我正在为OSX创建一个简单的屏幕保护程序,并希望为某些背景计算创建一个线程。
我在SO中找到了这个函数,它将在X秒后创建一个线程:
func backgroundThread(delay: Double = 0.0, background: (() -> Void)? = nil, completion: (() -> Void)? = nil) {
dispatch_async(dispatch_get_global_queue(Int(QOS_CLASS_USER_INITIATED.rawValue), 0)) {
if(background != nil){ background!(); }
let popTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC)))
dispatch_after(popTime, dispatch_get_main_queue()) {
if(completion != nil){ completion!(); }
}
}
}
但是当我将其添加到init
时,它似乎不起作用:
override init?(frame: NSRect, isPreview: Bool) {
super.init(frame: frame, isPreview: isPreview);
let fontSize: CGFloat = 20;
let frameHeight: CGFloat = self.frame.size.height;
let font = NSFont(name: "Times New Roman", size: fontSize);
let paragraph = NSMutableParagraphStyle.defaultParagraphStyle().mutableCopy() as! NSMutableParagraphStyle;
paragraph.alignment = NSTextAlignment.Center;
let textColor = NSColor(calibratedRed: 255.0, green: 255.0, blue: 255.0, alpha: 1.0);
self.backgroundThread(3.0, background: {
let w:String = "test";
let textRect: NSRect = NSMakeRect(1, (frameHeight-CGFloat(fontSize*CGFloat(1))-30), 80, 30);
if let actualFont = font {
let textFontAttributes = [
NSFontAttributeName: actualFont,
NSForegroundColorAttributeName: textColor,
NSParagraphStyleAttributeName: paragraph
];
w.drawInRect(NSOffsetRect(textRect, 0, 1), withAttributes: textFontAttributes);
}
});
}
它应该在3秒后在另一个线程中显示该字符串,但它不会。我错过了什么?
答案 0 :(得分:2)
GUI线程必须是主线程,而不是后台线程
所以使用完成闭包
self.backgroundThread(3.0, completion: {
或仅使用必要的代码
dispatch_after(3.0, dispatch_get_main_queue()) {
...
}
或使用像Eki
这样的框架