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Program type already present: android.support.annotation.PluralsRes error in Xamarin.Android project

I created a Xamarin.Android project and after I set the configuration:
- Dex compiler: D8
- Code Shrinker: R8
- Linking: Sdk Assembleies Only
I am presented with this error:
Program type already present: android.support.annotation.PluralsRes
I also have the LinkerPleaseInclude file.
I have to say that I am in Debug configuration.

I solved this issue by clearing cache for Nuget Packages.

I know I'm a bit late but since the answer for this matter did not work for me, here is how I solved it:
First of all, it's obviously a NuGet packages problem, so I searched in my .nuget folder at C:\Users{yourUser}.nuget\packages and looked inside some of the folders, in my case the Android support libraries folders, and saw that there were folders for many versions of that library excetp for the one I was referencing in my project wich was 28.0.0.3, the last version at this moment, the newest I had in the folder was for 28.0.0.1 so instead un uninstalling and installing everything again I just modified the android.csproj, changed the referenced versions for the support libraries for 28.0.0.1 and then it gave another error, I just literally downgraded some other libraries to 28.0.0.1 from Visual Studio NuGet package manager and then everything worked fine.
Have a nice one. It took weeks for me of trying to find out.

Neither of the above solutions worked for me. I encountered the error opening an Xamarin project that was created in VS 2015 on VS 2019. I changed the "Compile using android version" in the manifest to Android 9.0, updated the NuGet packages, but this error remained. I also attempted the tried-and-true deleting ".vs", "bin" and "obj" folders.
What finally got rid of the "Program type already present: android.support.annotation.PluralsRes" error was deleting everything in the "Packages" folder for the project. My understanding is that directory was eliminated in VS 2017, but suppose because the original project was VS 2015 it was still being utilized and causing the conflict.

I was getting
Program type already present: androidx.appcompat.content.res.AppCompatResources$ColorStateListCacheEntry error.
I had 2 references
a)Xamarin.AndroidX.Appcompat and
b)Xmarin.Androidx.appcompat.content.res.AppCompatResources
I removed the reference Xmarin.Androidx.appcompat.content.res.AppCompatResources
And now the project builds without errors

Android App Compile Not Generating Package Resources

When attempting to compile my Xamarin.Android app I get the compile error:
Error 3 The file "obj\Debug\android\bin\packaged_resources" does not exist. MyApp.UI.Droid
This error occurred after I made some changes (added some new classes - cannot remember what it was). But I didn't change any project settings, nor go delete actual files in the obj folder.
What is the cause of this error and how can I fix this?
Some information that may be useful:
The project is a Cross-Platform PCL project - Core, Android, and iOS Projects
The project uses MVVM Cross

I encountered the same issue. Ensure that your resource files do not include any special characters
The actual error you may be encountering is:
Invalid file name: must contain only [a-z0-9_.]
Change your build output verbosity in visual studio to see better log output.

I´ve had the same issue.
Then i´ve reviewed my resource file names.
Solution:
One file was using "-" in it´s name. (invalid character)
Then i replaced for "_" (underline).
PS:
=> file name: must contain only [a-z0-9_.]

You will need to grub down by switching on Verbose output. What is stopping the generation of packaged_resources?
In VS2013 choose Tools --> Options --> Build and execute, choose verbosity Diagnostic.
In VS2015, the same option is in Tools --> Options --> Projects and Solutions --> Build and Run.
In my case, it was a hyphen character in the name of the action property of an Intent filter, but choosing verbose output will point you to the line that has the problem.

Follow the steps below to identify the problem:
1 - In Visual Studio: Tools> Options> Projects and solutions> Build and Run.
1.1 - In the dropdown: MSBuild project build output verbosity:> Diagnostic.
1.2 - Close the dialog box.
2 - View> Output (Ctrl + W, O).
3 - Run the build or rebuild.
In the output find the line:
C:\Program Files
(x86)\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(1665,3):
error MSB6006: "aapt.exe" exited with code 1.
What is just above this error is what caused the error.

i also found that removing the packages in Tools/Preview Channel and Android N AND ALSO Android SDK Build Tools rev 24, done a build and worked.. This is a complete new portable project/android/ios

Another possibility is you have an issue with the installed Android SDK build tools. For me, when I removed the package for Revision 24 it worked.

