Android 音乐播放器的开发教程：运用Broadcast实现service与activity的通信

运用Broadcast实现service与activity的通信

       做到了这一步,现在的播放器应该可以显示歌曲列表,能够点击并播放音乐了哈,但是上面的按钮一个都不能点啊有没有,一旦放起来停都停不下来,不要着急,这一篇博客将介绍怎么将activity上的按钮都派上用场.

        

        前面介绍过了,播放歌曲是在一个service中进行的,而按钮在activity和fragment上,怎么才能让它们联系起来呢?这就要用到安卓的另外一个四大组件之一----Broadcast,通常翻译为广播(感觉又是怪怪的样子),Broadcast是一种广泛运用的在应用程序之间传输信息的机制。而BroadcastReceiver是对发送出来的 Broadcast进行过滤接受并响应的一类组件。这篇将介绍如何实现service和activity的通信.

        发送广播的方式很简单,只需要新建一个Intent,里面存放一些需要传出去的信息即可,例如

 Intent intent_to_activity = new Intent("color:#ff9966;">"com.dada.communication.RECEIVER");    //这个intent中的字符串可以自定义,只需要在广播接收器上与这个字符串一样即可,下面会提到的.

 intent_to_activity.putExtra("title", intent.getStringExtra("title"));
         intent_to_activity.putExtra("artist", intent.getStringExtra("artist"));
         intent_to_activity.putExtra("album", intent.getStringExtra("album"));
         intent_to_activity.putExtra("album_id", intent.getLongExtra("album_id", 0));

      

        这样就把信息存放在了intent_to_activity中了,之后再用一句话,sendBroadcast(intent_to_activity)将这个包含信息的intent发送出去,发送广播的工作就已经做完啦,发出广播之后,还需要接收这个消息,这里需要实现的是activity和service的通信,故一边发,另外一边接收,上面的代码是写在service中的,故接收器应写在activity中.

         定义广播的接收器,有三个步骤,

        第一步:      定义一个自定义Receiver类,需要继承Broadcast类,其中写入收到广播之后,需要执行的代码,例如:

 private class MsgReceiver extends BroadcastReceiver {
         @Override
         public void onReceive(Context context, Intent intent) {
             music_info_textView = (TextView)findViewById(R.id.music_info_textView);
             singer_info_textView = (TextView)findViewById(R.id.singer_info_textView);

             music_info_textView.setText(intent.getStringExtra("title"));
             singer_info_textView.setText(intent.getStringExtra("artist"));

         }
     }

         

        第二步:   实例化这个类,并创建一个IntentFilter,这个相当于一个广播的过滤器,对其进行操作,可以过滤出自己想要监听的广播.

 IntentFilter intentMsgFilter = new IntentFilter();

          第三步:   对IntentFilter操作,并将其与第一步定义的接收器绑定在一起.

 intentMsgFilter.addAction("color:#ff6666;">"com.example.communication.RECEIVER");        //注册歌曲信息的广播接收器,需要与上面发送广播的intent字符串一致
         registerReceiver(msgReceiver,intentMsgFilter);

        到这里,广播的收发就能进行了,是不是比较容易.下面就给出MainActivity.java和PlayerService.java的代码,红色部分为基于上一篇的改动,里面主要就是实现了播放与暂停键的相应,歌曲名和艺术家名的显示,还有进度条的更新.

MainActivity.java

 package com.example.dada.myapplication;

 import android.app.FragmentManager;
 import android.app.FragmentTransaction;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.net.Uri;
 import android.support.v7.app.ActionBarActivity;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.widget.ImageButton;
 import android.widget.SeekBar;
 import android.widget.TextView;

 import java.util.List;


 public class MainActivity extends ActionBarActivity
         implements MainFragment.OnFragmentInteractionListener,
                    MyMusicFragment.OnFragmentInteractionListener{


     private boolean isPause;                                               //记录当前播放器的状态
     private FragmentManager fragmentManager;
     private FragmentTransaction fragmentTransaction;
     private MyMusicFragment myMusicFragment;
     private MainFragment mainFragment;
     private FindSongs finder;                                              //查找歌曲的类
     public static List mp3Infos;                                  //歌曲列表
     public static int music_position;                                      //音乐的位置
 "color:#ff0000;">    private int current_position;                                          //当前进度条的位置

     "color:#ff0000;">private ImageButton play_button;                                       //播放按钮控件
     private TextView music_info_textView;                                  //显示歌曲信息的textview
     private TextView singer_info_textView;                                 //显示歌手信息的textview
     private SeekBar seek_bar;                                              //进度条控件

