I am new to kotlin, i have converted some code from java but it seems like there's something wrong, The R in findViewById(R.id.my_id) is highlighted in red and it shows this message : "Unresolved reference: R".. I've been looking for a solution but i seem not to figure it out, So what should i do?
Here's a screenshot :
The issue can be caused by many factors,
as mentioned by martomstom in this Answer the issue is sometimes caused by com.android.tools.build:gradle version, changing it's version to a more stable one would solve the problem: for example: com.android.tools.build:gradle:3.4.0-alpha02 with com.android.tools.build:gradle:3.2.1
Also, having libraries from the same group, but with different versions may cause the problem or even more runtime errors. use the exclude group method like the following : implementation('com.squareup.picasso:picasso:2.71828') { exclude(group: 'com.android.support') } in this case, picasso library uses android.support components, the android library version used in picasso is different than the one you're currently using in your app, so in order to solve this issue, we have to exclude it completely from its sub library and class groups.
It can also happen by the mismatch of resources and code, including this importation line in your activity may solve the problem too : import com.package.name.R
Sometimes it can happen because of the IDE, performances or memory.. Cleaning the project from time to time may save you some time, on Android Studio it would be something like this : Build -> Clean Project / Rebuild Project - Cleaning IDE cash also helps with performance and memory, on Android Studio it would look like this : File-> Invalidate Chases/ Restart -> Invalidate Cashes and Restart
I noticed that this problem happens to me the most of the time when importing new resources, Using prohibited characters in their names would fire the error, such as . , , - , UpperCase or special Letters
And as a suggestion , if you're using Kotlin, i really recommend using Kotlin extensions in your activity such as : import kotlinx.android.synthetic.main.activity_page.* or if you're using a custom view : kotlinx.android.synthetic.main.view_layout.view.*
after that, in onCreat() method of an activity , you'll only have to call the id, for example : my_edit_text_ID.text = "Kotlin Dbest!", or from a custom view : mCostumView.my_edit_text_ID.text = "Kotlin Dbest!"
EDIT :
I have faced this issue againe and the problem was the '' R '' library was imported from 2 different sources :
com.android.R
com.example.package.R
You must only import the '' R '' library with your application package name,
in this case com.example.package.R
Sometimes the library is not imported at all, to import it, click on the
unresolved reference R and press Alt + Enter
EDIT:
As tobltobs mentioned in the comments section: " Most of the time the problem is caused by another error which prevents the build system from creating generated sources. To find the root cause look at the gradle log (the "toggle view" icon below of the green hammer in the Build output) and look for errors unrelated to R or BuildConfig (also generated). If there is no other error left and the problem with R persists then maybe something of this list might help. "
EDIT:
As Patrick Beagan mentioned, Kotlin extensions are now deprecated - I'd advise using ViewBinding instead
I used com.android.tools.build:gradle:3.3.0-alpha13 and had the same issue. Changing to stable Version 3.2.1 solved this problem for me.
So this is a misleading error.
The fastest way to get to the root cause is to run:
bash gradlew assembleDebug --debug
then scroll up and look for the real error happening.
However, if it still doesn't seem like you have the answer you are looking for, then read on.
I'm going to explain the 30,000 foot view of what is happening. This is not EXACT order or EXACT flow, it is just pretty damn close ;) so if you know more then I do of the exact order and care to make corrections with links, feel free I won't stop ya :).
The Process
The R file is generated code.
There is an order to the generation.
Gradle will do it's magic, pull it's dependencies and kick off it's
warning and error tree first,
then Android converts all Kotlin to Java behind the scenes. Yup that's
right, our beloved Kotlin still has to be Java to compile for our
beloved ART virtual machine.
Then it runs through and does the adapters that you have created for
JVM Statics and a few other tasks.
Next up it compiles all the xml databinding files first to create the
generated databinding files.
If everything succeeds it moves on to processing the assets and
resources. Which creates pointers or IDs for each resource that you
reference in code. Next it will run through and begin compiling the
code and packaging process after that.
Pretty straight forward process, but here in lies the problem.
The misleading Error
If any step fails before the R generation is complete, then the R does not get generated. Sometimes a simple rebuild is all you need to do, sometimes a simple File->Invalidate Cache and Restart is all you need. However, more often than not you have a code issue in your gradle, your xml, your databinding or your adapters that are preventing the compiler from even reaching the R generation stage.
So the next question is
"Well shoot, how do we troubleshoot it if the errors are worthless or
non-existent".
Well first let's talk about the many ways these errors present themselves.
Duplicate Databinding class found
xml Binding Error at line #
Couldn't find matching signature of bind:customAdapterMethod
Can't find R file of the correct project, only shows import options for sub modules or incorrect namespace R files.