From Xamarin Forums:
First of all go and deinstall preview tools in your android sdk
manager. If you havent installed it but still get the same error then
go and deinstall Android SDK Build Tools Rev. 24.
The Problem we have here is that, if you have Appcombat, RecyclerView
or something like that in your project, the library rev of these
librarys are below rev 24. They are still on 23.2.1 but not on rev 24.
So if you installed Build-Tools Rev 24 and want to build your project
the build cant find the rev24 resource package of your librarys.
You can check it on your own Go in the SDK Manager and check "Obsolete" Then go to the folder Extras and there you can see
"Android Support Library (Obsolete) Rev 23.2.1. And then check if
there is Android Support Library Rev 24 in your Extras Folder. No? And
thats the Problem here. We got the Update for Build Tools to early and
have to wait for Library Update. Then we all can use Build Tools 24!
So only update to BuildTools Rev 24 when we got an update for support librarys and have the rev24 librarys.

Basically the problem is with special character of Resource FILE NAME.
In my case, I am keep getting error "The file "obj\Debug\android\bin\packaged_resources" does not exist.":
..\Resources\drawable\company-app-log.png having -(hyphen) between alpha characters is the root-cause of the issue.

Using Xamarin Studio here -
Sometimes this is caused by AXML errors.
Which if you turn on detailed / diagnostic in preferences you can
search the build output (or your packaging output) for the word ERROR.
For example, somebody checked in some AXML line(s) with -
android:Text="something"
and the uppercase T was causing this error -
Resources/layout/Somefile.axml(11): error APT0000: No resource identifier found for attribute 'Text' in package 'android'
Fixing the errors fixed the original message.

Firstly, i suggest you change "show out put from" Build to Xamarin to see the real error and its details as seen in my case
At first
And then
please make sure you installed your NDK properly. That was the issue with mine,
and please make sure the NDK directory is also set
hope this helps someone

I just lost 7 hours of my day.. You know what I did?
Project.Droid -> Resources -> RightClick on the Resource.Designer.cs -> Delete
I did fu****n' works ! ><
EDIT
Omg it did comes back... Why does Windows has all time so much of bugs... seriously..

Same annoying problem with me!
But I found a solution: read carefully this article:
https://gxconsultancy.wordpress.com/2016/04/04/to-use-xamarin-or-not-to-us-xamarin/
In short:
Make sure you have JDK 32bits version 8 at least - same for the JRE, included in the JDK installation kit from Oracle;
Set your project for using the Xamarin debugger (right-click your project, hit Properties / Android Options / Packaging / Debugger);
And now the most weird: delete the app/Resources/drawable folder; have a working Xamarin project and copy its "drawable" folders to the erratic project (usually there are several subfolders, like drawable-hdpi, drawable-mdpi and so fort).
Rebuild your Android project.

I had the problem so I deleted build-tools 24.0.0 and I used build-tools 23.0.3 and the problem solved. Try it!

make sure that your resources don't have any special character or start with number

Encountered same issue in VS 2015 and Xamarin 7.2.0.7. In my case, the issue happened just suddenly, and turned out the issue caused by wrong element name in axml, traced using Tiago's answers above.
So I didn't find the line Tiago mentioned with aapt.exe, but I then I tried to search for keyword failed in output. Then I found one telling me about margin. In android, margin is set using android:layout_margin. I played with element and forgot and put android:margin instead, thus also why it happened so sudden after so many successful run. Fixed it and the build succeeded.

In my case the error was caused because I set the version number in the manifest to 1.0. Apparently the version number must be an integer.

Had the same problem. My error was in the manifest: I had Version Code (Version number) set at "1.0.0" and it wasn't allowed. It only takes integers so I had to revert to "1".
I mixed up Version Code and Version Name.

For me this error was caused by having an invalid attribute value in a layout xml. I had
android:id="button"
changing it to
android:id="#+id/button"
fixed the error.

