R cannot be resolved to a variable eclipse android

R cannot be resolved to a variable eclipse android - java

I already tried all the answers present in this website. Deleted the "import android.R;" line. Even then every time I run my project it says "Your project contains errors, fix them before running your application". I'm working on Eclipse. As soon as I create a new android application project I am encountered with 2 errors which say “R cannot be resolved to a variable”. Here's my code for MainActivity.Java
package com.example.myfirstapp;
//import android.R;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentViewq(R.layout.activity_main);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}

just try this at your imports
import your_packgae_name.R;

If you are getting same problem when creating new project then the problem is with your SDK Version.
Update your SDK to rev. 22.0.1
After updating you will find new tool in SDK manager that is android SDK build tools.
thn install that tool also.
Hope this will help you.

Right click on the project's folder and then, Android Tools --> Run Lint - check for commons error. When this don't work, disable automated build, clean projet, run lint again --> build.
Ah also, in the proprierties -> Android, verify that build target is checked...

Delete the imported android.R (As what you did)
Re-import R
Eclipse will allow you to choose which should be imported. Choose the R from your package.

I had the same problem.
The R.Java was not generated(in the gen folder).
There was no error in the xml file.
The issue was that I did not update the sdk completely.
In the SDK manager we need to install the package whenever the "install(number) packages" button is enabled
and close and open the sdk manager to check for updates.
Close and reopen eclipse and check for updates in eclipse also.

Make sure this line,
setContentView(R.layout.activity_main);
in your code it contains "q".
Then build your application and then run

One of your xml files might have errors. Hence, R is not generated. Fix them and R will be generated and the errors will be removed.

Check if file "R.java" exists in folder "gen"
When aapt can not compile the resources, the R class can not be created. Look for errors in the resources of your Application.
More output you can find in the ErrorLog and Console window
(Eclipse Window menu->show view->Console (and choose "Android" in Console popup menu)).

check your drawables and make sure there is no file with capital letters to avoid error!
.

Did you start the project a while back and recently it has done this when you went to work on it? I had the same issue and recently came to find an answer. It could be that the problem is you need to go into the SDK manager and install a particular update as per the answer to this question: Eclipse error: R cannot be resolved to a variable

Try this once
Go to Project
Check Mark "Build Automatically"
and Restart Eclipse

Okay so I had the same problem, and I also tried everything:
Check for bad naming, remove the import statement, installed the Android SDK Build-tools, check the AndroidManifest.xml, reinstall eclipse and android SDK etc.
nothing worked.
And I was even working with a completely blank project (new -> android project)
I then found out that the android SDK comes with an already zipped eclipse, so I thought I might as well try that one.
So I uninstalled eclipse 64bit, and used the one which comes with the android SDK (http://developer.android.com/sdk/index.html#win-bundle) and now I dont get the error anymore, so give it a try.
I also found that using eclipse 64bit with a java 32bit version might cause problems. So it might be that the one that comes with the Android SDK vertion is the 32bit eclipse.
Hope this helps.

The problem was caused by incompatibility of version. Here are the steps to fix the problem:
Right click the project properties.
Select Android
Select correct Project build target.
I fixed mine.

I found this way working Awesome. Which is also slightly similar to Mr.AndyFaizan,
Check any of your xml files have errors or not.if yes R might not generate.
2.Fix the error at XML files. Then R will be generated automatically
Then import the R which is suitable for your package.
YES, your error "R cannot be resolved" Gone!!

if this error occur immediately after create your project on eclipse. the main reason is manifest.xml error.
application icon path is wrong. copy ic_launcher.png into drawable folders.

Related

android studio error cant resolve symbol [duplicate]

Want to improve this post? Provide detailed answers to this question, including citations and an explanation of why your answer is correct. Answers without enough detail may be edited or deleted.
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.

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

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.

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.

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

Check your xml files.
Clean Project.
This is it.
For example I had an entry in my strings.xml:
<string name="A">Some text</string>
And in activity_main.xml I used this string entry
<TextView
android:id="#+id/textViewA"
android:text="#string/A"/>
While'd been working with project, I deleted that
<string name="A">Some text</string>
And consequently activity_main.xml became not valid. As the result: cannot resolve R.
So, check your *.xml files and clean project.

