iOS开发实现父视图透明子视图不透明

要实现该效果其实很简单，但如果一直纠结把父视图用view.alpha=0.5属性设置父视图的话会很麻烦。

简单介绍两方法：

1:将透明父视图和要显示的子实体添加在同一个父视图上，先添加透明视图，在加子视图，这样看起来就是父视图透明子视图不透明。

```

-(void)createUI{

UIView *backView=[[UIView alloc]initWithFrame:CGRectMake(0, 100, 375, 400)];

backView.backgroundColor=[UIColor grayColor];

backView.alpha=0.5;

[self.view addSubview:backView];

UIView *yellowView=[[UIView alloc]initWithFrame:CGRectMake(50, 150, 275, 300)];

yellowView.backgroundColor=[UIColor yellowColor];

[self.view addSubview:yellowView];

}

2:父视图使用RGB方法设置颜色和透明度

-(void)createUI{

UIView *backView=[[UIView alloc]initWithFrame:CGRectMake(0, 100, 375, 400)];

backView.backgroundColor=[UIColor colorWithRed:140/255.0 green:140/255.0 blue:140/255.0 alpha:0.5];

[self.view addSubview:backView];

UIView *yellowView=[[UIView alloc]initWithFrame:CGRectMake(50, 50, 275, 300)];

yellowView.backgroundColor=[UIColor yellowColor];

[backView addSubview:yellowView];

}

```

上面两种方法都可以非常简单的实现父视图透明子视图不透明