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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.
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 just installed the new eclipse kepler (eclipse 4.3). It shows me hundreds of errors and warnings from third party javascript libraries.
I tried to disable the javasscript validation completely by unchecking "Enable JavaScript semantic validation" in "Preferences/JavaScript/Validator", but with no effect - Errors and warnings are still shown.
Is there another option to disable them or is this just a bug?
Can other people confirm this issue or is it just me? :)
Edit 1: Lavie Tobey pointed out, i should set all validations to "ignore" -> did not help
Edit 2:
Jim Garrison pointed out, i should disable the builder for the projects -> Actually I don't have a javascript builder in there. Disabled for testing purposes all of them, but did not help:
You can go Project properties/Javascript/Include Path/source and exclude the third party components.
There are two places you have to look. You have found the first. The second is in each project's Properties dialog, accessed by right-clicking on the project in Package Explorer and selecting "Properties". There, under Builders you may find a "Javascript Validation" entry, which you must disable.
You have to do this for every project that contains a Javascript Validation builder.
Try this: Open the .project in notepad and remove the javascript validator
I've found that in previous versions of Eclipse, the only way to really get these to go away is to enable it and change every case to "Ignore".
You can switch off (and configure) validation in Preferences/Validation or (for each project) Properties/Validation. However, this doesn't seem to force a cleanup of the messages.
Like it was said : be sure to go to PROJECT properties (right click on project, properties), and not Workspace (Eclipse/preference).
I searched like 20 min before hitting myself ;)
I solved this by choosing a PHP profile for my javascript instead.
Maybe you don't get the same functionality but for me this profile is just fine. Crashes, hangings & frustration went away.
I had the same issue for XML Validation. I deactivated the validators globally and in the projects itself, nothing worked for me. There wasn't even the slightest hint that anything changed. I even uninstalled XML Editor and Validation Plugins without any effect.
In the end the problem was solved in copy-pasting the XML files with a validation error, deleting the old files and renaming the copies files to the original ones. Somehow Eclipse did not re-validate the old files, but the new ones were okay.
I have a Maven Java project, imported using m2eclipse.
The target/ directory is not marked as 'Derived' by m2eclipse.
Problems:
It is validated, so any validation error appear twice. My example shows a JSP Problem, when I insert intentionally an error in a jsp.
When I want to open a resource with Ctrl-Shift-R, all files appear twice, and I run the risk of editing the copy instead of the original file.
Possibly see post eclipse-ignore-folder
Note: When I set manually the directory to derived, the validation problem doesn't disappear, so that would only be part of the solution...
Question:
Is there something I need to do, so that m2eclipse sets the target/ directory to 'Derived' ?
Yeah, that has been around for a while. I wrote a plug-in that allows you to mark directories as "derived" without having to find them all (http://eclipsefrills.sourceforge.net/). It's not great, and you still have to manually run the action to make it work, but it may help.
Odd, though, I have not noticed the problem lately, myself. I wonder if there is some setting in the preferences that takes care of this now.
Good luck.
I got rid of this problem by writing a custom plug-in KeepTargetDerivedPlugin. As its name suggests, it automatically keeps all target folders derived (unlike the other solutions, which require user action).
Still, e. g. the YA2O's plug-in can be used to mark derived folders of projects which already reside in the given Eclipse workspace.
Yes: open a bug report :)
I have been so annoyed by this problem that I wrote a plugin to solve it. You can get the source and jar from here.
I've downloaded, unzipped and setup Eclipse 3.4.2 with some plugins (noteable, EPIC, Clearcase, QuantumDB, MisterQ).
Now I find when I'm editing Java projects the code completion is not working. If I type String. and press ctrl+space a popup shows "No Default Proposals" and the status bar at the bottom shows "No completions available".
Any ideas?
Try restoring the default options in 'Windows > Preferences > Java > Editor > Content Assist > Advanced'
An example of the kind of data you see in this preference screen, however not necessarily what you currently have.
(From Vadim in this blog post " Content Assist Duplicates in Eclipse (Mylyn)":
if have duplicate Mylyn entries, uncheck the duplicate entries that do not contain "(Mylyn)" in their name)
The Eclipse help page defines the default list to restore:
Select the proposal kinds contained in the 'default' content assist list:
Other Java Proposals,
SWT Template Proposals,
Template Proposals,
Type Proposals
I'm adding an answer here in case someone else finds this on Google. Same symptoms; different problem. For me, the type caches had become corrupt.
From http://mschrag.blogspot.co.nz/2009/01/open-type-cant-find-your-class.html
Quit Eclipse
Go to workspace/.metadata/.plugins/org.eclipse.jdt.core
Remove *.index and savedIndexNames.txt
Restart Eclipse and search Ctrl+T for the offending type. The indexes will be rebuilt.
In case someone comes here and want to activate the autocomplete function, go to
Preferences -> Java -> Editor -> Content Assist.
Then in the Auto Activation section fill in Auto activation triggers for Java:
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ._
For those running Xfce + having IBus plugin activated, there might be keyboard shortcut conflict.
See more info on my blog: http://peter-butkovic.blogspot.de/2013/05/keyboard-shortcut-ctrlspace-caught-in.html
UPDATE:
as suggested by #nhahtdh's comment, adding the some more info to answer directly: IBus plugin in Xfce uses by default Ctrl+Space shortcut for keyboard layout switching. To change it, go to: Options and change it to whatever else you prefer.
