Accessing children of second pivot item from code behind with their x:Name returns null in Windows Phone 8.1

0
votes

I have a Pivot control with two PivotItems. The XAML markup looks like this:

<Pivot x:Name="myPivot">
    <PivotItem x:Name="pivot_item1" Header="header1">
        <StackPanel x:Name="StackPanel1">
            <TextBlock Text="page1"></TextBlock>
        </StackPanel>
    </PivotItem>
    <PivotItem x:Name="pivot_item2" Header="header2">
        <StackPanel x:Name="StackPanel2">
            <Button  x:Name="TestButton" Content="Test" Click="Button_Click"></Button>
        </StackPanel>
    </PivotItem>
</Pivot>

Now the problem is when I try to access the individual elements in code behind. For example in the OnNavigated method accessing StackPanel1 would work OK but accessing StackPanel2 returns null.:

StackPanel sp1 = StackPanel1; // OK
StackPanel sp2 = Stackpanel2; // null

Accessing any element in the second PivotItem by its x:Name returns null. I thought it might be because the second pivot item wasn't initialized yet, so I created a Button in the second PivotItem and tried to access it by its x:Name in the click handler like this:

private void Button_Click(object sender, RoutedEventArgs e)
{
    Button b = TestButton; //null
    Button b2 = (Button)sender; // OK
}

but this still returns null althought the button clearly is initialized. Can anyone please explain this to me and suggest a workaround? Thank you!

2
c#xamlwindows-runtimewindows-phone-8.1

2 Answers

1
votes

There is something wrong with your project or you have that Pivot inside another container. A Pivot should be the Top Container. It does not work well if is part of another top style container. You also might want to check the Constructor it should look like this

public MainPage()
{
    this.InitializeComponent();   // check here as well to see if it declares every UI element correctly
    this.NavigationCacheMode = NavigationCacheMode.Required;
}

Screen Shot of the Debug (as you can see , no nulls -- this is using your code you posted)

enter image description here

I suggest first creating a new WP8.1 runtime project and see if you can repeat your error.

0
votes

I think that your second PivotItem is not yet loaded and control is not available. Add Loaded event to the pivot and try this code:

private void appPivot_LoadedPivotItem(object sender, PivotItemEventArgs e)
{
    if ( e.Item.Name.CompareTo( "pivot_item1" ) == 0 )
    {
        StackPanel sp1 = StackPanel1;
    }
    else
    {
        StackPanel sp2 = StackPanel2;
    }
}