在如何使用Service以及如何使用startService中,
解釋了甚麼是Service以及如何使用啟動式的Service,
這篇要示範使用連繫(bound)的Service。
先宣告一個Service
public class MyService extends Service {
private MyBinder mBinder = new MyBinder();
public class MyBinder extends Binder {
public MyService getService() {
return MyService.this;
}
}
public IBinder onBind(Intent intent) {
return mBinder;
}
@Override
public boolean onUnbind(Intent intent) {
return super.onUnbind(intent);
}
public String getStr(){
return "service string";
}
}裡面有一個我們自己定義的Binder, 利用Binder可以跟Activity進行雙向的溝通,
Binder回傳Service的本體, 那麼就可以利用這個instance去執行Service內的任何方法。
接著來實作我們的Activity
public class MainActivity extends AppCompatActivity {
private MyService mService;
private ServiceConnection mLoaclServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
MyService.MyBinder mMyBinder = (MyService.MyBinder)service;
mService = mMyBinder.getService();
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
private TextView text;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bindService(new Intent(this, MyService.class), mLoaclServiceConnection, Context.BIND_AUTO_CREATE);
text = (TextView) findViewById(R.id.text);
Button getStr = (Button) findViewById(R.id.get_service_text);
getStr.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
text.setText(mService.getStr());
}
});
}
}在onCreate內先對service進行bind, 傳入我們自訂好的ServiceConnection物件,
Service會對這個物件呼叫Callback,
此時可以將回傳的Binder物件轉型回我們所定義的MyBinder,
透過getService就可以拿到Service的實體,
此時再call getServiceStr()方法就可以拿到Service內的字串了。
xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
<TextView android:text="Hello World!"
android:id="@+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/text"
android:id="@+id/get_service_text"
android:text="get service text"/>
</RelativeLayout>
