Java.lang.ClassNotFoundException sur une application qui fonctionne sur l'émulateur

Mon application fonctionne bien sur l'émulateur, mais j'ai eu cette erreur après avoir installé l'application sur les appareils réels en utilisant apk.

FATAL EXCEPTION: main
Process: com.example.wiserlab.macquest, PID: 9151
java.lang.RuntimeException: Unable to get provider com.example.wiserlab.macquest.model.CustomContentProvider: java.lang.ClassNotFoundException: Didn't find class "com.example.wiserlab.macquest.model.CustomContentProvider" on path: DexPathList[[zip file "/data/app/com.example.wiserlab.macquest-1.apk"],nativeLibraryDirectories=[/data/app-lib/com.example.wiserlab.macquest-1, /vendor/lib, /system/lib]]
        at android.app.ActivityThread.installProvider(ActivityThread.java:4777)
        at android.app.ActivityThread.installContentProviders(ActivityThread.java:4369)
        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4309)
        at android.app.ActivityThread.access$1500(ActivityThread.java:135)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5001)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
        at dalvik.system.NativeStart.main(Native Method)
    Caused by: java.lang.ClassNotFoundException: Didn't find class "com.example.wiserlab.macquest.model.CustomContentProvider" on path: DexPathList[[zip file "/data/app/com.example.wiserlab.macquest-1.apk"],nativeLibraryDirectories=[/data/app-lib/com.example.wiserlab.macquest-1, /vendor/lib, /system/lib]]

Je suis sûr que cette classe existe. Dois-je importer cette classe ailleurs?

Merci!