[Mono-bugs] [Bug 679789] mono-android-9794 -the application crash and i have runtime Exception of type ‘Java .Lang. NullPointerException’ was thrown .

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https://bugzilla.novell.com/show_bug.cgi?id=679789

https://bugzilla.novell.com/show_bug.cgi?id=679789#c1


Jonathan Pryor <jpryor at novell.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |CLOSED
                 CC|                            |jpryor at novell.com
         Resolution|                            |INVALID

--- Comment #1 from Jonathan Pryor <jpryor at novell.com> 2011-03-16 15:00:18 UTC ---
My guess is that you changed the code between then and now.

There are two ways (at least) to make this work.

Way 1: Don't inherit from Android.App.Activity, but instead
Android.App.TabActivity, as discussed in the TabActivity tutorial:
    http://mono-android.net/Tutorials/Hello_Views/Tab_Layout

Then, DO NOT create a new TabHost instance (as you did), but instead use the
TabActivity.TabHost property:

    // within a TabActivity subclass...
    protected override void OnCreate (Bundle bundle)
    {
        base.OnCreate(bundle);
        SetContentView(Resource.Layout.Main);
        TabHost.TabSpec spec;     // Resusable TabSpec for each tab   
        Intent intent;            // Reusable Intent for each tab   
        // Create an Intent to launch an Activity for the tab 
        intent = new Intent(this, typeof(MyHelloView));
        intent.AddFlags(ActivityFlags.NewTask);
        // Initialize a TabSpec for each tab and add it to the TabHost   
        spec = TabHost.NewTabSpec("MyHelloView");
        spec.SetIndicator("Hello",
Resources.GetDrawable(Resource.Drawable.Icon));
        spec.SetContent(intent);
        TabHost.AddTab(spec);
    }

Way 2: Inherit from ActivityGroup, lookup the TabHost instance using
FindViewById(), and Setup the TabHost instance, as is required by the
documentation:

http://developer.android.com/reference/android/widget/TabHost.html#setup(android.app.LocalActivityManager)

You'll want to inherit from ActivityGroup so you have access to the
LocalActivityManager property:


    [Activity (Label = "TabHost Bug?", MainLauncher = true)]
    public class Activity1 : ActivityGroup
    {
        protected override void OnCreate (Bundle bundle)
        {
            base.OnCreate(bundle);
            SetContentView(Resource.Layout.Main);
            TabHost TabHost =
FindViewById<TabHost>(Android.Resource.Id.TabHost);
            TabHost.Setup(LocalActivityManager);
            TabHost.TabSpec spec;     // Resusable TabSpec for each tab   
            Intent intent;            // Reusable Intent for each tab   
            // Create an Intent to launch an Activity for the tab 
            intent = new Intent(this, typeof(MyHelloView));
            intent.AddFlags(ActivityFlags.NewTask);
            // Initialize a TabSpec for each tab and add it to the TabHost   
            spec = TabHost.NewTabSpec("MyHelloView");
            spec.SetIndicator("Hello",
Resources.GetDrawable(Resource.Drawable.Icon));
            spec.SetContent(intent);
            TabHost.AddTab(spec);
        }
    }

Either of these mechanisms work for me, though inheriting from TabActivity
seems to be the easier way.

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