Swift-使用按钮手动滚动UITEXTVIEW

Question

我想使用一个按钮滚动 down 或 up in UITextView，但是我遇到了一个问题。

使用textView.setContentOffset(CGPoint(x: 0, y: MyTextView.contentOffset.y + 100), animated: true)可以使我的文本视图向下滚动，但是当我单击文本末尾的按钮时，它仍然会滚动...

喜欢..

e
f
g


===================  

，但我想要这个..

a
b
c
d
e 
f 
g
===================  

我的代码是

@IBAction func down(_ sender: UIButton) {
   MyTextView.setContentOffset(CGPoint(x: 0, y: MyTextView.contentOffset.y - 100), animated: true)
}
@IBAction func up(_ sender: UIButton) {
   MyTextView.setContentOffset(CGPoint(x: 0, y: MyTextView.contentOffset.y - 100), animated: true)
}

请帮助我！

Answer 1

尝试这个

@IBAction func down(_ sender: UIButton) {
    if (textView.contentSize.height>(textView.frame.size.height+textView.contentOffset.y+100)){
        textView.setContentOffset(CGPoint(x:0,y:textView.contentOffset.y + 100), animated: true);
    }
    else{
        textView.setContentOffset(CGPoint(x:0,y:(textView.contentSize.height - textView.frame.size.height)), animated: true)
    }
}

Answer 2

我已经测试并有效。检查一下

 @IBOutlet weak var textView: UITextView!
    @IBAction func up(_ sender: UIButton) {
        if textView.contentOffset.y < 100{
            textView.setContentOffset(CGPoint.zero, animated: true)
        }else{
            textView.setContentOffset(CGPoint(x: 0, y: textView.contentOffset.y-100), animated: true)
        }
    }
  
    @IBAction func down(_ sender: UIButton) {
        if textView.contentOffset.y >  textView.contentSize.width - textView.frame.size.height{
            textView.setContentOffset(CGPoint(x: 0, y: textView.contentSize.height-textView.frame.size.height), animated: true)
        }else{
            textView.setContentOffset(CGPoint(x: 0, y: textView.contentOffset.y+100), animated: true)
        }
    }

Answer 3

您可能想检查当前偏移量是什么，并且仅移动所需的金额。例如，为了向下滚动，请尝试以下类似。然后，您应该能够对其进行调整并进行相反的滚动。

struct Constants {
    static let preferredScrollAmount: CGFloat = 100.0
}
@IBAction func downButtonTapped(_ sender: UIButton) {
    // Get the current offset, content height, text view height and work out the scrollable distance for the text view
    let currentOffset: CGFloat = textView.contentOffset.y
    let contentHeight: CGFloat = textView.contentSize.height
    let textViewHeight: CGFloat = textView.frame.size.height
    let scrollableDistance = contentHeight - textViewHeight
    // Check that the current offset isn't beyond the scrollable area otherwise return (no need to scroll)
    guard currentOffset < scrollableDistance else { return }
    // Work out how far we can move
    let distanceWeCanMove = scrollableDistance - currentOffset
    // Get the distance we should move (the smaller value so it doesn't go past the end)
    let distanceToScroll = min(distanceWeCanMove, Constants.preferredScrollAmount)
    // Do the scrolling
    textView.setContentOffset(CGPoint(x: 0, y: currentOffset + distanceToScroll), animated: true)
}