用于移动形状的 JavaFx 按钮事件处理程序

Question

我上周刚开始使用 JavaFx，但在尝试在窗格中设置一个圆圈以响应按钮事件处理程序时遇到了问题。我设置了名称为左、右、上、下的按钮，按下时应该将圆圈移动到窗格内。我的问题是我根本无法让圆圈响应我的事件处理程序。我看到另一个教程结合了按键来移动圆圈，我正在尝试类似的东西但用按钮代替。如果能帮助我朝着正确的方向前进，我将不胜感激。

package movingball;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;

public class MovingBall extends Application{
  private CirclePane circlePane = new CirclePane();


@Override
public void start(Stage primaryStage) {
    StackPane pane = new StackPane();
    Circle circle = new Circle(50);
    circle.setStroke(Color.BLACK);
    circle.setFill(Color.WHITE);
    pane.getChildren().add(circle);

    HBox hBox = new HBox();
    hBox.setSpacing(10);
    hBox.setAlignment(Pos.CENTER);
    Button btLeft = new Button("Left");
    Button btRight = new Button("Right");
    Button btUp = new Button("Up");
    Button btDown = new Button("Down");
    hBox.getChildren().addAll(btLeft, btRight, btUp, btDown);

    btLeft.setOnAction(new LeftHandler());
    btRight.setOnAction(new RightHandler());
    btUp.setOnAction(new UpHandler());
    btDown.setOnAction(new DownHandler());


    BorderPane borderPane = new BorderPane();
    borderPane.setCenter(pane);
    borderPane.setBottom(hBox);
    BorderPane.setAlignment(hBox, Pos.CENTER);

    // Create a scene and place it in the stage
    Scene scene = new Scene(borderPane, 500, 350);
    primaryStage.setTitle("Move the Ball"); // Set the stage title
    primaryStage.setScene(scene); // Place the scene in the stage
    primaryStage.show(); // Display the stage
  }



class LeftHandler implements EventHandler<ActionEvent> {

    @Override
    public void handle(ActionEvent event) {
        circlePane.left();

    }

}

class RightHandler implements EventHandler<ActionEvent> {

    @Override
    public void handle(ActionEvent event) {
        circlePane.right();

    }

}

class UpHandler implements EventHandler<ActionEvent> {

    @Override
    public void handle(ActionEvent event) {
        circlePane.up();

    }

}

class DownHandler implements EventHandler<ActionEvent> {

    @Override
    public void handle(ActionEvent event) {
        circlePane.down();

    }

}

class CirclePane extends StackPane {
    private Circle circle = new Circle(50);

    public CirclePane() {
        getChildren().add(circle);
        circle.setStroke(Color.BLACK);
        circle.setFill(Color.WHITE);
    }

    public void left() {
        circle.setCenterX(circle.getCenterX() - 10);
    }

    public void right() {
        circle.setCenterX(circle.getCenterX() + 10);
    }

    public void up() {
        circle.setCenterY(circle.getCenterY() - 10);
    }

    public void down() {
        circle.setCenterY(circle.getCenterY() + 10);
    }
}


  public static void main(String[] args) {
    launch(args);
  }

}

Answer 1

第一个问题是您正在移动 CirclePane，但它不是场景的一部分。删除您在 start(...) 方法中创建的 pane 和 circle，并将 circlePane 放在 BorderPane 的中心。

第二个问题是StackPane会以圆为中心，随着圆的移动调整其坐标系使其保持居中。所以让 CirclePane 成为 Pane 的子类，而不是 StackPane。或者，您可以调用 circle.setManaged(false); 来防止 StackPane 定位 circle.

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