Ios 是否忽略UIColor.setFill（）错误消息？

我有两个并排循环的函数来不断绘制两个UIBezierPath，问题是，它们每个都有不同的颜色，所以我需要不断重复

UIColor.blackColor（）.setFill（）

和

UIColor（patternImage:UIImage（名为：“normalpaper.jpg”）.setFill（）

，缺点是它使控制台无法阅读，因为它不断地向你发送警告信息

<Error>: CGContextRestoreGState: invalid context 0x0. This is a serious error.
This application, or a library it uses, is using an invalid context  and is thereby
contributing to an overall degradation of system stability and reliability. This
notice is a courtesy: please fix this problem. It will become a fatal error in an
upcoming update.

下面是完整的CircleView类 （我对编程还是很陌生，所以可能效率很低）

苹果公司解释了所有这些，我强烈建议在继续使用自定义绘图代码之前阅读。请至少阅读上的部分。

---

问题是您正在

CircleView

s

drawRect

函数中创建并启动

NSTimer

s。绘图调用只能在正确的上下文中进行（这实际上是您看到的错误试图告诉您的）。通过在从

NSTimer

调用的函数中进行绘图，实际上是在

drawRect

函数外部进行绘图，在这种情况下没有有效的绘图上下文。而且，按照代码的原样，每次系统需要重新绘制视图时，您都将启动新的计时器；随着计时器开始重叠，这可能会很快失控

然而，只要稍微重新安排一下，我们就能做到这一点

请注意：这不一定是处理圆动画的正确方法，但它将解决您所询问的有关无效上下文错误的特定问题

从

drawRect

中取出所有内容，并将其替换为调用

eraseCircle

和

drawCircle

将您必须递增的逻辑

x

和

y

，以及

eraseX

和

eraseY

从

drawCircle

和

eraseCircle

中取出，并将其放在

timerDraw

和

timerErase

中

不要在

timerDraw

和

timerErase

中直接调用图形代码，而是通过调用来告诉视图系统需要重新绘制视图。这将标记您的视图需要重新绘制，并且视图系统将尽快自动再次调用您的

drawRect

函数

覆盖

didmovetoserview

并在那里启动计时器，使计时器再次工作；如果它们已经在运行，您还应该添加逻辑来停止它们

步骤1和3是使错误消失的关键点。

大概是这样的：

//Creating a view capable of painting the circle
class CircleView: UIView {
    // Timers
    var drawTimer: NSTimer?
    var eraseTimer: NSTimer?

    //Starting X Pos
    var x: CGFloat = 100
    var eraseX: CGFloat = 100

    //Starting Y Pos
    var y: CGFloat = 100
    var eraseY: CGFloat = 100

    override func drawRect(rect: CGRect) {
        eraseCircle()
        drawCircle()
    }

    override func didMoveToSuperview() {
        // If we have active timers, stop them
        if var drawTimer = self.drawTimer {
            // This stops the timer
            drawTimer.invalidate()
            self.drawTimer = nil
        }

        if var eraseTimer = self.eraseTimer {
            // This stops the timer
            eraseTimer.invalidate()
            self.eraseTimer = nil
        }

        // If we're actually part of the view hierarchy, start the timers
        if self.superview != nil {
            //Creating the looping draw timer
            self.drawTimer = NSTimer.scheduledTimerWithTimeInterval(
                0.2,
                target: self,
                selector: Selector("timerDraw"),
                userInfo: nil,
                repeats: true)

            //Creating the looping erase timer
            self.eraseTimer = NSTimer.scheduledTimerWithTimeInterval(
                0.3,
                target: self,
                selector: Selector("timerErase"),
                userInfo: nil,
                repeats: true)
        }
    }

    func drawCircle() {
        //Setting the draw color
        UIColor.blackColor().setFill()

        // Creating the rectangle's size
        var drawRect = roundDrawRect(10.0, angle: 7)

        //Drawing the rectangle
        drawRect.fill()

    }

    func eraseCircle() {
        //Setting the eraser color
        UIColor(patternImage: UIImage(named: "normalpaper.jpg")).setFill()

        // Creating the rectangle's size
        var eraseRect = roundEraseRect(10.0, angle: 7)

        //Drawing the rectangle
        eraseRect.fill()

