When using a custom button skin together with the DatePicker's calendar button one get's multiple NullPointerExceptions. SSCCE bellow.

REC76.java:

package rec.pkg76;

import java.net.URL;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.DatePicker;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class REC76 extends Application {

    @Override
    public void start(Stage primaryStage) {

        StackPane root = new StackPane();

        DatePicker datePicker = new DatePicker();
        root.getChildren().add(datePicker);

        Scene scene = new Scene(root, 300, 250);

        URL styleSheet = REC76.class.getResource("stylesheet.css");
        scene.getStylesheets().add(styleSheet.toExternalForm());

        primaryStage.setTitle("Hello World!");
        primaryStage.setScene(scene);

        primaryStage.show();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }

}


ButtonSkin.java:

package rec.pkg76;

import javafx.scene.control.Button;

public class ButtonSkin extends com.sun.javafx.scene.control.skin.ButtonSkin {

    public ButtonSkin(Button button) {
        super(button);
        // NullPointerExecption even if the button skin doesn't do anything
    }

}


stylesheet.css:

.button {
    -fx-skin: "rec.pkg76.ButtonSkin";
}