cannot resolve symbol R in Android Studio

Question

In every instance in all of my classes where I reference R id something  the R is in red and it says  cannot resolve symbol R    Also every time there is R layout something it is underlined in red and says  cannot resolve method setContentView      The project always builds fine  It is annoying to see this all the time  I have read many other questions on here about something similar but most involved importing projects from Eclipse  I am using what I believe to be the most recent version of Android Studio and the project was created with Android Studio and worked without any  cannot resolve R  problems  I would like to know what causes this if anyone knows

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Just import the R symbol from the root package  import rootpackage R    No rebuild  sync or another things

User · Answer

I have had this with   An uppercase letter in my drawable resources  Import Android R being added by Android Studio  or Eclipse   Error in xml file

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First check is there any error in any xml layout or not  if then resolve it first   Otherwise remove junit dependency from project and rebuild the project

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I had the same problem  I tried most of what others have mentioned above i e Gradle Sync  Validate cache and Restart  Clean and Rebuild project   restart android studio and still had the same problem     The issue for me here  and I m assuming others may have the same problem  I had space on the name of my newly created layout file   Instead of file example xml mine was file  example xml    Notice the space between file and      when you try to find the reference to this layout file you will experience an error   I suggest you look the most recent layout file that you just created  refactor the name slightly and then change your R layout to the new file in your activity fragment --    Then clean  rebuild  the project  Project will compile without any errors  At least in my case  this was the solution to my problem

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In my case  importing the aplication domain name followed by   R  solved the issue  Example    import com example myapp R

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Same problem  Started when I added a few images in my drawable folder and tried to access them  Also the images added were having the extension with capital letters  That seems to have crashed the build  since even if I renamed them  the message was the same and R was inaccessible  What I did is  in the  iml file I looked for the excludeFolder and removed them  like bellow       lt excludeFolder url  file    MODULE DIR  build apk    gt     lt excludeFolder url  file    MODULE DIR  build assets    gt     lt excludeFolder url  file    MODULE DIR  build bundles    gt     lt excludeFolder url  file    MODULE DIR  build classes    gt     lt excludeFolder url  file    MODULE DIR  build dependency-cache    gt     lt excludeFolder url  file    MODULE DIR  build incremental    gt     lt excludeFolder url  file    MODULE DIR  build libs    gt     lt excludeFolder url  file    MODULE DIR  build manifests    gt     lt excludeFolder url  file    MODULE DIR  build res    gt     lt excludeFolder url  file    MODULE DIR  build symbols    gt     lt excludeFolder url  file    MODULE DIR  build tmp    gt    After that I rebuilt the project and R magically re-appeared

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If you see this error after moving java files or directories to other locations  then you can guarantee that Android Studio has gotten confused   And guess what  undo-ing those actions doesn t fix the problem   So you try a clean  but that doesn t work   And restarting doesn t work either   But try File -  Invalidate Caches   Restart    -  Invalidate and Restart  Android Studio maintains information about which files are dependent on which other files   And since moving files around is not implemented correctly  moving files causes errors   And that s not all  caches of these dependencies are used in an attempt to speed up the build   This means you not only have to restart  but you need to invalidate those caches to restore  or more accurately  rebuild  sanity

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Nothing worked for me   then I need to update my android studio to make it working  After updating android studio to the latest version the issue is resolved

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This problem is caused because of the naming of files in  res  or  drawable  folder  You can t use any capital letter for naming a resource file  So  check if there is any such file and rename it with small letters   And  also  you can try this  Go to   File   Invalidate cache restart   These options have worked for me

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I had the same problem and most times it is resolved by    Sync project with gradle files Doing Build -  Clean Project Doing File -  Invalidate Caches   But this time the error persisted even after doing all these things and at last i found the culprit   The problem was in an xml file  where i have given ordinary string value for an android id instead of an id resource type   MISTAKE  android id  username    CORRECTION  android id   id username       Messing up things related to resources in xml files is a major   reason for this error Beware of the fact that it may not be shown as an error in the xml layout file    NOTE   In most cases the compiler shows you the source of error in the Message  Try to check it first before attempting other solutions

