Question

我正在尝试创建一个每秒显示一条新随机行的屏幕保护程序。它内置在JFrame中嵌入的JPanel中。

问题在于，每次构建随机行时，它都会触及JFrame的边缘。我设置它以使该行始终在JPanel中，但我不希望它每次都触及JFrame的边缘。

它永远不会在画面中间显示任何行。我确定这是一个简单的修复方法。我只是在寻找一双新鲜的眼睛。我可能没有正确理解坐标系，谢谢。

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.geom.GeneralPath;
import java.awt.geom.Line2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import java.util.Random;

public class ScreenSaver extends JPanel implements ActionListener{
    Timer timer;
    int x1;
    int y1;
    int x2;
    int y2;

public ScreenSaver() {
    timer = new Timer(1000, this);
    timer.start();
}

    @Override
public void actionPerformed(ActionEvent e){
    repaint();
}

public void GetRandomValues(){

    Random randh = new Random();
    Random randw = new Random();

    // get width of JPanel
    int w = getWidth();

    // get height of JPanel
    int h = getHeight();

     x1 = randh.nextInt(h);
     x2 = randh.nextInt(h);
     y1 = randw.nextInt(w);
     x2 = randw.nextInt(w);

}

    @Override
public void paintComponent(Graphics g) {

   super.paintComponent(g);

   Graphics2D g2 = (Graphics2D) g;
   GetRandomValues();

   g2.draw(new Line2D.Double(x1, y1, x2, y2));
}

 public static void main (String[] args){

    ScreenSaver s1 = new ScreenSaver();        

    // jf is the JFrame
    JFrame jf = new JFrame();
    jf.setTitle("ScreenSaver.java");
    jf.setSize(800, 500);
    // puts frame in middle?
    jf.setLocationRelativeTo(null);
    jf.setVisible(true);
    jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);



    // panel inside frame
    jf.add(s1);
}

}

Answer 1

使用单个Random对象，初始化一次，不要在每个计时器上重新分配它。此外，在坐标创建方面存在混淆。它应该是：

private Random random = new Random();

public void GetRandomValues(){
    // get width of JPanel
    int w = getWidth();

    // get height of JPanel
    int h = getHeight();

    x1 = random.nextInt(w);
    x2 = random.nextInt(w);
    y1 = random.nextInt(h);
    x2 = random.nextInt(h);
}

x坐标应受宽度约束，y坐标应按高度约束。你有另一种方式。

屏幕保护程序每秒显示随机Line2D.Double（JFrame中的JPanel）

1 个答案: