Java中的repaint（）方法未调用paint（）方法？

Question

这是我的代码

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;

import javax.swing.JFrame;
import javax.swing.JPanel;

import com.leappainter.model.GetXYCoordinatesPOJO;

public class DrawXY extends JPanel {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private int x;
    private int y;
    private int d;

    public int getX() {
        return x;
    }
    public void setX(int x) {
        this.x = x;
    }
    public int getY() {
        return y;
    }
    public void setY(int y) {
        this.y = y;
    }
    public int getD() {
        return d;
    }
    public void setD(int d) {
        this.d = d;
    }

    @Override
    public void paint(Graphics g) {
        super.paint(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setColor(Color.RED);
        g2d.drawOval(getX(), getY(), 30, 30);
        System.out.println("painting");
    }
    public void draw() {
        JFrame frame = new JFrame("Leap Draw");
        frame.add(new DrawXY());
        frame.setSize(600, 600);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    public void update(GetXYCoordinatesPOJO getxy) {
        // TODO Auto-generated method stub
        setX((int) getxy.getX());
        setY((int) getxy.getY());
        setD((int) getxy.getD());

        //System.out.println(getX());

        DrawXY draw = new DrawXY();
        draw.repaint();
        try {
            Thread.sleep(10);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

通过更新值的函数调用Update方法，但是两次后未调用paint方法。

Answer 1

您正在其他实例上调用重绘！

改变...

public void update(GetXYCoordinatesPOJO getxy) {
    // TODO Auto-generated method stub
    setX((int) getxy.getX());
    setY((int) getxy.getY());
    setD((int) getxy.getD());

    //System.out.println(getX());

    DrawXY draw = new DrawXY(); // < -- YOU CREATE NEW INSTANCE HERE
    draw.repaint();
    try {
        Thread.sleep(10);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

至

public void update(GetXYCoordinatesPOJO getxy) {
    // TODO Auto-generated method stub
    setX((int) getxy.getX());
    setY((int) getxy.getY());
    setD((int) getxy.getD());

    //System.out.println(getX());

    repaint();
    try {
        Thread.sleep(10);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

并查看VGR的评论... +1。