// android.view.WindowManager$BadTokenException: Unable to add window -- token null is not valid; is your activity running?
// at android.view.ViewRootImpl.setView(ViewRootImpl.java:567)
// at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:310)
// at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:85)
// at android.widget.PopupWindow.invokePopup(PopupWindow.java:1258)
// at android.widget.PopupWindow.showAsDropDown(PopupWindow.java:1110)
// at android.widget.PopupWindow.showAsDropDown(PopupWindow.java:1069)
// at android.widget.PopupWindow.showAsDropDown(PopupWindow.java:1048)
// at com.jaredrummler.materialspinner.MaterialSpinner.expand(MaterialSpinner.java:416)
// at com.jaredrummler.materialspinner.MaterialSpinner$3.run(MaterialSpinner.java:277)
// at android.os.Handler.handleCallback(Handler.java:739)
// at android.os.Handler.dispatchMessage(Handler.java:95)
// at android.os.Looper.loop(Looper.java:148)
// at android.app.ActivityThread.main(ActivityThread.java:5417)
// at java.lang.reflect.Method.invoke(Native Method)
// at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
// at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)