Cannot find symbol class in Android Studio

Question

I have two project A and B where B is added as a module of project A. I have added dependencies in A's Gradle build file. Now i can import B's class in A without any error (in editor) but can't build. Preferences is a class of project B.

Error

Error:(22, 23) error: cannot find symbol class Preferences  

A's build file

apply plugin: 'com.android.application'  android {     compileSdkVersion 21     buildToolsVersion "21.0.0"      defaultConfig {         applicationId "com.example.A"         minSdkVersion 9         targetSdkVersion 21         versionCode 1         versionName "1.0"     }     buildTypes {         release {             minifyEnabled false             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'         }     } }  dependencies {     compile fileTree(dir: 'libs', include: ['*.jar'])     compile 'com.android.support:appcompat-v7:21.0.3'     compile project(':B') } 

B's build file

import org.apache.tools.ant.taskdefs.condition.Os  apply plugin: "android-library"  android {     compileSdkVersion 18     buildToolsVersion "21.0.0"      defaultConfig {         minSdkVersion 9         targetSdkVersion 11     }      buildTypes {         release {             minifyEnabled true             proguardFiles 'proguard.cfg'         }     }     sourceSets.main {         jniLibs.srcDir 'src/main/jniLibs'         jni.srcDirs = [] //disable automatic ndk-build call     }      task ndkBuild(type: Exec) {         if (Os.isFamily(Os.FAMILY_WINDOWS)) {             commandLine 'ndk-build.cmd', '-C', file('src/main/jni').absolutePath         } else {             commandLine '/opt/adt-bundle-linux/android-ndk-r8e/ndk-build', '-C', file('src/main/jni').absolutePath         }         tasks.withType(JavaCompile) {             compileTask -> compileTask.dependsOn ndkBuild         }     }  }  dependencies {     compile 'com.android.support:support-v4:18.0.0' } 

I can successfully build the project(A) if remove the import.

Answer 1

It can happen if the library (be it a local module or external dependency) has a minifyEnabled true, but library's ProGuard configuration is missing or not correct (the class is eligible for removing by ProGuard). This leads to class not being compiled.

Answer 2

For me it was a similar problem but on proguard conf. proguard was active on a first library and inactive on a second.

Copie same proguard conf on all build.gradle has solved the "cannot find symbol class" error.