*15.9 (使用箭头键画线)

• 请编写一个程序，使用箭头键绘制线段。所画的线从面板的中心开始，当敲 击向右、向上、向左或向下的箭头键时，相应地向东、向北、向西或向南方向画线，如图 15-26b所示

代码展示：编程练习题15_9DrawLinesUsingArrows.java

package chapter_15;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.shape.Line;
import javafx.stage.Stage;

public class 编程练习题15_9DrawLinesUsingArrows extends Application{
	double x =150,y = 100;
	@Override
	public void start(Stage primaryStage) throws Exception {
		Pane pane = new Pane();
		pane.setOnKeyPressed(e ->{
			switch (e.getCode()) {
				case LEFT:{
					Line line = new Line(x, y, x-5, y);
					pane.getChildren().add(line);
					x = line.getEndX();
					y = line.getEndY();
					break;
				}
				case RIGHT:{
					Line line = new Line(x, y, x+5, y);
					pane.getChildren().add(line);
					x = line.getEndX();
					y = line.getEndY();
					break;
				}
				case UP:{
					Line line = new Line(x, y, x, y-5);
					x = line.getEndX();
					y = line.getEndY();
					pane.getChildren().add(line);
					break;
				}
				case DOWN:{
					Line line = new Line(x, y, x, y+5);
					pane.getChildren().add(line);
					x = line.getEndX();
					y = line.getEndY();
					break;
				}
				
			}
		});
		Scene scene = new Scene(pane, 300, 200);
	    primaryStage.setTitle("编程练习题15_9DrawLinesUsingArrows");
	    primaryStage.setScene(scene);
	    primaryStage.show();
	    pane.requestFocus();
	}
	public static void main(String[] args) {
		Application.launch(args);
	}
}

•  结果展示