My circles won't show. What am I missing here? - javafx-8

Question

In Javafx, I am trying to create a pane where I can add points through a mouse click event. When you click on the pane a circle should appear at your mouse position. The circles are being created, as I am tracking them in the console, but they are not showing in the graphics.
I did a similar program to this that auto drew an image that resized with the stage/window, I am using all the same techniques but that project didn't include event handling.
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Line;
import javafx.scene.paint.Color;
import javafx.event.EventHandler;
import javafx.scene.input.MouseEvent;
public class ClickToShape extends Application {
private ClickPane clickPane = new ClickPane();
#Override
public void start(Stage primaryStage) throws Exception {
Pane clickPane = new ClickPane();
clickPane.setOnMouseClicked(new ClickHandler());
// create the scene
Scene clickScene = new Scene(clickPane, 500, 500);
// set up the window/stage
primaryStage.setTitle("Click To Draw");
primaryStage.setScene(clickScene); // add the scene to the stage
primaryStage.show(); // fire it off
}
public static void main(String[] args) {
launch(args);
}
class ClickHandler implements EventHandler<MouseEvent> {
#Override
public void handle(MouseEvent e) {
System.out.println("MouseEvent occured");
clickPane.addPoint(e.getX(), e.getY());
}
}
}
class ClickPane extends Pane{
private ArrayList<Circle> points = new ArrayList<Circle>();
private Color color1 = Color.BLACK;
public void addPoint(double x, double y) {
System.out.println("A new point function ran");
Circle newPoint = new Circle (x, y, 300, color1 );
System.out.println(newPoint.toString());
points.add(newPoint);
getChildren().clear();
getChildren().add(newPoint);
}
}
There are no error messages.

Answer 1

the problem is that you instantiated two ClickPane objects, one outside the start method, and another inside the start method, you added the second one to the scene but used the first one to add points, and that's why points aren't showing in your scene
what you can do about this is delete the first line in your start method, so the application will be using the same instance to fire events as to add to the scene, the code would look like this
import java.util.ArrayList;
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.shape.Circle;
import javafx.scene.paint.Color;
import javafx.event.EventHandler;
import javafx.scene.input.MouseEvent;
public class ClickToShape extends Application {
private ClickPane clickPane = new ClickPane();
#Override
public void start(Stage primaryStage) throws Exception {
clickPane.setOnMouseClicked(new ClickHandler());
// create the scene
Scene clickScene = new Scene(clickPane, 500, 500);
// set up the window/stage
primaryStage.setTitle("Click To Draw");
primaryStage.setScene(clickScene); // add the scene to the stage
primaryStage.show(); // fire it off
}
public static void main(String[] args) {
launch(args);
}
class ClickHandler implements EventHandler<MouseEvent> {
#Override
public void handle(MouseEvent e) {
System.out.println("MouseEvent occured");
clickPane.addPoint(e.getX(), e.getY());
}
}
}
class ClickPane extends Pane{
private ArrayList<Circle> points = new ArrayList<Circle>();
private Color color1 = Color.BLACK;
public void addPoint(double x, double y) {
System.out.println("A new point function ran");
Circle newPoint = new Circle (x, y, 10, color1 );
System.out.println(newPoint.toString());
points.add(newPoint);
getChildren().setAll(newPoint);
}
}