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：

<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