如何使用NSTimer在UIView中绘制

Question

我尝试开发的应用程序的一个部分需要显示一组图像，而在显示周期内用户无需与手机交互。 用户可以启动显示顺序，但无需告诉手机何时停止。 该应用还需要能够在每个显示周期之间捕获图像。 我的意思是电话会显示图像，然后捕获照片并保存，然后显示下一张图像，循环继续进行。

我对图像捕获部分有很好的了解，但是我正在努力如何以上述方式显示我的图像集。 我知道实现此目标的困难之一是iPhone在显示周期上更新视图并在执行时编译所有代码，因此很难让两者互相等待。

我尝试使用NSTimer调用UIView来更新我的特定图像，但是该图像无法正确绘制。 我正在使用Core Graphics以越来越高的频率绘制条形或白色和黑色。 我认为创建和播放具有正确序列模式的电影是行不通的，因为我还需要每次显示模式时都必须告诉iPhone捕获图像。

任何想法或建议，不胜感激！

我的UIViewController：

import UIKit

class ViewController: UIViewController, UINavigationControllerDelegate {

// MARK: Properties
var orientation = "Vertical"
var numberOfBarPairs = UInt64(1)
var maximumNumberOfBarPairs = UInt64()
var binaryPattern = BinaryPattern()
var timer = NSTimer()

// Hide the status bar so the image displayed is full screen
var statusBarIsHidden = true

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

// MARK: Actions
@IBAction func displayBinaryPattern(sender: UIButton) {
    // Initiate the phase display

    // Capture the view's frame size and location
    let viewWidth = view.frame.width
    let viewHeight = view.frame.height
    //let viewSize = CGFloat(20)
    let viewOrigin = view.frame.origin

    // Set the frame that displays the binary patterns
    let frame = CGRectMake(viewOrigin.x, viewOrigin.y, viewWidth, viewHeight)

    // Set maximum number of bar pairs based on frame size
    maximumNumberOfBarPairs = 128 //Int(viewSize)/2

    // Instance a binary pattern and add it as a subview to the main view
    binaryPattern = BinaryPattern(frame: frame)

    // set display interval
    let displayInterval = 5.0

    // Set a timer to call drawBarPairs every interval
    timer = NSTimer.scheduledTimerWithTimeInterval(displayInterval, target: self, selector: Selector("updateView"), userInfo: nil, repeats: true)
}

func updateView() {
    numberOfBarPairs = numberOfBarPairs*2
    print("\(orientation), \(numberOfBarPairs)")

    view.addSubview(binaryPattern)

    // Cal the draw view
    binaryPattern.orientation = orientation
    binaryPattern.numberOfBarPairs = numberOfBarPairs

    // Stop the display when we reach a termination condition
    if numberOfBarPairs == maximumNumberOfBarPairs && orientation == "Horizontal" {
        // Stop the timer
        timer.invalidate()
    }

    // Change the orientaiton of the bar pairs when the number counter reaches the maximum
    if numberOfBarPairs == maximumNumberOfBarPairs && orientation == "Vertical" {
        orientation = "Horizontal"
        numberOfBarPairs = 0
    }
  }
}

我的UIView绘制模式：

import UIKit

class BinaryPattern: UIView {

// MARK: Properties
var numberOfBarPairs: UInt64 {
    didSet {
        print("Bars Set")
        setNeedsDisplay()
    }
}

var orientation: String {
    didSet {
        print("orientation set")
        setNeedsDisplay()
    }
}

override init(frame: CGRect) {
    self.numberOfBarPairs = 1
    self.orientation = "Vertical"
    super.init(frame: frame)
}

required init(coder aDecoder: NSCoder) {
    self.numberOfBarPairs = 1
    self.orientation = "Vertical"
    super.init(coder: aDecoder)!
}

override func drawRect(rect: CGRect) {

    // Obtains the current graphics context. Think of a graphics context as a canvas. In this case, the canvas is the View that we will be working with, but there are other types of contexts, such as an offscreen buffer that we later turn into an image. Note that contexts are stateful, or a value will remain that value until it is set with a method.
    let context = UIGraphicsGetCurrentContext()

    // Disable anti-aliasing, so pixel boundarys are shown jagged
    CGContextSetShouldAntialias(context, false)

    // Query the view frame size to draw the binary pattern within
    let frameHeight: CGFloat = 256
    let frameWidth: CGFloat = 256

    // Define white and black colors
    let blackColor: UIColor = UIColor.blackColor()
    let whiteColor: UIColor = UIColor.whiteColor()

    // Determine if bars should be vertical or horizontal
    if self.orientation == "Horizontal" {
        let barWidth = frameWidth
        let barHeight = frameHeight/CGFloat(2*self.numberOfBarPairs)

        // Generate the bar pairs and fill them with appropriate colors
     //   for bar in 1...self.numberOfBarPairs {
     //       let yOrigin1 = 2*(CGFloat(bar)-1)*barHeight
     //       let yOrigin2 = (2*CGFloat(bar)-1)*barHeight
     //       let xOrigin: CGFloat = 0

        let xOrigin: CGFloat = 0
        let yOrigin1: CGFloat = barHeight
        let yOrigin2: CGFloat = 0

            CGContextSetFillColorWithColor(context, blackColor.CGColor)
            CGContextFillRect(context, CGRectMake(xOrigin, yOrigin1, barWidth, barHeight))

            CGContextSetFillColorWithColor(context, whiteColor.CGColor)
            CGContextFillRect(context, CGRectMake(xOrigin, yOrigin2, barWidth, barHeight))
       // }
    }
    else {
        // Calculate the width of each bar by dividing the outer frame width by twice the number of bar pairs
        let barWidth = frameWidth/CGFloat(2*self.numberOfBarPairs)
        let barHeight = frameHeight

        print("Bar Width: \(barWidth), Bar Height: \(barHeight)\n")

        // Generate the bar pairs and fill them with appropriate colors
        for bar in 1...self.numberOfBarPairs {
        //    let xOrigin1 = 2*(CGFloat(bar)-1)*barWidth
            let xOrigin2 = (2*CGFloat(bar)-1)*barWidth
            let yOrigin: CGFloat = 0

            print("x Origin: \(xOrigin2)")

        //let xOrigin1 = barWidth
        //let xOrigin2: CGFloat = 50
        //let yOrigin: CGFloat = 0
            //CGContextSetFillColorWithColor(context, blackColor.CGColor)
            //CGContextFillRect(context, CGRectMake(xOrigin1, yOrigin, barWidth, barHeight))

            CGContextSetFillColorWithColor(context, whiteColor.CGColor)

            CGContextFillRect(context, CGRectMake(xOrigin2, yOrigin, barWidth, barHeight))

        }
    }
  }
}

Answer 1

计时器应调用视图的setNeedsDisplay。 然后，视图的drawRect将绘制视图的当前状态。