Android Dialog設置透明度

@Override
    public void show() {
        super.show();
        WindowManager m = ((Activity) mContext).getWindowManager();
        Display d = m.getDefaultDisplay();
        WindowManager.LayoutParams params = getWindow().getAttributes();
        params.width = (int) (d.getWidth() * 0.95);
        params.y = Util.dp2px(mContext, 120);
        params.dimAmount = 0.3f;
        getWindow().setAttributes(params);

    }