Android SeekBar实现音量调节

SeekBar可以通过滑块的位置来标识数值----而且拖动条允许用户拖动滑块来改变值，因此拖动条通常用于对系统的某种数值进行调节，比如调节音量等。

SeekBar允许用户改变拖动条的滑块外观，改变滑块外观通常通过如下属性来指定：android:thumb: 指定一个Drawable对象，该对象将自定义滑块。

为了让程序能响应拖动条滑块位置的改变，程序可以考虑为它绑定一个OnSeekBarChangeListener监听器。

以下是一个使用SeekBar来调节系统音量的实例：

XML代码：

 <SeekBar
                android:id="@+id/sound"
                android:layout_width="150px"
                android:layout_height="10px"
                android:max="100"  //设置拖动条最大值
                android:progress="10"   //设置拖动条当前值
                android:progressDrawable="@layout/seekbar_style"  //拖动条样式
                android:thumb="@layout/thumb" />    //滑块样式

seekbar_style.xml:

<?xml version="1.0" encoding="UTF-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">   

    <item android:id="@android:id/background">
        <shape>
            <corners android:radius="10dip" />
            <gradient android:startColor="#ffffffff"
                android:centerColor="#ff000000" android:endColor="#ff808A87"
                android:centerY="1" android:angle="270" />
        </shape>
    </item>   

    <item android:id="@android:id/progress">
        <clip>
            <shape>
                <corners android:radius="10dip" />
                <gradient android:startColor="#ffffffff"
                    android:centerColor="#ffFFFF00" android:endColor="#ffAABD00"
                    android:centerY="1" android:angle="270" />
            </shape>
        </clip>
    </item>
</layer-list>    

thumb.xml:

<?xml version="1.0" encoding="UTF-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- 按下状态 -->
    <item
        android:state_pressed="true"
        android:drawable="@drawable/thumb_normal"
        />      

    <!-- 普通无焦点状态 -->
    <item
        android:state_focused="false"
        android:state_pressed="false"
        android:drawable="@drawable/thumb_normal"
    />   

</selector>    

bacon_seekbar.xml:

<layer-list
  xmlns:android="http://schemas.android.com/apk/res/android"
>
  <item
    android:id="@+android:id/background"
    android:drawable="@drawable/thumb_normal" />
  <item
    android:id="@+android:id/SecondaryProgress"
    android:drawable="@drawable/thumb_normal" />
  <item
    android:id="@+android:id/progress"
    android:drawable="@drawable/thumb_normal" />
</layer-list>

JAVA代码：

public class PianoActivity extends Activity {
    /** Called when the activity is first created. */
     private ImageButton imageButton_white1;
    private MediaPlayer mediaPlayer01;
    public  AudioManager audiomanage;
    private TextView mVolume ;  //显示当前音量
     public  SeekBar soundBar;
     private int maxVolume, currentVolume;  

    private int volume=0;  //初始化声音

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mediaPlayer01 = new MediaPlayer();

        imageButton_white1=(ImageButton)findViewById(R.id.white1);
        final SeekBar soundBar=(SeekBar)findViewById(R.id.sound);  //音量设置
        mVolume = (TextView)findViewById(R.id.mVolume);
        audiomanage = (AudioManager)getSystemService(Context.AUDIO_SERVICE);  

        maxVolume = audiomanage.getStreamMaxVolume(AudioManager.STREAM_MUSIC);  //获取系统最大音量
        soundBar.setMax(maxVolume);   //拖动条最高值与系统最大声匹配
        currentVolume = audiomanage.getStreamVolume(AudioManager.STREAM_MUSIC);  //获取当前值
        soundBar.setProgress(currentVolume);
        mVolume.setText(currentVolume*100/maxVolume + " %");  

        soundBar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() //调音监听器
        {
            public void onProgressChanged(SeekBar arg0,int progress,boolean fromUser)
            {
                audiomanage.setStreamVolume(AudioManager.STREAM_MUSIC, progress, 0);
                currentVolume = audiomanage.getStreamVolume(AudioManager.STREAM_MUSIC);  //获取当前值
                soundBar.setProgress(currentVolume);
                mVolume.setText(currentVolume*100/maxVolume + " %");
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                // TODO Auto-generated method stub

            }
            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                // TODO Auto-generated method stub

            }
        });

TextView的XML没有给出，需要自己添加。

完成效果：