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.

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;

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" -> "Android" -> "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.

You should do two things, first clean the project (in build menu) - it deletes the build directory which may be the culprit:
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.
To clarify, I am running this on windows 10, but it should work on MacOS and Linux as well.

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. ..

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.

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.

I had to import my R package in android studio. For ex: import com.example.<package name>.R

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

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 <application> 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)

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

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 <manifest> in AndroidManifest.xml.
Set the new package location for android:name of <activity> 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.

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

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.

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

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.

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.

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!

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

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.

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.

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

This notation seems to work fine.
android:id="#+id/viewID"
Android Studio's design panel doesn't seem to work well.

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):
<excludeFolder url="file://$MODULE_DIR$/build/apk" />
<excludeFolder url="file://$MODULE_DIR$/build/assets" />
<excludeFolder url="file://$MODULE_DIR$/build/bundles" />
<excludeFolder url="file://$MODULE_DIR$/build/classes" />
<excludeFolder url="file://$MODULE_DIR$/build/dependency-cache" />
<excludeFolder url="file://$MODULE_DIR$/build/incremental" />
<excludeFolder url="file://$MODULE_DIR$/build/libs" />
<excludeFolder url="file://$MODULE_DIR$/build/manifests" />
<excludeFolder url="file://$MODULE_DIR$/build/res" />
<excludeFolder url="file://$MODULE_DIR$/build/symbols" />
<excludeFolder url="file://$MODULE_DIR$/build/tmp" />
After that I rebuilt the project and R magically re-appeared.

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 <Button/> 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.

Cannot resolve 'R'.. not sure why this is happening?? Android Studio HW [duplicate]

Want to improve this post? Provide detailed answers to this question, including citations and an explanation of why your answer is correct. Answers without enough detail may be edited or deleted.
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.

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

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.

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.

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

Check your xml files.
Clean Project.
This is it.
For example I had an entry in my strings.xml:
<string name="A">Some text</string>
And in activity_main.xml I used this string entry
<TextView
android:id="#+id/textViewA"
android:text="#string/A"/>
While'd been working with project, I deleted that
<string name="A">Some text</string>
And consequently activity_main.xml became not valid. As the result: cannot resolve R.
So, check your *.xml files and clean project.

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.

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;

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" -> "Android" -> "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.

You should do two things, first clean the project (in build menu) - it deletes the build directory which may be the culprit:
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.
To clarify, I am running this on windows 10, but it should work on MacOS and Linux as well.

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. ..

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.

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.

I had to import my R package in android studio. For ex: import com.example.<package name>.R

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

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 <application> 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)

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

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 <manifest> in AndroidManifest.xml.
Set the new package location for android:name of <activity> 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.

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

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

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.

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.

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!

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

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.

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.

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

This notation seems to work fine.
android:id="#+id/viewID"
Android Studio's design panel doesn't seem to work well.

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):
<excludeFolder url="file://$MODULE_DIR$/build/apk" />
<excludeFolder url="file://$MODULE_DIR$/build/assets" />
<excludeFolder url="file://$MODULE_DIR$/build/bundles" />
<excludeFolder url="file://$MODULE_DIR$/build/classes" />
<excludeFolder url="file://$MODULE_DIR$/build/dependency-cache" />
<excludeFolder url="file://$MODULE_DIR$/build/incremental" />
<excludeFolder url="file://$MODULE_DIR$/build/libs" />
<excludeFolder url="file://$MODULE_DIR$/build/manifests" />
<excludeFolder url="file://$MODULE_DIR$/build/res" />
<excludeFolder url="file://$MODULE_DIR$/build/symbols" />
<excludeFolder url="file://$MODULE_DIR$/build/tmp" />
After that I rebuilt the project and R magically re-appeared.

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 <Button/> 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.

How to fix "R.menu.main" in java when first developing an android app?

