Android Studio: ClassNotFoundException

Question

i was busy with my app for over a week, when suddenly:

11-12 07:59:17.860    1653-1653/nl.test.myapp E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{nl.test.MyApp/nl.test.MyApp.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "nl.test.myapp.MainActivity" on path: DexPathList[[zip file "/data/app/nl.test.myapp-2.apk"],nativeLibraryDirectories=[/data/app-lib/nl.test.myapp-2, /system/lib]]
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2137)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
        at android.app.ActivityThread.access$600(ActivityThread.java:141)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:5103)
        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:737)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.ClassNotFoundException: Didn't find class "nl.test.myapp.MainActivity" on path: DexPathList[[zip file "/data/app/nl.test.MyApp-2.apk"],nativeLibraryDirectories=[/data/app-lib/nl.test.MyApp-2, /system/lib]]
        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.newActivity(Instrumentation.java:1061)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2128)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
        at android.app.ActivityThread.access$600(ActivityThread.java:141)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:5103)
        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:737)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
        at dalvik.system.NativeStart.main(Native Method)

here is my AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="nl.test.myapp"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="7"
        android:targetSdkVersion="19" />

    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="nl.test.myapp.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity android:name=".welcomewizard.WelcomeWizardIntroPage"
            android:label="@string/app_name" />

        <activity android:name=".welcomewizard.WelcomeWizardPage1"
            android:label="@string/app_name" />

        <activity android:name=".welcomewizard.WelcomeWizardPage2"
            android:label="@string/app_name" />

        <activity android:name=".welcomewizard.WelcomeWizardPage3"
            android:label="@string/app_name" />

        <activity android:name=".welcomewizard.WelcomeWizardPage4"
            android:label="@string/app_name" />

        <activity android:name=".welcomewizard.WelcomeWizardFinishPage"
            android:label="@string/app_name" />

        <activity android:name=".CompanySelectorActivity"
            android:label="@string/compsel_actionbarlabel" />
    </application>

</manifest>

this was happening after some problems with my R.java (the id's for the views where incorrect), after rebuilding the project this problem happend

i've already tried the Invalidate Cashes/restart in the IDE File-menu

Update 14:51: this is my compiler.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
  <component name="CompilerConfiguration">
    <option name="DEFAULT_COMPILER" value="Javac" />
    <resourceExtensions />
    <wildcardResourcePatterns>
      <entry name="!?*.java" />
      <entry name="!?*.form" />
      <entry name="!?*.class" />
      <entry name="!?*.groovy" />
      <entry name="!?*.scala" />
      <entry name="!?*.flex" />
      <entry name="!?*.kt" />
      <entry name="!?*.clj" />
    </wildcardResourcePatterns>
    <annotationProcessing>
      <profile default="true" name="Default" enabled="false">
        <processorPath useClasspath="true" />
      </profile>
    </annotationProcessing>
  </component>
</project>

My MainActivity.java file (\src\main\java\nl\test\myapp\MainActivity.java) :

package nl.test.myapp;

import android.annotation.TargetApi;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.widget.RelativeLayout;

import nl.test.myapp.welcomewizard.WelcomeWizardIntroPage;

public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        setBackground(R.drawable.background_grey);

        Intent intent = new Intent(this, WelcomeWizardIntroPage.class);
        startActivity(intent);
        finish();
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
    private void setBackground(int drawable){
        int currentApiVersion = android.os.Build.VERSION.SDK_INT;
        if(currentApiVersion >= android.os.Build.VERSION_CODES.JELLY_BEAN){
            RelativeLayout layout = (RelativeLayout) findViewById(R.id.layout_main);
            layout.setBackground(getResources().getDrawable(drawable));
        }
    }
}

Masters

Have u forgot to import any libraries? – Kabul

no import-errors (or other errors at all) in my IDE – Masters

Answer 1

I created a new project in Android studio and copied everything from the old project into the new one. Now it's working again, without any(!) modifications to the code.

Masters

Answer 2

Close android studio. Navigate to the project folder. Delete all files relating to intelliJ (Android Studio) i.e

• .idea (folder)
• *.imi (files)

Also make sure that package name matches the package in the android manifest.xml.

Then reimport the project.

This happened to me because I renamed the root package and IntelliJ (android studio) didn't track this.

Uteutensil

Perhaps you meant .iml files? – Karonkaross

Answer 3

I had the same problem, turns out I screwed up with some final method. Be sure to check dalvikvm errors in logcat output before the FATAL EXCEPTION. I will give you some hints on the problem. In my case, I had a final method (isResumed) which was already defined in the base class - causing runtime crash. Wasn't complaining at compile time.

