Android :: Create Custom Global Methods In My Application Class?

I currently have an app that has many activities and needs to have a way of maintaining state between these activities.

I use the Application class to do this, declaring my global variables and using getters and setters to interact with my activities.

I was hoping to place a few custom methods in there, so that when I want to do a common task like, for instance, display an error message, I can declare the method in my application class and call it from any activity that uses it

EscarApplication application = (EscarApplication) this.getApplication();

EscarApplication being the name of my application class above.

I have tried to include this method in my application class:

CODE:.....

In the hope that I can call this method from activity without having to redeclare it, but when I call it using something like below I get an null pointer exception:

Visit.this.application.showError("Update error", "An error has occurred while trying to communicate with the server");

Visit being the name of my current activity above.

Should this work, or can I only use getters and setters to change global vars in an Application Class.

EDIT Stack Trace:

CODE:...............

The dialog is declared as such in the application class:AlertDialog alertDialog;

Created in that same class:alertDialog = new AlertDialog.Builder(this).create();

And the method to call it in that class is as follows:

CODE:.............

And finally, it is called from an activity like so:

CODE:........................