swift 如何在点击某个点时显示工具提示

Question

我正在使用以下代码绘制线条。线条边缘有点，我想在用户单击结束点时显示工具提示。代码片段如下，

 override func drawRect(rect: CGRect) {
        // Drawing code
      UIColor.brownColor().set()
    let context = UIGraphicsGetCurrentContext()
    //CGContextSetLineWidth(context, 5)
    CGContextMoveToPoint(context, 50, 50)
    CGContextAddLineToPoint(context,100, 200)
    CGContextStrokePath(context)

    // now add the circle on at the line edges

        var point = CGPoint(x:50 , y:50)
        point.x -= 5.0/2
        point.y -= 5.0/2
        var circle = UIBezierPath(ovalInRect: CGRect(origin: point, size: CGSize(width: 5.0,height: 5.0)))
        circle.fill()

        point = CGPoint(x:100 , y:200)
        point.x -= 5.0/2
        point.y -= 5.0/2
        circle = UIBezierPath(ovalInRect: CGRect(origin: point, size: CGSize(width: 5.0,height: 5.0)))
        circle.fill()

    }

当前显示的是下图，

我想显示如下所示的工具提示，

有没有人知道我如何识别这个特定的点被点击以及我将如何显示工具提示。我正在 swift.

中寻找解决方案

Answer 1

定义一个结构来保存您必须触摸的点，以及要显示的文本：

struct TouchPoint {
    var point: CGPoint // touch near here to show a tooltip
    var tip: String // show this text when touched
}

然后在您定义 drawRect 的 UIView 子类中，创建一个地方来保存它们：

var touchPoints: [TouchPoint] = [] // where we have to touch and what tooltip to show

drawRect 可以调用多次，所以每次都重新开始：

override func drawRect(rect: CGRect) {
    touchPoints = []
    // ...
    // add a touchPoint for every place to touch
    touchPoints.append(TouchPoint(point: point, tip: "point 1"))
}

您需要检测 UIView 上的点击，因此通过更改其初始化来添加手势识别器：

required init?(coder aDecoder: NSCoder) {
    // standard init for a UIView wiht an added gesture recognizer
    super.init(coder: aDecoder)
    addGestureRecognizer(UITapGestureRecognizer(target: self, action: Selector("touched:")))
}

那么您需要一种方法来查看触摸是否靠近触摸点，并显示正确的工具提示：

func touched(sender:AnyObject) {
    let tapTolerance = CGFloat(20) // how close to the point to touch to see tooltip
    let tipOffset = CGVector(dx: 10, dy: -10) // tooltip offset from point
    let myTag = 1234 // random number not used elsewhere
    guard let tap:CGPoint = (sender as? UITapGestureRecognizer)?.locationInView(self) else { print("touched: failed to find tap"); return }
    for v in subviews where v.tag == myTag { v.removeFromSuperview() } // remove existing tooltips
    let hitPoints:[TouchPoint] = touchPoints.filter({CGPointDistance([=14=].point, to: tap) < tapTolerance}) // list of tooltips near to tap
    for h in hitPoints { // for each tooltip to show
        let f = CGRect(origin: h.point+tipOffset, size: CGSize(width: 100, height: 20)) // fixed size label :-(
        let l = UILabel(frame: f)
        l.tag = myTag // just to be able to remove the tooltip later
        l.text = h.tip // draw the text
        addSubview(l) // add the label to the view
    }
}

func CGPointDistanceSquared(from: CGPoint, to: CGPoint) -> CGFloat { return (from.x - to.x) * (from.x - to.x) + (from.y - to.y) * (from.y - to.y) }

func CGPointDistance(from: CGPoint, to: CGPoint) -> CGFloat { return sqrt(CGPointDistanceSquared(from, to: to)) }

并且顺便使用新版本的 + 运算符对 CGPoint 执行向量加法：

func +(left: CGPoint, right: CGVector) -> CGPoint { return CGPoint(x: left.x+right.dx, y: left.y+right.dy) }

这对我来说没问题。额外的调整是根据文本字符串计算 UILabel 的大小，并移动 UILabel，使其不会运行离开 UIView 的边缘。祝你好运！

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