public class RedView {

@FXML
private Button button2;

@FXML
private Button button1;
private String url;

...

@FXML
public void handleButton1Action() throws IOException {
    FXMLLoader loader = new FXMLLoader(MidiCCCGuiController.class.getResource("MidiCCCGui.fxml"));
    Parent root = loader.load();

   MidiCCCGuiController control = loader.getController();
    control.setText("redview");
}
}