仿微信朋友圈点击图片变暗

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.StateListDrawable;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ImageView;

public class MaskImageView extends ImageView {

  public MaskImageView(Context context) {
    super(context);
  }

  public MaskImageView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public MaskImageView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }

  @Override
  public void setImageBitmap(Bitmap bm) {
    Drawable d = createStateDrawable(getContext(), new BitmapDrawable(getContext().getResources(), bm));
    setImageDrawable(d);
  }

  public StateListDrawable createStateDrawable(Context context, Drawable normal) {
    StateListDrawable drawable = new StateListDrawable();
    drawable.addState(View.PRESSED_ENABLED_STATE_SET, createPressDrawable(normal));
    drawable.addState(View.ENABLED_STATE_SET, normal);
    drawable.addState(View.EMPTY_STATE_SET, normal);
    return drawable;
  }

  public Drawable createPressDrawable(Drawable d) {
    Bitmap bitmap = ((BitmapDrawable) d).getBitmap().copy(Bitmap.Config.ARGB_8888, true);
    Paint paint = new Paint();
    paint.setColor(0x60000000);
    RectF rect = new RectF(0, 0, bitmap.getWidth(), bitmap.getHeight());
    new Canvas(bitmap).drawRoundRect(rect, 4, 4, paint);
    return new BitmapDrawable(getContext().getResources(), bitmap);
  }

}

来自：http://www.tuicool.com/articles/Qbqmyey