Can not be used in BroadcastReceiver!

[totond]

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window android.app.Activity.getWindow()' on a null object reference
                                                     at com.wizchen.topmessage.TopMessage.createView(TopMessage.java:108)
                                                     at com.wizchen.topmessage.TopMessageManager.showWarning(TopMessageManager.java:362)
                                                     at com.wizchen.topmessage.TopMessageManager.showWarning(TopMessageManager.java:278)
                                                     at com.wizchen.topmessage.TopMessageManager.showWarning(TopMessageManager.java:267)