用Java绘制矩形

Question

I have this code where I have random rectangles generating over the entire canvas. I also have 1 rectangle at the center.

I need to get the 1 rectangle at the center to move around when the user hovers the mouse over the canvas.

Here is my code

package sample;

import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import java.util.Random;


public class Main extends Application {

private static final int DRAW_WIDTH  = 800;
private static final int DRAW_HEIGHT = 500;

private Animation myAnimation;
private Canvas canvas;
private GraphicsContext gtx;

@Override
public void start(Stage stage) throws Exception
{

    stage.setTitle("tRIPPy BoXXX");

    canvas = new Canvas(DRAW_WIDTH, DRAW_HEIGHT);
    gtx = canvas.getGraphicsContext2D();
    gtx.setLineWidth(3);
    gtx.setFill(Color.BLACK);
    gtx.fillRect(0, 0, DRAW_WIDTH, DRAW_HEIGHT);


    VBox vBox = new VBox();
    vBox.getChildren().addAll(canvas);
    Scene scene = new Scene(vBox, DRAW_WIDTH, DRAW_HEIGHT);
    stage.setScene(scene);
    stage.show();
    myAnimation = new Animation();
    myAnimation.start();
}


class Animation extends AnimationTimer
{
    @Override

    public void handle(long now)
    {

        Random rand = new Random();
        double red   = rand.nextDouble();
        double green = rand.nextDouble();
        double blue  = rand.nextDouble();
        Color boxColor = Color.color(red,green,blue);
        gtx.setStroke(boxColor);
....

This is the box that I want to have moving around with the users mouse. I have tried some things on my own, however I can't get the rect to stay the way it is in the code.

      .....
      int rectX = 800 / 2;
      int rectY = 500 / 2;
      for (int side = 10; side <= 100; side += 10) {
        gtx.strokeRect(rectX - side / 2, rectY - side / 2, side, side);
      }


      int centerX = (int)(Math.random()*800);
      int centerY = (int)(Math.random()*800);
      for (int side = (int)(Math.random()*100); side <= Math.random()* 100; side += Math.random()*100)

      {
        gtx.strokeRect(centerX - side / 2, centerY - side / 2, side, side);

      }
    }
}


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

Answer 1

If you plan to move some graphics arround, why do you then start with a canvas? On a canvas you cannot move anything arround unless you constantly want to redraw everything again and again. Putting your rectangles into the scene graph is much better suited for this task.