服务的灵活使用,音乐框架,混合模式开启服务

混合开启要混合结束才能停止服务
主代码

package com.example.musicplayerframework;

import com.example.musicplayerframework.MusicPlayerService.MyIBinder;
import com.example.musicplayerframework.MusicPlayerService.MyIBinderVip;

import android.app.Activity;
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.Menu;
import android.view.MenuItem;
import android.view.View;

public class MainActivity extends Activity {
    private MyIBinderVip bind;
    private Mymain conn;
//  private MyIBinder vip;
    private IService  inter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 第一步通过Bind混合开启音乐服务
        Intent intent = new Intent(this, MusicPlayerService.class);
        conn = new Mymain();
        bindService(intent, conn, BIND_AUTO_CREATE);
        startService(intent);
    }

    // 播放下一首
    public void pre(View v) {
        bind.pre();
    }

    public void play(View v) {
        bind.play();
    }

    public void pause(View v) {
        bind.pause();
    }

    public void next(View v) {
        bind.next();
    }

    class Mymain implements ServiceConnection {

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
//          bind = (MyIBinder) service;//不能使用多态因为onBind方法return的是 new MyIBinderVip();
            bind = (MyIBinderVip) service;
            inter = (IService) service;//接口
            Log.e("tag", "onServiceConnected");
            
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            // TODO Auto-generated method stub
            Log.e("tag", "----->销毁21312313");
        }

    }
    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        unbindService(conn);
        Log.e("tag", "----->销毁");
        super.onDestroy();

    }
}

布局就四个Button添加点击
服务写

package com.example.musicplayerframework;

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

public class MusicPlayerService extends Service {
    
@Override
public void onCreate() {
    //MediaPlayer
    Log.e("tag","准备一个音乐播放器");
}

    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return new MyIBinderVip();
    }


    class MyIBinderVip extends Binder implements IService{

        public void next(){
            Log.e("tag", "播放下一首..甜蜜蜜");
        } 
        public void pre(){
            Log.e("tag", "播放下一首..一剪梅");
        }
        public void play(){
            Log.e("tag", "播放下一首..播放");
        }
        public void pause(){
            Log.e("tag", "播放下一首..暂停");
        }
        public void Vip(){
            Log.e("tag", "vip高品质播放");
        }
}
@Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // TODO Auto-generated method stub
    Log.e("tag", "onStartCommand");
        return super.onStartCommand(intent, flags, startId);
    }
@Override
    public void onDestroy() {
        // TODO Auto-generated method stub
    Log.e("tag", "救命我死了");
        super.onDestroy();
        
    }
}

接口写普通用户

package com.example.musicplayerframework;

public interface IService {
    public void next();
    public void pre();
    public void play();
    public void pause();
}

因为IService 这个借口被MyIBinderVip 给实现了,,在Activity中inter = (IService) service;//给借口赋值,值就是实现借口类,所以可以调用和强转

效果就是退出界面但是服务还开着放歌.只有我们的父类对象本身就是用子类new出来的时候, 才可以在将来被强制转换为子类对象.

往深了讲。子类强制转换为父类对象时，并没有实际丢失它原有内存空间（比父类多的那些部分）只是暂时不可访问。所以能再转回来。
另：父类对象可接受任何子类对象--此时发生自动转型--》转为父类类型--》所以能够再转回来。用instanceof 是防止错误的一种方式。