如何在所有视图的顶部添加UIView？

Question

我有这样的代码:

@interface Alert : UIView 
{

}
/*
- (void) initWithTitle:(NSString*)title message:(NSString*)message cancelButtonTitle:(NSString*)cancelButtonTitle otherButtonTitles:(NSString*)buttonTitle,... delegate:(id)delegate;
*/
@end


@implementation Alert

- (void) drawRect:(CGRect)rect 
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextClearRect(context, rect); // ??????? context

    CGContextSetRGBFillColor(context, 255, 0, 0, 1);
    CGContextFillRect(context, CGRectMake(20, 20, 100, 100));
}

- (void) show
{
    self.center = [[[UIApplication sharedApplication] keyWindow] center];
    [[[UIApplication sharedApplication] keyWindow] addSubview:self];
    [[[UIApplication sharedApplication] keyWindow] bringSubviewToFront:self];
}

然后我就这样使用它:

- (void)viewDidLoad
{
    [super viewDidLoad];
     Alert * alert = [[Alert alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
    [alert show];
    [alert release];
}

但它不起作用(我希望看到Alert高于所有其他视图).你可以帮帮我吗？

Answer 1

正确处理设备方向的推荐解决方案是

• pod AGWindowView它将自动处理任何旋转和帧更改,因此您不必担心这一点.
• 阅读并关注官方帖子https://developer.apple.com/library/content/qa/qa1688/_index.html

• 将视图添加到第一个子视图,而不是将其添加到窗口
  

  UIWindow* window = [UIApplication sharedApplication].keyWindow;
  if (!window) 
      window = [[UIApplication sharedApplication].windows objectAtIndex:0];
  [[[window subviews] objectAtIndex:0] addSubview:myView];
  

您也可以将其添加到窗口中.但它不会处理设备方向.

let window = UIApplication.sharedApplication().keyWindow!
let view = UIView(frame: CGRect(x: window.frame.origin.x, y: window.frame.origin.y, width: window.frame.width, height: window.frame.height))
window.addSubview(v);
view.backgroundColor = UIColor.blackColor()

Answer 2

还有另一种方法

在视图中添加以下方法将在每次推/弹出视图控制器时添加

-(void)viewWillAppear:(BOOL)animated
{
     [super viewWillAppear:animated];

     [[[UIApplication sharedApplication] keyWindow] addSubview:<yourViewObject>];
}

为了在下一个类中删除此视图，请添加以下代码行

-(void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    [<yourViewObject> removeFromSuperview];
 }