paintComponent正在执行两次

时间:2011-01-26 02:21:25

标签: java loops for-loop

这困扰我,我的代码工作并运行但是当我去运行它时,它似乎循环我的for循环两次,任何人都可以帮助我的逻辑?谢谢......

package pkgcirc;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.*;

/*
* Notes:
* Draw 20 circles
* radius/location (x/y/r) all random
* if (circle) is between radii pt (step thru loop) of all values, if its within ,
*  draw it cyan if it overlaps, else black
*  
*/
public class Main extends JPanel {
    int[] radius = new int [3];
    int[] xArray = new int [3];
    int[] yArray = new int [3];

    public Main()
    {       
        Random g = new Random();
        setPreferredSize (new Dimension(300, 200));
        for(int i = 0; i < radius.length; i++)
        {
            radius[i] = g.nextInt(50)+1;
            xArray[i] = g.nextInt(250)+1;
            yArray[i] = g.nextInt(150)+1;
        }
    }

    public void paintComponent(Graphics page)
    {
        super.paintComponent(page);
        for(int i = 0; i < radius.length; i++)
        {
            for (int j = 0; j < radius.length; j++)
            {
                int xpoint1 = xArray[i]+radius[i];
                int ypoint1 = yArray[i]+radius[i];
                int xpoint2 = xArray[j]+radius[j];
                int ypoint2 = yArray[j]+radius[j];
                int radius1 = radius[i];
                int radius2 = radius[j];
                boolean Collide = circlesCollide(xpoint1, ypoint1, radius1, radius2, xpoint2, ypoint2);

                if (i != j && Collide == false)
                {
                    page.setColor(Color.cyan);
                    page.fillOval(xArray[i] ,yArray[i], radius[i], radius[i]);
                    System.out.println("false");
                }
                else{
                    System.out.println("true");
                    page.setColor(Color.black);
                    page.drawOval(xArray[j] ,yArray[j], radius[j], radius[j]);
                }
            }
            System.out.println("BREAK");    
        }
    }

    public boolean circlesCollide(double x1, double y1, double r1, double x2, double y2, double r2){
        return (distance(x1, y1, x2, y2) <= (r1 + r2));
    }

    public double distance(double x1, double y1, double x2, double y2) {
        return Math.sqrt(((x2 - x1) * (x2 - x1)) + ((y2 - y1) * (y2 - y1)));
    }       

    public static void main (String[] args)
    {
        JFrame frame = new JFrame ("Circles");
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);

        frame.getContentPane().add (new Main());

        frame.pack();
        frame.setVisible(true);
    }
}

2 个答案:

答案 0 :(得分:5)

调用setPreferredSize()pack()会导致paintComponent()被调用两次,因为每次调用都需要重新绘制显示。

尝试删除pack()并将设置尺寸移到底部,如下所示: -

public Main() {
    Random g = new Random();

    //setPreferredSize(...); // commented this line

    for (int i = 0; i < radius.length; i++) {
        radius[i] = g.nextInt(50) + 1;
        xArray[i] = g.nextInt(250) + 1;
        yArray[i] = g.nextInt(150) + 1;
    }
}

public void paintComponent(Graphics page) {
        ...
}

public static void main(String[] args) {
    JFrame frame = new JFrame("Circles");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    frame.setSize(300, 200); // added this line

    frame.getContentPane().add(new Main());

    // frame.pack(); // commented this line

    frame.setVisible(true);
}

现在应该可以正常使用。

答案 1 :(得分:1)

       for(int i = 0; i < radius.length; i++)
       {
           for (int j = 0; j < radius.length; j++)
           {

您希望将两个元素的每个配对进行比较的大多数循环都是这样编写的:

       for(int i = 0; i < radius.length; i++)
       {
           for (int j = i; j < radius.length; j++)
           {

(注意第二个循环中的j = i。)

这也允许您删除i != j测试。 :)

编辑:哎呀; j = i表示您仍然需要进行i != j测试 - 如果您使用j = i+1,则可以删除i != j测试。叹。 :)