Popover不以按钮为中心 [英] Popover doesn't center on button

问题描述

我试图将一个弹出按钮放在一个按钮上。我似乎无法弄清楚我可能会出错的地方。它不是按钮中间的箭头，而是偏离屏幕宽度的一半。

I am trying to center a popover on a button. I can't seem to figure out where I might be going wrong. Instead of the arrow being in the middle of the button, it is off center by half the width of the screen.

 @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)
}

推荐答案

问题是混淆框架和边界的基本问题：

The problem is the elementary one of confusing frame and bounds:

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

不！你的意思是边界：

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，如果你想让它成为视图的rect，它是该视图的界限。

The reason is that the sourceRect is given in the coordinate space of the sourceView - that is, if you want it to be the view's rect, it's the bounds of that view.

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