    }

    func timerDraw(){
        //Incrementing the coords
        ++y
        ++x

        self.setNeedsDisplay()
    }

    func timerErase(){
        //Decrementing the coords
        eraseX = x - 2
        eraseY = y - 2

        self.setNeedsDisplay()
    }

    //Defining the rounded rect erasing (Circle)
    func roundEraseRect(radius: CGFloat, angle: CGFloat) -> UIBezierPath {

        //Creating the rounded rect (Circle)
        var roundedRect = UIBezierPath()

        roundedRect.moveToPoint(CGPointMake(eraseX,eraseY))
        println(CGPointMake(eraseX,eraseY))

        roundedRect.addArcWithCenter(CGPointZero, radius: radius,
            startAngle: 0, endAngle: angle ,
            clockwise: true)

        return roundedRect
    }

    //Defining the rounded rect drawing (Circle)
    func roundDrawRect(radius: CGFloat, angle: CGFloat) -> UIBezierPath {

        //Creating the rounded rect (Circle)
        var roundedRect = UIBezierPath()

        roundedRect.moveToPoint(CGPointMake(x,y))

        roundedRect.addArcWithCenter(CGPointZero, radius: radius,
            startAngle: 0, endAngle: angle ,
            clockwise: true)

        return roundedRect
    }
}

---

至于实现您正在尝试的动画的最佳方法，您可以只绘制一次圆，然后在

UIViewController

中使用计时器移动整个视图。或者，可能更好，使用。或者，如果您的最终产品将是一款游戏（甚至类似于游戏），那么不妨看看。

您在哪里调用

drawCircle（）

和

eraseCircle（）

？上下文在这里很重要，因为您只能在非常特定的时间和地点调用绘图代码。@MikeS嘿，Mike。我在一个自定义类中调用它们，该类添加在ViewController的正上方（而不是内部），它是一个名为CircleView的自定义类（我将其作为viewDidLoad内部的子视图添加），它的子类是一个UIView，因此它可以正确地绘制图像，问题是控制台被错误消息垃圾邮件。我将添加整个类供您检查，以确定您是否愿意。问题在于

drawRect

中的计时器。你能解释一下你想用这些做什么吗？@MikeS我想做的是让屏幕上的圆圈每隔0.2秒不断移动

+1x+1y

。计时器每0.2秒调用一次

drawCircle（）

函数，该函数以稍微不同的位置绘制圆。与

eraseCircle（）

函数相同，在稍微延迟后，在旧圆圈位置上绘制一个背景色圆圈，使其产生被擦除的错觉。或者至少，这是目标，它还没有在屏幕上画出图像。。仍然在解决问题。至少，您应该使用计时器，然后从

drawRect

内部移动所有绘图代码。但是请先阅读文档。你不需要线程。我现在会读到，至于移动整个背景，这是行不通的，因为我试图实现的目标有点像一个益智游戏，圆圈以预定的速度移动，你点击屏幕来改变它的周围环境，我也不知道这会转化成精灵工具包，我想我会看看那里。谢谢

//Creating a view capable of painting the circle
class CircleView: UIView {

//Starting X Pos
var x: CGFloat = 100
var eraseX: CGFloat = 100

//Starting Y Pos
var y: CGFloat = 100
var eraseY: CGFloat = 100

//Starting the loop of functions
override func drawRect(rect: CGRect) {

    //Creating the looping draw timer
    NSTimer.scheduledTimerWithTimeInterval(
        0.2,
        target: self,
        selector: Selector("timerDraw"),
        userInfo: nil,
        repeats: true)

    //Creating the looping erase timer
    NSTimer.scheduledTimerWithTimeInterval(
        0.3,
        target: self,
        selector: Selector("timerErase"),
        userInfo: nil,
        repeats: true)

}

func drawCircle() {

    //Setting the draw color
    UIColor.blackColor().setFill()

    // Creating the rectangle's size
    var drawRect = roundDrawRect(10.0, angle: 7)

    //Incrementing the coords
    ++y
    ++x

    //Drawing the rectangle
    drawRect.fill()

}

func eraseCircle() {

    //Setting the eraser color
    UIColor(patternImage: UIImage(named: "normalpaper.jpg")).setFill()

    //Decrementing the coords
    eraseX = x - 2
    eraseY = y - 2

    // Creating the rectangle's size
    var eraseRect = roundEraseRect(10.0, angle: 7)

    //Drawing the rectangle
    eraseRect.fill()

}

func timerDraw(){

    //DO DRAW LOOP HERE
    drawCircle()

