gradle build error while generating signed apk

Question

I have created an app ready to be uploaded om playstore. I have created Keystore password and all when the gradle builds I get the following error. This is the first time I am uploading an app on playstore. Below are the error and the build.gradle file...Please help me!!Any other information regarding uploading app is very helpful

Error:

Information:Gradle tasks [:app:assembleRelease]
Warning:okhttp3.Address: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Authenticator: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Cache: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Cache$2: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Cache$CacheResponseBody: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Cache$Entry: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.CacheControl: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.CertificatePinner: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Challenge: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Connection: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.ConnectionPool: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.ConnectionSpec: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.ConnectionSpec$Builder: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Cookie: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Dispatcher: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.EventListener: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.FormBody: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Handshake: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Headers: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.HttpUrl: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.HttpUrl$Builder: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Interceptor$Chain: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.MediaType: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.MultipartBody: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.MultipartBody$Builder: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.MultipartBody$Part: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.OkHttpClient: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.OkHttpClient$Builder: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Request: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Request$Builder: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.RequestBody: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.RequestBody$1: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.RequestBody$2: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.RequestBody$3: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Response: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Response$Builder: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.ResponseBody: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.ResponseBody$1: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.Route: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.WebSocket: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.WebSocketListener: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.internal.Util: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.internal.cache.CacheStrategy: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.internal.cache.DiskLruCache: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.internal.cache.DiskLruCache$Snapshot: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.internal.connection.RealConnection: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.internal.http.RealResponseBody: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.internal.ws.RealWebSocket: can't find referenced class javax.annotation.Nullable
Warning:okhttp3.package-info: can't find referenced class javax.annotation.ParametersAreNonnullByDefault
Warning:okio.AsyncTimeout: can't find referenced class javax.annotation.Nullable
Warning:okio.Buffer: can't find referenced class javax.annotation.Nullable
Warning:okio.BufferedSource: can't find referenced class javax.annotation.Nullable
Warning:okio.ByteString: can't find referenced class javax.annotation.Nullable
Warning:okio.DeflaterSink: can't find referenced class org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement
Warning:okio.HashingSink: can't find referenced class javax.annotation.Nullable
Warning:okio.Okio: can't find referenced class org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement
Warning:okio.Okio$4: can't find referenced class javax.annotation.Nullable
Warning:okio.RealBufferedSource: can't find referenced class javax.annotation.Nullable
Warning:okio.Segment: can't find referenced class javax.annotation.Nullable
Warning:okio.SegmentPool: can't find referenced class javax.annotation.Nullable
Warning:okio.package-info: can't find referenced class javax.annotation.ParametersAreNonnullByDefault
Warning:there were 181 unresolved references to classes or interfaces.
Warning:Exception while processing task java.io.IOException: Please correct the above warnings first.
Error:Execution failed for task ':app:transformClassesAndResourcesWithProguardForRelease'.
> Job failed, see logs for details
Information:BUILD FAILED in 5m 31s
Information:1 error
Information:63 warnings
Information:See complete output in console

build.gradle(app)

apply plugin: 'com.android.application'

android {
    compileSdkVersion 26
    buildToolsVersion '26.0.2'
    defaultConfig {
        applicationId "com.abcd.efgh"
        minSdkVersion 19
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation 'com.google.firebase:firebase-core:11.6.0'
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.readystatesoftware.systembartint:systembartint:1.0.3'
    compile 'com.google.android.gms:play-services-ads:11.6.0'
    compile 'com.wdullaer:materialdatetimepicker:3.4.0'
    compile 'com.android.support:design:27.0.2'
    compile 'com.android.support:appcompat-v7:27.0.2'
    compile 'com.squareup.okhttp3:okhttp:3.9.0'
    testCompile 'junit:junit:4.12'
}


apply plugin: 'com.google.gms.google-services'

Answer 1

What this looks like to me is a transitive dependency issue. Just as you don't want to re-create the wheel and use gradle to import other code well the creaters of the gradle dependencies don't want to re-create the wheel ether so they used gradle too. You end up with nested dependencies that may not use the most recent version. In fact you even excluded group: 'com.android.support', module: 'support-annotations' in the androidtestcompile version to avoid a transitive dependency conflict. I feel your pain. I would go to the gradle tab and try running any task with dependency in the name. Its very verbose to track this type of error, the stack trace you listed will help. Running lint could also help clean up your code and as Yordan mentioned proguard is not required but it does add security by obfusicating the code

Answer 2

You have minifyEnabled true for release and perhaps some needed classes for javax.annotation.Nullable are needed but are removed by minifying. If you don't need it for now you can just remove that tag for release. If you do need the flag you have to tinker and configure the minify to keep the class.