Class cannot initiated in activity:

• Check for activity in manifest.
• May be due to the declaration of  normal variable in class before oncreate function.
• clean the project and run.
• version miss-match(emulator).

I face similar problem for declaring variable in class like

class dim extends Activity

{

button btn;//this create me problems.

oncreate()

{

}

}

ERROR DETAIL:

08-05 16:39:36.371: ERROR/AndroidRuntime(279): FATAL EXCEPTION: main

08-05 16:39:36.371: ERROR/AndroidRuntime(279): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{COM.ARUN/COM.ARUN.ex}: java.lang.NullPointerException

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at android.os.Handler.dispatchMessage(Handler.java:99)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at android.os.Looper.loop(Looper.java:123)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at android.app.ActivityThread.main(ActivityThread.java:4627)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at java.lang.reflect.Method.invokeNative(Native Method)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at java.lang.reflect.Method.invoke(Method.java:521)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at dalvik.system.NativeStart.main(Native Method)

08-05 16:39:36.371: ERROR/AndroidRuntime(279): Caused by: java.lang.NullPointerException

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at android.app.Activity.findViewById(Activity.java:1637)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at COM.ARUN.ex.(ex.java:24)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at java.lang.Class.newInstanceImpl(Native Method)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at java.lang.Class.newInstance(Class.java:1429)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at android.app.Instrumentation.newActivity(Instrumentation.java:1021)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)

08-05 16:39:36.371: ERROR/AndroidRuntime(279):     ... 11 more