仅当键盘覆盖输入字段时才向上移动视图 [英] Move a view up only when the keyboard covers an input field

问题描述

我正在尝试为 iPhone 构建一个输入屏幕.屏幕有许多输入字段.其中大部分位于屏幕顶部，但底部有两个字段.当用户试图编辑屏幕底部的文本时，键盘会弹出并覆盖屏幕.我找到了一个简单的解决方案，可以在发生这种情况时向上移动屏幕，但结果是屏幕总是向上移动，并且当用户尝试编辑这些字段时，屏幕顶部的字段会移到无法触及的范围内.

I am trying to build an input screen for the iPhone. The screen has a number of input fields. Most of them on the top of the screen, but two fields are at the bottom. When the user tries to edit the text on the bottom of the screen, the keyboard will pop up and it will cover the screen. I found a simple solution to move the screen up when this happens, but the result is that the screen always moves up and the fields on top of the screen move out of reach when the user tries to edit those.

有没有办法让屏幕仅在底部字段被编辑时移动?

Is there a way to have the screen only move when the bottom fields are edited?

我使用了我在这里找到的这段代码:

I have used this code I found here:

override func viewDidLoad() {
    super.viewDidLoad()        
    NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillShow:"), name: UIKeyboardWillShowNotification, object: nil)
    NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillHide:"), name: UIKeyboardWillHideNotification, object: nil)
}

func keyboardWillShow(sender: NSNotification) {
    self.view.frame.origin.y -= 150
}

func keyboardWillHide(sender: NSNotification) {
    self.view.frame.origin.y += 150
}

推荐答案

您的问题在 Apple 提供的此文档.此页面上的示例代码(在 Listing 4-1)完全符合您的需要，只有当当前编辑应该在键盘下时才会滚动您的视图.你只需要把你需要的控件放在一个scrollView中.唯一的问题是这是 Objective-C，我认为你在 Swift 中需要它..so..这里是:

Your problem is well explained in this document by Apple. Example code on this page (at Listing 4-1) does exactly what you need, it will scroll your view only when the current editing should be under the keyboard. You only need to put your needed controls in a scrollViiew. The only problem is that this is Objective-C and I think you need it in Swift..so..here it is:

声明一个变量

var activeField: UITextField?

然后添加这些方法

 func registerForKeyboardNotifications()
{
    //Adding notifies on keyboard appearing
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWasShown:", name: UIKeyboardWillShowNotification, object: nil)
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillBeHidden:", name: UIKeyboardWillHideNotification, object: nil)
}


func deregisterFromKeyboardNotifications()
{
    //Removing notifies on keyboard appearing
    NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillShowNotification, object: nil)
    NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillHideNotification, object: nil)
}

func keyboardWasShown(notification: NSNotification)
{
    //Need to calculate keyboard exact size due to Apple suggestions
    self.scrollView.scrollEnabled = true
    var info : NSDictionary = notification.userInfo!
    var keyboardSize = (info[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue().size
    var contentInsets : UIEdgeInsets = UIEdgeInsetsMake(0.0, 0.0, keyboardSize!.height, 0.0)

    self.scrollView.contentInset = contentInsets
    self.scrollView.scrollIndicatorInsets = contentInsets

    var aRect : CGRect = self.view.frame
    aRect.size.height -= keyboardSize!.height
    if let activeFieldPresent = activeField
    {
        if (!CGRectContainsPoint(aRect, activeField!.frame.origin))
        {
            self.scrollView.scrollRectToVisible(activeField!.frame, animated: true)
        }
    }


}


func keyboardWillBeHidden(notification: NSNotification)
{
    //Once keyboard disappears, restore original positions
    var info : NSDictionary = notification.userInfo!
    var keyboardSize = (info[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue().size
    var contentInsets : UIEdgeInsets = UIEdgeInsetsMake(0.0, 0.0, -keyboardSize!.height, 0.0)
    self.scrollView.contentInset = contentInsets
    self.scrollView.scrollIndicatorInsets = contentInsets
    self.view.endEditing(true)
    self.scrollView.scrollEnabled = false

}

func textFieldDidBeginEditing(textField: UITextField!)
{
    activeField = textField
}

func textFieldDidEndEditing(textField: UITextField!)
{
    activeField = nil
}

请务必将您的 ViewController 声明为 UITextFieldDelegate 并在初始化方法中设置正确的委托:例如:

Be sure to declare your ViewController as UITextFieldDelegate and set correct delegates in your initialization methods: ex:

self.you_text_field.delegate = self

记得在 viewInit 上调用 registerForKeyboardNotifications，在退出时调用 deregisterFromKeyboardNotifications.

And remember to call registerForKeyboardNotifications on viewInit and deregisterFromKeyboardNotifications on exit.

func registerForKeyboardNotifications(){
    //Adding notifies on keyboard appearing
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWasShown(notification:)), name: NSNotification.Name.UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillBeHidden(notification:)), name: NSNotification.Name.UIResponder.keyboardWillHideNotification, object: nil)
}

func deregisterFromKeyboardNotifications(){
    //Removing notifies on keyboard appearing
    NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIResponder.keyboardWillHideNotification, object: nil)
}

@objc func keyboardWasShown(notification: NSNotification){
    //Need to calculate keyboard exact size due to Apple suggestions
    self.scrollView.isScrollEnabled = true
    var info = notification.userInfo!
    let keyboardSize = (info[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue.size
    let contentInsets : UIEdgeInsets = UIEdgeInsets(top: 0.0, left: 0.0, bottom: keyboardSize!.height, right: 0.0)

    self.scrollView.contentInset = contentInsets
    self.scrollView.scrollIndicatorInsets = contentInsets

    var aRect : CGRect = self.view.frame
    aRect.size.height -= keyboardSize!.height
    if let activeField = self.activeField {
        if (!aRect.contains(activeField.frame.origin)){
            self.scrollView.scrollRectToVisible(activeField.frame, animated: true)
        }
    }
}

@objc func keyboardWillBeHidden(notification: NSNotification){
    //Once keyboard disappears, restore original positions
    var info = notification.userInfo!
    let keyboardSize = (info[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue.size
    let contentInsets : UIEdgeInsets = UIEdgeInsets(top: 0.0, left: 0.0, bottom: -keyboardSize!.height, right: 0.0)
    self.scrollView.contentInset = contentInsets
    self.scrollView.scrollIndicatorInsets = contentInsets
    self.view.endEditing(true)
    self.scrollView.isScrollEnabled = false
}

func textFieldDidBeginEditing(_ textField: UITextField){
    activeField = textField
}

func textFieldDidEndEditing(_ textField: UITextField){
    activeField = nil
}

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