Not sure if this is a late answer, but this specific error message occurs for one of the two reasons:
(Most probably the case): In your layout file, you may have mentioned a resource (drawable/image) incorrectly. For example, the image was in the mipmap folder path but you have pointed it wrongly to the drawable folder path.
Per many comments, there could be a hyphen or special character in one your resources' names or it starts with a number. However, please note, in this specific case, you will mostly see a aapt.exe has stopped or appt.exe has exited with error code 1 error. I am not sure if you will get obj\Debug\android\bin\packaged_resources not found error. My experience says that point 1 above is the case.

Got this error in Visual Studio 2017 Xamarin android project on Windows.
After lot of experiments with resource's files I found, that filename length and extension of image file in the drawable folder affect the result of compillation!
drawable/abcde.png - compilled ok
drawable/abcdef.png - error, "obj\Debug\android\bin\packaged_resources" does not exist
If rename image to file without .png extension, compilled without errors.
Spended a lot of time and was confused :-/

I had the same problem. To solve I had to remove all nuget packages from droid project, and reinstalled xamarin.forms again (has to be same version used in other projects).

had the same issue. This was because i had an .png file that had a "-" character in it's name. Just enusure any of your resources don't have the "-" hyphen character

Third party library troubles on LayerType attribute even after building it on Android 3.2

So, I coded my entire app in Android 4.0.3. I used AmbilWarna color picker. Then I got this requirement to reduce the SDK requirement for Android 2.3. This is the point when EVERYTHING was working fine and superb
I have downgraded teh minimum SDK requirement. Everything runs fine except as soon as I include Ambil Warna as a library on my project, I start getting the error everywhere R is used, Saying that R cannot be resolved to a variable.
Upon a loot on the Console, this is what seems to be the real cause of the problem:
AmbilWarna\res\layout\ambilwarna_dialog.xml:18: error: No resource identifier found for attribute 'layerType' in package 'android'
I have set the Android SDK to 3.2 for AmbilWarna library project and on my project its at 2.3
Does anyone have any idea?

this is regarding this: http://developer.android.com/reference/android/view/View.html#attr_android:layerType
you are just trying to use a property for android that is not available on that api of the layout parser.
I just checked out the colorpicker code you are trying to use, and it's project.properties says it's written for target API-17 (android 4.2) and i'm tryng to compile it for API-10 (android 2.3.3)
simply remove those parts.
my diff
--- a/AmbilWarna/res/layout/ambilwarna_dialog.xml
+++ b/AmbilWarna/res/layout/ambilwarna_dialog.xml
## -19,7 +19,7 ##
android:id="#+id/ambilwarna_viewSatBri"
android:layout_width="#dimen/ambilwarna_hsvWidth"
android:layout_height="#dimen/ambilwarna_hsvHeight"
- android:layerType="software" />
+ />
and hope it's not mentioned in the code :)

I've had a lot of troubles too with my external libraries. What usually helped are one of these or multiple steps of these connected:
Delete ALL R.java imports in your Classes (there must not be any of them)
In Eclipse: Source => "Clean Up"
In Eclipse: Project => "Clean..." (This will rebuild your project from scratch and therefore regenerate your R.java)
Manually delete all R.java and save (located in /gen/)
Delete your external library project and readd it.
Step 3 usually did the job for me.
Also be aware that your minSdkVersion and targetSdkVersion fit to your library project (and the guidelines which are included)

I had the same problem, I thought I could just build and include the third party jar file and bring this over to my project - this resulted in the same problem as you - AmbilWarna\res\layout\ambilwarna_dialog.xml error: No resource identifier found for attribute 'layerType'.
To fix it I copied over the source files and all resources into my project (images/layouts etc etc), hey presto it worked.
Thanks http://code.google.com/p/android-color-picker/ for a nice clean easy to use colour picker!!

Proguard ParseException with Default proguard.cfg on Android

I am about to release an application but, while i was building it using Export Tool of Android SDK in Eclipse, i get the error below.
I didn't change the proguard.cfg.
It is in the root folder of my project.
I only add proguard.config=proguard.cfg to default.properties.
I read the forum and update proguard (just copied the files to the tools folder of Android SDK), but still I doesn't work. I couldn't figure out what the problem is with the 'Projects\Eclipse' ??
If you help me, I will be so glad...
[2011-08-08 02:32:46 - CoolProject] Proguard returned with error code 1. See console
[2011-08-08 02:32:46 - CoolProject] proguard.ParseException: Unknown option 'Projects\Eclipse' in argument number 9
[2011-08-08 02:32:46 - CoolProject] at proguard.ConfigurationParser.parse(ConfigurationParser.java:172)
[2011-08-08 02:32:46 - CoolProject] at proguard.ProGuard.main(ProGuard.java:484)

