xamarin - Xamarin跨平台中的全局异常处理

Question

您能否告诉我如何处理 Xamarin 跨平台项目中的全局异常(不导致应用程序崩溃)。

Answer 1

据我所知，没有“Xamarin.Forms”方法可以做到这一点。您需要 Hook Android 和 iOS，您可以做的就是创建一种以相同方式处理它们的方法。

不错的post彼得·诺曼(Peter Norman)对此进行了介绍。他描述说，要在 Android 中实现它，您可以在 MainActivity.cs 中执行此操作。

// In MainActivity
protected override void OnCreate(Bundle bundle)
{
    base.OnCreate(bundle);  

    AppDomain.CurrentDomain.UnhandledException += CurrentDomainOnUnhandledException;
    TaskScheduler.UnobservedTaskException += TaskSchedulerOnUnobservedTaskException;  

    Xamarin.Forms.Forms.Init(this, bundle);  
    DisplayCrashReport();  

    var app = new App();  
    LoadApplication(app);
}  

‪#‎region‬ Error handling
private static void TaskSchedulerOnUnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs unobservedTaskExceptionEventArgs)
{
    var newExc = new Exception("TaskSchedulerOnUnobservedTaskException", unobservedTaskExceptionEventArgs.Exception);
    LogUnhandledException(newExc);
}  

private static void CurrentDomainOnUnhandledException(object sender, UnhandledExceptionEventArgs unhandledExceptionEventArgs)
{
    var newExc = new Exception("CurrentDomainOnUnhandledException", unhandledExceptionEventArgs.ExceptionObject as Exception);
    LogUnhandledException(newExc);
}  

internal static void LogUnhandledException(Exception exception)
{
    try
    {
        const string errorFileName = "Fatal.log";
        var libraryPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal); // iOS: Environment.SpecialFolder.Resources
        var errorFilePath = Path.Combine(libraryPath, errorFileName);  
        var errorMessage = String.Format("Time: {0}\r\nError: Unhandled Exception\r\n{1}",
        DateTime.Now, exception.ToString());
        File.WriteAllText(errorFilePath, errorMessage);  

        // Log to Android Device Logging.
        Android.Util.Log.Error("Crash Report", errorMessage);
    }
    catch
    {
        // just suppress any error logging exceptions
    }
}  

/// <summary>
// If there is an unhandled exception, the exception information is diplayed 
// on screen the next time the app is started (only in debug configuration)
/// </summary>
[Conditional("DEBUG")]
private void DisplayCrashReport()
{
    const string errorFilename = "Fatal.log";
    var libraryPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
    var errorFilePath = Path.Combine(libraryPath, errorFilename);

    if (!File.Exists(errorFilePath))
    {
        return; 
    }

    var errorText = File.ReadAllText(errorFilePath);
    new AlertDialog.Builder(this)
        .SetPositiveButton("Clear", (sender, args) =>
        {
            File.Delete(errorFilePath);
        })
        .SetNegativeButton("Close", (sender, args) =>
        {
            // User pressed Close.
        })
        .SetMessage(errorText)
        .SetTitle("Crash Report")
        .Show();
} 

‪#‎endregion‬

对于 iOS，您可以在 AppDelegate.cs 中添加这样的代码。

//iOS: Different than Android. Must be in FinishedLaunching, not in Main.
// In AppDelegate
public override bool FinishedLaunching(UIApplication uiApplication, NSDictionary options)
{
    AppDomain.CurrentDomain.UnhandledException += CurrentDomainOnUnhandledException;
    TaskScheduler.UnobservedTaskException += TaskSchedulerOnUnobservedTaskException;  
    // Rest of your code...
}  

/// <summary>
// If there is an unhandled exception, the exception information is diplayed 
// on screen the next time the app is started (only in debug configuration)
/// </summary>
[Conditional("DEBUG")]
private static void DisplayCrashReport()
{
    const string errorFilename = "Fatal.log";
    var libraryPath = Environment.GetFolderPath(Environment.SpecialFolder.Resources);
    var errorFilePath = Path.Combine(libraryPath, errorFilename);

    if (!File.Exists(errorFilePath))
    {
        return;
    }

    var errorText = File.ReadAllText(errorFilePath);
    var alertView = new UIAlertView("Crash Report", errorText, null, "Close", "Clear") { UserInteractionEnabled = true };
    alertView.Clicked += (sender, args) =>
    {
        if (args.ButtonIndex != 0)
        {
            File.Delete(errorFilePath);
        }
    };
    alertView.Show();
}

它还包括在调试应用程序时显示日志的功能。当然，您可以实现自己的日志记录或处理方法。您可以查看的一件事是 HockeyApp 。默认情况下，这会处理未处理的异常，并将它们发送回给您等。

更新，因为在 Google 上仍然可以找到此内容:对于崩溃报告和分析，您现在需要开始查看 App Center 。这是 HockeyApp 和 Xamarin Insights(以及其他构建、分发和推送通知等)的发展，现在充当与应用程序相关的所有内容的任务仪表板，而不仅仅是 Xamarin。

对于 UWP 和 WinPhone 8.1，Application 对象中应该有一个 UnhandledException 处理程序。查看this answer了解更多信息。我引用:

For XAML-based apps, you can use UnhandledException; however, that only captures exceptions that come up through the XAML (UI) framework and you don't always get a lot of information about what the root cause is, even in InnerException.

Update for Windows 8.1: UnhandledException also will capture exceptions that are created by an async void method. In Windows 8, such exceptions would just crash the app. LunarFrog has a good discussion of this on their website.

基本上，您应该在 App.xaml.cs 中的 App() 的构造函数中添加一个事件处理程序:this.UnhandledException += (o, s) => {}。