安卓学习-界面-ui-SeekBar

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linearLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:padding="10dp" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="改变图片透明度"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <SeekBar
        android:id="@+id/seekBar1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:max="255"
        android:progress="255"
        android:thumb="@drawable/ic_launcher"
         />

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/pic1" />

</LinearLayout>

public class MainActivity extends Activity{

    SeekBar seekBar1;
    ImageView imageView1;
    
    Handler handler=new Handler(){
        public void handleMessage(Message msg) {
            if(msg.what==123){
                int alpha =msg.getData().getInt("alpha");
                imageView1.setImageAlpha(alpha);
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        imageView1=(ImageView)findViewById(R.id.imageView1);
        seekBar1=(SeekBar)findViewById(R.id.seekBar1);
        seekBar1.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
            
            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                // TODO 自动生成的方法存根
                
            }
            
            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                // TODO 自动生成的方法存根
                
            }
            
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress,
                    boolean fromUser) {
                Message msg=new Message();
                msg.what=123;
                Bundle data=new Bundle();
                data.putInt("alpha", progress);
                msg.setData(data);
                handler.sendMessage(msg);
                
            }
        });
    }

}