import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
// pickOnBounds + -fx-shape bug.
public class RoundButtonClick extends Application {
  public static void main(String[] args) { launch(args); }
  @Override public void start(Stage stage) throws Exception {
    ToggleButton button = new ToggleButton("Add");
    /* set the shape of button to be circle */
    button.setStyle(
            "-fx-font-size: 40; -fx-shape: \"m 307.14285,366.64789 c 27.7,0 50,22.3 50,50 0,27.7 -22.3,50 -50,50 -27.7,0 -50,-22.3 -50,-50 0,-27.7 22.3,-50 50,-50 z\";"
    );
    button.setMinHeight(Button.USE_PREF_SIZE);
    button.prefHeightProperty().bind(button.widthProperty());
    button.setMaxHeight(Button.USE_PREF_SIZE);
    button.setPickOnBounds(true);
// clip based workaround.
// Circle circularClip = new Circle();
// circularClip.centerXProperty().bind(button.widthProperty().divide(2));
// circularClip.centerYProperty().bind(button.heightProperty().divide(2));
// circularClip.radiusProperty().bind(button.widthProperty().divide(2));
// button.setClip(circularClip);
    StackPane layout = new StackPane();
    layout.getChildren().setAll(
            button
    );
    layout.setStyle("-fx-background-color: cornsilk; -fx-padding: 20px;");
    
    stage.setScene(new Scene(layout, 180, 180));
    stage.show();
  }
}

To reproduce, run the attached sample, click inside the circular ToggleButton and the ToggleButton will toggle as expected.
Click outside the ToggleButton anywhere within the enclosing rectangular bounds of the button in it's parent and the ToggleButton will still toggle, even though it is not supposed to based on it's shape and the pickOnBounds setting.