How to Prevent Unexpected Closure of the .NET MAUI ComboBox Dropdown?

This article demonstrates how to prevent the Syncfusion® .NET MAUI ComboBox dropdown from closing unexpectedly when placed inside a ScrollView and using WindowSoftInputModeAdjust.Resize on Android. This issue occurs as the layout resizes when the keyboard appears, causing the dropdown to close. You can handle this scenario by using the OnSizeAllocated and DropDownClosing events.

Steps to Prevent Dropdown Closure:

1. Track layout resizing using a flag.
2. Override OnSizeAllocated to detect when the layout is resized.
3. Handle the DropDownClosing event to prevent closing during resizing.

C#

public partial class MainPage : ContentPage
{
    private bool isResizing; // Flag to track resizing

    public MainPage()
    {
        InitializeComponent();
        App.Current.On<Microsoft.Maui.Controls.PlatformConfiguration.Android>()
           .UseWindowSoftInputModeAdjust(WindowSoftInputModeAdjust.Resize);
    }

    protected override void OnSizeAllocated(double width, double height)
    {
        base.OnSizeAllocated(width, height);
        isResizing = true;
    }

    private async void SfComboBox_DropDownClosing(object sender, Syncfusion.Maui.Core.DropDownCancelEventArgs e)
    {
        if (isResizing)
        {
            e.Cancel = true; // Prevent closing during resizing
        }
        await Task.Delay(200); // Add required delay to ensure UI updates properly after resizing
        isResizing = false;
    }
}

XAML

<ScrollView>
    <VerticalStackLayout>
        <editors:SfComboBox x:Name="comboBox"
                            Placeholder="Select an item"
                            DropDownClosing="SfComboBox_DropDownClosing">
            <editors:SfComboBox.ItemsSource>
                <x:Array Type="{x:Type x:String}">
                    <x:String>Apple</x:String>
                    <x:String>Banana</x:String>
                    <x:String>Cherry</x:String>
                </x:Array>
            </editors:SfComboBox.ItemsSource>
        </editors:SfComboBox>
    </VerticalStackLayout>
</ScrollView>

Explanation

• OnSizeAllocated: Detects when the screen resizes due to keyboard appearance.
• isResizing flag: Prevents the dropdown from closing when resizing occurs.
• DropDownClosing event: Cancels the closing when isResizing is true.
• Task.Delay(200): Ensures a short delay to update the UI after resizing.

Download the complete sample from GitHub.

Conclusion

I hope you enjoyed learning how to prevent the unexpected closure of the .NET MAUI ComboBox Dropdown.

For more information, refer to our .NET MAUI ComboBox’s feature tour page for additional capabilities. You can also explore our .NET MAUI ComboBox documentation for further details.

If you’re a Syncfusion® customer, access our .NET MAUI components on the License and Downloads page. If you are new to Syncfusion®, try our 30-day free trial to experience the .NET MAUI ComboBox and other powerful .NET MAUI components.

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