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I have a similar problem and here is what I did   Clean Project and Sync Project with Gradle       check buildTools version in my sdk   From build gradle  module   change minSdkVersion from 8 to 9   defaultConfig           applicationId  PackageName          minSdkVersion 9         targetSdkVersion 22         versionCode 1         versionName  1 0          But all this didn t help   Finally I found the answer  this worked in my case   Change from build gradle module app    android       compileSdkVersion 21     buildToolsVersion  21 0 1                  Or   Select File   Project Structure change Build Tools Version to 21 1 1

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I have a special case for this problem    In my project  every thing goes well  it can compile and build successfully  but in my Android Studio IDE and I also tried Intelligent IDEA  they are in the same situation  the R java file can not be resolved well and always be drop in red line    Just like this    This almost made me crazy  I can t bear the read color when I am programing    At last I found this tricky problem is cause by my R java s file size  My project is very a huge one  it supports many multi-languages and multi screen sizes  There are so many resources that my R java s file size is about  2 5M   The max size of a file in Android Studio is 2 5M in default settings  so files bigger than this limit can t not be resolved well  And you can change the default settings in  AndroidStudio-root bin idea properties    change this line   idea max intellisense filesize 2500   to    idea max intellisense filesize 5000   Then restart Android studio  the red color dismissed  I can program happily again

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Have you updated your SDK tools recently  Launch the android SDK manager and make sure you have the latest SDK tools  which is now separate from the platform tools  I had this same issue when I first updated my SDK manager  the SDK build tools package did not show up for install update until I closed and reopened the SDK manager

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On OS X with Android Studio 0 2 13  I did  Jump to Declaration  on the com  lt  project   R import in one of my activities  When I went back to the activity file all the warnings were gone   Edit  You need to build the current build variant before this will work

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I found that in big projects  the autogenerated R java is bigger than 2 55MB  the default limit by Intellij  this causes the file to be generated but not resolved  to solve it simply increase that limit    in Android Studio Help -  Edit Custom Properties         Accept and add this  idea max intellisense filesize 3000  3000 or any value greater than the R file size       finally  restart your Android Studio

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In the latest versions of Android Studio  at least for me  the following works    Tools  -   Android  -   Sync Project with Gradle Files   In latest Android Studio 3 1 3  July 2018    Sync Project with Gradle Files  is available in main menu bar

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In an Instant App activity of a non-base feature you can call R id fromFeatureOne and R is fromFeatureTwo  So items from different resources are referred as of a single resource origin    Both will be highlighted as acceptable and you can even jump to source  But build will result in an error   cannot find symbol R id  which is quite tricky to find the reason  as nothing is highlighted   The solution is to call com example feature one R is fromFeatureOne and com example feature two R is fromFeatureTwo   Also issued a bug at Google  https   issuetracker google com u 0 issues 77537714

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I had this this issue too  A simple  gradlew clean  and  gradlew build  did the trick     Click on Build- Clean Project and that will perform a gradle clean

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You just have to check your Xml file   If there is an error then you can t resolve this error  Just solve error in xml then try   OR  Clean Your Project from Build -  Clean

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This happened to me fairly recently when I updated much of a project s libraries  R was not found  but I could build and run the project just fine  It wasn t crashing  The IDE simply showed red everywhere   I tried to   Check for damaged improper XMLs and images  none found Check for invalid resource file names  e g  capitalized   none found Downgrade some libraries because maybe it was a resource conflict  not resolved Lowered compileSdkVersion and targetSdkVersion because  in the past  I encountered resource issues due to this  In this project however  that was not the case  Clean  didn t help Rebuild project  didn t help Invalidate caches Restart multiple times  didn t help Adjusted idea max intellisense filesize to a very high value  didn t help Did a Lint run  no errors found   In the end  I found that downgrading my Gradle build tools  from 3 3 1 to 3 2 1  solved the problem  That was the only change I had to do  The rest  updated  Now  all my libraries are updated without issues   buildscript       repositories           google           jcenter             dependencies             classpath  com android tools build gradle 3 3 1          classpath  com android tools build gradle 3 2 1          classpath  com google gms google-services 4 2 0              NOTE  Do not place your application dependencies here  they belong            in the individual module build gradle files

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Take into account the following IDE functionalities    Sync Project with gradle files Build -  Clean Project Build -  Rebuild Project File -  Invalidate caches     My simple solution is    Check that there is no error line in the dependencies of the build gradle of the app or in all the resource files in the  res directory  where some common errors are when the attribute values are left without references when using      string       style      Make sure you are not getting an error of the type Android resource linking failed when the project is rebuilt  Open the file that contains the line with the error Cannot resolve symbol  R  Scrolling to the last line of the class with said error line Click on a position to the right of the closing key   of the class       In this way  the IDE alert dialog appears to perform the import of the R-class    GL

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This was a big headache for me  In my case the error appeared after configuring  Google Play Services  in Android Studio  installing   build gradle config   This in turn requires minsdk   7 but the error is very unclear about it  actually a complaint about this only appears as  info    Anyhow   upon changing minsdk to 8 both in the manifest file and the build gradle file and rebuilding the project  the error was gone   So   a general advice about this  if I may generalize - you probably have some problem in your manifest file  or some other configuration file  that is preventing a proper build  Try looking really hard at the error report  even the messages titled  info  for any hint about what it might be

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In my case the code was working properly before I updated android studio  After update R file was not generated  I was working on a custom view and had an attribute    lt attr name  showText  format  boolean    gt    in my declare stylable  This same attribute was also used by by the System s ui    lt style name  Base Widget AppCompat CompoundButton Switch  parent  android Widget CompoundButton  gt       lt item name  track  gt  drawable abc switch track mtrl alpha lt  item gt       lt item name  android thumb  gt  drawable abc switch thumb material lt  item gt       lt item name  switchTextAppearance  gt  style TextAppearance AppCompat Widget Switch lt  item gt       lt item name  android background  gt  attr selectableItemBackgroundBorderless lt  item gt       lt item name  showText  gt false lt  item gt    this line  lt  style gt    I renamed the previous showText to showTextFormat then gradle sync which regenerated the R java file

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most of times  this issue is caused by the xml files  take a look at the xml files  looking for any errors

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sometime due to incomplete sync it creates problem     so just follow the steps and it will do your work for sure  Click on Build- gt Clean Project and that will perform a gradle clean

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Apparently in my case the problem was resolved by adding an     at the end   import android R

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Type 1   close the Project and delete  gradle file in your project and then Rebuild the project Type 2  If type 1 does not works  then just take back up of of that project9Zip file  and then delete the project  Then extract the Zipped project and just import the extracted project  it will works perfectly  because it works for me

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I m working on a multi-module projects  And this happened to me when I moved all of the ui code to a new module   Here is how I solve the problem  I find out that when I create the new ui module  in the  res values  it creates a new strings xml with nothing useful in it   I delete that strings xml file  rebuild the project  and it works

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Check the Manifest file and make sure the package name is correct package  quot com packagename your quot

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I followed everything above and it didn t work  In my case I had to setup the JDK when I had every single Java Function in red for the Android-L preview      On Mac    Click once on what is Red  or underlined  in your code  i e  Activity  String   Click on the Red Light Bulb Point that appears on the left  Select  Setup JDK   Verify if annotations jar and android jar are in the current SDK version you are using  my case SDK 20 Android-L   You should also have the  res  folder  but I somehow still had it in the settings  If not  select the SDK and press  -   Then press     and locate the SDK folder on your computer  Mac  Applications   Android Studio app   sdk   Select the version of the SDK you require  in my case 20 Android-L   Press Add  Build and Sync    Then everything came back to normal for me

User · Answer

In my case  res someLayout xml file goes some error then i resolve it   Then Clear the project  Error is gone

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If you have any error on  xml file no matter what you do you can not fix that issue  I would suggest that  -first  check your XML file to look for any error and   -second look for event log what Android studio caught the error and it will give you which file and where the error is   That is how I fixed my R issue

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I got this error after upgrading the gradle plugin from version 1 3 1 to  classpath group   com android tools build   name   gradle   version   2 2 1    It forced me to change all references like  import  applicationId  R    to  import  package  R    And in my library project  appcontext getPackageName    stopped working correctly  I used it to get the correct app resources via reflection but after upgrading the gradle plugin it started to return the flavor-specific applicationId  instead of the package    you can read more about this here

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Make sure you have AndroidManifest xml in the project    It happened to me that I imported a project that didn t have the manifest yet so Android Studio wouldn t recognize it as an Android project  Then I pulled the project in GIT and it downloaded the manifest but still not working   Then I restarted Android Studio and it said something like  Framework detected android    So make sure your project is configured as an Android project

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This notation seems to work fine    android id    id viewID    Android Studio s design panel doesn t seem to work well

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I had the same issue  Android Studio 3 2 The project compiles and runs fine  but I am getting  Cannot resolve symbol  R  on-screen warnings  Does not help    Build- Clean Project  Build- Rebuild Project File- Invalidate Caches Restart   Helps   either   in build gradle  dependencies           classpath  com android tools build gradle 3 3 0          replace with      dependencies               classpath  com android tools build gradle 3 2 1                  or  Update Android Studio to 3 3

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One more thing to try      Delete the Build folder Rebuild the project by syncing gradle   I had already tried many of the other suggestions here  like    cleaning the project  restarting Android Studio  fixing errors in my xml  syncing project with Gradle files  and updating the build tools version    but none of these worked    I finally just manually deleted the whole build folder  after backing up my project  and then restarted Android Studio  After that I made a minor edit  added and deleted a space  in my app build gradle file and then clicked sync   I probably could have just done Tools   Android   Sync Project with Gradle Files from the menu   After that it worked  Something had gotten corrupted in the build folder and starting over with a fresh build fixed it   I don t know if anyone reads this far down the list of solutions  but I ll add this answer anyway

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I think I have the ultimate solution  I did a research and found that Android Studio hates  White Spaces  in installation paths or directories  It doesn t accept a SDK  placed at a directory that contains a white space  For example  C  Program Files x86  Android sdk   This directory is not valid as it contains a white space  Here  I have already answered a question where a guy was unable to change his JDK path in Android Studio because there was a white space in his SDK directory  This is weird  but it seems that Android Studio hates directories with white spaces  So the solution is -      Install the Android Studio as well as Android SDK in a directory or path where  there isn t any white space    For example- Install Android Studio in  C  AndroidStudio    And install Android SDK in  C  Sdk    Both this directories are valid as there isn t any white space  Every path that doesn t contain white spaces is valid  It also resolves other problems like  Failed to resolve  junit junit 4 12  or  Gradle sync project failed  etc

User · Answer

It s simple  Sync project with Gradle

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For me  the issue was that I upgraded to a version of Gradle that seems to have some bugs  3 4 0-alpha02 was what I updated to and found this to be the culprit of the  Cannot resolve symbol R  error  I reverted to 3 3 0-alpha10  i e  classpath  com android tools build gradle 3 3 0-alpha10   and it solved the issue    This obviously isn t a long-lasting solution as I ll need to upgrade sooner or later but as of Nov 3  2018 3 4 0-alpha02 is the latest version and it hinders my development by not letting me hop around the IDE by clicking on R references

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Just go to Android Top menu list  click on Build Menu  in under Build click on Rebuild Project

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In my case  it was solved by updating Android Studio from 3 1 to 3 3  To update your Android Studio  File -  Settings -  System Settings -  Updates and then click on check now

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Note   This might help you only if your project is very large  TL DR - The generated R file exceeded 2 56 MB and Android Studio was not indexing it  you can follow the solution for that here     File size exceeds configured limit  2560000   code insight features not available  Was facing a similar issue  But none of the answers here seemed to do the trick   The R file was larger than 2 56 MB  on opening the generated R file  I got a message saying  Code insights may not be available   Changing the default in idea properties to allow for a larger file did the trick   Apologies for formatting  on mobile

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In the new android studio 2 2  If your TargetSDK   lt  15 then you also might find this issue  Change this in the gradle build then follow the steps as per previous answers  Sync gradle files and rebuild  You can also invalidate caches and restart the studio that sometimes also helps

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There seems to be many causes for this issue  Recently  I added an activity to test with called NewActivity  This created a file called res menu new xml and gradle did not like that name because new is a reserved word      gradlew clean   or       Tools  - gt   Android  - gt   Sync Project with Gradle Files    Those are definitely good things to try  but you may have some other issues you need to resolve before you run those commands

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Check your xml files  Clean Project    This is it   For example I had an entry in my strings xml    lt string name  A  gt Some text lt  string gt    And in activity main xml I used this string entry   lt TextView android id    id textViewA  android text   string A   gt    While d been working with project  I deleted that    lt string name  A  gt Some text lt  string gt    And consequently activity main xml became not valid  As the result  cannot resolve R   So  check your   xml files and clean project

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Your code is just scrambled  The answer is fairly simple   Just go to Build --  Clean Project   That should do the trick   Check also your version of Android Studio   I m currently using Android Studio 3 0 1

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In my case I needed to fix some errors in my layout XML files  There was no icon which indicated that the files contained errors  However  when I clicked them I notices a few red lines  After fixing them  R was found

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In my case  after having the same error  Cannot resolve symbol R  with android studio version 0 8 9  what I did was go to File- Project structure and changed the JDK location to oracle JDK which I manually installed  So in my case in linux instead of  usr lib jvm java-7-oracle which was the preset one  I changed it to  home phvz App jdk1 8 0 20 saved the settings and the R symbol issue was fixed immediately

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None of these worked for me on Ubuntu 12 04   I had to do the following   sudo apt-get install lib32stdc  6 sudo apt-get install lib32z1   After that  I followed some other advice in this thread  did Build -  Clean Project and everything was fine

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I had my XML files in a LAYOUT folder instead of MENU folder   This was as a result of moving to Android Studio from Eclipse   Solution for me was simple     move my XML files to the MENU folder and recompile

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Build -  clean project or Rebuild project or File -  Invalidate Caches   Restart    -  Invalidate and Restart

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This is a very old question  but it still happens a lot and there is no truly comprehensive answer here    I have had this problem more times than I want to admit  It can be caused by a wide variety of issues that mostly all have to do with your project structure not matching what s expected  Here s a list of all the problems I ve had   Importing from Eclipse to Android Studio does not always work smoothly  especially with older versions of Android Studio  Make sure you re using the correct directory tree  It should look like this for a moderately mature app   AppName            AppName is your app s name  obviously      gradle        This is a compiler created directory  You should normally leave it alone      idea          Ditto     build          This too     gradle         And this     app          build          libs          src              androidTest       Tests based on the Android instrumentation runner should go here             main                  java                      fully               Typically com                         qualified       the domain name  Longer package                                          names may have deeper folder trees                             AppName     All your java files go here                 res                      drawable-           One of these for each resolution you support                     layout              All of your general layouts                     menu                All of your menu layouts                     values              All of your resource xml files                     xml                 PreferenceScreen layouts go here                 AndroidManifest xml             debug                       test              Pure jUnit tests should go here          gitignore         app iml         build gradle      This is the gradle file you should be making most changes to         proguard-rules pro      gitignore     build gradle          This gradle file should mostly be left alone     gradle properties     gradlew     local properties     AppName iml     settings gradle   It may not look like this in your IDE  There is a drop-down above the file tree that displays your files in different ways  and it defaults on my system to one called Android that breaks your files out into their different types  It s easier to fix this kind of problem from the one called Project  and even easier directly from your OS s file system  because Android Studio collapses folders that only contain another folder onto a single line   Especially if you ever change the name of your app  you need to make sure that the source tree main java com domain AppName is updated  Also make sure that the package tag in your AndroidManifest xml is correct   If there are errors in either your Gradle files or your AndroidManifest xml  this will prevent Android Studio from properly building your resource files  Gradle files can be broken by upgrading Android Studio sometimes  especially from the pre-1 0 versions  Sometimes this is because it stops supporting older versions of the Gradle plugin  so you need to update your version numbers  It can sometimes be hard to find what the current versions are  As of today  7 17 15  my apps are compiling fine with com android tools build gradle 1 2 3  This is in the dependencies block in the outermost gradle file    If your AndroidManifest references a non-existent drawable or string resource or activity  it will break and cause this error  Sometimes if anything references a nonexistent drawable or string resource you will get this error   If you have a file in your resources that is corrupted  or an invalid xml file  you will get this error   In my experience  sometimes Android Studio just hiccups for no reason  and you need to restart it and or your PC  I don t know why  but sometimes it works   If you have two xml resources with the same name  in directories that do not override each other  you can have this problem  For instance  you can have the same name in drawable-mhdpi and drawable-xhdpi because they override each other depending on the target device  but if you have the same name in layout and in menu  it will cause a problem  Rename or delete one of the files   If only some resources are having this problem  those resources are most likely in the wrong directory   In one case I had to completely reinstall Android Studio  I don t know what was wrong  but it worked   In one case I moved my entire project to a different directory and re-imported it as a new project  I don t know what was wrong  but it worked   Xml files with reserved words for names can cause this problem  Rename or delete them   There are a few ways your Gradle file can end up referencing a version of the build-tools that you do not have installed  Correct this by changing Gradle or downloading the appropriate build-tools   Finally  after you ve fixed whatever is wrong  you need to clean your Gradle project  You do this by going to the Build menu at the top and selecting Clean Project

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I also got this issue and I solved it in this way  First Go to Gradle and click clean  Secondly Click Build   Make sure not to Clean from android studio

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I was facing this problem when I imported google-services json file to implement Analytics  I already had global tracker xml file in the xml folder  During build  while merging contents from google-services json file  the error was started occurring    The error is resolved after removing the goolgle-services json file

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Try to ensure that the full package name is on the first line   Say you have a file named LoginActivity java and the package called com domainname project   The first line for LoginActivity java should be  package com domainname project    This is the equivalent of specifying  namespace  in dot net  Also ensure the package matches the package within which your   java file is contained

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I recently had this issue and the clean build etc  didn t resolve it  I guessed I had an issue somewhere but wasn t sure where to look to find it  was it in the manifest  resource xml files etc     When something is wrong  you can find out what it is by doing a code analysis run   From the menu at the top choose   Analyze -  Inspect code  scan the whole project using the  Default  profile   Your inspection results will contain an element called  Android   In here you will get a list of anything that is causing issues in your resources and manifest file  The errors will open up the generated xml files from your build which will show any errors in red   My exact issue was caused because I was using flavour based manifest files and I copied some permissions inside the  lt application gt  tag in the flavour by accident     UPDATE  I did have an issue after where Android Studio still showed the error after the fix  even though I could now build and run perfectly fine while the error was still there   I am running a canary build so putting it down to that for now

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I had same problem and it solved by    1  Sync Project with gradle files 2  Build - gt  Clean Project 3  Build - gt  Rebuild Project 4  File - gt  Invalidate caches    imp step 5  Check your xml files properly

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One thing which works for me every time is   go to --  build gradle  Module  app  file of your project --  do a little change  for example  put a  lt space gt  somewhere and remove it back  --  then android studio will ask you to sync your gradle file--  at top right corner of the file --  select  sync now    After syncing completes  it ll resolve the issue in most of the cases

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I am facing an error  Unable to resolve symbol R  the R appears in java file in red  I ve solved it    Do not save any image with Capital letters  like ABC png  First delete the image or rename it   Clean project  Rebuild Project

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See the below Image Goto File -  Project Setting -  Set All Setting like image and Sync it will put all latest setting in you project    if your project imaported successfull then you have to do this  beacause it will import all update setting and gradle

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None of the above answers helped me   I finally realized that the issue was that the  build  folder was missing from Android Studio   I found a number of lines in the projects  iml  file excluding  build      After removing those  the build file appeared and the errors disappeared

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Cleaning  Rebuild and  Cache Remove  won t help me  Updating Android Studio Fixed the issue

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I had the unresolved R problem because of the same image png file in two places  One in res anim and the same file in res drawable-hdpi  This caused R to become unresolved   I created the problem by making a splash screen image and repeatedly moving it from the Moray graphics directory to the Android project directly  I must have dropped it into res anim folder by accident  I fixed the problem by removing the duplicate image file from the res anim folder and Android studio corrected itself

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IN my case the reason was having some images in res folder with name contain a capital letter    just rename it with small letter and rebuild

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First solution  Rebuild your gradle or invalidate restart your system    Second solution  delete  gradle and  idea folder from your android project  So you can solve  R  problem   and also remove redline error occur without any reason you get

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There are many causes for this error    Sometimes it occurs for replacing an image file keeping same name  Suppose you deleted an item from your layout  xml say a  lt Button  gt  but it is still declared in any Activity or Fragment  java  Many more    Best way to track the error is Rebuild it rather clean or sync doing some intentional error   If it doesn t solve your problem then there must have to be some flaw or runtime error or error occurred due to improper use of resources in may be both java or xml file in your code or design which is forcing gradle to stop because  R esource file can t index your resources properly and you have to admit that   If your project ran before you made the changes then comment out the changes you have made and try to rebuild the project   It will surely work since there will be no changes   To track down the exact error  check the changes by breaking the changes into smaller module   For example - If you are making a list visible with a button click and inserting list values in the adapter  first check if you are able to make it visible or not then check for adapter errors