Yeah that is right, but also I did something that I didn't know :)
My solution was:
I updated to latest Android SDK.
I changed SDK path property under Eclipse: Window > Preferences > Android > SDK Location as something like c:\Progra~1\android-sdk. The Progra~1 can be used for writing Program Files witout spaces. You can use DIR /X command in command prompt on Windows to get no space versions of Paths.
I moved my Eclipse Workspace to a location without spaces like D:\
The changes above didn't enough to solve the problem. I got "Conversion to Dalvik format failed with error 1" error dialog witout any explanation on output console. Then I found that topic and did what that reply says.
Then it worked ;)
I am using Windows 7 Ultimate x86. I hope it works for others too.
Arda.

Your project path probably contains a space. This should be fixed in the latest version of the Android SDK (at least for the Ant build). Otherwise, you should use a path without spaces for the time being.

Conversion to Dalvik format failed with error 1 with javax/net/SocketFactory.class

Encounter this problem when trying to Build Project getting such output in console:
[2010-07-19 23:29:23 - myProject]
trouble processing "javax/net/SocketFactory.class":
[2010-07-19 23:29:23 - myProject]
Attempt to include a core VM class in something other than a core library.
It is likely that you have attempted to include the core library from a desktop
virtual machine into an application, which will most assuredly not work. If
you really intend to build a core library -- which is only appropriate as
part of creating a full virtual machine binary, as opposed to compiling an
application -- then use the "--core-library" option to suppress this error
message. If you go ahead and use "--core-library" but are in fact building
an application, then please be aware that your build will still fail at some
point; you will simply be denied the pleasure of reading this helpful error
message.
[2010-07-19 23:29:23 - myProject] 1 error; aborting
[2010-07-19 23:29:23 - myProject] Conversion to Dalvik format failed with error 1
I was looking for my project to use the package javax, not found, clean all also does not help. what I am doing wrong?
Update
Sorry guys, but I could not find good fix for that, I want to emphasize the fact, that i dont use SocketFactory class in my project at all! source code was not changed before this problem, and that's why i think that problem in eclipse or adt or something else, BUT if i use ant(generated by sdk) to build this project there is no problem!!!
I solve this problem by removing Eclipse, Android SDK, Eclipse workspace, and just reinstall them, after this all works fine for now.
Hope this will help someone.

I had the same problem..
This worked for me
project-->properties->java build path->libraries-> remove all including android jars
now go the project browser, right click on the project you are working on,
then android tools---> fix project properties...
do a clean and then build...

I solved the problem (at least for me).
Here's what I did:
Go to Project » Properties » Java Build Path » Libraries
Remove all except the "Android X.Y" click OK.
Go to Project » Clean » Clean projects selected below » select your project and click OK.
That did the trick for me.
Hope it works for you as well
Update: well actually I might have to retract my opinion.. the actions removed the error messages but now I am missing certain classes and methods... arggghhhh

I just restarted Eclipse, and the error didn't appear anymore!

I had the same problem,and solved it as follows:
First clean all jars; (This problem must because your some jars)
Delete the project;
Reimport project;
Make sure your sdk is right, and project select one sdk version;
(This is my issue to solve the problem) Right click your project, and select "build-path", next select "add Librarys", and add your private jars;
clean-build, the problem has fixed;

I just had the same problem and I tried all of the solutions listed here with no success (I was starting to get annoyed). Then I removed the project from the workspace and then imported it again, and there were no problems!

