Android Activity has leaked window

Android Activity has leaked window

I am getting following error in my logcat.
What i am trying to do is to get files from server. The same code is
running f9 with sdcard but when i get files from thorugh thread then i am
getting following error in my logcat.
ERROR/WindowManager(20040): Activity idtech.ESDN.Map has leaked window
com.android.internal.policy.impl.PhoneWindow$DecorView@416a97b0 that was
originally added here android.view.WindowLeaked: Activity idtech.ESDN.Map
has leaked window
com.android.internal.policy.impl.PhoneWindow$DecorView@416a97b0 that was
originally added here at android.view.ViewRootImpl.(ViewRootImpl.java:380)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:292) at
android.view.WindowManagerImpl.addView(WindowManagerImpl.java:224) at
android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:149)
at android.view.Window$LocalWindowManager.addView(Window.java:547)
at android.app.Dialog.show(Dialog.java:277)
at idtech.ESDN.Map$LoadFile.onPreExecute(Map.java:59)
at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
at android.os.AsyncTask.execute(AsyncTask.java:534)
at idtech.ESDN.Map.onActivityResult(Map.java:221)
at android.app.Activity.dispatchActivityResult(Activity.java:5194)
at
android.app.ActivityThread.deliverResults(ActivityThread.java:3180)
at
android.app.ActivityThread.handleSendResult(ActivityThread.java:3227)
at android.app.ActivityThread.access$1100(ActivityThread.java:137)
at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1258)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4838)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
at dalvik.system.NativeStart.main(Native Method)