Android Studio marks R in red with error message “

Question

In every project I've tried to create in Android Studio, all usages of R are marked in red with the error message "cannot resolve symbol R", but the compilation succeeds and the application runs. This is really annoying, as it blocks auto-completion and shows huge red waved lines all over my code.

I'm running Android Studio 1.7.0 and creating the project with default settings. A screenshot is attached:

This is my build.gradle:

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.4'
    }
}
apply plugin: 'android'

dependencies {
    compile files('libs/android-support-v4.jar')
}

android {
    compileSdkVersion 17
    buildToolsVersion "17.0.0"

    defaultConfig {
        minSdkVersion 7
        targetSdkVersion 16
    }
}

This is how the Project Structure looks like:

Any idea how to fix this?

Answer 1

Click on Build -> Rebuild Project and then click Tools -> Android -> Sync Project with Gradle Files.

Answer 2

Cleaning the Project helped in my case

Go to

Build -> Clean Project

Answer 3

Sometimes these build errors will continue out of nowhere. If this happens to you, try this:

Recheck the validity of the XML in your resource files: If your R.java file was not generated for the last build, you will see errors in your project wherever you reference a resource. This can be caused by a typo in one of your XML files. Layout XML is not always validated, so typos in these files may not be pointedly brought to your attention. Finding the typo and saving the file should cause R.java to regenerate.

Clean your project! Select Build → Clean Project This will rebuild the project from scratch, which may result in an error-free build.

Sync your project with Gradle! Select Tools → Android → Sync Project with Gradle Files Android Studio will rebuild the project from scratch with the correct project settings, which can help to resolve issues after changing your Gradle configuration.

Run Android Lint! Lint may give you good information regarding a problem. If the above does not work, this is where you will most likely find your problem. To run Lint, select Analyze → Inspect Code → select Whole project → OK Carefully analyze Lint suggestions; start with errors and then warnings.

Good luck.

Answer 4

I found that this issue was caused because I had errors in my XML files. Once you fix the XML errors, do a clean/build, it fixed the issue.

Answer 5

When creating a project from a sample,while not importing the existing project is good (prevents clashes with gradle, .idea, .iml, build, jars and apks, i.e. all unnecessary build-generated files), after creating a new project, copying and pasting all relevant resources, I'd recommend :

checking packages and imports from packages within the project {AndroidManifest declaration and all imports in java classes}, all resources (drawable, mip-map, layouts and menus & your build.gradle (a sample of build.gradle to use with the latest sdk can be provided on request)) to see if they are there & if declared strings and ids actually exist and have been used, after which your only error should be the question asked:

Bulid->Clean Project

Tools->Android->Sync Project with Gradle Files

File->Invalidate Caches and Restart

In worst cases restarting your machine helps.

The above should work. Feel free to ask questions if necessary, i.e. post comments.

Answer 6

this causes mainly because of errors in xml file, check your latest xml changes and rebuild it, same issue with me.