Question

JAVA动画一直闪烁，求解，球沿着十字路口来回走，但是十字架总是闪烁

package xiancheng;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;

import java.awt.Stroke;

import javax.swing.JFrame;

public class JoinDemo extends JFrame {
public static void main(String[] args) {
new JoinDemo();
}

private int x = 200, y = 300, r = 100;

public JoinDemo() {
this.setTitle("球车");
this.setSize(800, 600);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
this.setVisible(true);
new UpdateThread().start();
}

public void paint(Graphics g) {
Graphics2D g2d=(Graphics2D)g;
Stroke stroke=new BasicStroke(12.0f);//设置线宽为12.0
g2d.setStroke(stroke);
g2d.setColor(Color.green);
g.drawLine(0, 300, 800, 300);
g.drawLine(400, 0, 400, 600);
Image image = createImage(getWidth(), getHeight());
Graphics gg = image.getGraphics();
bufferedPaint(gg);
gg.dispose();
g.drawImage(image, 0, 0, null);
}

private void bufferedPaint(Graphics gg) {
gg.fillOval(x, y, r, r);
}

class UpdateThread extends Thread {
public void run() {
for (int j = 0; j <= 200; j++) {
x++;
repaint();
sleep(10);
}
for (int j = 0; j <= 300; j++) {
y--;
repaint();
sleep(10);
}
for (int j = 0; j <= 300; j++) {
y++;
repaint();
sleep(10);
}
for (int j = 0; j <= 200; j++) {
x--;
repaint();
sleep(10);
}
}

private void sleep(int millis) {
try {
Thread.sleep(millis);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}

}

Answer 1

闪烁的原因请百度 swing 双缓冲
这里我只是给你一种简单的解决办法：

public class JoinDemo extends JFrame {
    public static void main(String[] args) {
        new JoinDemo();
    }
 
    private int x = 200, y = 300, r = 100;
    private Graphics2D g2d;
    private BufferStrategy bs;
    
    public JoinDemo() {
        this.setTitle("球车");
        this.setSize(800, 600);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setVisible(true);
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        this.createBufferStrategy(2);
        bs =this.getBufferStrategy();
        g2d =(Graphics2D)bs.getDrawGraphics();
        new UpdateThread().start();
    }
    
    public void draw() {
         Image image = createImage(getWidth(), getHeight());
         Graphics gg = image.getGraphics();
         bufferedPaint(gg);
         gg.dispose();
         g2d.drawImage(image, 0, 0, null);
         Stroke stroke=new BasicStroke(12.0f);
         g2d.setStroke(stroke);
         g2d.setColor(Color.green);
         g2d.drawLine(0, 300, 800, 300);
         g2d.drawLine(400, 0, 400, 600);
         bs.show();
         
    }
    private void bufferedPaint(Graphics gg) {
        gg.fillOval(x, y, r, r);
    }
 
    class UpdateThread extends Thread {
        public void run() {
            for (int j = 0; j <= 200; j++) {
                x++;
                draw();
                sleep(10);
            }
            for (int j = 0; j <= 300; j++) {
                y--;
                draw();
                sleep(10);
            }
            for (int j = 0; j <= 300; j++) {
                y++;
                draw();
                sleep(10);
            }
            for (int j = 0; j <= 200; j++) {
                x--;
                draw();
                sleep(10);
            }
        }
 
        private void sleep(int millis) {
            try {
                Thread.sleep(millis);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
 
}

追问

确实不闪了。但是有个问题是小车被绿线挡住了。
怎么让车子在绿线的上层显示。

追答

因为我调试的时候换了绘制顺序，你可以自己把它换回来

追问

初学者哈哈能详细解释一下 这段代码吗

追答

哪不明白？

追问

public void draw() { 这一段不明白。

追答

这里我几乎是原样使用你的绘制逻辑呀，只是调了下画圆和画线的顺序，最后的bs.show();是调BufferStrategy的方法，作用是把绘制的图像显示出来。

追问

其实这代码也是我从网上找的，然后凭感觉修改了一下
至于Image image = createImage(getWidth(), getHeight()); 是啥意思。。。我也不清楚，刚学java两天

追答

正常的绘制逻辑：

public void draw() {
        //清空屏幕
        g2d.clearRect(0, 0, getWidth(), getHeight());
        //画线
        Stroke stroke=new BasicStroke(12.0f);
        g2d.setStroke(stroke);
        g2d.setColor(Color.green);
        g2d.drawLine(0, 300, 800, 300);
        g2d.drawLine(400, 0, 400, 600);
        //画圆
        g2d.setColor(Color.BLACK);
        g2d.fillOval(x, y, r, r);
        //显示
        bs.show();
}

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