NotFoundException class extends Android MultiDexApplication class

I spend hours trying to solve this problem, but cannot find a solution between dozens of answers to similar problems.

So this is my problem. I am creating a simple android app with multiple apps and I need to do some action when the app starts. So, I extended the MultiDexApplication class, added the classpath to the application element in the AndroidManifest.xml file, but it fails every time it starts with the following exception:

java.lang.RuntimeException: Unable to instantiate application rmpt.app.MyApplication: java.lang.ClassNotFoundException: Didn't find class "rmpt.app.MyApplication" on path: DexPathList[[zip file "/data/app/rmpt.app-1.apk"],nativeLibraryDirectories=[/data/app-lib/rmpt.app-1, /vendor/lib, /system/lib, /system/lib/arm]]
   at android.app.LoadedApk.makeApplication(LoadedApk.java:509)
   at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4472)
   at android.app.ActivityThread.access$1300(ActivityThread.java:144)
   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1355)
   at android.os.Handler.dispatchMessage(Handler.java:99)
   at android.os.Looper.loop(Looper.java:150)
   at android.app.ActivityThread.main(ActivityThread.java:5162)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:525)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:744)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
   at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassNotFoundException: Didn't find class "rmpt.app.MyApplication" on path: DexPathList[[zip file "/data/app/rmpt.app-1.apk"],nativeLibraryDirectories=[/data/app-lib/rmpt.app-1, /vendor/lib, /system/lib, /system/lib/arm]]
   at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:53)
   at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
   at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
   at android.app.Instrumentation.newApplication(Instrumentation.java:975)
   at android.app.LoadedApk.makeApplication(LoadedApk.java:504)
   at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4472) 
   at android.app.ActivityThread.access$1300(ActivityThread.java:144) 
   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1355) 
   at android.os.Handler.dispatchMessage(Handler.java:99) 
   at android.os.Looper.loop(Looper.java:150) 
   at android.app.ActivityThread.main(ActivityThread.java:5162) 
   at java.lang.reflect.Method.invokeNative(Native Method) 

      

        
        
        
      

    

If I remove the android: name attribute from the AndroidManifest.xml file (so it uses the default Android app class) everything works fine, but I NEED does some action in the onCreate method of my app.

I am leaving my files here so you can see them and maybe see something wrong (already 2 days trying to solve this problem for me)

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="rmpt.app">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme"
        android:name=".MyApplication">

        <activity android:name=".view.LoginActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>
</manifest>

      

        
        
        
      

    

MyApplication.java

package rmpt.app;

import android.support.multidex.MultiDexApplication;

public class MyApplication extends MultiDexApplication {

    @Override
    public void onCreate() {
        super.onCreate();

        // do my stuff
    }
}

      

        
        
        
      

    

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "25.0.2"

    defaultConfig {
        applicationId "rmpt.app"
        minSdkVersion 18
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        multiDexEnabled true

        jackOptions {
            enabled true
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    dexOptions {
        javaMaxHeapSize "2g"
    }

    packagingOptions{
        exclude 'META-INF/LICENSE.txt'
        exclude 'META-INF/LICENSE'
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.4.0'
    compile 'com.android.support:multidex:1.0.1'
    compile 'com.google.android.gms:play-services:9.4.0'
    compile 'com.android.support:design:23.4.0'

}

      

        
        
        
      

    

I am working on macOS 10.11.6