Android实现音量调节的方法

<?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>

package com.ljq.activity;
import android.app.Activity;
import android.app.Service;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.ToggleButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
public class AudioActivity 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.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(AudioActivity.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;
      }
    }
  };
}