Couldn't find DataBindingUtility or DataBinding for activity/fragment
And many other various ways as well, too many to list them all
Next, let's talk about potential candidates causing the problem. As there are sooo many lol.
Gradle Syncing issues
Bad versions of Gradle or Tools, you may have gone too far forward in your last gradle file modification. Try stepping back one version and "invalidate cache and restart" if that fixed it, great, if not, read on.
Caching Issues (File->Restart and Invalidate Cache)
xml elements with wrong namespace
xml elements with bad IDs or references IDs out of order (i.e. you say align to right of an element that is lower in the xml document then the sibling element that is trying to reference it)
xml data binding issues referencing namespace or member that doesn't exist or is not typed correctly
xml data binding issues in non-auto-filled spots like custom attributes using adapters as those are harder to spot. i.e. bind:myCustomMethod=#"myObject.mistypedProperty()"
JVM Static adapters with issues or duplicated signatures
Duplicated or bad character in the Strings or Dimens file or any other xml file for that matter
Private variable marked for #Binding without properties to access it
Member variable marked for #Binding that matches a parent class method causing duplications that manifests itself in almost impossible errors
Mismatch of types like using an adapter that takes (Int) but you are passing (Int?) via data binding and it isn't recognized with JVM Statics until compile time
You selected IMPORT on a popup to import R file of a sub module instead of the application file
Having bindable members in a child or parent class, but not giving fully qualified namespace to class cast in the XML usage of the parent or child class. As the databinding compiler is not smart enough to realize the variable provided for class Foo is also parentFoo baseclass, so you have to qualify it as android:text="#((com.path.parentFoo)foo).parentMethod"
Having a method name in a class, that matches a "generated property from #Binding member variable" i.e. firstName as a variable, but then having a method called getFirstName in a parent or child class, because you are now matching a method name that will get auto generated, thus causing dataBindingUtility duplication class errors.
There are more causes, but this should give you a series of places to look, but the list can go on and on seriously.
Unfortunately this happens a lot in bleeding edge technologies where the UI tools are not up to speed with the terminal based tools yet. So I suggest you run from the project root in a terminal with
bash gradlew assembleDebug --debug
When it fails, and it will. Start scrolling up through the logs until you find the red where you see what is actually failing and preventing the next stage from occurring.
You will find this especially useful when you start dealing with databinding.
TIP:
When you start dealing with databinding, make sure you compile and run often because the goal is to recognize right away before doing other files to make sure you didn't break generation and make your life MUCH easier to know code you just added caused the issue before getting too far.
Times to compile and run to confirm no issues before moving on.
If you add a few JVM statics compile and run
If you add variables to your XML to use
If you bind to properties of your model in 1 file
If you add a binding to a JVMStatic
If you add bindable members or properties to an model
If you refactor moving observable member variables or properties into children or base classes
Any other xml or binding related elements that can effect the generated code.
Like I mentioned above, the reason is to avoid getting so many changes, that it becomes a troubleshooting nightmare to find a generic vague, horrible error related to generated databinding code. I'm sure the tools will improve, but for now, do yourself a favor and compile and run often when changing Databinding related items.
Happy Coding
Use gradle commands.
In Android Studio, on the right menu:
Gradle -> :app -> Tasks -> build -> clean.
After that, Gradle -> :app -> Tasks -> build -> build
I had wrong import statement import android.R instead of import my.project.package.R. Fixing it solved the problem
I had the same problem, and I tried not to downgrade from gradle version 3.3 to gradle version 3.2.1. Instead I updated Android Studio to version 3.3, which made the trick for me ;-)
This worked for me. How much work it is depends on how big your project is. I started a new project, created the required modules (XML, Kotlin, colors, strings, etc.), then copied the code into the modules in the new project from the modules in the old project. Copying XML saves a lot of time compared to recreating the UI. All in all, it take a little while, but I have spent much more time tring to fix the unresolved reference error without it.
TRY THIS
Go to the content_main.xml file and there you need to change the
android:id="#+id/??????"> line of code to whatever id you have given to your file.
Replace question mark ?????? with the related file id name.(IF you dont know the id go to the design tab on the bottom and click on the related Asset.
On the right side below attributes, you can find the ID you have given to it.
If it is blank you can freshly name it and Android Studio will write the code.
Then restart Android Studio. Hope this will help. Happy coding.
I believe that I came across the real answer (though by accident).
I also, as the OP had my KT file fail to location R. as well as other classes that happen to be in java. What I noticed was that there was a case difference I the filenames. Once I corrected the import statements to match the case of the package (aka, folder) the errors resolved.