   "color:#ff0000;">  private MsgReceiver msgReceiver;                                       //service发过来的广播接收器
     private BarReceiver barReceiver;                                       //进度条的接收器

     private Intent intent_to_service;                                      //向service发送广播的intent


     /*
     这个方法是activity和fragment通信的一种方法
     在MainFragment中调用这个方法,可以在activity中做出相应的反应
      */
     public void onMainFragmentInteraction(int msg){

         /*
         对其中的参数msg做出判断,如果为CHANGE_TO_MY_MUSIC_FRAGMENT
         则执行跳转
          */
         if(msg == AppConstant.PlayerMsg.CHANGE_TO_MY_MUSIC_FRAGMENT){

             /*
             在这里并没有直接切换Fragment
             而是调用了activity实现MyMusicFragment的那个接口
             对后面的开发能带来一点便利之处
              */
             onMyMusicFragmentInteraction(AppConstant.PlayerMsg.CHANGE_TO_MY_MUSIC_FRAGMENT);
         }
     }

     public void onMyMusicFragmentInteraction(int msg){

         myMusicFragment = new MyMusicFragment();       //创建了MyMusicFragment的实例
         FragmentManager fragmentManager = getFragmentManager();   //得到FragmentManager
         FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction(); //得到fragmentTransaction


         if(msg == AppConstant.PlayerMsg.CHANGE_TO_MY_MUSIC_FRAGMENT){



             fragmentTransaction.replace(R.id.fragment_layout, myMusicFragment);
             fragmentTransaction.addToBackStack(null);        //这句话是将被替换的MainFragment加入到一个专门存放fragment的栈中,在回退的时候显示上一个Fragment
             fragmentTransaction.commit();

         }

         if(msg == AppConstant.PlayerMsg.BACK_TO_MAIN_FRAGMENT){

             fragmentTransaction.replace(R.id.fragment_layout, mainFragment);
             fragmentTransaction.addToBackStack(null);
             fragmentTransaction.commit();
         }
     }

     public void onMyMusicFragmentInteraction(int msg,int position){
         if(msg == AppConstant.PlayerMsg.LIST_CLICK){
             if (mp3Infos != null) {
                 isPause = false;
                 initService(position);
             }
         }
     }

 "color:#ff0000;">/*

 "color:#ff0000;">这个方法是重写了activity里自带的方法onStart()

 "color:#ff0000;">里面要带上super.onStart();不然会报错的

 "color:#ff0000;">*/
 "color:#ff0000;">    @Override
     protected void onStart(){

         super.onStart();
         IntentFilter intentMsgFilter = new IntentFilter();
         IntentFilter intentBarFilter = new IntentFilter();


         intentMsgFilter.addAction("com.example.communication.RECEIVER");        //注册歌曲信息的广播接收器
         registerReceiver(msgReceiver,intentMsgFilter);

         intentBarFilter.addAction("com.example.communication.BAR");             //注册进度条的广播接收器
         registerReceiver(barReceiver,intentBarFilter);
     }


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

         music_position = 0;
 "color:#ff0000;">        current_position = 0;
         finder = new FindSongs();

 "color:#ff0000;">        msgReceiver = new MsgReceiver();
         barReceiver = new BarReceiver();

         mp3Infos = finder.getMp3Infos(getContentResolver());

 "color:#ff0000;">        intent_to_service = new Intent("com.example.communication.PLAY");

         seek_bar = (SeekBar)findViewById(R.id.process_bar);
         play_button = (ImageButton)findViewById(R.id.play_button);
         play_button.setImageResource(R.drawable.play_photo);
 "color:#ff0000;">        play_button.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
                 if(isPause){
                     isPause = false;
                     play_button.setImageResource(R.drawable.pause_photo);
                 }
                 else{
                     isPause = true;
                     play_button.setImageResource(R.drawable.play_photo);
                 }

 "color:#ff0000;">/*

 "color:#ff0000;">将音乐播放到了的当前位置和当前的状态

 "color:#ff0000;">以广播的形式发送给service

 "color:#ff0000;">来让service可以接着刚才暂停的位置开始播放

 "color:#ff0000;">而不是重新播放

 "color:#ff0000;">*/

 "color:#ff0000;">                intent_to_service.putExtra("position",current_position);
                 intent_to_service.putExtra("isPause",isPause);
                 sendBroadcast(intent_to_service);
             }
         });

         mainFragment = new MainFragment();           //创建了刚才定义的MainFragment实例
         fragmentManager = getFragmentManager();      //得到FragmentManager
         fragmentTransaction = fragmentManager.beginTransaction();   //得到fragmentTransaction,用于管理fragment的切换
         fragmentTransaction.replace(R.id.fragment_layout, mainFragment).commit();  //将MainActivity里的布局模块fragment_layout替换为mainFragment
     }


