經過拖動滑動塊來改變圖片透明度

1. 佈局文件
   

<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"
        />

2.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);
        //當拖動條的滑塊發生變化時觸發該方法
        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) {

            }
        });
    }
}