Possible reason for "Error:cannot generate view binders java.lang.NullPointerException"

Question

I am using Android Studio for my Android projects. I faced an issue when builds crash with strange stacktrace, like this:

Error:Execution failed for task ':app:compileDevDebugJavaWithJavac'. java.lang.RuntimeException: failure, see logs for details. cannot generate view binders java.lang.NullPointerException at android.databinding.tool.reflection.ModelMethod.isBoxingConversion(ModelMethod.java:155) at android.databinding.tool.store.SetterStore.isBetterParameter(SetterStore.java:946) at android.databinding.tool.store.SetterStore.getBestSetter(SetterStore.java:838)

and it was seemed that the databinding became broken as whole.

I made refactoring before and moved classes between packages.

I'm running on the same problem. In my case, I think it's because there is an inner class, but I{m not sure. I made several changes, but there is no clue at all of what's going on in the logs — Chisko
– Chisko, Commented Feb 14, 2017 at 4:03

atlascoder · Accepted Answer · 2017-02-04 23:12:57Z

51

In my case, I relied on Android Studio when renaming and moving classes between packages. But it didn't proceed correction for XMLs of layouts where were references on refactored classes in the type attribute of variable element in data.

So my previous type's value pointed to non existing files and build crashed.

It's simple mistake but it may take more time to find the source. Hope this would help someone.

answered Feb 4, 2017 at 23:12

atlascoder

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4 Comments

muthuraj Over a year ago

This. I wasted nearly an hour because of this. I wish Android studio would show the actual error on databinding issues.

AdamMc331 Over a year ago

Was there any way you can modify the compiler errors to tell you what file did this? Or was it a lot of guessing?

atlascoder Over a year ago

@AdamMc331 unfortunately, I didn’t try to do it. It’s easy to open layouts files and see that lint marked wrong tokens

Hassaan J. Over a year ago

Thanks. Wasted a lot of time on this. Issue was that I had copied an xml file from a previous version and the path of the viewModel was changed in previous model. Once I rechecked and renamed it, the error was fixed.

dzboot02 · Accepted Answer · 2019-11-05 18:49:45Z

For me, this started happening after updating Android Studio to version 3.5.2

To fix it, I downgraded Android Gradle Plugin

buildscript { repositories { //.......... } dependencies { classpath 'com.android.tools.build:gradle:3.5.1' //...... } }

Daniels Šatcs · Accepted Answer · 2019-02-15 16:56:52Z

Make sure you import all classes you reference in xml bindings

I had code something like:

android:visible="@{obj instanceof A}"

I was getting that same error.

Turns out that class A was not imported on top. Adding <import type="com.company.A"> tag resolved the problem.

P.S. android:visible is a custom binding adapter I have.

Steven · Accepted Answer · 2020-08-31 12:21:32Z

If this question is still relevant. For me I figured that in my xml layout file I was including a class (not an instance of one) as a variable, i.e I had this code

<variable name="Converters" type="com.example.flexapp.utils.Converters" />

and it should have been

<import type="com.example.flexapp.utils.Converters"/>

since this was a class and not an object.

Pouya Danesh · Accepted Answer · 2019-07-01 10:49:39Z

in my case my problem was in a LongClickListener that the method for this listener must have returned a boolean but my method returned void so when I added the correct return statement it worked just fine.

keep in mind if you use a data binding method you must return the correct value or else the error it throws is not helpful at all.

Damn, it took me a full evening tryna get my moved classes and packages back to where they were before the error ...n then boom, I saw this n corrected my code n viola!! It worked

AdamMc331 · Accepted Answer · 2018-11-27 16:12:28Z

You may have stumbled upon this question after migrating to Android X. If that's the case, and you're positive your XML files are okay, but it's still not working, you should start looking at libraries that generate code.

Libraries that generate code cannot be easily converted by the Jettifyer. Some info here - https://blog.danlew.net/2018/11/14/the-reality-of-migrating-to-androidx/

In my case, I updated the obvious ones, but I still was missing something. So, what I did was go into my develop branch (that wasn't Android X), ran a build, and dug into the build folder to see all of the libraries that generated code. Once I did that, I was able to look at the suspects one by one until I found the dependency that was causing this issue. You could either update it, or, in my case, remove it, and this error was resolved. :)

this is the same for me, after finding the contents generated code/builds still caching the support library. By running clean, invalidate+restart, delete .gradle cache and build directory solved my issue, also by providing a jetifier.blacklist if we don't want to upgrade to AndroidX for that particular libs, check here

senthil kumar · Accepted Answer · 2017-07-03 11:59:12Z

The getter function for any instance that you refer from your xml file might not have been defined or the getter function might not have public access specifier.

Ulrich Beutenmüller · Accepted Answer · 2020-03-07 11:34:32Z

1

Downgrading Android Gradle Plugin to 3.5.1 fixed the issue for me

answered Mar 7, 2020 at 11:34

Ulrich Beutenmüller

111 bronze badge

1 Comment

heat Over a year ago

Hi, you could add a more specific answer, like how to downgrade or a link to why this happen on 3.5.2 Thank you your participation.

Linh · Accepted Answer · 2017-07-31 03:19:48Z

I face this problem when I define variable like this (Android Studio don't warning anything)

<data> <variable name="onGlobalLayoutA" type="ViewTreeObserver.OnGlobalLayoutListener"/> <import type="android.view.ViewTreeObserver"/> </data>

And I solve it by

<data> <variable name="onGlobalLayoutA" type="android.view.ViewTreeObserver.OnGlobalLayoutListener"/> </data>

Hope this would help someone.

zsolt világos · Accepted Answer · 2018-06-29 20:25:28Z

In my case, the reason was that I used a type for a variable which is another module and that module is added as 'implementation ' in build script. Changing to 'api ' resolved the issue.

Clearly not the same issue as the one posted by atlascoder but I mention regardless, maybe someone gits this article with the same problem as I had.

kotlinski · Accepted Answer · 2019-12-04 08:39:59Z

As @hiddeneyes02 mentioned, this started happen when upgrading from Android Gradle Plugin from 3.5.1 to 3.5.2, this seems to be the bug: https://issuetracker.google.com/issues/143778134

When I built the project with the command tool I got the same errors as in this post: When building Android project with Android Gradle Plugin v. 3.5.2 my builds fail

Ramiro G.M. · Accepted Answer · 2021-08-14 17:07:42Z

In my case I wrote wrong the name of my view model variable inside the XML file. I had it named VProgressBar instead of vProgressBar:

android:visibility="@{fatherViewModel.vProgressBar}"

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