Android：Service：与Activity进行相互通信的本地服务
通过startService()和stopService()启动关闭服务。适用于服务和Activity之间没有调用交互的情况。如果相互之间需要方法调用或者传递参数，需要使用bindService()和unbindService()方法启动关闭服务。
采用Context.bindService()方法启动服务，在服务未被创建时，系统会先调用服务的onCreate()方法，接着调用onBind()方法，这个时候调用者和服务绑定在一起。如果客户端要与服务进行通信，那么，onBind()方法必须返回Ibinder对象。如果调用者退出了，系统就会先调用服务的onUnbind()方法，接着调用onDestroy()方法。如果调用bindService()方法前服务已经被绑定，多次调用bindService()方法并不会导致多次创建服务及绑定(也就是说onCreate()和onBind()方法并不会被多次调用)。如果调用者希望与正在绑定的服务解除绑定，可以调用unbindService()方法，调用该方法也会导致系统调用服务的onUnbind()-->onDestroy()方法。
Activity与服务进行通信，开发人员通常把通信方法定义在接口里，然后让Ibinder对象实现该接口，而Activity通过该接口引用服务onBind()方法返回的Ibinder对象，然后调用Ibinder对象里自定义的通信方法。例子如下：
本例是一个本地服务，即服务与Activity在同一个应用内部。
接口：
public interface ICountService {
public intgetCount();
}
服务类：
public class CountService extends Service {
private boolean quit;
private int count;
private ServiceBinder serviceBinder = newServiceBinder();
public class ServiceBinder extends Binder implementsICountService {
@Override
public intgetCount() {
return count;
}
}
@Override
public IBinder onBind(Intent intent) {
returnserviceBinder;
}
@Override
public void onCreate() {
super.onCreate();
new Thread(newRunnable() {
@Override
public void run(){
while (!quit) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {}
count++;
}
}
}).start();
}
@Override
public void onDestroy() {
super.onDestroy();
this.quit = true;
}
}
客户端Activity：
public class ClientActivity extends Activity {
privateICountService countService;
@Override
public voidonCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
this.bindService(newIntent(this, CountService.class), this.serviceConnection, BIND_AUTO_CREATE);
}
@Override
protected voidonDestroy() {
super.onDestroy();
this.unbindService(serviceConnection);
}
privateServiceConnection serviceConnection = new ServiceConnection() {
@Override
public voidonServiceConnected(ComponentName name, IBinder service) {
countService =(ICountService) service;//对于本地服务，获取的实例和服务onBind()返回的实例是同一个
int i =countService.getCount();
Log.v("CountService","Count is " + i);
}
@Override
public voidonServiceDisconnected(ComponentName name) {
countService =null;
}
};
}
实现根据学号查询学生
Service：提供一个查询的方法
public class StudentService extends Service{
private String[] names = {"张飞","李小龙","赵薇"};
private IBinder binder = new StundentBinder();
public String query(int no){
if(no>0 && no<4){
return names[no - 1];
}
return null;
}
@Override
public IBinder onBind(Intent intent) {
return binder;
}
private class StundentBinder extends Binder implements IStundent{
public String queryStudent(int no) {
return query(no);
}
}
}
public interface IStundent {
public String queryStudent(int no);
}
public class MainActivity extends Activity {
private EditText studentno;
private ServiceConnection conn = new StudentServiceConnection();
private IStundent iStundent;
private TextView resultView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
resultView = (TextView) this.findViewById(R.id.resultView);
studentno = (EditText) this.findViewById(R.id.studentno);
Button button = (Button) this.findViewById(R.id.button);
button.setOnClickListener(new ButtonClickListener());
Intent service = new Intent(this, StudentService.class);
bindService(service, conn, BIND_AUTO_CREATE);
}
private class StudentServiceConnection implements ServiceConnection{
public void onServiceConnected(ComponentName name, IBinder service) {
iStundent = (IStundent)service;
}
public void onServiceDisconnected(ComponentName name) {
iStundent = null;
}
}
@Override
protected void onDestroy() {
unbindService(conn);
super.onDestroy();
}
private final class ButtonClickListener implements View.OnClickListener{
public void onClick(View v) {
String no = studentno.getText().toString();
String name = iStundent.queryStudent(Integer.valueOf(no));
resultView.setText(name);
}
}
}