I had the same problem with R reference too.
Finally Android Studio 3.3 has been released and using 'com.android.tools.build:gradle:3.3.0' the problem has been fixed!
I update Android Studio to version 3.3.1 and solved this problem.
Downgrading gradle version worked for me.
I changed :
Gradle version from : 4.10.4 to 4.4.1
and Gradle Plugin version from : 3.3.1 to 3.1.3
If your are experiencing this issue in Kotlin because you cannot reference the elements of the xml layout by ids. (e.g. R.id.adView) then try removing the line import android.R from your kotlin file.
For me it was because I had created a new package and R wasn't available until I imported it from the package above
I faced the same issue. I restarted my Android Studio, invalidate caches, Sync Gradle but nothing was working. Then I looked into my file and there are 2 imports of my R. 1 import was related to my application package and the other was related to Android.
import com.example.myApp.R
import android.R // This import was added accidentally during the build.
Removing second import related to android solved this issue.
I had an issue because of this import:
import android.os.Build.VERSION_CODES.*
In the latest version it contains R
I had same problem while using auto-manifest plugin. Adding AndroidManifest.xml explicitly solved the problem to me.
I used to File --> Invalidate Caches... and issue resolved.
Just restarting Android Studio solved it for me.
I also had this problem, Gradle Sync, and Invalidate Cache, and Restarting Android Studio Didn't help. Upgrading and Downgrading Gradle were also not helpful.
What worked for me is: Make Project (Ctrl + F9) and then try to run the project.
I solved this error by following Android Studio's lint tools to upgrade the version of a dependency in the project-level gradle file. In this case, I upgraded androidx.navigation:navigation-safe-args-gradle-plugin from 2.3.2 to 2.5.2 (latest version), then synced the project.
Here is the solution,
File->Project Structure->Project, select Android Gradle Plugin Version as 3.2.1 from the drop-down. then click apply.
Related
I have an app which I am compiling against API level 21:
and then debug it on a real device with API level 23:
The problem is when I try debugging through the Android OS's own classes, I get 'Source code does not match the bytecode'. Why is this happening? The test device the app is running on is API level 23, and the source file being debugged is level 23 as well.
I am really confused. Can anyone explain why I am seeing this message and how I can fix it?
There's an open issue for this in Google's IssueTracker.
The potential solutions given in the issue (as of the date of this post) are:
Click Build -> Clean
Disable Instant Run, in Settings -> Build, Execution, Deployment
Here is my solution:
If you got more than one library version, this may help.
set a breakpoint on the lib source code
let the code run to the breakpoint
you will got these tips
click the arrow icon
you will get this
double click to select the correct lib (normally the highest version of the lib is correct)
I have clicked the "disable" button by mistake, you can enable it in the debugger setting
If you do not have the tips in the step 3, maybe you can check whether you have checked the setting options
You should use an Android emulator with the same api level as the compileSdkVersion.
In your case you should use Android emulator with api level 21.
If you use Gradle, it is probably a problem with Gradle caches. (Reference). Alas, even if you run
gradle --refresh-dependencies
, it is not refreshing really all dependencies. Some rubbish remains. (Reference).
So, the most sure (but drastic and long) variant is to clear all inside from the [user]/.gradle/caches. Or to find your problem project there and clear only its caches.
My app is compiled on API LEVEL 29, but debugging on real device on API LEVEL 28.I got the warning source code does not match the bytecode in AndroidStudio.I fixed it thought these steps:
Go to Preferences>Instant Run: uncheck the instant run
Go to Build>Clean Build
Re-RUN the app
Now, the debug runs normal.
These are the steps that worked for me (For both Mac and Windows):
Click on "File"
Click on "Invalidate Caches / Restart ..."
Choose: "Invalidate and Restart"
Note: It will take less than a minute for small projects, but since my project was big (approximately one million lines of code), it took 20 minutes.
I tried all the solution given here and none of them worked for me. In version 2019.1.3 I just clean & rebuild artifact and it worked; first do Build -> Build Artifacts... -> <select your artifact> -> Clean then click Build or Rebuild from same place.
Go to Project Settings > Artifacts. Select the artifact which has the problem. There is an option "Include in project build". This needs to be checked(enabled). For older versions of IntelliJ this option is "Make on build".
Probably this error message can have more than one cause, my case was not like the one from the OP, in my case this was due to a 3rd party library that required additional libraries.
For example: you manually add X.jar to your LIB, but this X.jar requires Z.jar to work.
It took me sometime to figure out, the message was not helping at all. I had to debug the app until I reached the crashing class, and in that class make sure that all imports were satisfied.
