调用 iOS Alert 时出现 UI 一致性错误 [英] UI consistency error when calling iOS Alert
问题描述
我有一个 iOS Xamarin 项目,但出现以下错误:
I have an iOS Xamarin project were I am getting the following error:
UIKit Consistency error: you are calling a UIKit method that
can only be invoked from the UI thread.
出现此错误的代码如下:
This error occurs with the following code:
在我的欢迎视图页面中,我有一个名为 SyncButton
的按钮被点击.单击此按钮应该会使用 REST 将数据与服务器同步.
In my Welcome view page I have a button called SyncButton
that gets clicked. This click of the button is supposed to sync data with a server using REST.
在我的 WelcomeController 中,我有:
In my WelcomeController I have:
....
SyncButton.TouchUpInside += async (object sender, EventArgs e) => {
SyncButton.Enabled = false;
await welcomeDelegate.syncButtonCore (cred, iOSErrorAlert);
SyncButton.Enabled = true;
};
....
public void iOSErrorAlert(string LoginErrorTitle, string LoginErrorMessage){
var Alert = UIAlertController.Create (LoginErrorTitle, LoginErrorMessage, UIAlertControllerStyle.Alert);
Alert.AddAction (UIAlertAction.Create ("OK", UIAlertActionStyle.Cancel, null));
PresentViewController (Alert, animated: true, completionHandler: null);
}
当确实出现超时或其他一些错误时应该发出警报.
Alerts should happen when there is a timeout or some other error really.
SyncButtonCore()
包含在如下所示的委托类中:
The SyncButtonCore()
is contained in a delegate class that looks like this:
public async Task syncButtonCore(UserCredentials cred, RequestWithAlertDelegate.ErrorAlert NativeAlert){
await Task.Run (async ()=>{
RequestWithAlertDelegate requestWithAlert = new RequestWithAlertDelegate();
string URL = URLs.BASE_URL + URLs.CASELOAD + "/" + cred.PID;
await requestWithAlert.RequestWithRetry(URL, cred.UserID, cred.Password, NativeAlert, null, async delegate (string Response1){...}, 1);
我的 RequestWithAlert
类在哪里:
public async Task RequestWithRetry (string URL, string UserID, string Password, ErrorAlert NativeAlert, SyncAction Action, AsyncAction Action2, int times)
{
...make sure legit credentials...
if (LoginError) {
NativeAlert (LoginErrorTitle, LoginErrorMessage);
}
在最后一段代码中,我在 NativeAlert() 函数中遇到错误的地方.这最终会抛出在我的代码开头提到的 UIKit 错误
Where I am getting my error at the NativeAlert() function in that last bit of code. Which ultimately throws the UIKit error mentioned at the beginning in my code at
var Alert = UIAlertController.Create (LoginErrorTitle, LoginErrorMessage, UIAlertControllerStyle.Alert);
我不确定我在这里做错了什么,以及为什么我不允许创建此警报,因为我在我的 WelcomeController
中定义了它,这是我的 UIThread 应该正确的地方?
I'm not sure what I am doing wrong here and why I am not allowed to create this alert because I define it in my WelcomeController
which is where my UIThread should be correct?
推荐答案
问题出在我的 iOSErrorAlert()
函数中.我需要用 InvokeOnMainThread()
包围它,因为 UI 操作应该在主线程中执行(我没有这样做,因为我将它传递给其他类/线程).谢谢@Paulw11 的评论.
Problem was in my iOSErrorAlert()
function. I needed to surround it with the InvokeOnMainThread()
because UI actions should be performed in the main thread (which I was not doing because I was passing it around to other classes/threads). Thank you @Paulw11 for the comment.
不得不替换这个:
public void iOSErrorAlert(string LoginErrorTitle, string LoginErrorMessage){
var Alert = UIAlertController.Create (LoginErrorTitle, LoginErrorMessage, UIAlertControllerStyle.Alert);
Alert.AddAction (UIAlertAction.Create ("OK", UIAlertActionStyle.Cancel, null));
PresentViewController (Alert, animated: true, completionHandler: null);
}
有了这个:
public void iOSErrorAlert(string LoginErrorTitle, string LoginErrorMessage){
InvokeOnMainThread (() => {
var Alert = UIAlertController.Create (LoginErrorTitle, LoginErrorMessage, UIAlertControllerStyle.Alert);
Alert.AddAction (UIAlertAction.Create ("OK", UIAlertActionStyle.Cancel, null));
PresentViewController (Alert, animated: true, completionHandler: null);
});
}
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