android - Unable to instantiate activity - ClassNotFound - Fails on one eclipse but not other

I am receiving a 'Unable to instantiate activity' error when I try to load up my program. One thing that baffles me is the exact same code works on my older PC. I just built a new one with new eclipse / android SDK / etc. I have both machines running the same code, one works fine and the other gives this error.

Any thoughts?

Edit: One thing I notice in the stack is

Caused by: java.lang.ClassNotFoundException: com.voldaran.puzzle.graBLOX.PopActivity in loader dalvik.system.PathClassLoader[/data/app/com.voldaran.puzzle.graBLOX-2.apk]

It lists graBLOX-2.apk . Why is it using '-2.apk'?

When I manually reproduce this error on the working machine, it does not display that last []'d part.

Android Manifest

<application android:icon="@drawable/icon" android:label="@string/app_name">
    <activity android:name=".PopActivity"
              android:label="@string/app_name"
              android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
              android:finishOnTaskLaunch="true"
              android:configChanges="orientation|keyboardHidden"
              android:screenOrientation="portrait"
              >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

Stack

 04-21 17:33:42.284: E/AndroidRuntime(4045): FATAL EXCEPTION: main
04-21 17:33:42.284: E/AndroidRuntime(4045): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.voldaran.puzzle.graBLOX/com.voldaran.puzzle.graBLOX.PopActivity}: java.lang.ClassNotFoundException: com.voldaran.puzzle.graBLOX.PopActivity in loader dalvik.system.PathClassLoader[/data/app/com.voldaran.puzzle.graBLOX-2.apk]
04-21 17:33:42.284: E/AndroidRuntime(4045):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at android.os.Looper.loop(Looper.java:130)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at android.app.ActivityThread.main(ActivityThread.java:3683)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at java.lang.reflect.Method.invokeNative(Native Method)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at java.lang.reflect.Method.invoke(Method.java:507)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at dalvik.system.NativeStart.main(Native Method)
04-21 17:33:42.284: E/AndroidRuntime(4045): Caused by: java.lang.ClassNotFoundException: com.voldaran.puzzle.graBLOX.PopActivity in loader dalvik.system.PathClassLoader[/data/app/com.voldaran.puzzle.graBLOX-2.apk]
04-21 17:33:42.284: E/AndroidRuntime(4045):     at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at java.lang.ClassLoader.loadClass(ClassLoader.java:551)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
04-21 17:33:42.284: E/AndroidRuntime(4045):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561)

I was happening pretty much the same situation (project made initially in 32 bit machine, then imported in another 64 bit machine).

In Android projects under Eclipse Juno (64 bit):

Click mouse right button on the project in "Project Explorer", then select "Properties"
Select "Java Build Path" in the list at left.
Make click on "Order and Export" tab.
Mark the two checkboxes for "Android Private Libraries" and "Android Dependencies", respectively, then click OK button.
Clean project(s) and run.

Urban

Try this. Add this piece of code inside your PopActivity and call this function from inside its default constructor.

private static void fixClassLoaderIssue()
{
ClassLoader myClassLoader = MyClass.class.getClassLoader();
Thread.currentThread().setContextClassLoader(myClassLoader);
}

I had a similar issue and this fixed it. Now this solution doesnt really answer why the problem exists, but I really couldnt find that out.
For reference check this answer.

Did you try a project clean? That usually solves my classloader issues.

In my case It was wrong package name in AndroidManifest file.

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    *package="com.app"*
    android:versionCode="1"
    android:versionName="1.0" >

来源：https://stackoverflow.com/questions/10263248/android-unable-to-instantiate-activity-classnotfound-fails-on-one-eclipse

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