(Particualry: I added MercadoLibre-0.3.4.jar, which required commons-httpclient.jar)
Hope this helps!
This can also happen in case you have enabled ProGuard. In buildTypes set minifyEnabled false, shrinkResources false, useProguard false
I tried the solutions given here while working on an application that used Bluetooth Low Energy(BLE). I tried,
Clean Build
Disabled Instant Run
Invalidate Caches / Restart
all of these failed.
What I did was debug the points where I thought I was getting the warning, I still got the warning but the application was working fine. You can disregard the warning.
You can created AVD, select API Level equal your tagetApi andr compileApi, it works for me.
So I created an account just so I could help fix this problem that is plaguing a lot of people and where the fixes above aren't working.
If you get this error and nothing here helps. Try clicking the "Resume program play button" until the program finishes past the error. Then click in the console tab next to debug and read the red text.
I was getting that source code error even though my issue was trying to insert a value into a null Array.
Step 1 Click the resume button
Step 2 Click the console tab and read the red text
here is cause of why I got this error "source code does not match bytecode". My cause doesn't have anything to do with any API, compiler version..... It is caused by when inflate a layout view into a root view while I mistakenly initiate the inflator in else where (a chuck of "result handler" code that put on top of onCreate function of android app code). Somehow the debugger doesn't give me right hint of this (ex, inflator is not initialized or has instance) when breakpoint is set and stop here.
This happened to me when accidentally I have added the same library multiple times.
implementation 'androidx.appcompat:appcompat:1.1.0'
The above library was added multiple times.
If clean, rebuild, invalidate cache and restart etc. techniques are not working, then try deleting the previous APK and reinstalling the new APK.
Android Studio takes source version equal to Target Version in your application. Compilation performed with source version equal to above mentioned Compile Version. So, take care that in your project Compile Version == Target Version (adjust module's build.gradle file).
I had the same issue and found a solution. If you have a line flagged in red, it will give you this error, but if you un-flag all of the lines it will work normally.
by flagged I mean when you click on the left side where the line numbers are and it highlights the line.
If that is not clear here are pictures.
go from:
flagged line
to:
not flagged line
I have a project in Accurev for which I created a workspace. I did File > Import > Existing Projects into Workspace. After the import, the first thing that I have done is Configure Build path (Project>properties>Java Build Path). Still, I can find a lot of errors. I'm new to Java and I'm searching the Java errors in google and fixing them. Please suggest, How can I solve the similar errors for multiple files.
For Example,
The Empty block should be documented (I have it in 3 files)
The parameter customerExpression should not be assigned ( Multiple files )
The import java.util.List is never used ( Multiple files ). There are some other imports which were used inside the company are never used.
Apart from Java Problems, I do have
Classpath Dependency Validator Message
EJB Validator Message
HTML, JSP Problems etc which I feel can be solved once I solve Java Problems. I was told that Java problems are important. COrrect me if I'm wrong.
Please suggest.
Thanks
Like #Carlos Heuberger said these are seems like warnings not errors they won't cause any problem for your project to run. People usually don't care that much of warnings.
If you want to get rid of those warnings eclipse have quick fix actions for some of them. To do that head one of the warnings and right click then select quick fix. This should pop out a screen which summarize the action that eclipse will take.
Or you can simply hide them.
If you want to hide all the validation warnings go Window>Preferences>Validation then click Disable All button. This will disable all validation messages in your workspace.
For java warnings go through Windows>Preferences>Java>Compiler>Errors/Warnings and change the warning options according to your preferences. In my workspace under the Code Style section Undocumented empty block is setted to ignore so i don't get that warning in my workspace unlike yours.
Hope that helps.
i read a lot of posts but cannot resolve this yet.
There is my error lines and structure of project:
Some libraries and configs I take from another project... And don't know where I went wrong.
I will give you source code of files if needed
Thank you for any help.
I've also been getting this error since upgrading from Android Studio 2 to 3. The code compiles, but the IDE isn't recognizing the native functions. (This may be due to a preprocessor macro I've created that simplifies JNI function names.)
I've suppressed this error in Java by adding #SuppressWarnings("JniMissingFunction") before my class declaration.
Ok, so this missing 'JNI function' isn't a big deal. I know it's highlighted red, but the function is being linked, just not in a way that the IDE can determine.
First, here's the relevant source code: https://github.com/koreader/crengine/blob/master/android/jni/cr3engine.cpp#L770
CrEngine is linking the functions at run time. The reason why your IDE isn't picking them up is because the CrEngine functions start with Java_org_ instead of Java_com_. If you were relying on the engine to automatically link, this would be an issue, but as stated before, they are being explicitly linked at runtime with jniRegisterNativeMethods.