So I downloaded everything that the Android app tutorial told me to, and I am and using Eclipse, but I keep getting an error message on main in R.menu.main:
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
I've imported android.R; and it didn't work; I deleted that line and I went to Project>Clean and it still didn't fix itself. Other people on this topic keep saying to import the "R file" from your package but I checked all of the packages and classes and there is nothing called R. I tried importing the res folder and that didn't work either.
Help?

You should have a main.xml file in your res folder to point to. If you have that and it's still not working then it might be a problem with the R file. That has been known to cause issues. You shouldn't need to import R since it builds automatically.
Chances are there is an error in your xml file. This will cause the R file to not build. Fix that issue and rebuild your project and you should be fine

To what Android app tutorial are you referring?
I'm going to assume that you're so new at this that you have a thousand questions no matter where you turn. The trick for me, at that stage, was to just get something, anything, working. After that, I'd just keep building, carefully, inside of that first success (well, a copy of it, actually... I was that paranoid).
So... I'm offering here to quickly take you through the steps in creating an app in your Android/Eclipse environment. If things start breaking down then perhaps your setup isn't right. But if your setup is good then you should have a running app in about ten minutes.
From that, you'll see that you don't have to worry about a lot of the details in the answers given for your Stackoverflow [this] post (at least, not until you gain more experience).
(note that this stuff, in greater detail, is found here but I'm going to give you a seriously "let's just get this going already" version)
In the Eclipse menus...
File -> New -> Android Application Project
a "New Android Application" dialog window will come up
Type "MyTestApp" in the Application Name field and simply accept everything else.
Click Next.
You'll be getting four more dialog windows after that first one. Accept all of the defaults on each of them and simply keep clicking Next until you get to the last dialog. There, just click Finish.
At this point, the project is being created. Depending on your computer, this might take a few seconds. You can see progress with the messaging displayed in the bottom right corner of the Eclipse window. See nothing there... it's created.
If your Android/Eclipse setup is good then you should soon see a "MyTestApp" project in the Package Explorer. The project will be open (you'll see a bunch of folders in a hierarchy). "activity_main.xml" will be highlighted under the "layout" folder, all of this under the MyTestApp project folder.
Click the MyTestApp project folder, to select it. Then, in the Eclipse menus...
Project -> Build Project
Again, watch the status messaging at the bottom right of the Eclipse window. If your computer is quick then you may not look in time to catch them. See nothing there... your project is built.
In the Eclipse menus...
Run -> Run
Select Android Application in the dialog and click OK.
At this point, you may or may not get a device dialog. If you do, choose to Launch a new Android Virtual Device (an emulator). You may need to go to the Manager (there's a button for this), to set up a device. I use AVD_for_Nexus_One_by_Google. I know that one works.
Be forewarned that the emulator will seem to take forever to start up. Be patient. Be VERY patient. You should see the app running shortly.
So, assuming you see a running application in the emulator... let's see what you ended up not having to worry about...
If you examine the auto-generated MainActivity.java file, in the project that you just created, you'll see that the code that you were concerned about...
getMenuInflater().inflate(R.menu.main, menu);
... seems fine. No error indications.
You'll also notice that there is no "R-type" import at the top of the source code.
Notice, if you dig down to the bottom of the "gen" folder, under your "MyTestApp" project folder, in the Package Explorer, that there's an R.java file. This is automatically generated when the project is built and is the file to which your getMenuInflater refers.
The point to all of this is that you'll have (if your Android/Eclipse setup is good) something working, giving you a launch point to play with other things.
Good luck. I've sure been having a blast.

Because you use R.menu.main so your program will find in the res/menu folder for a file main.xml. So all you need is to create a new file main.xml in res/menu.
And don't import android.R to your class.

Instead of
import android.R;
use
import com.example.R;
where com.example is your own project's namespace.
If you want to find the generated file in your project, it should be under the gen directory. If your project compiles properly, the R file should get generated and placed there automatically. If this doesn't happen, this is when the Project Clean is recommended.

public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.activity_main, menu);
return true;
}
Make sure you have the main.xml file in the res\menu folder
Remove "import android.R;"

Errors like these could happen because you have an error in the XML file main.xml
Make sure you have no errors in all your resources files and that everything is correct. When there's something wrong there, all references to the res folder from your source code will fail. Also make sure not to import android.R as these are resources from the Android SDK. Just remove that import and it should refer to the resources folder in your project.

nothing to do with coding.just install the proper tools and packages using Android sdk manager. If you wanna use android 4.0 (API 14) install all the packages and install packages under Tools. It worked for me.

