Question

所以我的问题的关键是在Java中将多个组件绘制成一个JFrame。我试图两次使用相同的组件来绘制两条不同的线，但只出现一条。我在不同的文件中处理三个不同的类，这可能会让我更难。我尝试了可行的解决方案，但无法使用here，here，here，here和其他地方。我怀疑我做错了多次，因为我仍然想要完全理解JFrame，JPanel和LayoutManager s。谁能证明我哪里出错？

我的测试人员课程如下：

import javax.swing.JFrame;

public class TransportSlabTester
{
    public static void main(String[] args)
    {
        System.out.println("Estimation at 100 sections: ");
        TransportSlab slab1 = new TransportSlab(10000,1,5,100);
        System.out.println();

        JFrame frame = new JFrame("Attenuated Profile");
        frame.setSize(600,600);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        TransportSlabGraph component = new TransportSlabGraph();
        //analytical is a method from a 3rd class that returns double[]
        component.attProfileArray(slab1.analytical(),slab1.getThickness());
        frame.add(component);
        component = new TransportSlabGraph();
        //euler is a method from a 3rd class that returns double[]
        component.attProfileArray(slab1.euler(),slab1.getThickness());
        frame.add(component);
        frame.setVisible(true);
    }
}

现在，扩展JPanel的类：

import java.awt.*;
import java.awt.geom.Line2D;
import java.math.*;
import javax.swing.JPanel;

public class TransportSlabGraph extends JPanel
{
    double[] N, xAxes, yAxes;
    final int edge = 100; //Distance from edge of frame
    String[] xlabel = new String[11];
    String[] ylabel = new String[11];

    /**
     *
     * @param inputN Data array of type {@code double[]}
     * @param thickness Thickness set by the original constructor
     */
    public void attProfileArray(double[] inputN, double thickness)
    {
        N = new double[inputN.length];
        //Create labels for the tick marks of the x and y axis from rounded #'s
        BigDecimal bd1, bd2;
        for (int i = 0; i <= 10; i++)
        {
            bd1 = new BigDecimal((thickness/10)*i);
            MathContext mc = new MathContext(2); //Round to one decimal place
            bd2 = bd1.round(mc);
            xlabel[i] = String.valueOf(bd2.doubleValue());
            ylabel[i] = String.valueOf((inputN[0]*i)/(inputN.length-1));
        }
        //Set up data array and the axes
        for (int i = 0; i < N.length; i++)
        {
            N[i]=inputN[i];
            xAxes = new double[N.length];
            yAxes = new double[N.length];
        }
    }
    @Override
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        //Get frame dimensions to scale drawn components
        int w = getWidth();
        int h = getHeight();
        double xInc = (double)(w-2*edge)/(N.length-1);
        double scale = (double)(h-2*edge)/N[0];
        g2.draw(new Line2D.Double(edge, h-edge, w-edge, h-edge)); //draw x axis
        g2.draw(new Line2D.Double(edge, edge, edge, h-edge)); // draw y axis
        //Create evenly spaced tick marks for both axes and label them
        for (int i = 0; i <= 10; i++)
        {
            g2.draw(new Line2D.Double(edge+((w-edge-edge)/10.0)*i, h-edge-10, edge+((w-edge-edge)/10.0)*i, h-edge+10)); //x ticks
            g2.draw(new Line2D.Double(edge-10, h-edge-((h-edge-edge)/10.0)*i, edge+10, h-edge-((h-edge-edge)/10.0)*i)); //y ticks
            g2.drawString(xlabel[i],(int)(edge+((w-edge-edge)/10.0)*i),h-edge+20);
            g2.drawString(ylabel[i],edge-30,(int)(h-edge-((h-edge-edge)/10.0)*i));
        }
        //Scale data and convert to pixel coordinates
        for (int i = 0; i < N.length; i++)
        {
            xAxes[i] = edge+i*xInc;
            yAxes[i] = h-edge-scale*N[i];
        }
        //Only set the data line's color
        g2.setPaint(Color.BLUE);
        //Draw the data as a series of line segments
        for (int i = 1; i < N.length; i++)
        {
            g2.draw(new Line2D.Double(xAxes[i-1],yAxes[i-1],xAxes[i],yAxes[i]));
        }
    }
}

Answer 1

问题＃1

Component的实例只能位于一个Container内（一次）。

您需要为要添加的每个Component创建一个新实例。我会推荐工厂模式......

问题＃2

JFrame，但默认使用BorderLayout，只允许单个组件驻留在每个可用的布局位置。

您也会遇到问题，因为您的TransportSlabGraph课程并没有覆盖它的getPreferredSize方法，这意味着，默认情况下，该组件的实例将提供一个许多布局管理器的默认大小为0x0。

考虑将布局管理器更改为GridLayout以开始。

请查看Laying Out Components Within a Container了解详情

Java JFrame绘制多行

1 个答案:

问题＃1

问题＃2