java - 试图用JPanel画线

我正在尝试使用JPanel画线，但我碰到了一些墙。我可以使两侧朝下，但是一旦涉及到从x线中减去，一切都会出错。

package GUIstuff;
import java.awt.Graphics;
import javax.swing.JPanel;

public class DrawPanel extends JPanel{

public void paintComponent (Graphics g){

    super.paintComponent(g);

    int width = getWidth();
    int height = getHeight();

    int drawCounter = 0; // counters for all the while statements
    int drawCounter2 = 0;
    int drawCounter3 = 0;
    int drawCounter4 = 0;



    int x1 = 0; // cords change with the while statemetns
    int x2 = 0;
    int y1 = 0;
    int y2 = 0;
    while (drawCounter <= 15){ // counter
    y2 = 250;
    g.drawLine(x1, y1, x2, y2);
    x2 = x2 + 15;
    y1 = y1 + 15;
    drawCounter++;  }


    int u1 = 0;
    int u2 = 0;
    int v1 = 0;
    int v2 = 0;
    while (drawCounter2 <= 15){
    u2 = 250;
    g.drawLine(u1, v1, u2, v2);
    u1 = u1 + 15;
    v2 = v2 + 15;
    drawCounter2++;
    }

    int a1 = 0;
    int a2 = 0;
    int b1 = 0;
    int b2 = 0;

    while (drawCounter3 <= 15){
    a2 = 250;
    g.drawLine(a1, b1, a2, b2);
    b1 = b1 + 15;
    a2 = a2 - 15;
    drawCounter3++;

    }
 }
}

这是我的跑步班

package GUIstuff;
import javax.swing.JFrame;


public class DrawPanelTest {

public static void main (String args[]){

    DrawPanel panel = new DrawPanel();

    JFrame application = new JFrame();

    application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    application.add(panel);
    application.setSize (250, 250);
    application.setVisible(true);


}

}

我在左下角和右上角有一条线，但是当我尝试从x中减去时，我得到的线越过了整个框。

最佳答案

在进行自定义绘画时，您应该覆盖getPreferredSize()方法，以便可以按其首选大小显示面板。

绘制线条时，两个变量相同，两个变量不同。适当时使用width / height变量，而不是对数字进行硬编码。在下面的示例中，我做了左侧和底部。底部显示了减法。我让您找出另外两个方面的模式。

另外，我使面板更具动态性，因此可以轻松配置要绘制的线条数和线条之间的间距。

import java.awt.*;
import javax.swing.*;

public class DrawSSCCE extends JPanel
{
    private int lines;
    private int lineGap;

    public DrawSSCCE(int lines, int lineGap)
    {
        this.lines = lines;
        this.lineGap = lineGap;
    }

    @Override
    public Dimension getPreferredSize()
    {
        int size = lines * lineGap;
        return new Dimension(size, size);
    }

    @Override
    public void paintComponent(Graphics g)
    {
        int width = getWidth();
        int height = getHeight();

        //  Draw lines starting from left to bottom

        int x = lineGap;
        int y = 0;

        for (int i = 0; i < lines; i++)
        {
            g.drawLine(0, y, x, height);
            x += lineGap;
            y += lineGap;
        }
        //  Draw lines starting from bottom to right

        x = 0;
        y = height - lineGap;

        for (int i = 0; i < lines; i++)
        {
            g.drawLine(x, height, width, y);
            x += lineGap;
            y -= lineGap;
        }

        //  Draw lines starting from right to top

        //  Draw lines starting from top to left

    }

    private static void createAndShowUI()
    {
        JFrame frame = new JFrame("DrawSSCCE");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add( new DrawSSCCE(15, 15) );
        frame.pack();
        frame.setLocationByPlatform( true );
        frame.setVisible( true );
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowUI();
            }
        });
    }
}