Check the logs:

E/dalvikvm( 9984): Method Lcom/your/package/ui/SomeActivity;.isResumed overrides final Landroid/app/Activity;.isResumed
W/dalvikvm( 9984): failed creating vtable
...
D/AndroidRuntime( 9962): Shutting down VM
...
E/AndroidRuntime(10065): FATAL EXCEPTION: main
E/AndroidRuntime(10065): Process: com.yourpackage.ui, PID: 10065
E/AndroidRuntime(10065): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.yourpackage.ui/com.yourpackage.ui.HomeActivity}: java.lang.ClassNotFoundException: Didn't find class "com.yourpackage.ui.HomeActivity" on path: DexPathList[[zip file "/data/app/com.yourpackage.ui-2.apk"],nativeLibraryDirectories=[/data/app-lib/com.yourpackage.ui-2, /vendor/lib, /system/lib]]
...

Thetos

This happened to me too, when I used it with Picasso. I used two booleans isFound and isConnected for my own validation. Turns out this was where I was going wrong. Changing variable name to something like is_Connected did the trick. – Flashlight

Answer 4

I ran into this. My app had been running fine and one day it just started running into these ClassNotFoundExceptions. My code hadn't changed at all.

As far as I can tell, it ended up being a bug in the build of Android Studio. I had recently updated to the latest release on the canary channel.

Switching back to an older release on the dev channel got things working again:

1. Go into Settings / Appearance & Behavior / System Settings / Update
2. Change to Dev Channel and Check Now.

Heterogeneous

Answer 5

I had the similar problem. I remembered, that previously "not enough memory" message was shown and the application uploading process could not finish, stopping on dexDebug with error. Then I released enough memory, but application started with ClassNotFoundException.
The solution that worked for me was to delete all "build" folders in the project. I suppose that gradle can put corrupted files to "build" folder when there is not enough memory.

Willms

Answer 6

You can check Multidex mechanism. The reason may be method numbers overflow.

1. Add MultiDex.install(this); to your Application:

   @Override
   protected void attachBaseContext(Context base) {
        super.attachBaseContext(base);
        MultiDex.install(this);
   }
   

2. and add

   afterEvaluate {
      tasks.matching {
          it.name.startsWith('dex')
      }.each { dx ->
          if (dx.additionalParameters == null) {
              dx.additionalParameters = []
          }
          dx.additionalParameters += '--multi-dex' // enable multidex
      }
   }
   

to your app module's gradle.build

Cardenas

Upvoted!! This was the only answer that solved my problem here – Tallyho

Answer 7

This happened to me too, and none of the postings here helped. My problem was also caused by my having renamed the root package. My ClassNotFoundException was showing a DexPathList which was the old path to my package. I found the cause was in my Gradle Script called "build.gradle (Module: app)" I had a line saying: applicationId "old package name". I changed this to the new package name, did a gradle sync, and everything worked.

Charlena

I also made the same mistake but didn't realize. thank you! you helped me. – Gareth

Answer 8

i don't know this will help you..anyway try to use application theme as @style/Theme.AppCompat..we must use as per developers forum.

<application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/Theme.AppCompat" >

       <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

Vaios

Nope, doesn't change a thing – Masters

are you sure, you have mainactivity in the nl.test.myapp package? – Vaios

try my latest answer..developer.android.com/training/basics/actionbar/styling.html.. – Vaios

Answer 9

   try: 
   <activity
        android:name=".MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

Boring

Answer 10

Looks like you have a namespace typo somewhere. Search for MyApp and change it to myapp.

Aculeate

Hmm then why it's complaining about nl.test.MyApp.MainActivity? – Veasey

Answer 11

Your MainActivity.java is excluded from compile, so this class isn't included in .apk. Remove line:

<file url="file://$PROJECT_DIR$/src/nl/test/MyApp.java" />

from the excludeFromCompile section of the .idea/compiler.xml file (or you can do this from IDE settings).

Source

Kabul

please go through the link what i have added.The bug seems to be as same as yours – Kabul

thanks, but i have added my compiler.xml file in my question, you can take a look – Masters

Answer 12

As i can see in your Log ,

nativeLibraryDirectories=[/data/app-lib/nl.test.myapp-2, /system/lib

For that you can change your lib to libs , I did this and it resolved my problem.

you would see some error mark on project to resolve that go to project properties and java build path, Remove all the libraries from there . You will not see this error again. :)

Outhouse

Answer 13

When using Android Studio, please ensure that the "src" folder that contains your Java class is marked as "Source Root". Otherwise, it will not make it into the APK.

Absence

Answer 14

In my case it was manifest declaration of android.app.Application in project and actual code in module.

Northern

Answer 15

If you're creating an android library, you may simply have forgotten to import your library in your app build.gradle with the implementation project keyword :

dependencies { implementation fileTree(dir: 'libs', include: ['*.jar']) testImplementation 'junit:junit:4.12' implementation 'com.android.support:design:27.0.2' implementation 'com.android.support:mediarouter-v7:27.0.2' implementation project(':mylib-module:mymodule') implementation 'com.google.firebase:firebase-core:10.0.1' }

Hope this helps :)

Pauli

Answer 16

GO to Build Menu and Clean Project.

The above solution worked perfectly fine for me.

Iatrics

Answer 17

https://mcmap.net/q/921837/-android-studio-classnotfoundexception worked for me with the little addition that I also had to delete the projectFilesBackup/!

Prognostic