Check the lib of your project. It may be that you have include two such jar files in which same class is available or say one class in code can be refrenced in two jar files. In such case also eclipse stops assisting code as it is totally confused.
Better way to check this is go to the file where assist is not working and comment all imports there, than add imports one by one and check at each import if code-assist is working or not.You can easily find the class with duplicate refrences.
Another solution which worked for me is to go to Java--> Appearence --> Type Filters and do disable all
None of these worked for me.
I was experiencing this issue in only once particular class. What finally worked for me was to delete the offending class and recreate it. Problem solved... mystery not so much!
If you have installed Google Toolbar for IE, may be you can face the same problem. Because, the toolbar capture the shortcut ctrl+Space.
I had this problem and like #Marc, only on a particular class. I discovered that I needed to designate Open With = Java Editor. As a Eclipse newbie I hadn't even realized that I was just using a plain text editor.
In the package explorer, right-click the file and chose "Open With".
I faced this problem, and spent hours trying to figure out the issue. tried to follow the steps mentioned in the different answers above, the solution I found is on the same lines as Mona suggested, but slightly different. Tried to add as a comment to Mona's answer but no option was available.
Issue with my eclipse was, classpath somehow got corrupted and all the jars and dependent projects were missing. after taking the latest .classpath from repository it worked fine.
Check that you did not filter out many options inside the Window > Preferences > Java > Appearance > Type Filters
Items in this list will not be appear in quick fix, be autocompleted, or appear in other various places like the Open Type dialog.
I also face this issue but it is resolved in different way.
Steps that I follow may be helpful for others.
Right click on project (the one you are working on)
Go to Properties > Java Build Path > JRE System Library
Click Edit... on the right
Choose the JRE 7
Once you have you configuration checked and completion is still not working:
make sure you have the right directory structure.
Do you see the right icon beside the file?:
It will tell you how the file will be treated by Eclipse:
I am posting this answer as I had that story with with Maven webapp artifact. By default Maven-WebApp does not create folder for sources and I put my Java into resources, wondering for 5 minutes what was going on... :)
Running STS on Java Spring Boot projects, here's what works for me :
Maybe this helps other people who come across the same issue.
My setup: old Gradle project (version Gradle 2.12) made by someone else, imported using the Gradle Import Wizard into STS (Eclipse Oxygen.2 (4.7.2)).
Code completion did not work either (and I still have hollow Js at the Java files), but at least I got the code completion to work by doing:
right click on the project folder > Properties > Gradle > Configure Workspace Settings > Java > Editor > Content Assist > Advanced
check "Java Proposals in upper window.
2x Apply & Close
I have run into this problem since upgrading to Eclipse 2019-09. Based on some of the suggestions above, this is what worked for me.
I had to go to Eclipse -> Preferences -> Java -> Editor -> Content Assist -> Advanced.
I found out that if I turn on any of the key binding proposals, Java Non-Type, Java, Java (Task-Focused) or Java Type proposal, then I was able to use auto complete. If I turned them all on, then not only did auto complete work, but I got duplicate methods listed. I am guessing, but I will probably used Java Type Proposals. Any clarification of what differs for these four types would be appreciated.
In my case, Intellisense had only disappeared in a few classes in one project. It turned out this was because of a missing library on the build path (although it worked previously).
So definitely check all the errors or problems in Eclipse and try to find if a library may be missing
For those who use the latest 3-19 eclipse build:
It just happened to me when upgrading from Oxygen to 3-19 eclipse version, so I assume the auto-complete feature does not migrated correctly during the upgrade process.
The only solution that worked for me was to create a new eclipse workspace, and import the project/s to it. It might take a few minutes, but it worth it - comparing to the time spent on other solutions...
I ran into this and it ended up being I was opening the file with the text editor and not the java editor.
For me the issue was a conflict between several versions of the same library. The Eclipse assist was using an older version than maven.
I had to go to the .m2 directory and delete the unwanted lib version + restart eclipse.
I experience problems on Eclipse Neon when editing a file which does not belong to the project directory. When I copy the same file to the project root directory, not even to the src directory, the completion starts working.
When the file is opened from a different directory, only completion for JRE works. That is for example: java. completes, but junit. does not.
Just in case anyone got to a desperate point where nothing works... It happened to us that the content assist somehow shrunk so no suggestion was shown, just the "Press Ctrl+Space for non-Java..." could be seen.
So, it was just a matter of dragging the corner of the content assist to enlarge the pop-up.
I know, embarrassing. Hope it helps.
Note: this was an Ubuntu server with Xfce4 using Eclipse Oxygen.
If you're experiencing this in an enum, or when initializing an array with anonymous classes, it's a known bug in Eclipse. See Eclipse content assist not working in enum constant parameter list.
We can change the settings as per our requirement.
Suppose we want to make java proposal as highest priority we need to do changes as shown below.
Windows > Preferences > Java > Editor > Content Assist > Advanced
Choose Java proposal and click on up button
For me in Sep 2021 it was an odd Eclipse bug. I had a multi-line string inside an annotation in my Class. This caused just that particular class to fail when trying to code complete (even though the class compiled just fine).