抬起手指时如何阻止 UITextView 滚动（Swift 4）

Question

I have a textView whose content may exceed the height of the view, so I would like to be able to scroll down, stopping when I want, and to scroll back up when returning after having stopped.

Problems :

When scrolling (with two fingers), two things happen:

• the top lines scroll into the view above
• when fingers are lifted from the screen, the view just bounces back to the top.

Questions :

• How do I prevent the data from scrolling above the textView frame into the view above it?
• How do I stop the scrolling when they take their fingers off the screen? What event(s) get called when the user lifts their fingers?

import UIKit

class ScrollableView: UIView, UITextViewDelegate {

    var displayData = UITextView()

    override func draw(_ rect: CGRect) {
        super.draw(rect)        
        displayData.delegate = self

        getContent()
        calculateFrameBounds()
        displayTallTable()
    }

    func getContent() {
    }

    func calculateFrameBounds() {
    }

    func displayTallTable() {
        displayData.frame = CGRect(x: x, y: y, width: w, height: h)        
        self.addSubview(displayData)
    }
}

Answer 1

Use the touchesEnded function, this function is called whenever a touch event is ended.

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
            // implement in this function, when fingers are lifted this function is called.
        }
        

Answer 2

Partial answer:

To be able to stop and resume scrolling, it turns out that the height of UITextView ( displayData ) needs to be smaller than its contents. All I needed to do was set its height to that of the UIView containing it.

The UITextView ( displayData ) is inside a UIView container. To prevent displayData 's text from scrolling into the adjacent views (above and below the UIView container) I only had to turn on clipsToBounds on the UIView container like this: super.clipsToBounds = true (or check the box in IB).

This is only a partial solution, however. Because I have gaps between the UITextView ( displayData ) and the top and bottom of its UIView container, the data still scrolls off the UITextView and into the gaps of the UIView.

I have tried all of the following without success:

displayData.clipsToBounds = true
displayData.contentInset = UIEdgeInsets.zero
displayData.layer.masksToBounds = true

Any help with this last piece would be greatly appreciated!