Android实现背景变暗

好图

// 产生背景变暗效果

WindowManager.LayoutParams lp = ((Activity)mContext).getWindow().getAttributes();

lp.alpha =0.4f;

((Activity)mContext).getWindow().addFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);

((Activity)mContext).getWindow().setAttributes(lp);

//恢复透明度

WindowManager.LayoutParams lp = ((Activity)mContext).getWindow().getAttributes();

lp.alpha =1f;

((Activity)mContext).getWindow().addFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);

((Activity)mContext).getWindow().setAttributes(lp);