     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         // Inflate the menu; this adds items to the action bar if it is present.
         getMenuInflater().inflate(R.menu.menu_main, menu);
         return true;
     }

     @Override
     public boolean onOptionsItemSelected(MenuItem item) {
         // Handle action bar item clicks here. The action bar will
         // automatically handle clicks on the Home/Up button, so long
         // as you specify a parent activity in AndroidManifest.xml.
         int id = item.getItemId();

         //noinspection SimplifiableIfStatement
         if (id == R.id.action_settings) {
             return true;
         }

         return super.onOptionsItemSelected(item);
     }

     private void initService(int position) {
         music_position = position;
         Mp3Info mp3Info = mp3Infos.get(position);

 "color:#ff0000;">        seek_bar.setMax((int)mp3Info.getDuration());          //获取当前播放歌曲的长度,设置进度条的最大值
         /*
         这里新建了一个Intent
         里面存放各种即将传给Service的数据
         要启动自定义PlayerService类
         还需要在AndroidManifest中加入如下代码


             android:name="com.example.dada.myapplication.PlayerService"
             android:exported="false"
             >


          */
         Intent intent = new Intent("com.example.communication.MSG_ACTION");
         play_button.setImageResource(R.drawable.pause_photo);
         intent.putExtra("url", mp3Info.getUrl());
         intent.putExtra("title", mp3Info.getTitle());
         intent.putExtra("artist", mp3Info.getArtist());
         intent.putExtra("album", mp3Info.getAlbum());
         intent.putExtra("album_id", mp3Info.getAlbum_id());
         intent.putExtra("MSG", AppConstant.PlayerMsg.PLAY_MSG);
         intent.setClass(MainActivity.this, PlayerService.class);
         startService(intent);
     }

 "color:#ff0000;">    private class MsgReceiver extends BroadcastReceiver {
         @Override
         public void onReceive(Context context, Intent intent) {
             music_info_textView = (TextView)findViewById(R.id.music_info_textView);
             singer_info_textView = (TextView)findViewById(R.id.singer_info_textView);

 "color:#ff0000;">/*

 "color:#ff0000;">从接收到的广播的intent中取出发送过来的信息

 "color:#ff0000;">这里是取出了歌曲名和艺术家名

 "color:#ff0000;">*/

 "color:#ff0000;">            music_info_textView.setText(intent.getStringExtra("title"));
             singer_info_textView.setText(intent.getStringExtra("artist"));

         }
     }

     private class BarReceiver extends BroadcastReceiver{
         @Override
         public void onReceive(Context context, Intent intent) {

 "color:#ff0000;">/*

 "color:#ff0000;">取出后,更新进度条当前的位置

 "color:#ff0000;">*/
                 current_position = intent.getIntExtra("position",0);
                 seek_bar.setProgress(current_position);
         }
     }
 }

PlayerService.java

 package com.example.dada.myapplication;

 import android.app.Notification;
 import android.app.NotificationManager;
 import android.app.PendingIntent;
 import android.app.Service;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.media.MediaPlayer;
 import android.os.Handler;
 import android.os.IBinder;
 import android.os.Looper;
 import android.os.Message;
 import android.view.animation.AnimationUtils;
 import android.widget.RemoteViews;

 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;


 public class PlayerService extends Service implements AppConstant {

     private int current_position;

     private String musicPath;
     private String music_artist;
     private String music_title;
     private String notification_msg;

     private boolean isPause = true;
     private boolean isChangToNext;

 "color:#ff0000;">    private PlayReceiver playReceiver;           //自定义的广播接收器

     public static MediaPlayer mediaPlayer = new MediaPlayer();

 "color:#ff0000;">    private Intent intent_to_activity = new Intent("com.example.communication.RECEIVER");   //发送广播的intent
     private Intent intent_to_progressBar = new Intent("com.example.communication.BAR");

 "code" class="java" style="font-family: Verdana, Geneva, Arial, Helvetica, sans-serif;">"color:#ff0000;"> "color: rgb(255, 0, 0); font-family: Verdana, Geneva, Arial, Helvetica, sans-serif;">/*这里运用到了Handler对各种消息的处理,主要是用它来更新UI

