Question

背景

我previously learned如何使用手势识别器或continueTrackingWithTouch来获取当前触摸位置的持续更新，然后使用它们执行以下操作：

然而，现在，我想学习如何使用目标做同样的事情。我已经可以使用TouchDown和TouchUpInside来触及事件并触摸事件，但我不知道如何获得持续更新。我假设它将使用ValueChanged事件，但到目前为止还没有工作。

这就是我的尝试：

ViewController.swift

import UIKit
class ViewController: UIViewController {

    @IBOutlet weak var myCustomControl: MyCustomControl!
    @IBOutlet weak var trackingBeganLabel: UILabel!
    @IBOutlet weak var trackingEndedLabel: UILabel!
    @IBOutlet weak var xLabel: UILabel!
    @IBOutlet weak var yLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()

        // these work
        myCustomControl.addTarget(self, action: "myTouchDown", forControlEvents: UIControlEvents.TouchDown)
        myCustomControl.addTarget(self, action: "myTouchUpInside", forControlEvents: UIControlEvents.TouchUpInside)

        // this doesn't work
        myCustomControl.addTarget(self, action: "myValueChangedEvent:",
            forControlEvents: UIControlEvents.ValueChanged)
    }

    // this works
    func myTouchDown() {
        trackingBeganLabel.text = "Touched down"
    }

    // this works
    func myTouchUpInside() {
        trackingEndedLabel.text = "Touch up inside"
    }

    // this doesn't work, function never gets called
    func myValueChangedEvent(sender: UIControl) { 
        let location = sender.convertPoint(CGPointZero, toView: myCustomControl) 
        xLabel.text = "x: \(location.x)"
        yLabel.text = "y: \(location.y)"
    }
}

MyCustomControl.swift

import UIKit
class MyCustomControl: UIControl {
    // currently empty. Do I need to add something here?
}

备注

获得@ CaseyWagner的回答后更改了代码。编译器不再抛出错误，但UIControlEvents.ValueChanged永远不会被触发。
这个问题是我尝试为this answer的方法1：添加目标部分提供完整的答案。

Answer 1

使用UIControlEvents.ValueChanged代替myCustomControl.addTarget(self, action: "didDragInsideControl:withEvent:", forControlEvents: UIControlEvents.TouchDragInside)（另请注意，操作方法会收到两个参数）：

func didDragInsideControl(control: MyCustomControl, withEvent event: UIEvent) {
    let touch = event.touchesForView(control)!.first!
    let location = touch.locationInView(control)
    xLabel.text = "x: \(location.x)"
    yLabel.text = "y: \(location.y)"
}

处理程序函数如下所示：

domain.com?someKey=someValue&someOtherKey=someOtherValue

Answer 2

如果没有看到其他代码，看起来您可能需要：

 let location = sender.convertPoint(CGPointZero, toView: myCustomControl)

Answer 3

在@UIApplicationMain

AppDelegate

创建名为main.swift的新文件，并将该代码添加到该文件中

import UIKit
import Foundation
UIApplicationMain(Process.argc, Process.unsafeArgv, NSStringFromClass(AppClass), NSStringFromClass(AppDelegate))

创建名为＆＃34; AppClass＆＃34;的新类和UIApplication的子类

在该方法中编写以下代码导入UIKit

class AppClass: UIApplication {
    override func sendEvent(event: UIEvent)
    {
        super.sendEvent(event)
        print("send event") // this is an example
        // ... dispatch the message...
     }   
}

这里，在sendEvent方法中，您将获得应用程序（所有屏幕）中发生的所有事件，所有触摸事件，所以在这里您可以使用此UIEvent并执行任何任务（如果需要）

如何从Swift中的valueChanged事件中获取触摸坐标

3 个答案: