CODEWITHSUNDEEP
c#xamarinxamarin.formsxamarin.android
uncle_scrooge
uncle_scrooge

Reputation: 429

Navigating native to forms in Xamarin gives null reference exception

I have 4 tabs in Xamarin.Android project(natively). 3 tabs are loaded natively,but one tab I am loading is a Forms page(content page). Here is the codes for tabs-

    public override Android.Support.V4.App.Fragment GetItem(int position)
        {

            switch (position)
            {
                case 0:
                    return new tab1Fragment();

                case 1:
                    return new tab2Fragment();

                case 2:
                    return new tab3Fragment();                   

                case 3:
                   var fragment = new FormsPage1().CreateSupportFragment(Android.App.Application.Context);
                    return fragment;

                default:
                    return null;
            }
        }

The forms page is loaded successfully,but when I touch anywhere in that page,it crashes.Here is the exception-

System.NullReferenceException: Object reference not set to an instance of an object.
at Android.Views.View.n_DispatchTouchEvent_Landroid_view_MotionEvent_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_e)
  at (wrapper dynamic-method) System.Object.55(intptr,intptr,intptr)
 Unhandled Exception from source=AndroidEnvironment
 System.NullReferenceException: Object reference not set to an instance of an object.
  at Xamarin.Forms.Platform.Android.PlatformRenderer.DispatchTouchEvent (Android.Views.MotionEvent e) 
at Android.Views.View.n_DispatchTouchEvent_Landroid_view_MotionEvent_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_e)

Updating the Xaml-

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         xmlns:local="clr-namespace:ClientApp"
         x:Class="ClientApp.FormsPage1">

<StackLayout>
    <!-- Place new controls here -->
    <Label Text="Welcome to Xamarin.Forms!" 
       HorizontalOptions="Center"
       VerticalOptions="CenterAndExpand" />
</StackLayout>

When I debugged more the view of the fragment always null,I am suspecting that this is causing the issue, but not sure..Please help ..

Upvotes: 5

Views: 1574

Answers (2)

Ivan I
Ivan I

Reputation: 9990

I would expect this problem to appear because you are using the app's Context and not the activity Context. In most cases it is fine as a context provider, but sometimes it causes problems.

I am not sure of your project structure to recommend the best solution of how to get the activity context, but the CurrentActivity plugin should work in all cases.

Upvotes: 5

divyang4481
divyang4481

Reputation: 1783

user Xamarin.Forms.Forms.Init(this, null); in your code before you create fragment

   if (__fragment1  == null)  
    {  

        // iOS  
        //Forms.Init()  
        //var iosViewController = new MyFormsPage().CreateViewController();  



        Xamarin.Forms.Forms.Init(this, null);  
        // #2 Use it  
        _fragment1 = new MainPage().CreateFragment(this);  
    }

Upvotes: 2

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