Android学习：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 + " %");          }        @Overridepublic void onStartTrackingTouch(SeekBar seekBar) {// TODO Auto-generated method stub}@Overridepublic 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：