toast.LENGTH_LONG).show();
}
}
});
}
@Override
protected void onStart() {
super.onStart();
// Bind to LocalService
Intent intent = new Intent(this, LocalService.class);
Log.i(TAG, "onStart.....onBind");
bindService(intent, mConnection, Service.BIND_AUTO_CREATE);
}
@Override
protected void onStop() {
super.onStop();
// UnBind from the service
if(mBound) {
unbindService(mConnection);
mBound = false;
}
}
// Defines callbacks for service binding, passed to bindService()
private ServiceConnection mConnection = new ServiceConnection() {
@Override
// 在Service断开的时候调用这个函数
public void onServiceDisconnected(ComponentName name) {
// 另外说明在这里打log或者是使用Toast都不能显示，不知道是怎么回事
mBound = false;
}
@Override
// 在Service连接以后调用这个函数
public void onServiceConnected(ComponentName name, IBinder service) {
// we have bound to LocalService, cast the IBinder and get LocalService instance
// 获得Service中的Binder对象
// 另外说明在这里打log或者是使用Toast都不能显示，不知道是怎么回事
LocalBinder binder = (LocalBinder) service;
// 通过Binder对象获得Service对象，然后初始化mService
mService = binder.getService();
Log.i(TAG, "onServiceConnected.....");
System.out.println("onServiceConnected.....");
mBound = true;
}
};
}
public class LocalService extends Service {
// Binder given to clients
// 返回一个Binder对象
private final IBinder mBinder = new LocalBinder();
// Random number generator
private final Random mGenerator = new Random();
/***
* Class used for the client Binder.Because we know this service always
* runs in the same process as its clients
*/
public class LocalBinder extends Binder {
LocalService getService() {
// return this instance of LocalService so clients can call public method
return LocalService.this;
}
}
@Override
// 如果是通过startService()函数启动的时候，这个函数是不起作用的。
// public void onServiceConnected(ComponentName name, IBinder service) 返回的Activity
// IBinder service 对象
public IBinder onBind(Intent intent) {
// IBinder通信关键是利用Activity中的IBider对象获得service对象，然后调用service中的函数
// 传给Activity一个Binder对象，通过这个Binder对象调用getService()获得Service对象
return mBinder;
}
// method for clients
public int getRandomNumber() {
return mGenerator.nextInt(100);
}
}