Why do I get "Cannot resolve symbol" when trying to use class from library?

Question

Intro

I have an app and I currently started working om some backend code. To prevent code duplication, I want to move some of my code into a library.

This is what I did:

For my library I created a jar file, using IntelliJ IDEA (Project Structure - Artifacts - etc.)
I copied the jar file into the lib folder of my Android App
I included the dependency (in the build.gradle I put implementation files('libs/numbers-lib.jar'))

Problem

Now when I try to use one of the classes I get Cannot resolve symbol 'Level' (see also screenshot). What am I missing?

EDIT: I already cleaned/rebuilt my project and invalidated caches.

EDIT2: Here is my gradle (upon request)

apply plugin: 'com.android.application'

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "com.my.example"
        minSdkVersion 21
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        multiDexEnabled true
        targetSdkVersion 27
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    productFlavors {
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support:design:27.1.1'
    implementation 'junit:junit:4.12'
    implementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    androidTestImplementation 'com.android.support.test:rules:1.0.2'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    implementation 'postgresql:postgresql:9.0-801.jdbc4'
    implementation files('libs/numbers-lib.jar')
}

EDIT3: Here is a screenshot. You can see that the library has the correct Class...

@DKV: The only thing I did not do was to do a right click and click on **Add as library**. However, I don't get that option in my version of Android Studio (version 3.2.1) — MWB, Dec 16 '18 at 11:20

score 1 · Answer 1 · answered Dec 16 '18 at 11:22

1

Put your lib jar file in app/libs, in your project gradle file append this line to dependencies :

compile fileTree(dir: 'libs', include: ['*.jar'])

answered Dec 16 '18 at 11:22

Koorosh Ghorbani

507
4
14

This line is already in my gradle file (I updated my post to add my gradle file). – MWB Dec 16 '18 at 11:26

score 0 · Answer 2 · answered Dec 16 '18 at 11:40

0

change

implementation fileTree(include: ['*.jar'], dir: 'libs')

to

implementation fileTree(dir: 'libs', include: ['*.jar'])

and don't forgot to place your jar in libs folder.

answered Dec 16 '18 at 11:40

Zaid Mirza

3,540
2
24
40

@ZaidMriza: The order of the two does not matter. I tried your version as well, double checked that the `jar` was in the `libs` folders, but still... same error. – MWB Dec 16 '18 at 11:46
try to remove this line implementation files('libs/numbers-lib.jar') and then try – Zaid Mirza Dec 16 '18 at 11:49
Tried it, but no luck... (I also cleaned/rebuilt again, just to be sure) – MWB Dec 16 '18 at 11:53

score 0 · Accepted Answer · answered Dec 18 '18 at 17:46

0

It turned out I had to put my library classes into a package before creating the library.

answered Dec 18 '18 at 17:46

MWB

1,830
1
17
38

1

Not much to explain I guess. I made a package in my project, moved the class files into this package and created the library – MWB Jun 22 '20 at 08:18

Why do I get "Cannot resolve symbol" when trying to use class from library?

3 Answers3