When adding new jar files to lib folder getting class not found exception of previous module lib in studio

I have an app that has as minSdkVersion API 16, When I added new jar files activation, additionnal, mail, itextpdf for sending pdf file throw email. Its throwing exception below for previously added module library:

Caused by: java.lang.ClassNotFoundException: Didn't find class "com.viewpagerindicator.TabPageIndicator" on path: DexPathList[[zip file "/data/app/com.inbridge.avakaash-1.apk"],nativeLibraryDirectories=[/data/app-lib/com.inbridge.avakaash-1, /vendor/lib, /system/lib]]

If I remove these new jar files then its working fine...

this is my gradle:

   apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion '23.0.3'
    useLibrary 'org.apache.http.legacy'
    defaultConfig {
        applicationId "com.inbridge.avakaash"
        minSdkVersion 16
        targetSdkVersion 23
        multiDexEnabled true
    }
    packagingOptions {
        exclude 'META-INF/DEPENDENCIES'
        exclude 'META-INF/NOTICE'
        exclude 'META-INF/LICENSE'
        exclude 'META-INF/LICENSE.txt'
        exclude 'META-INF/NOTICE.txt'
    }
    buildTypes {
        release {
            minifyEnabled false
            shrinkResources true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    dexOptions {
        incremental true
        javaMaxHeapSize "4g"
    }
}

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    compile project(':library')
    compile files('libs/YouTubeAndroidPlayerApi.jar')
    compile project(':payUMoneysdk')
    compile files('libs/httpclient-win-4.4.1.jar')
    compile files('libs/httpmime-4.2.3.jar')
    compile files('libs/gcm.jar')
    compile 'com.android.support:appcompat-v7:23.0.0-alpha2'
    compile 'com.google.android.gms:play-services:8.4.0'
    compile 'com.google.android.gms:play-services-ads:8.4.0'
    compile 'com.google.android.gms:play-services-identity:8.4.0'
    compile 'com.google.android.gms:play-services-gcm:8.4.0'
    compile 'com.google.android.gms:play-services-auth:8.4.0'

    compile files('libs/activation.jar')
    compile files('libs/additionnal.jar')
    compile files('libs/mail.jar')
    compile files('libs/itextpdf-5.5.9.jar')
    compile 'com.android.support:multidex:1.0.1'
}

This is my settings.gradle

include ':library'
include ':payUMoneysdk'
include ':avakaash'

Please any one help me to resolve this error...

Solution

The problem is that multiDexEnabled true in not enough when you're targeting devices older than 5.0 Lollipop. If you want to support KitKat and older then in addition to this flag, you also have to deploy the secondary dexes make your main Application class, as explained in the official docs.

There are multiple ways to do this:

You can make your your Application class extend from MultiDexApplication
```
public class MyApplication extends MultiDexApplication {
```

You can add the following lines to your Application class:

public void onCreate(Bundle arguments) {
  MultiDex.install(getTargetContext());
  super.onCreate(arguments);
}

If you don't use a custom Application class, you can enable it via the AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.app">
  <application
      ...
      android:name="android.support.multidex.MultiDexApplication">
  </application>
</manifest>