Depending upon how you have run through the setup of your project, generally the folder res/menu may not be autogenerated. In order to inflate a menu you must therefore have a menu to inflate.
Create a new directory within res called 'menu'; then within said directory create an xml file called 'main'. It is this file which the menuInflater will inflate.

I had the same Problem then I clicked on the Sync Project with Gradle files and it worked for me
You can find that Option in Tools->Android->Sync Project with Gradle files

Right click the "res" folder < new < directory.
Name it "menu"
Inside that directory create a new xml called main_menu
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="#+id/edit_item"
android:title="Edit" />
<item
android:id="#+id/delete_item"
android:title="Delete" />

The version of Android may not have the folder res / menu. If so, create and copy the xml into the folder to troubleshoot.

eclipse can not locate my foregroundcameraplugin.xml file

so im making this cordova / phonegap application.
I found out that The default Phonegap (Cordova) Camera Plugin calls the native camera and this makes Android Garbage Collector to kill background applications.
so I found a plugin that fixes this :
https://code.google.com/p/foreground-camera-plugin/
now I followed the steps as these guys told. and I'm having the following problems that I cant resolve and need help on.
There was a problem with the cameraActivity.java it did not recognize thegenerated file R.java
then I used an import statement to make it have access to this file
import statement : import java.android.R;
after this eclipse doesnt recognize the foregroundcameraplugin.xml.
besides this my my styles.xml files in values-v11 and values-v14 directories are giving an error
"Error retrieving parent for item; no reources found that match the given name #android: Theme.Holo.Light.DarkActionBar "
this is how my forground camera plugin looks like :
If anyone knows how too fix this please let me know
thank you

I was able to reply the error with the new Eclipse Kepler and found the solution: upgrade your ADT to version 22 and install Android SDK Build-tools by SDK manager. I have also commited a new classpath file for ForegroundCameraPlugin project with some changes (included Android Private Libraries). Thanks to your contact and the help of this link: Eclipse giving error, missing R.java file after recent update

R.layout.main couldn't be resolved

I am building an application and I added a new activity to generate a view. I compiled it. My application can not find anything that is on the format R.id.xxx or R.layout.xxx, I've tried also cleaning my project, closing Eclipse and opening Eclipse again, but nothing. The most strange thing is that before everything was working well. But now it can not recognize even the R.layout.main that is default of my principal activity. Anyone have an idea?
Also I have tried almost everything here: R cannot be resolved - Android error
but no result!
Solved
Thanks to woopsy, also I found the reference to this kind of problem
http://source.android.com/source/using-eclipse.html
it happens because Eclipse sometimes imports R when you press the combination ctrl+shift+O

Remove all your imports for the Activity and then have eclipse fix imports. I have had problems where eclipse wants to import a different R than the one I need.

First of All Check You have R.java File then check
import android.R;
Enter Yourpackages like import com.mypackages.prj;

If you are using eclipse, take a backup of your layout main.xml file and then from the eclipse new file interface create a new "Android XML File" and call it main.xml. copy back from the backup the contents into this new file.
try this.

check your xml files. there might be something wrong in it which is causing R not to build up automatically. To observe such errors, switch your view to Console tab

this is a common error. You need to just search your R.java file in generated section of your project directory in Eclipse. Need to import if the R.java file into the package then import . R;
I hope it will work for you. It was absolutely worked for me...enjoy programming

friends take care that u haven't imported R class, if you have delete "import android.R". The reason is there are two R things one R.java and R.class and we need the java, where we dont need to import rather than referring it. It worked for me and may be to you too.

I found the solution...For me works it
Poject->Properties->Android->Project Build Target (here choose android4.4 or 5.1.1 Android Open Source Project)->Ok
Project->Build All
This function ...

This problem can fix with this process: -
File---->Invalidate cache/restart.
it will restart your android studio and fix that problem

We Keep Coding

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