Question

I want to change the icons and what they do in code in my WP7 application. I’ve tried in the MainPage constructor and in the MainPage_Loaded but it says ApplicationBar (x:Name) is null all the time.

How can I change it since I use same page and different states?

Answer 1

Unfortunately the application bar buttons are not accessible via code at the moment. I followed one of the examples of the official Mircosoft Training Kit for WP7 to accomplish that task. Here is the XAML and some code:

<phone:PhoneApplicationPage.ApplicationBar>
    <shell:ApplicationBar>
        <shell:ApplicationBarIconButton IconUri="/icons/appbar.pin.png" IsEnabled="True" Text="Anpinnen" x:Name="appPinPage" Click="appPinPage_Click" />
    </shell:ApplicationBar>
</phone:PhoneApplicationPage.ApplicationBar>

Please note that ApplicationBar is a property of PhoneApplicationPage so that you do not have to give an explicit name to the ApplicationBar object that you assign to the ApplicationBar property of the PhoneApplicationPage. Here is an example of changing the picture of the button in the xaml code above. That code is called in the overridden OnNavigatedTo() method of the PhoneApplicationPage.

        if (this.ViewModel.IsPinned())
        {
            ((ApplicationBarIconButton)this.ApplicationBar.Buttons[0]).Text = Resource1.txtUnpin;
            ((ApplicationBarIconButton)this.ApplicationBar.Buttons[0]).IconUri = new Uri("/icons/appbar.unpin.png", UriKind.Relative);
        }
        else
        {
            ((ApplicationBarIconButton)this.ApplicationBar.Buttons[0]).Text = Resource1.txtPin;
            ((ApplicationBarIconButton)this.ApplicationBar.Buttons[0]).IconUri = new Uri("/icons/appbar.pin.png", UriKind.Relative);
        }