通过拖动滑动块来改变图片透明度

布局文件<ImageView
android:id="@+id/image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/dog1" />
<SeekBar
android:id="@+id/seekBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:max="255"
android:progress="255"
android:thumb="@drawable/bar"
/>

Java控制亮度文件public class MainActivity extends AppCompatActivity {
ImageView imageView ;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = (ImageView)findViewById(R.id.image);
SeekBar seekBar = (SeekBar)findViewById(R.id.seekBar);
//当拖动条的滑块发生变化时触发该方法
seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
imageView.setImageAlpha(progress);
}

@Override
public void onStartTrackingTouch(SeekBar seekBar) {

}

@Override
public void onStopTrackingTouch(SeekBar seekBar) {

}
});
}
}