Gradle: Exclude file from Android assets folder

I run into the same problem and it seems adding a "!" works to indicate the file should be excluded:

aaptOptions {
    ignoreAssetsPattern "!myfile.txt" 
}

"assets.exclude" might work also by adding a "!" but I haven't tested it...

I think this should do what you want:

android {
    aaptOptions {
        ignoreAssetsPattern "myfile.txt"
    }
}

Source: http://tools.android.com/tech-docs/new-build-system/user-guide#TOC-aapt-options