Bug 29761 - UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object at Xamarin.Forms.Platform.Android.ListViewAdapter.GetView (int,Android.Views.View,Android.Views.ViewGroup)
Summary: UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set ...
Status: RESOLVED FIXED
Alias: None
Product: Forms
Classification: Xamarin
Component: Android ()
Version: 1.4.3
Hardware: PC Windows
: High critical
Target Milestone: ---
Assignee: Rui Marinho
URL:
Depends on:
Blocks:
 
Reported: 2015-05-05 13:25 UTC by Jon Douglas [MSFT]
Modified: 2015-08-17 14:30 UTC (History)
9 users (show)

Tags: android crash xaml listview viewcell U7K AC
Is this bug a regression?: ---
Last known good build:

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Status:
RESOLVED FIXED

Description Jon Douglas [MSFT] 2015-05-05 13:25:24 UTC
*Description

Unhandled Exception occurs when navigating to a page with a Native ListView and custom ViewCellRenderer. Previously this occurred in the sample "WorkingWIthNativeListView"(https://github.com/xamarin/xamarin-forms-samples/tree/master/WorkingWithListviewNative) via Code before upgrading to 1.4.3.6358-pre2, but now it is occurring within XAML as well.

05-05 13:18:23.765 I/MonoDroid(31116): UNHANDLED EXCEPTION:
05-05 13:18:23.768 I/MonoDroid(31116): System.NullReferenceException: Object reference not set to an instance of an object
05-05 13:18:23.768 I/MonoDroid(31116): at Xamarin.Forms.Platform.Android.ListViewAdapter.GetView (int,Android.Views.View,Android.Views.ViewGroup) <IL 0x002b8, 0x017d4>
05-05 13:18:23.768 I/MonoDroid(31116): at Android.Widget.BaseAdapter.n_GetView_ILandroid_view_View_Landroid_view_ViewGroup_ (intptr,intptr,int,intptr,intptr) [0x0001a] in /Users/builder/data/lanes/monodroid-mavericks-monodroid-5.1-series/d23da369/source/monodroid/src/Mono.Android/platforms/android-21/src/generated/Android.Widget.BaseAdapter.cs:509
05-05 13:18:23.787 I/MonoDroid(31116): at Android.Runtime.JNIEnv.CallNonvirtualVoidMethod (intptr,intptr,intptr,Android.Runtime.JValue*) [0x00084] in /Users/builder/data/lanes/monodroid-maverick05-05 13:18:23.768 I/MonoDroid(31116): at (wrapper dynamic-method) object.2192210b-80ca-4034-b34a-45f305f9be74 (intptr,intptr,int,intptr,intptr) <IL 0x00023, 0x00073>
05-05 13:18:23.777 W/art     (31116): JNI RegisterNativeMethods: attempt to register 0 native methods for md52ce486a14f4bcd95899665e9d932190b.JavaProxyThrowable

Debug Output:

https://gist.github.com/JonDouglas/c08bd9a75cd0b3f5a355

*Reproduction

1) Download attached solution

2) Run on Android device(API 15+)

3) Select the "C" tab, and you should run into the Unhandled Exceptions noted in the Debug Output

*Xamarin.Forms Version
1.4.3.6358-pre2

*Version Information

Microsoft Visual Studio Ultimate 2013
Version 12.0.31101.00 Update 4
Microsoft .NET Framework
Version 4.6.00057

Installed Version: Ultimate

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Windows Phone SDK 8.0 - ENU

ApiPortVS   1.0
API portability analyzer.

ASP.NET and Web Tools   12.4.51016.0
Microsoft Web Developer Tools contains the following components:
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Common Azure Tools   1.3
Provides common services for use by Azure Mobile Services and Microsoft Azure Tools.

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JetBrains ReSharper 8.2   Full Edition build 8.2.0.2160 on 2014-03-21T01:53:08
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Microsoft Azure Mobile Services Tools   1.3
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Xamarin   3.11.445.0 (5061f92)
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Xamarin.Android   5.1.0.115 (d23da369e436488f38c8ab8fe8a9ae7d9ea5256b)
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Xamarin.Forms Intellisense   1.0
Provides intellisense for Xamarin.Forms in the XML editor.

Xamarin.iOS   8.10.0.0 (7741cc495ab0baf04ff0405d0604bc27f0ecae2e)
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Xamarin.iOS Unified Migration   1.0
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Xamarin.TestCloud.Integration   1.0
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Information about my package
Comment 3 Parmendra Kumar 2015-05-13 07:25:51 UTC
I have already reported the same bug 27951 and it was working fine with Xamarin.Forms 1.4.3-pre2.

Now I have again check this issue and observed that this issue is working fine when I download this sample from https://github.com/xamarin/xamarin-forms-samples/tree/1.4.3 
commit 622c063d129d1b0990a098dad7f46a375423de34  I am able to reproduce this issue if I download the sample from the master lane as provided in comment #1.

So this issue seems to be resolved with Xamarin.forms 1.4.3-pre2 in branch  https://github.com/xamarin/xamarin-forms-samples/tree/1.4.3
Comment 4 Andres Castro 2015-05-13 07:35:20 UTC
This bug is referring to using Xaml and a ViewCellRenderer. I was able to reproduce the error by converting the viewcell to xaml. https://github.com/acastr7/xamarin-forms-samples/tree/master/WorkingWithListviewNative
Comment 5 Rui Marinho 2015-06-11 11:01:11 UTC
Hi Andres Castro can you remove the reference to the assembly when declaring the local namespace. will be something like this:

xmlns:local="clr-namespace:WorkingWithListviewNative"

And see if it works ok. 

Thanks
Comment 6 Rui Marinho 2015-06-15 18:27:49 UTC
this should be fixed in 1.4.3 final
Comment 7 Josue Yeray 2015-07-06 11:06:09 UTC
This is not resolved. Same problem as described here in 1.4.3.6374, downgrading not help. This is a critical issue that need to be addressed asap as it is impacting directly on apps that where working before.
Comment 8 Rui Marinho 2015-07-06 13:23:00 UTC
@Josue can you please provide a sample case?

Thanks
Comment 10 Rui Marinho 2015-08-17 14:30:59 UTC
This particular issue was fixed in 1.4.4 final stable. If you still see this issue please reopen.