package com.ispring.startservicedemo;

import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.IBinder;
import android.widget.Toast;

import java.io.IOException;

public class MusicService extends Service {

  private MediaPlayer mediaPlayer = null;

  private boolean isReady = false;

  @Override
  public void onCreate() {
    //onCreate在Service的生命周期中只会调用一次
    super.onCreate();

    //初始化媒体播放器
    mediaPlayer = MediaPlayer.create(this, R.raw.music);
    if(mediaPlayer == null){
      return;
    }

    mediaPlayer.stop();
    mediaPlayer.setOnErrorListener(new MediaPlayer.OnErrorListener() {
      @Override
      public boolean onError(MediaPlayer mp, int what, int extra) {
        mp.release();
        stopSelf();
        return false;
      }
    });

    try{
      mediaPlayer.prepare();
      isReady = true;
    } catch (IOException e) {
      e.printStackTrace();
      isReady = false;
    }

    if(isReady){
      //将背景音乐设置为循环播放
      mediaPlayer.setLooping(true);
    }
  }

  @Override
  public int onStartCommand(Intent intent, int flags, int startId) {
    //每次调用Context的startService都会触发onStartCommand回调方法
    //所以onStartCommand在Service的生命周期中可能会被调用多次
    if(isReady && !mediaPlayer.isPlaying()){
      //播放背景音乐
      mediaPlayer.start();
      Toast.makeText(this, "开始播放背景音乐", Toast.LENGTH_LONG).show();
    }
    return START_STICKY;
  }

  @Override
  public IBinder onBind(Intent intent) {
    //该Service中不支持bindService方法，所以此处直接返回null
    return null;
  }

  @Override
  public void onDestroy() {
    //当调用Context的stopService或Service内部执行stopSelf方法时就会触发onDestroy回调方法
    super.onDestroy();
    if(mediaPlayer != null){
      if(mediaPlayer.isPlaying()){
        //停止播放音乐
        mediaPlayer.stop();
      }
      //释放媒体播放器资源
      mediaPlayer.release();
      Toast.makeText(this, "停止播放背景音乐", Toast.LENGTH_LONG).show();
    }
  }
}

package com.ispring.startservicedemo;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;


public class MusicActivity extends Activity implements Button.OnClickListener {

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

  @Override
  public void onClick(View v) {
    if(v.getId() == R.id.btnStart){
      //播放背景音乐
      Intent intent = new Intent(this, MusicService.class);
      startService(intent);
      //退出当前Activity
      this.finish();
    }else if(v.getId() == R.id.btnStop){
      //停止播放音乐
      Intent intent = new Intent(this, MusicService.class);
      stopService(intent);
    }
  }
}