Soft keyboard resizing navbar

I have a searchbar in my page , as soon as the soft keyboard appears , it is resizing my navbar making it smaller.
Here is my layout below.

        <Grid>
            <Frame
            x:Name="navigationFrame"
            Grid.Row="0"
            Padding="0"
            CornerRadius="0">
                <Grid
                x:Name="navGrid">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="3*"/>
                        <ColumnDefinition Width="*"/>
                    </Grid.ColumnDefinitions>
                    <Label
                    Grid.Column="1"
                />
                </Grid>
            </Frame>

            <ListView 
                    Grid.Row="1"
                    Margin="15,15,15,15">
        </ListView>
    </Grid>

Any idea why this is happening ?