Solution: Unable to execute dex: Multiple dex files

multiple_dex.md

This error means that there is a duplicated library used on one or many libraries.

To fix it, we should exclude them from our dependencies. On the build.gradle add the following line

dependencies {...}
configurations {
    all*.exclude group: 'x', module: 'library'
}

replace x with library to exclude for example:

configurations {
    all*.exclude group: 'com.nineoldandroids', module: 'library'
}

If you want to exclude it only from one library use the following

dependencies {
    compile (project(':myproject')){
      exclude group: 'x', module: 'library'
    }
}