Android 播放音频

package com.example.test2;

import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.app.Activity;
import android.app.Service;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.ToggleButton;

public class MainActivity extends Activity {

    private Button btnPlay=null, btnUpper=null, btnLower=null;
    private ToggleButton tbMute=null;
    private MediaPlayer mediaPlayer=null; //声频
    private AudioManager audioManager=null; //音频
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    
        audioManager=(AudioManager)getSystemService(Service.AUDIO_SERVICE);
        btnPlay=(Button)findViewById(R.id.btnPlay);
        btnUpper=(Button)findViewById(R.id.btnUpper);
        btnLower=(Button)findViewById(R.id.btnLower);
        btnPlay.setOnClickListener(listener);
        btnUpper.setOnClickListener(listener);
        btnLower.setOnClickListener(listener);
        tbMute=(ToggleButton)findViewById(R.id.tbMute);
        tbMute.setOnCheckedChangeListener(new OnCheckedChangeListener(){
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                audioManager.setStreamMute(AudioManager.STREAM_MUSIC, !isChecked); //设置是否静音
            }
        });
    }
    
    View.OnClickListener listener=new View.OnClickListener(){
        public void onClick(View v) {
            @SuppressWarnings("unused")
            Button btn=(Button)v;
            switch (v.getId()) {
            case R.id.btnPlay://播放音乐
                mediaPlayer=MediaPlayer.create(MainActivity.this, R.raw.music);
                mediaPlayer.setLooping(true);//设置循环播放
                mediaPlayer.start();//播放声音    
                break;
            case R.id.btnUpper://增多音量
                //adjustStreamVolume: 调整指定声音类型的音量
                audioManager.adjustStreamVolume(AudioManager.STREAM_MUSIC, 
                        AudioManager.ADJUST_RAISE, 
                        AudioManager.FLAG_SHOW_UI);    //调高声音
                break;
            case R.id.btnLower://减少音量
                //第一个参数：声音类型
                //第二个参数：调整音量的方向
                //第三个参数：可选的标志位
                audioManager.adjustStreamVolume(AudioManager.STREAM_MUSIC, 
                        AudioManager.ADJUST_LOWER, 
                        AudioManager.FLAG_SHOW_UI);//调低声音
                break;
            }
        }
    };

}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <Button android:id="@+id/btnPlay" 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" 
        android:text="播放音乐" />
    <LinearLayout android:orientation="horizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal">
        <ToggleButton android:id="@+id/tbMute"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" 
            android:textOn="静音"
            android:textOff="正常"
            android:checked="true"
            android:layout_gravity="center_vertical" />
        <Button android:id="@+id/btnUpper"
            android:text="增大音量" 
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
        <Button android:id="@+id/btnLower"
            android:text="减小音量" 
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </LinearLayout>
</LinearLayout>