Carefully read the documentation for
RadioButtons and
Buttons. The android docs are designed to leave a bread crumb trail of things you need in place. In short:
1) Set an onClick listener in the xml for the button
android:onClick="btnDisplayClicked"
2) Set an onClick listener in the xml for the radio buttons
android:onClick="radioButtonItemSelected"
3) Declare the radio button listener method in the activity. This is where you would do a switch on the Id of the radio button and set the result to a member variable.
public void radioButtonItemSelected(View view) { }
4) Declare the button listener in the activity. This is where you generate your toast based on the member variable.
public void onRadioButtonClicked(View view) { }
There are of course a lot of different ways you can go about this such as programatically defining the UI and listeners but this is the simplest to get started.