 "font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:#ff0000;">   在下面代码的自定义广播接收器类中,收到消息后,会给这个myHandler发送消息

 "font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:#ff0000;">再由这个myHandler做统一的处理

 "color: rgb(255, 0, 0); font-family: Verdana, Geneva, Arial, Helvetica, sans-serif;">*/

 "color:#ff0000;">    private Handler myHandler = new Handler() {

 "color:#ff0000;">
         public void handleMessage(Message msg) {
             if (msg.what == PlayerMsg.PLAY_MSG) {
                 current_position = mediaPlayer.getCurrentPosition();
                 intent_to_progressBar.putExtra("position",  current_position);
                 sendBroadcast(intent_to_progressBar);
                 myHandler.sendEmptyMessageDelayed(PlayerMsg.PLAY_MSG, 1000);
             }
             if (msg.what == PlayerMsg.PAUSE) {
                 stopMusic();
             }
         }
     };

     @Override
     public IBinder onBind(Intent intent) {
         return null;
     }

     public int onStartCommand(Intent intent, int flags, int startId) {

         notification_msg = null;

 "color:#ff0000;">/*

 "color:#ff0000;">这里就是前面讲到的接收广播的三部曲

 "color:#ff0000;">*/
         "color:#ff0000;">playReceiver = new PlayReceiver();
         IntentFilter intentPlayFilter = new IntentFilter();
         intentPlayFilter.addAction("com.example.communication.PLAY");
         registerReceiver(playReceiver, intentPlayFilter);

         try {
             int msg = intent.getIntExtra("MSG", 0);
             musicPath = intent.getStringExtra("url");
             "color:#ff0000;">SendBroadcastToActivity(intent);

             if (msg == AppConstant.PlayerMsg.PLAY_MSG) {

 "color:#ff0000;">/*

 "color:#ff0000;">向myHandler发送消息,由myHandler做出处理

 "color:#ff0000;">*/
               "color:#ff0000;">  myHandler.sendEmptyMessage(PlayerMsg.PLAY_MSG);
                 playMusic(0);
             }
         } catch (Exception e) {
             e.printStackTrace();
         }
         return 0;
     }

     private void playMusic(int position) {
         try {
             mediaPlayer.reset();
             mediaPlayer.setDataSource(musicPath);
             mediaPlayer.prepare();
             mediaPlayer.setOnPreparedListener(new MyPreparedListener(position));

         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     private class MyPreparedListener implements MediaPlayer.OnPreparedListener {

         private int position;

         public MyPreparedListener(int position) {
             this.position = position;
         }

         public void onPrepared(MediaPlayer mp) {
             if (position > 0)
                 mediaPlayer.seekTo(position);
             mediaPlayer.start();
         }
     }

     private void stopMusic() {
         if (mediaPlayer != null) {
             mediaPlayer.pause();
         }
     }

     public void onDestory() {
         if (mediaPlayer != null) {
             mediaPlayer.stop();
             mediaPlayer.release();
         }
     }

   "color:#ff0000;">  private void SendBroadcastToActivity(Intent intent) {                                //向activity发送广播的函数

         music_title = intent.getStringExtra("title");
         music_artist = intent.getStringExtra("artist");
         intent_to_activity.putExtra("title", intent.getStringExtra("title"));
         intent_to_activity.putExtra("artist", intent.getStringExtra("artist"));
         intent_to_activity.putExtra("album", intent.getStringExtra("album"));
         intent_to_activity.putExtra("album_id", intent.getLongExtra("album_id", 0));
         sendBroadcast(intent_to_activity);
     }

     private class PlayReceiver extends BroadcastReceiver {                             //播放与暂停广播接收器

         public PlayReceiver() {
             super();
         }

         @Override
         public void onReceive(Context context, Intent intent) {

             isPause = intent.getBooleanExtra("isPause", true);
             isChangToNext = intent.getBooleanExtra("isChangeToNext", false);

             if (isPause) {
                 myHandler.sendEmptyMessage(PlayerMsg.PAUSE);
             } else {
                 current_position = intent.getIntExtra("position", 0);
                 playMusic(current_position);
                 myHandler.sendEmptyMessage(PlayerMsg.PLAY_MSG);
             }
         }
     }

 }

      上面好长好长的代码,实现的就是能暂停和播放,进度条能显示播放进度,activity能显示歌曲信息,其中包含了两个Broadcast的收发,一个handler的应用.广播在android开发中用的还是比较多的,感觉也是比较好用的哈.