当用户在屏幕上拖动时，有没有办法让 UITextField 移动？

Question

I'm new to coding so I'm trying some small projects in swift. Right now, I'm trying to make a text box inside the ViewController move when the user drags it along the screen. For the text box, I am currently using a UITextField but I have no idea how to program its movement according to drag.

Answer 1

You'll want to add a UIPanGestureRecognizer to your view. There's all sorts of built in gesture recognizers for detecting various gestures like a tap or in this case a pan (drag). You can check them out here: https://developer.apple.com/documentation/uikit/uigesturerecognizer

Here we'll create a pan gesture recognizer, and add it to our view. Assume myView is your UITextField. A good place to do this is in your view controller's viewDidLoad() method.

let pan = UIPanGestureRecognizer(target: self, action: #selector(handlePan(sender:)))
myView.addGestureRecognizer(pan)

The moment your finger touches the screen, we say that a touch sequence has begun. The touch sequence ends when there are no more fingers on the screen. The pan gesture will determine if this touch sequence looks like a pan, and if so, the method handlePan will be called at various stages. Here, the gesture itself will be passed into the method, which we use to determine translation and move our view accordingly. Add this as a method of your view controller.

@objc func handlePan(sender: UIPanGestureRecognizer) {
    let translation = sender.translation(in: sender.view)
    self.myView.center.x += translation.x
    self.myView.center.y += translation.y
    sender.setTranslation(CGPoint.zero, in: sender.view)
}

The first line gets the translation in the view which the gesture is attached to (myView). We then adjust myView's position based on this translation, and then we set the translation to zero. This is so that the next time this method is called, the translation will be a delta relative to the previous call.

The property sender.state will tell you the state the gesture is currently in, for example, .began , .changed , .ended . Since a pan is a continuous gesture, our method will be called many times, whenever there's a finger movement.