Android Activity ClassNotFoundException - tried everything

Question

I've just refactored an app into a framework library and an application, but now when I try and start the app in the emulator I get the following error stack trace:

06-02 18:22:35.529: E/AndroidRuntime(586): FATAL EXCEPTION: main 06-02 18:22:35.529: E/AndroidRuntime(586): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.matthewrathbone.eastersays/com.matthewrathbone.eastersays.EasterSimonSaysActivity}: java.lang.ClassNotFoundException: com.matthewrathbone.eastersays.EasterSimonSaysActivity in loader dalvik.system.PathClassLoader[/data/app/com.matthewrathbone.eastersays-1.apk] 06-02 18:22:35.529: E/AndroidRuntime(586):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585) 06-02 18:22:35.529: E/AndroidRuntime(586):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 06-02 18:22:35.529: E/AndroidRuntime(586):  at android.app.ActivityThread.access$2300(ActivityThread.java:125) 06-02 18:22:35.529: E/AndroidRuntime(586):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 06-02 18:22:35.529: E/AndroidRuntime(586):  at android.os.Handler.dispatchMessage(Handler.java:99) 06-02 18:22:35.529: E/AndroidRuntime(586):  at android.os.Looper.loop(Looper.java:123) 06-02 18:22:35.529: E/AndroidRuntime(586):  at android.app.ActivityThread.main(ActivityThread.java:4627) 06-02 18:22:35.529: E/AndroidRuntime(586):  at java.lang.reflect.Method.invokeNative(Native Method) 06-02 18:22:35.529: E/AndroidRuntime(586):  at java.lang.reflect.Method.invoke(Method.java:521) 06-02 18:22:35.529: E/AndroidRuntime(586):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 06-02 18:22:35.529: E/AndroidRuntime(586):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 06-02 18:22:35.529: E/AndroidRuntime(586):  at dalvik.system.NativeStart.main(Native Method) 06-02 18:22:35.529: E/AndroidRuntime(586): Caused by: java.lang.ClassNotFoundException: com.matthewrathbone.eastersays.EasterSimonSaysActivity in loader dalvik.system.PathClassLoader[/data/app/com.matthewrathbone.eastersays-1.apk] 06-02 18:22:35.529: E/AndroidRuntime(586):  at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:243) 06-02 18:22:35.529: E/AndroidRuntime(586):  at java.lang.ClassLoader.loadClass(ClassLoader.java:573) 06-02 18:22:35.529: E/AndroidRuntime(586):  at java.lang.ClassLoader.loadClass(ClassLoader.java:532) 06-02 18:22:35.529: E/AndroidRuntime(586):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 06-02 18:22:35.529: E/AndroidRuntime(586):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577) 06-02 18:22:35.529: E/AndroidRuntime(586):  ... 11 more 

Usually this means that the manifest file is wrong in some way, but I've double checked everything I can think of.

Here is my activity class:

package com.matthewrathbone.eastersays;  import android.os.Bundle;  import com.rathboma.simonsays.Assets.Season; import com.rathboma.simonsays.SeasonPicker; import com.rathboma.simonsays.SimonSaysActivity;      public class EasterSimonSaysActivity extends SimonSaysActivity {        @Override       protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);       }        @Override       protected void onDestroy() {         // TODO Auto-generated method stub         super.onDestroy();       }        @Override       public SeasonPicker getSeasonPicker() {        return new SeasonPicker(){         @Override         public Season getSeason() {           // TODO Auto-generated method stub           return Season.EASTER;         }        };       }     } 

As you can see, it's listed correctly in the manifest:

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"     package="com.matthewrathbone.eastersays"     android:versionCode="1"     android:versionName="1.0" >      <uses-sdk android:minSdkVersion="7" android:targetSdkVersion="15" />      <application         android:icon="@drawable/ic_launcher"         android:label="@string/app_name" >         <activity             android:name=".EasterSimonSaysActivity"             android:label="@string/app_name" >             <intent-filter>                 <action android:name="android.intent.action.MAIN" />                  <category android:name="android.intent.category.LAUNCHER" />             </intent-filter>         </activity>     </application>  </manifest> 

I have no idea how to fix this, and would appreciate any help. I've scanned many similar questions on SO without seeing this particular behavior.

More info:

• I've checked inside the generated APK and the class has an entry in the classes.dex file
• I've tried cleaning/building the project in eclipse
• I've tried using a totally new device image that doesn't have a copy of the APK on it already
• I've changed the library project into a regular java, then changed back into an android project, no difference
• Adding the abstract SimonSaysActivity to the manifest makes no difference.
• I've tried making every dependency an android library project, and syncing the android version that they require, it did not help

Found the solution (see below). To everyone that posted an answer / comment: You all rock, thanks for helping me work through the problems!

Looks like this is introduced by an SDK tools upgrade. Thanks to @Nick below in the comments for this link: http://iqadd.com/item/noclassdeffounderror-adt-fix

Answer 1

I spent some time play with my own project, and I am able to replicate your problem and get exactly the same exception stack trace when trying to run my main project, so I think this could be the cause:

Just like what I thought, it is all about how you reference your Android library project in the Android main project, a simple Eclipse configuration settings.

The Wrong Way:
Right click main project, choose Properties -> Java Build Path -> Projects -> Add..., this add the Android library Project as a dependency project in Android main project's build path, this does not work. If all required Android-related resources are defined in main project, you will not get any error at compile time, but when run the application, you get the exception described in the question.

The Correct Way:
Right click main project, choose Properties -> Android, in the Library section, add your Android library project here. Check out official dev guide Referencing a library project. This should fix all your problem. Also note that you have to use relative path reference the actual Android library project, as stated in the Library Project - Development considerations.

Hope this helps.

Answer 2

i've tested the code that you've given , and it works fine. try changing the "extends SimonSaysActivity " to simply "extends Activity " and see for yourself that it works .

the reason that it doesn't work is either SimonSaysActivity doesn't extend Activity (which i don't think you've made this mistake) , or the order of the build path is wrong .

to go to the order of the build path , go to :

project->properties->Java build path->order and export . 

my basic order is : project src , project gen , android 4.0.3 , android dependencies .

this problem usually occurs when you use libraries .