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I am developing an Android app that sends e-mails using the GMail API. I have used the example code at Android Quickstart and Sending Email and everything works fine when I debug the app. The problem arises when I build the release version with minifyEnabled=true. In that case, the call to service.users().messages().send(userId, message).execute(); goes into error with IOException. The message of the exception is "404 Not Found".

The Proguard file includes all the -keep class and -dontwarn that I have found in other posts:

-dontwarn com.google.**
-dontwarn java.awt.**
-dontwarn javax.security.**
-dontwarn java.beans.**

-keep class com.google.**
-keep public class Mail {*;}
-keep class com.sun.activation.** {*;}
-keep class com.sun.activation.registries {*;}
-keep class javamail.** {*;}
-keep class javax.mail.** {*;}
-keep class javax.activation.** {*;}
-keep class com.sun.mail.dsn.** {*;}
-keep class com.sun.mail.handlers.** {*;}
-keep class com.sun.mail.smtp.** {*;}
-keep class com.sun.mail.util.** {*;}
-keep class mailcap.** {*;}
-keep class mimetypes.** {*;}
-keep class myjava.awt.datatransfer.** {*;}
-keep class org.apache.harmony.awt.** {*;}
-keep class org.apache.harmony.misc.** {*;}

I don't think it is a problem of credentials as e-mails are sent if I sign the app with minifyEnabled=false. I also tested the release version of the app on the emulator, setting minifyEnabled=true and debuggable=true. In this case e-mails are sent but the APK is larger when it is debuggable so I think that something fundamental is retained ase.

Dependecies in the gradle file are the following

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    testCompile 'junit:junit:4.12'
    compile('com.google.api-client:google-api-client-android:1.22.0') {
        exclude group: 'org.apache.httpcomponents'
    }
    compile('com.google.apis:google-api-services-gmail:v1-rev47-1.22.0') {
        exclude group: 'org.apache.httpcomponents'
    }
    compile 'org.achartengine:achartengine:1.2.0'
    compile 'com.android.support:appcompat-v7:23.4.0'
    compile 'com.astuetz:pagerslidingtabstrip:1.0.1'
    compile 'com.google.android.gms:play-services:9.4.0'
    compile 'com.facebook.android:facebook-android-sdk:4.12.0'
    compile 'com.android.support:multidex:1.0.1'
    compile 'com.google.android.gms:play-services-ads:9.4.0'
    compile 'com.google.android.gms:play-services-auth:9.4.0'
    compile 'com.google.android.gms:play-services-gcm:9.4.0'
    compile 'pub.devrel:easypermissions:0.1.5'
}

I am not sure about exclude group: 'org.apache.httpcomponents' but removing it does not solve the problem.

Francesco Finazzi
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    `-keep class com.google.** {*;}` instead of `-keep class com.google.**` solved the problem, though not sure this is an optimal solution. – Francesco Finazzi Aug 04 '16 at 15:58

1 Answers1

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I ran into this exact same issue and while your -keep class com.google.** {*;} does fix the problem, it's a bit heavy handed and may leave things unprotected that you don't want unprotected. As per the Google API Documentation regarding ProGaurd, you should add the following lines to your ProGuard configuration.

-keepclassmembers class * {
  @com.google.api.client.util.Key <fields>;
}

-keepattributes Signature,RuntimeVisibleAnnotations,AnnotationDefault

This allows the Google APIs to work properly while being protected with ProGuard.

vane
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