.NET Maui - prevent tab navigation if there's unsaved data or condition

[mucheye]

Description

How to prevent my application from switching tabs if a certain condition is not met in .NET Maui?
0

How to prevent my application from switching tabs if a certain condition is not met in .NET Maui?

I need to verifiy a condition before tab navigates to the clicked tab. If the condition is not met, then stop the navigation.

Below is my Tab bar xaml code along with the on property changed C# code. I cannot get the

GetDeferral();

from my C# code
private void WorkOrderTabBar_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
if (sender is TabBar listener && listener.CurrentItem?.Navigation.NavigationStack.Count > 1)
{
//listener
var navigation = listener.CurrentItem.Navigation;
var pages = navigation.NavigationStack;

        for (var i = pages.Count - 1; i >= 1; i--)
        {
            navigation.RemovePage(pages[i]);
        }
    }
}

    </Tab>
    <Tab
 Title="Report Info1"
 AutomationId="WorkOrdersDetailsTab1"
 Icon="reportinfo1.png"
 Route="WorkOrdersDetailsTab">
        <ShellContent
     Title="Work Orders Details Page Content Shell"
     AutomationId="WorkOrdersDetailsPageShellContent"
     ContentTemplate="{DataTemplate local:WorkOrderDetailsPage1}" />

    </Tab>
</TabBar>

This is the App Shell XAML:

<TabBar x:Name="Demo"
        Route="Demo"
        >
    <Tab IsEnabled="{Binding IsEnabled1}"
  Title="Report Info"
 AutomationId="WorkOrdersDetailsTab"
 Icon="reportinfo.png"
 Route="WorkOrdersDetailsTab">
        <ShellContent
     Title="Work Orders Details Page Content Shell"
     AutomationId="WorkOrdersDetailsPageShellContent"
     ContentTemplate="{DataTemplate local:WorkOrderDetailsPage}" />
    </Tab>
    <Tab IsEnabled="{Binding IsEnabled2}"
 Title="Report Info1"
 AutomationId="WorkOrdersDetailsTab1"
 Icon="reportinfo1.png"
 Route="WorkOrdersDetailsTab">
        <ShellContent
     Title="Work Orders Details Page Content Shell"
     AutomationId="WorkOrdersDetailsPageShellContent"
     ContentTemplate="{DataTemplate local:WorkOrderDetailsPage1}" />
    </Tab>
</TabBar>

This is the App Shell code behind:

namespace dap111; //put in your namespace

public partial class AppShell : Shell
{
ShellViewModel shellVm;

public AppShell()
{
    InitializeComponent();

    BindingContext = shellVm = new ShellViewModel();
    shellVm.IsEnabled1 = true;
    shellVm.IsEnabled2 = true;
}

protected override void OnNavigating(ShellNavigatingEventArgs args)
{
    base.OnNavigating(args);

    if (args.Source == ShellNavigationSource.ShellSectionChanged)
    {
        var aCondition = true;
        if (aCondition)
        {
            shellVm.IsEnabled1 = false;
        }
    }
}

}

This is the view model

using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;

namespace dap111 //put in your namespace
{
public class ShellViewModel : INotifyPropertyChanged
{
public bool _IsEnabled1;
public bool IsEnabled1
{
get => _IsEnabled1;
set
{
if (_IsEnabled1 != value)
{
_IsEnabled1 = value;
OnPropertyChanged(); // reports this property
}
}
}

    public bool _IsEnabled2;
    public bool IsEnabled2
    {
        get => _IsEnabled2;
        set
        {
            if (_IsEnabled2 != value)
            {
                _IsEnabled2 = value;
                OnPropertyChanged(); // reports this property
            }
        }
    }

    public ShellViewModel()
    {
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged([CallerMemberName] string name = "") =>
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}

}