安卓Service和Broadcast实现简单的音乐播放器桥本环奈-

做实验的时候使用Service和Broadcast实现了一个功能较为简单的音乐播放器，可以对音乐进行播放、暂停和停止。
主要思路：
1、使用Service在后台播放音乐
2、Broadcast发送广播通知Activity更改界面
程序运行界面：

图1 播放界面

图2 暂停界面

图3 停止界面

实现代码：

1、布局界面XML如下

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"     xmlns:app="https://schemas.android.com/apk/res-auto"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:orientation="vertical"> <androidx.appcompat.widget.Toolbar         android:id="@+id/musicbar"         android:layout_width="match_parent"         android:layout_height="60dp"         android:background="?attr/colorPrimary"         android:minHeight="?attr/actionBarSize"         android:theme="?attr/actionBarTheme"         app:navigationIcon="@drawable/logo"         app:titleTextColor="@color/white" /> <View         android:id="@+id/view"         android:layout_width="match_parent"         android:layout_height="100dp" /> <ImageView         android:id="@+id/photo"         android:layout_width="250dp"         android:layout_height="250dp"         android:layout_gravity="center"         android:layout_marginBottom="20dp"         app:srcCompat="@drawable/qielogo" /> <TextView         android:id="@+id/musictext"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_gravity="center"         android:layout_marginBottom="100dp"         android:text="暂无播放音乐"         android:textSize="28dp" /> <LinearLayout         android:layout_width="match_parent"         android:layout_height="match_parent"         android:background="@color/white"         android:orientation="horizontal"> <ImageButton             android:id="@+id/start"             android:layout_width="90dp"             android:layout_height="90dp"             android:layout_weight="1"             android:background="@color/white"             android:scaleType="centerInside"             app:srcCompat="@drawable/start" /> <ImageButton             android:id="@+id/stop"             android:layout_width="90dp"             android:layout_height="90dp"             android:layout_weight="1"             android:background="@color/white"             android:scaleType="centerInside"             app:srcCompat="@drawable/stop" /> </LinearLayout> </LinearLayout> 

2、主Acitivy如下

package com.example.test6; import androidx.appcompat.app.AppCompatActivity; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.ImageButton; import android.widget.ImageView; import android.widget.TextView;  public class Music extends AppCompatActivity {     TextView musictext;     ImageView photo;     ImageButton startbutton;     Integer state = 2;     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_music);          IntentFilter inf = new IntentFilter();         inf.addAction("com.user.action");         registerReceiver(broad,inf);          musictext = findViewById(R.id.musictext);         photo = findViewById(R.id.photo);         startbutton = findViewById(R.id.start);         ImageButton stopbutton = findViewById(R.id.stop);          startbutton.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 switch (state){ case 1:                         state = 2; break;                     default:                         state = 1; break; }                 Log.v("当前状态","1");                 Intent intent = new Intent(Music.this,MusicService.class);                 intent.putExtra("action",state);                 startService(intent);                 Log.v("intent传值","1"); } });          stopbutton.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 Intent intent = new Intent(Music.this,MusicService.class);                 stopService(intent); } }); }      @Override     protected void onDestroy() {         super.onDestroy();         unregisterReceiver(broad); }      public BroadcastReceiver broad = new BroadcastReceiver() {         @Override         public void onReceive(Context context, Intent intent) {             int i = intent.getIntExtra("action",-1);             switch(i){ case 1:                     musictext.setText("China-X");                     photo.setImageResource(R.drawable.yjtp);                     startbutton.setImageResource(R.drawable.pause); break; case 2:                     startbutton.setImageResource(R.drawable.start);                     musictext.setText("音乐暂停"); break; case 3:                     state = 3;                     musictext.setText("暂无播放音乐");                     photo.setImageResource(R.drawable.qielogo);                     startbutton.setImageResource(R.drawable.start); break; } } }; } 

3、Service类如下

package com.example.test6; import android.app.Service; import android.content.Intent; import android.media.MediaPlayer; import android.os.IBinder; import android.util.Log;  public class MusicService extends Service {      public IBinder onBind(Intent intent){ return null; }      private MediaPlayer mp;      public void onCreate(){         super.onCreate(); }      public void onStart(Intent intent,int startId){         super.onStart(intent,startId);         int i = intent.getIntExtra("action",0);         if(i==1){             if(null==mp) {                 mp = MediaPlayer.create(this, R.raw.mymusic);                 mp.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {                     @Override                     public void onCompletion(MediaPlayer mp) {                         stopSelf(); } }); }             mp.start(); }else if(i==2){             if(mp!=null&&mp.isPlaying()){                 mp.pause(); } }         Log.v("zhuangtai",String.valueOf(i));         Intent in = new Intent("com.user.action");         in.putExtra("action",i);         sendBroadcast(in); }      public void onDestroy(){         super.onDestroy();         mp.stop();         Intent in = new Intent("com.user.action");         in.putExtra("action",3);         sendBroadcast(in); } }