This happened to me this way,
I have a quite an old project which I had to start working again today. I use 'Universal Image Downloader' library for basically every project where I have to deal with lots of images. So in this old project I had the source files of 'Universal Image Downloader' included to it's 'src' path. Back then I was a newbie and slowly I started developing my own library which could handle every day simple Android development tasks very easily. Obviously I included the 'Universal Image Downloader' to this.
After dusting off the old project today the first thing I did was to reference my library to speed up the development process but as I was trying to debug I ran into the "Conversion to Dalvik format failed with error 1" over and over again. First I thought it was the support library but even after clearing all libraries and adding only mine and doing a quick 'Fix project properties' I still got it. After trying various solutions I noticed this in the console "java.lang.IllegalArgumentException: already added: Lcom/nostra13/universalimageloader/cache/disc/BaseDiscCache;"
It was as simple as that... I'm trying to compile a class which has already been compiled.
Solution : I just simply removed all the class files I got from 'Universal Image Downloader' library from the 'src' directory. Since my library references "Universal Image Downloader" library the old project started working just fine.

Hit same problem shown on your log when trying to run an example project which was imported into eclipse.
Additional Info: in eclipse's Problems View I see the following error:
"The project cannot be built until build path errors are resolved"
In my case the imported project find the libraries just right(by just right I mean I can see the external path to each of the android libs in this case 2 libs, android.jar and maps.jar). So no shuffling of libs in my case, but might be your problem.
I followed Spock's suggestion of cleaning the project which I had to clean multiple times until it somehow resolve its issues. After, issue was solved I had to specify an AVD for the project to run and soon after was up and running on the emulator. Also, note that my eclipse is set up to Build Automatically.
In my case I'm not missing any class files or anything after the clean as the build is properly generating them.
Regards!

I was getting the same error. My problem was that i had an android device hooked up to debug with. As soon as I unplugged it I was able to export.

The answer I found was checking the source and library build path in the project's properties. Most likely there will be a duplicate as in something being referenced in both the source and library tabs. So delete the extra in the source tab and then clean the project and you should be good to go.

Either:
javax.net.SocketLibrary is in your source code, or
javax.net.SocketLibrary is included in a JAR file in your project

Under certain conditions it gets its knickers in a twist and the best fix I've found is to remove referenced jars, clean, add them back in and then compile again.
I believe the error can be caused by including the same classes twice.
This error will also occur (and you won't be able to get rid of it by cleaning) when using classes that are not part of the Android environment.

To summarise the information in the link bimbim.in provided (well my understanding when I glanced over it)
The Android Davik VM tries to compile the jars but finds some stuff that it can't compile to .dex files
so
Just create a "lib" directory in the root of the project (where the src, bin res directories are) and add them to the build path. Project Properties... Java Build Path... Libraries.. Add JARs..

I could resolve this issue by creating a new project, looks like the some project settings were creating this issue and could not really find the root cause for that. But, dumping the existing source code onto the new project resovled this issue. If anyone has found the root cause for this problem pls do let me know.

I had the same problem and solved it as follows:
- Go to Project/Properties/Java Build Path/Libraries and remove all JARs except Android
- Do a project clean
- Add the JARs again as External JARs (first time I added them internally, so that might be the problem)
After that the error was gone.

I solved the problem by updating available packages in the Android SDK et AVD manager. No need to remove Eclipse.

Whenever the Project is having the ambitious data. This problem is caused. May be android can't able to find which one choose.

From what I understand, this same cryptic error could be caused from a wide variety of reasons. I've got "Conversion to Dalvik format failed with error 1" error too. In my case the problem was that for some reason Project -> Properties -> Java Compiler was not set to "Enable project specific settings" with proper Java 1.5 settings, but was left to defaults instead (1.6 in my case). Debug, build and test on devices/emulators worked fine, but export always failed with the above error message.
If unsure about the proper settings, create the same project on some alternative location and just copy all needed files from the old project into the new one. This fixed the issue for me.
The next problem with the same error message came from using proguard. Updating to the latest version by replacing the one that came with android sdk, fixed that.
Hope this helps

My problem was having a jar file in my src folder. Removing jars from the build path works, but only if you don't need the jar in question. For people who need the jar in question, make sure that your jar file is not in the project folder (maybe just src subtree, but I would keep it separate to test). Put it on your desktop or something and try the "Add external jar.." option. Be sure to remove the jar from the project filesystem before adding another external. Having both is what causes the problem.

I have done it as the instruction of the first answer and it works.(Linux)
I think the problem may caused by SDK or ADT updates.
I do have to clear all the lib in Java Building path and then use android tools to fix the project. After cleaning and rebuild, it works as before.