Do a clean and update your build tools to 25.0.3 (or better) in your gradle.build file. Update your SDKs and NDK. Then rebuild. Some of the errors I saw could be caused by older build tools.
I am trying to refactor my package using Eclipse
org.sheehan.activity
to
org.sheehan.stocks.activity
For some reason my project just blows up when I do this and R doesn't get regenerated. How can I refactor properly?
UPDATE:
I updated my Android Manifest to reflect the change. R still doesn't get regenerated. Even after a clean. The compiler is complaining about org.sheehan.activity.R
I resolved by:
Android Tools > Rename Package Application
If you renamed properly, all your references across your project should have gotten updated. After doing this, clean your project by going to Project > Clean. This should fix it.
Fixing missing reference to R in eclipse:
Refactor -> Rename`
Build -> Clean
Android Tools -> Fix Project Properties
select the base package of your project in the eclipse package explorer, press F2 (Rename), in the rename dialog: SELECT ALL the checkboxes.:
That should do it
The package name doesn't update in the XML files. Specifically your manifest which needs to know the base package.
For more advanced imports and refactors, literally closing the Eclipse IDE can refresh a cache that causes random errors like "End position lies outside document range" or the "what once worked now doesn't hair puller outter errors."
Signs you should close Eclipse when trying to rename things are:
When you import a project, do some refactoring (like trying to change the package name), then delete the project and try again, you will see immediate R.java errors when you didn't before
When you are importing projects that have manually generated R.java files that have custom imports like "com.ns.proj.R" and don't see the name update in Preview
The box that asks if you want to "Rename subpackages" is checked unexpectedly
the code in the "Preview>>" looks as if it's been complied before instead of black and white code with the proper names replaced
you get XML errors in the manifest activity name like this
android:name="com.ns.proj.CustomCocom.ns.proj.CustomControlse="#android:style/Theme.Light.NoTitleBar"
when it should be
android:name="com.ns.proj.CustomControls"
android:style="Theme.Light.NoTitleBar"
There are too many to name obviously, however this is as important as "keep your eye on the ball" in sports. Something that is so easy to forget, yet things like these apply to other software programs like Dreamweaver (e.g. when you use the Dreamweaver "Put" option instead of FTP dragging with FileZilla and you notice your domain isn't updating your changes online). I called Adobe when I first started as a developer 8 years ago because I knew I wasn't doing anything wrong. They said sometimes the generated files to perform the action get corrupted...in other words, IDE's have bugs too!
In general, close the IDE before you off yourself...it could save your life!
Right click in your Project, go to
Android Tools > Rename Package Application
Sometimes if Project > Clean doesn´t work, so Delete /gen and /bin folders of your project.
I keep getting this when trying to start a new project
ERROR: Unable to open class file C:\Users\Levi\Desktop\Android\workspace\Droid1\gen\com\androidbook\droid1\R.java: No such file or directory
I tried changing preferences to alter build path to project, but it still wouldnt work,,,
Is subfolder on desktop a bad place to install Eclipse?
Clean works sometimes and should be tried. I also find that blowing away the gen directory and refreshing will cause it be to rebuilt. Try that as well.
However, sometimes even that doesn't work and I've been forced to remove the project from Eclipse and then re-import it. This, unfortunately, works for me every time if the above has not.
Good luck.
Im also getting that error, running a Project->Clean in Eclipse helps for me.
Project->Clean should certainly fix this (unless your resources won't compile for some seperate reason).
I remember that the first time I ran Eclipse (in mid 2009, can't remember if it was Galileo or Ganymede or whatever) on Windows Vista, it presented several problems that were eventually traced to Eclipse itself being in a directory whose path contained a space...
Usually, the above tips (refresh, clean) work for me. But lately I had a very persistant instance of this error, which was caused by something else:
One of the layout .xml files in res/layout contained a reference to a custom view (org.company.project1.MyView). However, I had changed the package path (org.company.project2.MyView), so the reference had become invalid.
Thus, if everything fails try browsing your layout .xml files for invalid custom element definitions.
Cheers
after spending hours trying to ultimatly discover the issue behind the Class Issue not being found, resolved,or directory not there issue....
sometimes yes the issue is due to a bad binary or xml... as sometime a clean will do the trick or a xml edit will solve the day.. when all else fails.... this may do it..
"create a new workspace"
go into the workspace.... and then
Switch to your old workspace... in the newly formed workspace...
this was my silver bullet. so frustrating to not have a solid answer.
using Version: Helios Service Release 2
Build id: 20110218-0911