我正在尝试将我的旧代码从 objective-c 转换为 swift。
但是我在 self.image.drawInRect() 上得到以下错误:
fatal error :无法解包 Optional.None
我有一个名为 Canvas 的类,它是 UIImageView 的子类,它在 Storyboard上设置,并在我唯一的 ViewController 上初始化:
init(coder aDecoder: NSCoder!) {
pref = NSUserDefaults.standardUserDefaults()
currentPlay = Play()
canvas = Canvas(coder: aDecoder)
super.init(coder: aDecoder)
}
这是我的 Canvas.Swift
import UIKit
class Canvas: UIImageView {
var path:UIBezierPath = UIBezierPath()
var drawColor:UIColor = UIColor.greenColor()
var lastLocation:CGPoint = CGPoint()
init(coder aDecoder: NSCoder!) {
super.init(coder: aDecoder)
}
// handling touches
override func touchesBegan(touches: NSSet!, withEvent event: UIEvent!) {
let touch:UITouch = touches.anyObject() as UITouch
lastLocation = touch.locationInView(self.superview)
}
override func touchesMoved(touches: NSSet!, withEvent event: UIEvent!) {
let touch:UITouch = touches.anyObject() as UITouch
let location = touch.locationInView(self.superview)
UIGraphicsBeginImageContext(self.frame.size)
self.image.drawInRect(self.frame)
path = UIBezierPath()
path.lineWidth = 8;
path.lineCapStyle = kCGLineCapRound;
drawColor.setStroke()
path.moveToPoint(CGPointMake(lastLocation.x, lastLocation.y))
path.addLineToPoint(CGPointMake(location.x, location.y))
path.stroke()
self.image = UIGraphicsGetImageFromCurrentImageContext();
lastLocation = location
path.closePath()
UIGraphicsEndImageContext();
}
override func touchesEnded(touches: NSSet!, withEvent event: UIEvent!) {
// nothing yet
}
}
ps:如果我删除 drawInRect 线,如果通过 touchedMoved,我可以暂时获得绘图...但是由于上下文被重置,它不会保留在图像上
最佳答案
UIImageView 通常是用图像初始化的 - 但在您的情况下,您正在取消存档并假设 image 属性包含有效图像。由于 image 属性是隐式展开的(它被定义为 var image: UIImage!
),它不会给你一个编译时错误,而是在运行时崩溃。
要打开图像并在图像可用时使用 drawInRect
将 self.image.drawInRect(self.frame)
替换为
if let image = self.image {
image.drawInRect(self.frame)
}
关于ios - Swift drawInRect 无法展开 Optional.None,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24562527/