小编LH1*_*H16的帖子

在我看来,我有三个按钮.在viewDidLoad()中设置cornerRadus之后:button.layer.cornerRadius = 20我在日志中收到以下错误消息:

 <Error>: CGContextSaveGState: invalid context 0x0. 
If you want to see the backtrace, please set 
CG_CONTEXT_SHOW_BACKTRACE environmental variable.

问题:

• 如何设置CG_CONTEXT_SHOW_BACKTRACE环境变量？
• 或者我该如何修复此警告？

好的,我现在从消息中回溯了.这对我没有任何意义.一些帮助请...

Aug  7 14:27:00  <Error>: CGContextSaveGState: invalid context 0x0. Backtrace:
      <-[UIStatusBarItemView updateContentsAndWidth]+33>
       <-[UIStatusBarItemView initWithItem:data:actions:style:]+477>
        <+[UIStatusBarItemView createViewForItem:withData:actions:foregroundStyle:]+134>
         <-[UIStatusBarLayoutManager _createViewForItem:withData:actions:]+163>
          <-[UIStatusBarLayoutManager _prepareEnabledItemType:withEnabledItems:withData:actions:itemAppearing:itemDisappearing:]+36
           <-[UIStatusBarLayoutManager prepareEnabledItems:withData:actions:]+92>
            <-[UIStatusBarForegroundView _setStatusBarData:actions:animated:]+797>
             <-[UIStatusBarForegroundView setStatusBarData:actions:animated:]+332>
              <__51-[UIStatusBar _prepareToSetStyle:animation:forced:]_block_invoke+360>
               <+[UIView(Animation) performWithoutAnimation:]+65>
                <-[UIStatusBar _prepareToSetStyle:animation:forced:]+866>
                 <-[UIStatusBar _requestStyleAttributes:animationParameters:forced:]+391>
                  <-[UIStatusBar requestStyle:animationParameters:forced:]+437>
                   <-[UIStatusBar requestStyle:animated:forced:]+90>
                    <-[UIStatusBar _evaluateServerRegistration]+250>
                     <__45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke+590>
                      <-[UIView(Hierarchy) _postMovedFromSuperview:]+544>
                       <-[UIView(Internal) _addSubview:positioned:relativeTo:]+1967>
                        <-[UIStatusBarWindow setStatusBar:]+288>
                         <-[UIApplication _createStatusBarWithRequestedStyle:orientation:hidden:]+340>
                          <-[UIApplication _runWithMainScene:transitionContext:completion:]+950>
                           <-[UIApplication workspaceDidEndTransaction:]+188>
                            <-[FBSSerialQueue …

我已经阅读了3次文档,但我仍然不知道它的作用.有人可以ELI5(解释就像我五岁)吗？这是我使用它的方式:

fun main(args: Array<String>) {
    val UserModel = UserModel()
    val app = Javalin.create().port(7000).start()

    with (app) {
        get("/users") {
            context -> context.json(UserModel)
        }
    }
}

在使用UITableView时,有两种类型的方法,即数据源和委托仍然应该连接到同一父视图控制器类.

有没有办法在不同的类中定义委托和数据源？

为什么我们需要分离作为代表和数据源？

注意:此问题适用于UICollectionView和类似的对象

我正在尝试将我的iOS应用程序中的位置共享给WhatsApp，我希望它看起来像这样：

我正在做的是用以下代码发送vCard：

 func vCardURL(from coordinate: CLLocationCoordinate2D, with name: String?) -> URL {
    let vCardFileURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("Shared Location.loc.vcf")

    let vCardString = [
        "BEGIN:VCARD",
        "VERSION:3.0",
        //"PRODID:-//Apple Inc.//iPhone OS 10.3.2//EN",
        "N:;My Location;;;",
        "FN:My Location",
        "item1.URL;type=pref:https://maps.apple.com/?ll=50.359890\\,12.934560&q=My%20Location&t=m",
        "item1.X-ABLabel:map url",
        "END:VCARD"
        ].joined(separator: "\n")

    do {
        try vCardString.write(toFile: vCardFileURL.path, atomically: true, encoding: .utf8)
    } catch let error {
        print("Error, \(error.localizedDescription), saving vCard: \(vCardString) to file path: \(vCardFileURL.path).")
    }

    print(vCardString)

    return vCardFileURL
} // end of function

//调用上方的聚会

let vURL = LocationVCard.vCardURL(from: self.newLocation.coordinate, with: "Berlin")

                let activityViewController …

我正在尝试从WKWebView打印.网页和图片工作正常.

仅当我打印PDF文件时,页面都是空白的.

这是我用来创建printController的代码:

let printController = UIPrintInteractionController.sharedPrintController()

let printInfo = UIPrintInfo(dictionary:nil)
printInfo.outputType = UIPrintInfoOutputType.General
printInfo.jobName = urlField.text!
printInfo.duplex = UIPrintInfoDuplex.LongEdge

let formatter: UIViewPrintFormatter = webView.viewPrintFormatter()
formatter.contentInsets = UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)

printController.printFormatter = formatter
printController.printInfo = printInfo
printController.showsPageRange = true
printController.showsNumberOfCopies = true

printController.presentFromBarButtonItem(printButton, animated: true, completionHandler: nil)

有人能帮助我走向正确的方向吗？有这个问题的解决方案吗？