Gradle fails with "Ambiguous method overloading for method java.io.File#<init>"

Question

When gradle building my project, I'm getting this error:

FAILURE: Build failed with an exception.

• Where:
  Build file 'App/build.gradle' line: 45

• What went wrong:
  A problem occurred evaluating project ':App'.
  Ambiguous method overloading for method java.io.File#.
  Cannot resolve which method to invoke for [null, class java.lang.String] due to overlapping prototypes between:
  [class java.lang.String, class java.lang.String]
  [class java.io.File, class java.lang.String]
  

Said line is the first proguardFile rule:

buildTypes {     release {         debuggable false         jniDebugBuild false         signingConfig signingConfigs.(System.getenv("SIGNING_CONFIG") ?: "release")         runProguard true         proguardFile getDefaultProguardFile('proguard-android-optimize.txt')         proguardFile 'proguard-rules.txt'     } } 

I haven't got any local.properties file, nor opened the project in Android Studio.

What is wrong with my project? How can I fix this error?

Answer 1

The error message has been changed in September 2014. It is now clearer and explicitely points out that the problem is that Gradle can't find the SDK; the rest of the answer still applies to old versions (<0.13) of the Gradle plugin.

---

This is due to Gradle not being able to find the SDK location, and thus failling when doing something that needs the Android SDK, such as getting the default Proguard file location.

Actually, this is what Gradle will tell you if you temporarily comment out that line:

SDK location not found. Define location with sdk.dir in the local.properties file or with an ANDROID_HOME environment variable.

You can fix it:

• By defining the SDK location in local.properties: simply add sdk.dir=/path/to/sdk to that file.

• By setting the SDK location in environment variable ANDROID_HOME: you just need to set the environment variable by adding ANDROID_HOME=/path/to/sdk before gradle.

  Example: ANDROID_HOME=/path/to/sdk gradle build.

When using a version control system, it is perfectly fine to set the location locally in your own local.properties, as manually setting the environment variable every time you need to use Gradle would be annoying. Just make sure to not check it into your repository.