import java.time.LocalDate;
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.scene.Scene;
import javafx.scene.control.ComboBox;
import javafx.scene.control.DatePicker;
import javafx.scene.layout.VBox;
import javafx.stage.FileChooser;
import javafx.stage.Stage;

public class RT38288 extends Application {

    @Override public void start(Stage stage) throws Exception {
        DatePicker datePicker = new DatePicker(LocalDate.now());

        ComboBox<String> comboBox = new ComboBox<String>(FXCollections.observableArrayList("A", "B"));
        comboBox.setEditable(true);

        stage.setScene(new Scene(new VBox(datePicker, comboBox), 300, 200));
        stage.show();

        datePicker.setOnAction(e -> {
            if (stage.isShowing()) {
                new FileChooser().showOpenDialog(stage);
            }
        });

        comboBox.setOnAction(e -> {
            if (stage.isShowing()) {
                new FileChooser().showOpenDialog(stage);
            }
        });
    }
}