IOS开发—Using UIGestureRecognizer with Swift Tutoria

Custom UIGestureRecognizer

At this point you know pretty much everything you need to know to use the built-in gesture recognizers in your apps. But what if you want to detect some kind of gesture not supported by the built-in recognizers?

Well, you could always write your own! Now you’ll try it out by writing a very simple gesture recognizer to detect if you try to “tickle” the monkey or banana by moving your finger several times from left to right.

Create a new file with the iOS\Source\Swift File template. Name the file TickleGestureRecognizer.

Then replace the contents of TickleGestureRecognizer.swift with the following:

import UIKit
 
class TickleGestureRecognizer:UIGestureRecognizer {
 
  // 1
  let requiredTickles = 2
  let distanceForTickleGesture:CGFloat = 25.0
 
  // 2
  enum Direction:Int {
    case DirectionUnknown = 0
    case DirectionLeft
    case DirectionRight
  }
 
  // 3
  var tickleCount:Int = 0
  var curTickleStart:CGPoint = CGPointZero
  var lastDirection:Direction = .DirectionUnknown
}

This is what you just declared step by step:

1. These are the constants that define what the gesture will need. Note that requiredTickles will be inferred as an Int, but you need to specify distanceForTickleGesture as a CGFloat. If you do not, then it will be inferred as a Double, and cause difficulties when doing calculations with CGPoints later on.
2. These are the possible tickle directions.
3. Here are the three variables to keep track of to detect this gesture:
   • tickleCount: How many times the user has switched the direction of their finger (while moving a minimum amount of points). Once the user moves their finger direction three times, you count it as a tickle gesture.
   • curTickleStart: The point where the user started moving in this tickle. You’ll update this each time the user switches direction (while moving a minimum amount of points).
   • lastDirection: The last direction the finger was moving. It will start out as unknown, and after the user moves a minimum amount you’ll check whether they’ve gone left or right and update this appropriately.

Of course, these properties here are specific to the gesture you’re detecting here – you’ll have your own if you’re making a recognizer for a different type of gesture, but you can get the general idea here.

One of the things that you’ll be changing is the state of the gesture – when a tickle is completed, you’ll need to change the state of the gesture to ended. In the original Objective-C UIGestureRecognizer, state is a read-only property, so you will need to create a Bridging Header to be able to redeclare this property.

The easiest way to do this is to create an Objective-C Class, and then delete the implementation part.

Create a new file, using the iOS\Source\Objective-C File template. Call the file Bridging-Header, and click Create. You will then be asked whether you would like to configure an Objective-C bridging header. Choose Yes. Two new files will be added to your project:

• MonkeyPinch-Bridging-Header.h
• Bridging-Header.m

Delete Bridging-Header.m. 

Add this Objective-C code to MonkeyPinch-Bridging-Header.h:

#import <UIKit/UIGestureRecognizerSubclass.h>

Now you will be able to change the UIGestureRecognizer’s state property in TickleGestureRecognizer.swift.

Switch to TickleGestureRecognizer.swift and add the following functions to the class:

override func touchesBegan(touches: NSSet!, withEvent event: UIEvent!)  {
  let touch = touches.anyObject() as UITouch
  self.curTickleStart = touch.locationInView(self.view)
}
 
override func touchesMoved(touches: NSSet!, withEvent event: UIEvent!) {
  let touch = touches.anyObject() as UITouch
  let ticklePoint = touch.locationInView(self.view)
 
  let moveAmt = ticklePoint.x - curTickleStart.x
  var curDirection:Direction
  if moveAmt < 0 {
    curDirection = .DirectionLeft
  } else {
    curDirection = .DirectionRight
  }
 
  //moveAmt is a Float, so self.distanceForTickleGesture needs to be a Float also
  if abs(moveAmt) < self.distanceForTickleGesture {
    return
  }
 
  if self.lastDirection == .DirectionUnknown || 
     (self.lastDirection == .DirectionLeft && curDirection == .DirectionRight) || 
     (self.lastDirection == .DirectionRight && curDirection == .DirectionLeft) {
    self.tickleCount++
    self.curTickleStart = ticklePoint
    self.lastDirection = curDirection
 
    if self.state == .Possible && self.tickleCount > self.requiredTickles {
      self.state = .Ended
    }
  }
}
 
override func reset() {
  self.tickleCount = 0
  self.curTickleStart = CGPointZero
  self.lastDirection = .DirectionUnknown
  if self.state == .Possible {
    self.state = .Failed
  }
}
 
override func touchesEnded(touches: NSSet!, withEvent event: UIEvent!) {
  self.reset()
}
 
override func touchesCancelled(touches: NSSet!, withEvent event: UIEvent!) {
  self.reset()
}

There’s a lot of code here, but I’m not going to go over the specifics because frankly they’re not quite important. The important part is the general idea of how it works: you’re overriding the UIGestureRecognizer’s touchesBegan, touchesMoved, touchesEnded, and touchesCancelled functions, and writing custom code to look at the touches and detect the gesture.

Once you’ve found the gesture, you want to send updates to the callback function. You do this by changing the state property of the gesture recognizer. Usually once the gesture begins, you want to set the state to .Began, send any updates with .Changed, and finalize it with .Ended.

But for this simple gesture recognizer, once the user has tickled the object, that’s it – you just mark it as ended. The callback you will add to ViewController.swift will get called and you can implement the code there.

OK, now to use this new recognizer! Open ViewController.swift and make the following changes.

Add to the top of the class:

var hehePlayer:AVAudioPlayer? = nil

In viewDidLoad, right after TODO, add:

let recognizer2 = TickleGestureRecognizer(target: self, action: Selector("handleTickle:"))
recognizer2.delegate = self
view.addGestureRecognizer(recognizer2)

At end of viewDidLoad add:

self.hehePlayer = self.loadSound("hehehe1")

Add at the beginning of handlePan: (gotta turn off pan to recognize tickles):

//comment for panning
//uncomment for tickling
return;

At the end of the class add the callback:

func handleTickle(recognizer:TickleGestureRecognizer) {
  self.hehePlayer?.play()
}

So you can see that using this custom gesture recognizer is as simple as using the built-in ones!

Compile and run and “he he, that tickles!”

内容总结

以上是互联网集市为您收集整理的IOS开发—Using UIGestureRecognizer with Swift Tutoria全部内容，希望文章能够帮你解决IOS开发—Using UIGestureRecognizer with Swift Tutoria所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错，欢迎将互联网集市网站推荐给程序员好友。

内容备注

版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 gblab@vip.qq.com 举报，一经查实，本站将立刻删除。

内容手机端