Ios 爆米花不'；t居中按钮

我正试着把一个爆米花放在一个按钮的中心。我似乎不知道我可能会错在哪里。而不是箭头在按钮的中间，它偏离了屏幕宽度的一半。

 @IBAction func buttonClicked(sender: AnyObject){
    var popoverViewController = self.storyboard?.instantiateViewControllerWithIdentifier("ServiceOptions") as! ServiceOptionsPopover
    popoverViewController.delegate = self
    popoverViewController.modalPresentationStyle = .Popover
    popoverViewController.preferredContentSize   = CGSizeMake(300, 300)

    let popoverPresentationViewController = popoverViewController.popoverPresentationController

    popoverPresentationViewController?.permittedArrowDirections = .Up
    popoverPresentationViewController?.delegate = self
    popoverPresentationViewController?.sourceView = sender as! UIButton
    popoverPresentationViewController?.sourceRect = sender.frame

    presentViewController(popoverViewController, animated: true, completion: nil)
}

以下是正确的方法：

@IBAction func buttonClicked(sender: UIButton){
    var popoverViewController = UIViewController()
    popoverViewController.view.frame = CGRectMake(0,0, 300, 300)
    popoverViewController.view.backgroundColor = UIColor.redColor()
    popoverViewController.modalPresentationStyle = .Popover
    popoverViewController.preferredContentSize   = CGSizeMake(300, 300)

    let popoverPresentationViewController = popoverViewController.popoverPresentationController

    popoverPresentationViewController?.permittedArrowDirections = .Up
    popoverPresentationViewController?.sourceView = sender
    popoverPresentationViewController?.sourceRect = CGRectMake(0, 0, sender.bounds.width,sender.bounds.height) // see this line of code

    presentViewController(popoverViewController, animated: true, completion: nil)
}

---

问题是混淆框架和边界的基本问题：

popoverPresentationViewController?.sourceView = sender as! UIButton
popoverPresentationViewController?.sourceRect = sender.frame

不！你的意思是：

popoverPresentationViewController?.sourceView = sender as! UIButton
popoverPresentationViewController?.sourceRect = (sender as! UIButton).bounds

---

原因是

sourceRect

是在

sourceView

的坐标空间中给出的-也就是说，如果您希望它是视图的rect，它是该视图的边界。

iOS 9中有一个问题。在故事板中设置锚定：

…导致箭头未位于锚点的中心：

要解决此问题，请将其添加到

prepareforsgue:sender:

：

// Fixes popover anchor centering issue in iOS 9
if let popoverPresentationController = segue.destinationViewController.popoverPresentationController, sourceView = sender as? UIView {
  popoverPresentationController.sourceRect = sourceView.bounds
}

---

在我的例子中，问题是不同的，弹出框显示的是带有自定义视图的UIBarButtonItem。对于iOS 11，如果使用UIBarButtonItem的自定义视图，则自定义视图需要是自动布局友好的

使用此类别，可以快速应用约束

UIView+NavigationBar.h

@interface UIView (NavigationBar)

    - (void)applyNavigationBarConstraints:(CGFloat)width height:(CGFloat)height;
    - (void)applyNavigationBarConstraintsWithCurrentSize;

@end

UIView+NavigationBar.m

#import "UIView+NavigationBar.h"

@implementation UIView (NavigationBar)

- (void)applyNavigationBarConstraints:(CGFloat)width height:(CGFloat)height
{
    if (width == 0 || height == 0) {
        return;
    }

    NSLayoutConstraint *heightConstraint = [NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:height];
    NSLayoutConstraint *widthConstraint = [NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:width];
    [heightConstraint setActive:TRUE];
    [widthConstraint setActive:TRUE];
}

- (void)applyNavigationBarConstraintsWithCurrentSize {
    [self applyNavigationBarConstraints:self.bounds.size.width height:self.bounds.size.height];
}

@end

然后你可以做：

UIButton *buttonMenu = [UIButton buttonWithType:UIButtonTypeCustom];
[buttonMenu setImage:[UIImage imageNamed:@"menu"] forState:UIControlStateNormal];
buttonMenu.frame = CGRectMake(0, 0, 44, 44);
[buttonMenu addTarget:self action:@selector(showMenu:) forControlEvents:UIControlEventTouchUpInside];

//Apply constraints 
[buttonMenu applyNavigationBarConstraintsWithCurrentSize];

UIBarButtonItem *menuBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:buttonMenu];

应用约束时，popover将在自定义视图上正确显示，例如，将警报显示为popover的代码为：

UIAlertController *controller = [UIAlertController alertControllerWithTitle:@"Menu" message:@"" preferredStyle:UIAlertControllerStyleActionSheet];
//Add actions ....

UIPopoverPresentationController *popController = [controller popoverPresentationController];
popController.sourceView = buttonMenu;
popController.sourceRect = buttonMenu.bounds;

[self presentViewController:controller animated:YES completion:nil];

---

非常好的回答。截图帮助我确定这正是我遇到的问题，不是为我工作。我正在使用这个代码。让popoverViewController=segue.destinationViewController popoverViewController.modalPresentationStyle=UIModalPresentationStyle.Popover popoverViewController.popoverPresentationController！。如果让popoverPresentationController=segue.destinationViewController.popoverPresentationController，sourceView=sender as，则委派=自我？UIView{popoverPresentationController.sourceRect=sourceView.bounds}对我来说就像一个魅力！