进程内与Service通信

安卓的组件之间一般来说是不会有交流的，但是可以通过BindService的方式实现在Activity与Service的通信。这个通信的媒介就是IBinder。

例如有下面的需求：在Activity内”指挥”一个Service去播放一段音频，当Activity退出时就不再播放，即不支持后台。当用户进行某个操作之后，再点播放，音乐就支持后台。

代码如下：

MainActivity.java

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package com.example.ahtcfg24.serviceplayerdemo;

import android.app.Activity;
import android.app.Service;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import static android.view.View.OnClickListener;

public class MainActivity extends Activity {
    public static final String TAG = "Connected";
    private Button button, button2;
    private Intent intent;
    private MyService.MyBinder myService;
    private ServiceConnection connection;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.button);
        button2 = (Button) findViewById(R.id.button2);

        button.setOnClickListener(new ButtonListener());
        button2.setOnClickListener(new ButtonListener());

        intent = new Intent(MainActivity.this, MyService.class);
        connection = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                Log.i(TAG, "--->音乐服务已连接");
                myService = (MyService.MyBinder) service;
                myService.playMedia();//播放
            }

            @Override
            public void onServiceDisconnected(ComponentName name) {
                Log.i(TAG, "--->音乐服务已崩溃");
            }
        };
    }


    private class ButtonListener implements OnClickListener {
        @Override
        public void onClick(View v) {
            switch (v.getId()) {
                case R.id.button:
                    bindService(intent, connection, Service.BIND_AUTO_CREATE);
                    break;
                case R.id.button2:
                    startService(intent);
                    break;
                default:
                    break;
            }
        }
    }
}

activity_main.xml

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<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:paddingBottom="@dimen/activity_vertical_margin"
                android:paddingLeft="@dimen/activity_horizontal_margin"
                android:paddingRight="@dimen/activity_horizontal_margin"
                android:paddingTop="@dimen/activity_vertical_margin"
                tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="40dp"
        android:text="播放"/>

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/button"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="49dp"
        android:text="后台播放"/>
</RelativeLayout>

MyService.java

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package com.example.ahtcfg24.serviceplayerdemo;

import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;

public class MyService extends Service {
    public static final String TAG = "MyService";
    private MediaPlayer player;

    @Override
    public IBinder onBind(Intent intent) {

        Log.i(TAG, "--->onBind");
        return new MyBinder();
    }

    @Override
    public void onCreate() {
        player = MediaPlayer.create(getApplicationContext(), R.raw.music);
        player.setLooping(true);//设置可循环播放
        Log.i(TAG, "--->onCreate");
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.i(TAG, "--->onStartCommand");

        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        Log.i(TAG, "--->onDestroy");
        super.onDestroy();
        player.stop();//Service结束时就停止播放
    }

    @Override
    public boolean onUnbind(Intent intent) {
        Log.i(TAG, "--->onUnbind");

        return super.onUnbind(intent);
    }

    class MyBinder extends Binder {
        public void playMedia() {
            player.start();//播放
        }
    }
}

点击查看源代码

参考资料1参考资料2

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