仅在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构建输入屏幕。屏幕有许多输入字段。它们大部分位于屏幕顶部，但两个字段位于底部。
当用户尝试编辑屏幕底部的文本时，键盘将弹出，它将覆盖屏幕。
我找到了一个简单的解决方案，可以在发生这种情况时将屏幕向上移动，但结果是屏幕总是向上移动，屏幕顶部的字段在用户移动时无法触及试图编辑那些。

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.

在编辑底部字段时，有没有办法让屏幕仅移动？

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

我使用了这个代码，我发现这里：

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的这份文件。此页面上的示例代码（位于清单4-1 ）完全符合您的需要，只有在当前编辑应位于键盘下方时才会滚动视图。您只需要将所需的控件放在scrollViiew中。
唯一的问题是这是Objective-C，我认为你需要它在Swift中...所以它是：

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
}

请务必声明你的ViewController为 UITextFieldDelegate 并在初始化方法中设置正确的委托：
ex：

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

self.you_text_field.delegate = self

请记得致电 viewInit上的registerForKeyboardNotifications 和 deregist退出时的erFromKeyboardNotifications 。

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

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

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[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue.size
    let 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 activeField = self.activeField {
        if (!aRect.contains(activeField.frame.origin)){
            self.scrollView.scrollRectToVisible(activeField.frame, animated: true)
        }
    }
}

func keyboardWillBeHidden(notification: NSNotification){
    //Once keyboard disappears, restore original positions
    var info = notification.userInfo!
    let keyboardSize = (info[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue.size
    let 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.isScrollEnabled = false
}

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

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

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