android - Proguard error when trying to generate signed APK

Question

I'm trying to generate a signed APK, but I'm getting the following error:

    Error:Execution failed for task ':app:transformClassesAndResourcesWithProguardForRelease'.
> java.io.IOException: proguard.ParseException: Expecting separator ';' before '(' in line 90 of file '/Users/OSX/Desktop/PROJECT/12345/name/app/build/intermediates/proguard-rules/release/aapt_rules.txt'

I went through the aapt_rules.txt and this is the line 90 of the file:

# onClick res/layout/content_main.xml #generated:15
-keepclassmembers class * { *** getBitData (MainActivity)(...); }

Here is my buildTypes in gradle:

buildTypes {
    release {
        minifyEnabled true
        shrinkResources true
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}