مشکل در اجرای دیالوگ خارج اکتیویتی 

من یک کلاسی دارم که با استفاده از Async Task اطلاعات رو میخونم

حالا زمانی که در این Async task از دیالوگ اسفاده میکنم باید یک context بدم به دیالوگ چون در کلاس اکتیویتی نیستم از G.context استفاده کردم 

اما زمانی که برنامه به خط dialog.show() میرسه کرش میکنه 

 private static class serverTask extends AsyncTask<List<String>, Void, String>
    {

        private final ProgressDialog dialogs = new ProgressDialog(G.context);

        private final AlertDialog    alerts  = new AlertDialog.Builder(G.context).create();


        @Override
        protected void onPreExecute() {

            dialogs.setMessage("Logging in...");
            dialogs.show();

        }


        @Override
        protected String doInBackground(List<String>... lists) {
          
        }


        @Override
        protected void onPostExecute(String result)
        {
        }

 10-15 16:27:27.953: E/AndroidRuntime(15289): FATAL EXCEPTION: main
10-15 16:27:27.953: E/AndroidRuntime(15289): Process: uncocoder.com.project, PID: 15289
10-15 16:27:27.953: E/AndroidRuntime(15289): android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.view.ViewRootImpl.setView(ViewRootImpl.java:536)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:259)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.app.Dialog.show(Dialog.java:286)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at uncocoder.com.project.app.StructUser$serverTask.onPreExecute(StructUser.java:100)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at uncocoder.com.project.app.StructUser.login(StructUser.java:65)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at uncocoder.com.project.app.ActivityLogin$1.onClick(ActivityLogin.java:69)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.view.View.performClick(View.java:4438)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.view.View$PerformClick.run(View.java:18422)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.os.Handler.handleCallback(Handler.java:733)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.os.Handler.dispatchMessage(Handler.java:95)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.os.Looper.loop(Looper.java:136)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at android.app.ActivityThread.main(ActivityThread.java:5001)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at java.lang.reflect.Method.invokeNative(Native Method)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at java.lang.reflect.Method.invoke(Method.java:515)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
10-15 16:27:27.953: E/AndroidRuntime(15289): 	at dalvik.system.NativeStart.main(Native Method)
10-15 16:27:29.103: E/InputDispatcher(790): channel '44462260 uncocoder.com.project/uncocoder.com.project.app.ActivityMain (server)' ~ Channel is unrecoverably broken and will be disposed!
10-15 16:27:29.723: E/AsyncInputConnection(29076): onUpdateSelection: oss=0, ose=0, nss=0, nse=0, cs=0, ce=0