[Swift] Implement swipe processing

Introduction

While developing the app, I used swipe gestures. So this time, I will summarize the swipe gestures.

Development environment

• macOS Catalina version10.15.7
• Xcode version12.2
• Swift5

Various gestures

You can watch videos of various gestures from Apple's Human Interface Guidelines. Human Interface Guidelines

Looking at the guidelines, what's the difference between flicking and swiping? I thought, so I looked it up.

What is the difference between flicking and swiping?

Flick: The image of lightly flicking the screen with your finger. Used for character input. Swipe: An image of sliding while touching the screen. Used for screen transitions, etc.

Reference site: Differences between "swipe" and "flick" and how to use them: basic smartphone operations that you can't hear anymore

It's certainly called flick input. (Maybe it was hard to imagine because I'm used to tap input for character input)

Swipe processing implementation

Whole code

import UIKit

//Add UIGestureRecognizerDelegate
class ViewController: UIViewController, UIGestureRecognizerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        //Create an instance for swiping up
        let upSwipe = UISwipeGestureRecognizer(
            target: self,
            action: #selector(ViewController.didSwipe(_:))
        )
        upSwipe.direction = .up
        self.view.addGestureRecognizer(upSwipe)
        
        //Create an instance for a right swipe
        let rightSwipe = UISwipeGestureRecognizer(
            target: self,
            action: #selector(ViewController.didSwipe(_:))
        )
        rightSwipe.direction = .right
        self.view.addGestureRecognizer(rightSwipe)
        
        //Create an instance for the down swipe
        let downSwipe = UISwipeGestureRecognizer(
            target: self,
            action: #selector(ViewController.didSwipe(_:))
        )
        downSwipe.direction = .down
        self.view.addGestureRecognizer(downSwipe)
        
        //Create an instance for a left swipe
        let leftSwipe = UISwipeGestureRecognizer(
            target: self,
            action: #selector(ViewController.didSwipe(_:))
        )
        leftSwipe.direction = .left
        self.view.addGestureRecognizer(leftSwipe)

    }

    //Method executed when swiping
    @objc func didSwipe(_ sender: UISwipeGestureRecognizer) {
        
        //Specify the execution process in the swipe direction in the case statement
        switch sender.direction {
        case .up:
            //What you want to do when swiping up
        case .right:
            //What you want to do when you swipe right
        case .down:
            //The process you want to execute when swiping down
        case .left:
            //The process you want to execute when swiping left
        default:
            break
        }
    }
}

Reference: [Swift/UIKit] Tap/long press/swipe to recognize

Commentary

The swipe process is the same except for the specified direction, so here we will briefly explain using the code for the above swipe process.

//Create an instance for swiping up
let upSwipe = UISwipeGestureRecognizer(
    target: self,
    action: #selector(ViewController.didSwipe(_:))
)
upSwipe.direction = .up
self.view.addGestureRecognizer(upSwipe)

As with tap and long press, first create an instance. At that time, specify the method you want to execute during the swipe gesture. The reason why # selector is used when specifying the method and @ objc when defining the method are as follows.

target-action is a mechanism implemented in Objective-C, and it is necessary to specify the method in Objective-C in target-action. Therefore, @objc is added when defining the method. Also, in Swift, you can specify Objective-C methods with #selector. Reference: [Swift] Tap, implement long press processing!

upSwipe.direction = .up

Specify the swipe direction from direction. There are four swipe directions in all. right, left, up, down Official Document UISwipe Gesture Recognizer .Direction

self.view.addGestureRecognizer(upSwipe)

I'm adding a swipe event to the view with addGestureRecognizer ().

//Method executed when swiping
@objc func didSwipe(_ sender: UISwipeGestureRecognizer) {

    //Specify the execution process in the swipe direction in the case statement
    switch sender.direction {
    case .up:
        //What you want to do when swiping up
    case .right:
        //What you want to do when you swipe right
    case .down:
        //The process you want to execute when swiping down
    case .left:
        //The process you want to execute when swiping left
    default:
        break
    }
}

Here is the process to be executed at each swipe. The switch statement is used to set the process to be executed depending on the swipe direction.

[Bonus] How to disable and enable gestures?

When I was first investigating how to disable and enable gestures, I found an article that the following code can be used.

UIApplication.shared.beginIgnoringInteractionEvents() //Invalidation
UIApplication.shared.endIgnoringInteractionEvents() //activation

However, when I implemented it, the following warning appeared.

beginIgnoringInteractionEvents()' was deprecated in iOS 13.0: Use UIView's userInteractionEnabled property instead

Apparently, the above code has been deprecated since iOS 13. You said that you should use userInteractionEnabled.

Click here to disable and enable using userInteractionEnabled.

self.view.isUserInteractionEnabled = false //Gesture disabled
self.view.isUserInteractionEnabled = true //Gesture enabled (default value)

Reference: Official document isUserInteractionEnabled

Summary

This time I have summarized what I learned about swipe processing. I learned that the swipe process that I usually use casually is implemented like this.

that's all.