.NET Maui simple hierarchical debug view window

README.md

This adds a simple hierarchical debug view window. A simple recursive visitor triggers every 2 seconds and updates the string contents of the debug window. I added this code to a net9.0-maccatalyst app. To get the windowing working you have to do https://learn.microsoft.com/en-us/dotnet/maui/user-interface/controls/window?view=net-maui-9.0#ipados-and-macos-configuration

App.xaml.cs

using System.Timers;

public partial class App : Application
{
    private Label? debugLabel;
    private System.Timers.Timer? debugUpdateTimer;
    private Window? debugWindow;

    public App()
    {
        InitializeComponent();

        MainPage = new AppShell();

        StartDebugUpdateTimer();
    }

    private void StartDebugUpdateTimer()
    {
        // Set up the timer to update every 2 seconds
        debugUpdateTimer = new(2000); // 2000ms = 2 seconds
        debugUpdateTimer.Elapsed += (sender, args) =>
        {
            
            // Get the UI hierarchy string
            if (debugWindow == null)
            {
                MainThread.BeginInvokeOnMainThread(() =>
                {
                    // Create a Label to display the debug text
                    debugLabel = new Label
                    {
                        Text = "Loading debug info...",
                        FontSize = 14,
                        LineBreakMode = LineBreakMode.WordWrap,
                        Padding = new Thickness(10)
                    };

                    // Create a ScrollView to contain the Label
                    var scrollView = new ScrollView
                    {
                        Content = debugLabel
                    };

                    debugWindow = new Window(
                        new ContentPage
                        {
                            Title = "Debug UI Hierarchy",
                            Content = scrollView
                        })
                    {
                        Width = 700,
                        Height = 500,
                        X = 100,
                        Y = 100
                    };
                    Application.Current?.OpenWindow(debugWindow);
                    Application.Current?.ActivateWindow(debugWindow);
                });
                return;
            }

            string debugText = DebugLogger.GetVisualTreeAsString();

            // Update the Label on the UI thread
            MainThread.BeginInvokeOnMainThread(() =>
            {
                debugLabel.Text = debugText;
            });
        };

        // Start the timer
        debugUpdateTimer.Start();
    }

    protected override void OnStart()
    {
        base.OnStart();

        // Ensure the timer starts when the app starts
        debugUpdateTimer?.Start();
    }

    protected override void OnSleep()
    {
        base.OnSleep();

        // Stop the timer when the app goes to sleep
        debugUpdateTimer?.Stop();
    }

    protected override void OnResume()
    {
        base.OnResume();

        // Resume the timer when the app resumes
        debugUpdateTimer?.Start();
    }
}

DebugLogger.cs

using System.Text;
using Microsoft.Maui;
using Microsoft.Maui.Controls;

public static class DebugLogger
{
    public static string GetVisualTreeAsString()
    {
        if (Application.Current == null)
        {
            return "No current application instance found.";
        }

        var stringBuilder = new StringBuilder();
        stringBuilder.AppendLine("========== UI Hierarchy ==========");

        foreach (var window in Application.Current.Windows)
        {
            stringBuilder.AppendLine($"Window: {window.Title}");
            if (window.Page != null)
            {
                AppendElementHierarchy(stringBuilder, window.Page, 1);
            }
        }

        stringBuilder.AppendLine("==================================");
        return stringBuilder.ToString();
    }

    private static void AppendElementHierarchy(StringBuilder stringBuilder, IView element, int indentLevel)
    {
        string indent = new string(' ', indentLevel * 2);
        stringBuilder.AppendLine($"{indent}- {element.GetType().Name}");

        if (element is Layout layout) // Handles StackLayout, Grid, FlexLayout, etc.
        {
            foreach (var child in layout.Children)
            {
                AppendElementHierarchy(stringBuilder, child, indentLevel + 1);
            }
        }
        else if (element is ContentView contentView && contentView.Content != null) // Handles ContentView
        {
            AppendElementHierarchy(stringBuilder, contentView.Content, indentLevel + 1);
        }
        else if (element is ScrollView scrollView && scrollView.Content != null) // Handles ScrollView
        {
            AppendElementHierarchy(stringBuilder, scrollView.Content, indentLevel + 1);
        }
        else if (element is Frame frame && frame.Content != null) // Handles Frame
        {
            AppendElementHierarchy(stringBuilder, frame.Content, indentLevel + 1);
        }
        else if (element is Border border && border.Content != null) // Handles Border
        {
            AppendElementHierarchy(stringBuilder, border.Content, indentLevel + 1);
        }
        else if (element is Shell shell) // Handles Shell Navigation
        {
            foreach (var item in shell.Items)
            {
                AppendShellItemHierarchy(stringBuilder, item, indentLevel + 1);
            }
        }
    }

    private static void AppendShellItemHierarchy(StringBuilder stringBuilder, ShellItem item, int indentLevel)
    {
        string indent = new string(' ', indentLevel * 2);
        stringBuilder.AppendLine($"{indent}- ShellItem: {item.Title}");

        foreach (var section in item.Items)
        {
            stringBuilder.AppendLine($"{indent}  * Section: {section.Title}");
            foreach (var content in section.Items)
            {
                if (content is ShellContent shellContent && shellContent.Content is Page page)
                {
                    AppendElementHierarchy(stringBuilder, page, indentLevel + 2);
                }
            }
        }
    }
}