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

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. The layout resizes when the keyboard appears in the WindowSoftInputModeAdjust.Resize mode, causing the dropdown to close. You can handle this dropdown closing using the OnSizeAllocated and DropDownClosing events.

To prevent the dropdown from closing during resizing, use the following approach:

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# Code

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 closing when isResizing is true.
• Task.Delay(400): Ensures a short delay to update the UI after resizing.

Download the complete sample from the GitHub.

Conclusion

We hope you enjoyed learning how to prevent the Syncfusion .NET MAUI ComboBox dropdown from closing unexpectedly when resizing occurs due to WindowSoftInputModeAdjust.Resize

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.

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