ClassNotFoundException when the class is there?

I'm a bit stuck on this. Android is throwing a ClassNotFoundException even though there is such a class.

04-20 09:07:50.179: E/AndroidRuntime(525): FATAL EXCEPTION: main
04-20 09:07:50.179: E/AndroidRuntime(525): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.company.app/com.company.app.Main}: java.lang.ClassNotFoundException: com.company.app.Main
04-20 09:07:50.179: E/AndroidRuntime(525):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1880)
04-20 09:07:50.179: E/AndroidRuntime(525):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
04-20 09:07:50.179: E/AndroidRuntime(525):  at android.app.ActivityThread.access$600(ActivityThread.java:123)
04-20 09:07:50.179: E/AndroidRuntime(525):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
04-20 09:07:50.179: E/AndroidRuntime(525):  at android.os.Handler.dispatchMessage(Handler.java:99)
04-20 09:07:50.179: E/AndroidRuntime(525):  at android.os.Looper.loop(Looper.java:137)
04-20 09:07:50.179: E/AndroidRuntime(525):  at android.app.ActivityThread.main(ActivityThread.java:4424)
04-20 09:07:50.179: E/AndroidRuntime(525):  at java.lang.reflect.Method.invokeNative(Native Method)
04-20 09:07:50.179: E/AndroidRuntime(525):  at java.lang.reflect.Method.invoke(Method.java:511)
04-20 09:07:50.179: E/AndroidRuntime(525):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
04-20 09:07:50.179: E/AndroidRuntime(525):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
04-20 09:07:50.179: E/AndroidRuntime(525):  at dalvik.system.NativeStart.main(Native Method)
04-20 09:07:50.179: E/AndroidRuntime(525): Caused by: java.lang.ClassNotFoundException: com.company.app.Main
04-20 09:07:50.179: E/AndroidRuntime(525):  at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
04-20 09:07:50.179: E/AndroidRuntime(525):  at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
04-20 09:07:50.179: E/AndroidRuntime(525):  at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
04-20 09:07:50.179: E/AndroidRuntime(525):  at android.app.Instrumentation.newActivity(Instrumentation.java:1023)
04-20 09:07:50.179: E/AndroidRuntime(525):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1871)
04-20 09:07:50.179: E/AndroidRuntime(525):  ... 11 more

There is such a class called Main in Main.java.

public class Main extends FragmentActivity which is in the package com.company.app.

It was working before but when I went back to work on the app today it just stopped working. I don't know what happened.

It is defined correctly in the Manifest.

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

    <uses-sdk android:minSdkVersion="4" />
    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" 
        android:theme="@android:style/Theme.Light" >
        <activity
            android:label="@string/app_name"
            android:name=".Main" >
            <intent-filter >
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Few things I've tried:

Restarting Eclipse
Restarting the emulator
Uninstalling and reinstalling the app in the emulator
Cleaning the project.
Checking if gen and src is in the Source tab of the build path.

As it looks right now, I may have to abandon the current project and start from scratch.

Any help would be much appreciated.

UPDATE:

The app works if Main extends Activity instead of FragmentActivity. Perhaps it is something with the Android Support package?

UPDATE 2:

I'm pretty sure it is. When I don't use the support package and I use the normal Fragment classes in Android 3.0 and up, the app works fine.

The problem is now fixed. :)

For some reason the Android support package removed itself from the /libs directory in the project and it was referencing it from an external location (outside the workspace directory).

I will mark Abdu Egal's first answer as correct as he directed me on the right track.

回答1:

It seems that there is an error in the onCreate of your main activity. Did you provide an onCreate(Bundle savedInstance) if so , try to clear it and see if it works then.

If that does not work, try to use extend Activity instead of extend FrameActivity.

Good luck

回答2:

From your quition detail i assume that you forgot to declare your FrameActivity into AndroidManifest.xml , kindly check your AndroidManifest.xml file entry.

回答3:

I think you used the FragmentActivity the wrong way, I guess FragmentActivities should be a part of a normal activity, see below:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">
    <fragment
        android:name="com.mamlambo.tutorial.tutlist.TutListFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:id="@+id/tutlist_fragment"
        android:layout_weight="45">
    </fragment>
    <fragment
        android:name="com.mamlambo.tutorial.tutlist.TutViewerFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:id="@+id/tutview_fragment"
        android:layout_weight="55">
    </fragment>
</LinearLayout>

Taken from this link (part 9)

http://mobile.tutsplus.com/tutorials/android/android-sdk_fragments/

回答4:

Right click on your project folder => Properties => Java Build Path => Order and Export => check the box "Android Private Libraries" if not checked. Make a clean. And it works !

回答5:

I got the same problem with MobilTuts sample, problem was with support library. I have changed the build target to a higher API than 10, something like 15 for example, and then all errors vanished.

Project Properties --> Android --> Project Build Target --> Set it to 15 .e.g

Recommendation: set MIN API inside manifest to 8 at lest.