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Build   Clean Project  This worked for me  Had the same problem a few times  and this seems to set it right  Unless you have changed something or called a variable R  This issue usually happens out of nowhere  when it happens to me  so I imagine its just Android studios freaking out  haha  Have a good one  and good luck with your projects

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I had the same problem  and it happens when I create a new project    What I do is    check for SDK updates    then android studio updates   then reopen the project   open the andoridmanifest xml    erase a space between a      in the android label and save     That works for me

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I faced this issue when I manually renamed the domain folder of my app  To fix this issue  I had to    Set the proper package folder structure of  lt manifest gt  in AndroidManifest xml  Set the new package location for android name of  lt activity gt  in AndroidManifest xml  Clear cache by      File Menu -  Invalidate Caches   Restart       The issue will be gone  once the Android studio restarts and builds the fresh index

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i did make project and it works but before that try to check the package name in your manifest  rebuild and clean your project  if the problem didn t resolve  than make your project

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Have a look at the Gradle Console  In my case  I had included a resource with the wrong file extension   AAPT  libpng error  Not a PNG file  app mergeDebugResources FAILED  FAILURE  Build failed with an exception    After renaming the file and Sync Project with Gradle Files everything was fine

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Do  Build   Clean Project  IMPORTANT  Make sure you don t have any Errors after Clean Project in Message Pane  Alt 0   If you find any red circles with exclamation mark  than you must remove those errors in your code    Mostly these errors are related to  string  or  array   Clean Project again and done

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I added some images to drawable resourses  and one of my images was named as  super jpg   which turn out to be a cause    Renaming the image and after that syncronization the project with gradle files fixed the error

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After I do  Build- clean project  and  Sync project with gradle   Both them are not resolve  I down build gradle version from 3 3 0    3 2 1  revert as project init state  and it resolve my problem

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Simply defining an app namespace in your xml file can cause this   This was a completely innocuous line that only selected out one symbol  out of many  to make unresolved   Simply removing the entire line  greyed in the pic below  enabled my code to reference to unresolved symbol  Even when I added the line back it decided to build without problem   Go figure

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I ve got this problem especially when I accidentally corrupt a layout or a menu resource file  The scenario that I ve hit cannot resolve symbol R is when I forget to add    id  that where I ve to define an id in a menu item   With a corrupted menu resource file  I get this error if I try to build the project with it  Because that R is a container class for resources  it seems gradle cannot bind R when it cannot parse resources   xml files   The solution is simply fixing the resource files  cleaning up the project and rebuild again

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I had android textAllCaps    false  in the androidmanifest which was creating havoc to the R file  I deleted it and all is fine   I think the target sdk was not set high enough

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To Fix  can not resolve symbol r  error  Try these solutions    Build -  Clean Project  Build -  Build Project  Build -  Make Project  Third icon from left in Toolbar -  Sync project with gradle files  File -  Invalidate caches and restart  Make sure you are using compatible gradle version in application level gradle file    e g     classpath  com android tools build gradle X X X     I hope these solutions can help you   Thanks for reading

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You can delete one of your layout files  does not matter which one   after that you need to build project  Project will build and after that you need to return your layout file by CTRL   Z  In my case  if I tried to build my project before deleting of layout file  it did not help me  But this way is ok

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Just clean your project and Sync Project with Gradle File   And the problem will be resolved

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I see this problem may cause a lot of things  In my case  I had some textView in one of the activities   xml files  I put inside it text in the editor  to change it later via code  this way   NAME   lt here will be name gt    Apparently    lt   and     chars broke importing R in my project from every place  I changed it and it started to work  I just forgot I can t use those characters in   xml files  because they build its structure  It is worth having this in mind

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Dudes  I think there are a lot of shots in the dark here  In some cases Clean and Sync Project will help only after you fixed the problem   Step1  So go and look at the top of each file where the package is specified as follows pakage  YourURL YourProject   and insure that the correct package  Your Own Project  is specified   You will find this in java files and AndroidManifest xml and it is critical for the java files to reference the correct package  as that package contains the resources   R   you are pointing to  Should they not match up the error cannot resolve Symbol R occurs   Step2  Clean  Sync  whatever  Done  So why does this occur randomly or what did I do wrong    If you copy and paste code  you should pay close attention to the  package   as explained above  More importantly  when you paste code  it immediately runs through a sort of debugger  Excuse my bad tech term  to show you  presumed errors   which immediately takes in consideration the  Wrong Package   and you get all the errors  Therefore  even though you immediately corrected the notation after pasting  the debugger has already refreshed  Which is why  Clean  Sync  Whatever  works SOMETIMES

