Cannot resolve R.java, duplicate class

问题

I just start using Android Studio for a week and it works great for me, but when I started Android Studio today I get the error: 'error: duplicate class: mypackage.R'. I saw this error before when I used Eclipse so I tried to rebuild the project a few times and restarting Android Studio, this didn't help.

After reading some Stackoverflow questions I tried to deleted R.java and rebuild again, now I don't get any error while rebuilding. The only problem is that Android Studio cannot resolve R, so every line which uses R gets an error (project builds and run).

I also tried to delete all the R.class files but this doesn't help either. I checked if some class imports android.R, but they all don't, they just import 'mypackage.R'. I even deleted all my files and checked out a older version of my project but I still have the same problem.

Edit:

If I don't delete R.java the compiler doesn't give any error. Just when I try to build I get a lot of errors like: 'error: cannot find symbol variable button_login'. If I search the R.java file for 'button_login' I just find it. I did this with multiple errors.

Edit2:

When I deleted all the libaries the project now builds. But the problem is that I need those libaries (HTTPComponents). I added them from maven (File --> Project Structure --> Libaries --> +-sign') and added them to my settings.graddle:

buildscript {
    repositories {
        maven { url 'http://repo1.maven.org/maven2' }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.4'
    }
}
apply plugin: 'android'

dependencies {
    compile files('libs/android-support-v4.jar')
    compile group: 'org.apache.httpcomponents', name: 'httpclient', version: '4.2.5'
    compile group: 'org.apache.httpcomponents', name: 'httpmime', version: '4.2.5'

    //compile 'org.apache.httpcomponents-httpclient:4.2.5' doesn't work either
    //compile 'org.apache.httpcomponents-httpmime:4.2.5' doesn't work either
}

android {
    compileSdkVersion 17
    buildToolsVersion "17.0.0"

    defaultConfig {
        minSdkVersion 15
        targetSdkVersion 16
    }
}

When I run gradlew.bat --stacktrace --info assemble I get errors that Gradle is unable to find the libaries from the maven repository. I checked the repository but they are available. http://search.maven.org/#browse%7C1628757896

回答1:

Unfortunately I run into this as well, sometimes frequently, mostly happens when I put my computer to sleep and back on while Eclipse is on. Sometimes recompiling and validating the project works.

I did find this solution online somewhere, lost the link and do not claim credits for this:

Disable auto build, and clean the project then
Right click your project -> properties -> Java Build Path -> Source -> Add Folder -> add gen and src
Then compile

If that doesn't work, try to delete the gen folder and do that process

Let me know.

回答2:

Delete the Build folder generated by Android Studio automatically!

回答3:

Problem is simple usually. You have fresh instal of studio? So you just fogot add SDK support for those version Android in wich try to compile project. Android Studio can`t generate R file. Start SDK manager, install all missing SDK version and rebuld project.

Another problem can be if you use 64bit OS. You ned to install 32 bit lib, because aapt can`t work with 64bit libs.

in Ubuntu install ia32-libs
Fedora described here
in other distr find libs in google (just google:ia32-libs for "mydistr"), i cant describe all of them ;)

P.S. sorry for my English ;)

回答4:

Delete all class file in your_package_name(androisTest) folder only keep ApplicationTest file.

回答5:

If you are using some library from which you are getting this error, just delete the build folder under your app source and rebuild the project. I was using OpenCV library for which I w as getting this error and that got resolved by deleting the build folder and rebuilding the project.