从Swift中的另一个类访问ViewController中的对象

Question

我有一个ViewController，有一个名为myView的UIView和一个名为myImageView的UIImageView。 在下面的代码中，我有一个名为viewLine的类，该类附加到名为myView的UIView上。

我遇到的麻烦是调用touchesEnded时，我想在ViewController中更改myImageView的alpha。 当我尝试此操作时，不会更改myImageView的alpha。

（或者，当我尝试通过将viewLine类移入主ViewController来实现此目标时，出现以下错误- override func drawRect(rect: CGRect) - 方法不会覆盖其超类和self.setNeedsDisplay() 任何方法 - 值类型为“ ViewController”的成员没有成员“ setNeedsDisplay” 。）

问题：

1-如何修改名为viewLine的类中的代码以访问ViewController故事板上的其他UI对象或函数，例如myImageView ？ 即在touchesEnded被调用后， myImageView从名为viewLine的类中更改myImageView的Alpha？

2-我在ViewController中有一个sliderLineSize滑块，在ViewController中有一个变量lineSize 。 UISlider sliderLineSize更改lineSize 。 但是， lineSize用于viewLine类的drawRect部分。 如何传递或访问类中ViewController中设置的变量？

（3-如何将viewLine类合并到主ViewController中？）

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var myView: UIView!
    @IBOutlet weak var myImageView: UIImageView!

    var lineSize: Int = 1

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
        myImageView.alpha = 0.5
    }

    @IBAction func sliderLineSize(sender: UISlider) {
        lineSize = Int(sender.value)
    }

}

class viewLine: UIView {

    let path=UIBezierPath()
    var incrementalImage:UIImage?
    var previousPoint:CGPoint = CGPoint.zero
    var strokeColor:UIColor?

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override func drawRect(rect: CGRect) {
            incrementalImage?.drawInRect(rect)
            path.lineWidth = lineSize
            path.stroke()
    }

    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let touch: AnyObject? = touches.first
        let currentPoint = touch!.locationInView(self)
        path.moveToPoint(currentPoint)
        previousPoint=currentPoint
        self.setNeedsDisplay()
    }

    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let touch: AnyObject? = touches.first
        let currentPoint = touch!.locationInView(self)
        let midPoint = self.midPoint(previousPoint, p1: currentPoint)
        path.addQuadCurveToPoint(midPoint,controlPoint: previousPoint)
        previousPoint=currentPoint
        path.moveToPoint(midPoint)
        self.setNeedsDisplay()
    }

    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
        self.drawBitmap()
        self.setNeedsDisplay()
        path.removeAllPoints()
    }

    func midPoint(p0:CGPoint,p1:CGPoint)->CGPoint {
        let x=(p0.x+p1.x)/2
        let y=(p0.y+p1.y)/2
        return CGPoint(x: x, y: y)
    }

    func drawBitmap() {
        UIGraphicsBeginImageContextWithOptions(self.bounds.size, true, 1)
        strokeColor?.setStroke()
        if((incrementalImage) == nil){
            let rectPath:UIBezierPath = UIBezierPath(rect: self.bounds)
            UIColor.whiteColor().setFill()
            rectPath.fill()
        }
        incrementalImage?.drawAtPoint(CGPointZero)
        path.stroke()
        incrementalImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
    }

}

Answer 1

我查找了有关如何从其子视图引用ViewController的信息，发现的最好的选择是StackOverflow回答说：“遵循MVC模式，ViewController知道其Views，但是View不应该知道ViewController。相反，您应该声明委托协议”（来源： Swift-如何将视图控制器的引用传递给子UIView类？ ）

因此，我的解决方案是编写一个自定义委托协议，并使ViewController遵守该协议。 前面提到的答案中的代码有些过时，无法编写委托协议，但是Pure Swift类中的问题的开头与使用静态方法的协议相符-向上转换的问题显示了如何正确编写可在我的Xcode 7.2中使用的协议。

我的情节提要有一个这样的图：

• 视图
  • 我的视图（链接到您的代码）
  • 我的图像视图（背景是我选择的静态图像）

我将ViewLineUIView类重命名为viewLine ，因为我认为这将是基础超类的更具描述性的名称。 代码如下。

码：

import UIKit

protocol ViewLineUIViewDelegate: class {
    func onTouchesEnded(viewLine: ViewLineUIView)
}

class ViewController: UIViewController, ViewLineUIViewDelegate {

    @IBOutlet weak var myView: UIView!
    @IBOutlet weak var myImageView: UIImageView!
    @IBOutlet weak var sliderValue: UISlider!

    var viewLineDelegate: ViewLineUIView!

    override func viewDidLoad() {
        super.viewDidLoad()
        viewLineDelegate = myView as? ViewLineUIView
        viewLineDelegate!.delegate = self

        //update lineWidth to initial value of slider
        updateLineWidth()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    func onTouchesEnded(viewLine: ViewLineUIView) {
        myImageView!.alpha = 0.5
    }

    //Updating lineWidth!
    @IBAction func onSliderChange(sender: UISlider) {
        updateLineWidth()

    }

    func updateLineWidth() {
        let drawView = myView as! ViewLineUIView
        //you can change this "10" value to your max lineWidth
        drawView.path.lineWidth = CGFloat(sliderValue.value*10)
        print("New value is: " + String(drawView.path.lineWidth))
    }


}

class ViewLineUIView: UIView {

    weak var delegate: ViewLineUIViewDelegate?

    let path=UIBezierPath()
    var incrementalImage:UIImage?
    var previousPoint:CGPoint = CGPoint.zero
    var strokeColor:UIColor?

    required init?(coder aDecoder: NSCoder) {
        //Initialize lineWidth so that compiler doesn't complain
        super.init(coder: aDecoder)
    }

    override func drawRect(rect: CGRect) {
        incrementalImage?.drawInRect(rect)
        path.stroke()
    }

    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let touch: AnyObject? = touches.first
        let currentPoint = touch!.locationInView(self)
        path.moveToPoint(currentPoint)
        previousPoint=currentPoint
        self.setNeedsDisplay()
    }

    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let touch: AnyObject? = touches.first
        let currentPoint = touch!.locationInView(self)
        let midPoint = self.midPoint(previousPoint, p1: currentPoint)
        path.addQuadCurveToPoint(midPoint,controlPoint: previousPoint)
        previousPoint=currentPoint
        path.moveToPoint(midPoint)
        self.setNeedsDisplay()
    }

    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
        self.drawBitmap()
        self.setNeedsDisplay()
        path.removeAllPoints()

        delegate?.onTouchesEnded(self)
    }

    func midPoint(p0:CGPoint,p1:CGPoint)->CGPoint {
        let x=(p0.x+p1.x)/2
        let y=(p0.y+p1.y)/2
        return CGPoint(x: x, y: y)
    }

    func drawBitmap() {
        UIGraphicsBeginImageContextWithOptions(self.bounds.size, true, 1)
        strokeColor?.setStroke()
        if((incrementalImage) == nil){
            let rectPath:UIBezierPath = UIBezierPath(rect: self.bounds)
            UIColor.whiteColor().setFill()
            rectPath.fill()
        }
        incrementalImage?.drawAtPoint(CGPointZero)
        path.stroke()
        incrementalImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
    }

}

如您所见，编辑路径的lineWidth很简单，您无需创建其他委托协议。 ViewController可以直接访问其子视图。 您应该只知道需要强制转换。