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In the project gradle i e build gradle just update the com android tools build gradle as  dependencies    classpath  com android tools build gradle 3 2 1

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For me it s important to say Android Studio in the begin will give trouble for learn  but like have here the solution Clean Project can fix this  always check the packed name and don t try to mess with the logic about  I Like the software but sometimes I try to think if the way is right or not  also I Like Linux but for me Android Studio to be rewrite all software maybe this will not happen  Anyway good luck

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I had a hard time fixing this myself    Make sure you have no errors in your layout xml files  Go to Build   Clean project   It worked for me  hope it works for you too

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change the latest sdk version that was work for me  1 Click file and then click project structure 2 then select  app  then click ok its worked for me

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The above answers are also the ways to fix the error but if does not work for anyone  then i have an option      Just Close the project and nothing else and start it again so it will load References    Follow the ScreenShots

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R java file contains the link between xml and java page   R cannot be resolved  arise only if there is a problem with some of your resource files  So the best and effective way is delete the last done xml or drawable in res file  and then again start from there according to android coding norms  This is the only way  The effective and right way    Also use Git for proper tracking of code

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What worked for me was    Created a new project  Found that the R is wokring  Compared all the configurations  Found that difference in gradle file  compile  com android support appcompat-v7 23 4 0  Sync  and it worked again

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This is caused of recently deleted xmls In Android Studio Clean your project from these xmls by choosing   build -  clean project

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None of the above answers fixed my problem  So I added my solution just in case someone run into similar issue  In my build gradle dependencies I had   compile  com android support appcompat-v7 22     and my compilesdk version was compileSdkVersion 21  so android studio wasn t happy  I simply updated my compilesdkversion to 23 and made sync   I also updated the dependency as  compile  com android support appcompat-v7 23 1 1    to match my support library in  Tools--  Android--  SDK Manager --  SDK Tools tab --  Android Support Library --  version  Now everything is fine  Happy coding

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I think if you put your Activities files to another folder than the default one  You need to import the com example yourproject R  this is your project R file NOT Android R file  to ALL activities using R  For example  in MainActivity file insert this line   import com example yourproject R

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You should do two things  first clean the project  in build menu       Next  Sync project with Gradle files  under file       This is the placement for the items in Android Studio 3 6 1 on Windows 10    If all else fails  Invalidate Caches and Restart  under file  usually does the trick  This closes down the whole program and takes the most amount of time in my opinion

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I had to import my R package in android studio  For ex  import com example  lt package name gt  R

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I had similar problem currently  The problem was that in my project I had more modules  E g  app module and library module  Although both  the class and the R string resource was from the app module I somehow had import com package library R in there  Somehow Android Studio did not recognize this as an error and Gradle Sync build my project without problems  But when I tried to run Unit Tests Gradle build failed with the described error   package com package app  import com package library R         class SomeClass             public void someMethod          Toast make context  R string message  TOAST LONG  show            When the R string messsage resource is actually in my com packagename app module and not com packagename library module  Removing the import     solved my problem

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I was using gradle 3 3 0  It was the main culprit  Wasted 6 50 hours from my life  Gradle 3 2 1 removed the error   classpath  com android tools build gradle 3 2 1    Problem resolved after changing the gradle version  Details history can be found here

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In my case  I was  trying to clean and rebuild the project  The issue was not fixed because there existed an error in layout file  To recreate  I have added a typo on an attribute in app namespace   lt  xml version  quot 1 0 quot  encoding  quot utf-8 quot   gt   lt menu xmlns android  quot http   schemas android com apk res android quot  xmlns app  quot http   schemas android com apk res-auto quot  gt       lt item         android id  quot   id add user quot          android icon  quot  android drawable ic menu add quot          android title  quot Add User quot          app showAsActioin  quot always quot            gt   lt  menu gt   Android Studio was not inspecting attributes of the app namespace  It seems file is error free  Now while building the project  It says Cannot resolve symbol  R   The errors are shown in the build log   Fixing the typo fixes it  Watch on Android issues section on build log

[android] "cannot resolve symbol R" in Android Studio

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