}

func timerErase(){

    //DO ERASE LOOP HERE
    eraseCircle()

}

//Defining the rounded rect erasing (Circle)
func roundEraseRect(radius: CGFloat, angle: CGFloat) -> UIBezierPath {

    //Creating the rounded rect (Circle)
    var roundedRect = UIBezierPath()

    roundedRect.moveToPoint(CGPointMake(eraseX,eraseY))
    println(CGPointMake(eraseX,eraseY))

    roundedRect.addArcWithCenter(CGPointZero, radius: radius,
        startAngle: 0, endAngle: angle ,
        clockwise: true)

    return roundedRect
}

//Defining the rounded rect drawing (Circle)
func roundDrawRect(radius: CGFloat, angle: CGFloat) -> UIBezierPath {

    //Creating the rounded rect (Circle)
    var roundedRect = UIBezierPath()

    roundedRect.moveToPoint(CGPointMake(x,y))

    roundedRect.addArcWithCenter(CGPointZero, radius: radius,
        startAngle: 0, endAngle: angle ,
        clockwise: true)

    return roundedRect
}




}

class ViewController: UIViewController {

//Creating a view capable of painting the circle
class CircleView: UIView {
    // Timers
    var drawTimer: NSTimer?
    var eraseTimer: NSTimer?

    //Starting X Pos
    var x: CGFloat = 100
    var eraseX: CGFloat = 100

    //Starting Y Pos
    var y: CGFloat = 100
    var eraseY: CGFloat = 100

    override func drawRect(rect: CGRect) {
        eraseCircle()
        drawCircle()
    }

    override func didMoveToSuperview() {
        // If we have active timers, stop them
        if var drawTimer = self.drawTimer {
            // This stops the timer
            drawTimer.invalidate()
            self.drawTimer = nil
        }

        if var eraseTimer = self.eraseTimer {
            // This stops the timer
            eraseTimer.invalidate()
            self.eraseTimer = nil
        }

        // If we're actually part of the view hierarchy, start the timers
        if self.superview != nil {
            //Creating the looping draw timer
            self.drawTimer = NSTimer.scheduledTimerWithTimeInterval(
                0.2,
                target: self,
                selector: Selector("timerDraw"),
                userInfo: nil,
                repeats: true)

            //Creating the looping erase timer
            self.eraseTimer = NSTimer.scheduledTimerWithTimeInterval(
                0.3,
                target: self,
                selector: Selector("timerErase"),
                userInfo: nil,
                repeats: true)
        }
    }

    func drawCircle() {
        //Setting the draw color
        UIColor.blackColor().setFill()

        // Creating the rectangle's size
        var drawRect = roundDrawRect(10.0, angle: 7)

        //Drawing the rectangle
        drawRect.fill()

    }

    func eraseCircle() {
        //Setting the eraser color
        UIColor(patternImage: UIImage(named: "normalpaper.jpg")).setFill()

        // Creating the rectangle's size
        var eraseRect = roundEraseRect(10.0, angle: 7)

        //Drawing the rectangle
        eraseRect.fill()

    }

    func timerDraw(){
        //Incrementing the coords
        ++y
        ++x

        self.setNeedsDisplay()
    }

    func timerErase(){
        //Decrementing the coords
        eraseX = x - 2
        eraseY = y - 2

        self.setNeedsDisplay()
    }

    //Defining the rounded rect erasing (Circle)
    func roundEraseRect(radius: CGFloat, angle: CGFloat) -> UIBezierPath {

        //Creating the rounded rect (Circle)
        var roundedRect = UIBezierPath()

        roundedRect.moveToPoint(CGPointMake(eraseX,eraseY))
        println(CGPointMake(eraseX,eraseY))

        roundedRect.addArcWithCenter(CGPointZero, radius: radius,
            startAngle: 0, endAngle: angle ,
            clockwise: true)

        return roundedRect
    }

    //Defining the rounded rect drawing (Circle)
    func roundDrawRect(radius: CGFloat, angle: CGFloat) -> UIBezierPath {

        //Creating the rounded rect (Circle)
        var roundedRect = UIBezierPath()

        roundedRect.moveToPoint(CGPointMake(x,y))

        roundedRect.addArcWithCenter(CGPointZero, radius: radius,
            startAngle: 0, endAngle: angle ,
            clockwise: true)

        return roundedRect
    }
}