//新建一個UIView並設定它的位置和大小
UIView *view1 = [[UIView alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
//為新建的UIView設定背景顏色
    view1.backgroundColor = [UIColor redColor];
    //透明度
    view1.alpha = 0.2;
    //是否隱藏
    view1.hidden = YES;
    //設定中心點為螢幕的中心點
    view1.center = self.view.center;
    //標籤值
    view1.tag = 99;
    //根據標籤值找到view1,下面這個resultView就是view1
    UIView *resultView = [self.view viewWithTat:99];
    //將UIView放到窗體中
    [self.view addSubview:view1];
    //將子檢視移動到前面
    [self.view bringSubviewToFront:resultView];
    //將子檢視移動到後面
    [self.view sendSubviewToBack:resultView];
    //銷燬view1
    [view1 removeFromSuperview];