上一篇中介绍了Service的第一种方式，startService，这一篇来讲解一下另一张方式 bindService。

当创建一个能提供绑定功能的服务时，我们必须提供一个IBinder对象，客户端能使用这个对象与服务进行交换。在Android中有三种定义方式：

1、扩展Binder类 (条件：服务和应用在同一个进程当中，是最常见的情况)

2、使用Messager

3、使用AIDL (Android Interface Defination Language)

Bound Services

A bound service is the server in a client-server interface. A bound service allows components (such as activities) to bind to the service, send requests, receive responses, and even perform interprocess communication (IPC). A bound service typically lives only while it serves another application component and does not run in the background indefinitely.

这里以扩展Binder类为例讲解如何创建Bound Services.

Binder

extends Object
implements IBinder

java.lang.Object
↳	android.os.Binder

很明显，Binder实现了IBinder这接口。

通过扩展Binder类创建Bound Service的步骤如下：

a、在Service类中，创建一个Binder实例，包含客户端能调用的公共方法，返回当前服务对象;

b、在onBind()方法中返回Binder实例;

c、在客户端,从onServiceConnected方法中获得Binder实例。

工程目录结构：

运行界面：

源代码：

MainActivity.java:

package com.service.activity;import com.service.activity.BinderService.MyBinder;import android.app.Activity;import android.content.ComponentName;import android.content.Context;import android.content.Intent;import android.content.ServiceConnection;import android.os.Bundle;import android.os.IBinder;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class MainActivity extends Activity {private Button btnStartService;private Button btnstopService;private boolean isConnected = false;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        btnStartService = (Button)findViewById(R.id.btnStartService);        btnStartService.setOnClickListener(listener);        btnstopService = (Button)findViewById(R.id.btnStopService);        btnstopService.setOnClickListener(listener);    }        private OnClickListener listener = new OnClickListener() {@Overridepublic void onClick(View v) {switch (v.getId()) {case R.id.btnStartService:funBindService();break;case R.id.btnStopService:funUnBindService();break;default:break;}}private void funBindService() {Intent intent = new Intent(MainActivity.this, BinderService.class);bindService(intent, conn, Context.BIND_AUTO_CREATE);}private void funUnBindService() {if(isConnected == true){unbindService(conn);}}};private ServiceConnection conn = new ServiceConnection() {@Overridepublic void onServiceDisconnected(ComponentName name) {isConnected = false;}//与Service连接时被回调@Overridepublic void onServiceConnected(ComponentName name, IBinder iBinder) {MyBinder myBinder = (MyBinder)iBinder;BinderService service = myBinder.getService();service.MyMethod();isConnected = true;}};}

BinderService.java

package com.service.activity;import android.app.Service;import android.content.Intent;import android.os.Binder;import android.os.IBinder;import android.util.Log;public class BinderService extends Service{private static final String TAG = "BinderService";private MyBinder myBinder = new MyBinder();//内部类，扩展自Binder类public class MyBinder extends Binder{public BinderService getService(){return BinderService.this;}}//复写onBind方法，并且返回IBinder的实现类@Overridepublic IBinder onBind(Intent intent) {Log.i(TAG, "onBind");return myBinder;}public void MyMethod(){Log.i(TAG, "MyMethod");}@Overridepublic boolean onUnbind(Intent intent) {Log.i(TAG, "onUnbind");return super.onUnbind(intent);}@Overridepublic void onDestroy() {Log.i(TAG, "onDestroy");super.onDestroy();}}

main.xml:

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="vertical" >    <Button     android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="启动service"        android:id="@+id/btnStartService"/><Button     android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="停止service"        android:id="@+id/btnStopService"/></LinearLayout>

点击启动service,日志输出信息：

点击停止service,日志输出信息：

Android之Service学习篇二：Service启动方式之boundService

Bound Services

Binder

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