java - 如何根据计算的平均值在 jpanel 中绘制矩形

Question

我有一个 GUI，可以在其中输入数据并计算 5 组不同数据的平均值。它们存储在一个数组中，五个平均值位于五个位置。如何让它在 jpanel 中绘制矩形，使其看起来像这 5 个平均值的图表？

Answer 1

..make it draw rectangles in a jpanel to look like a graph...

假设您正在谈论条形图，

看一下这个例子:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;


import javax.swing.JFrame;
import javax.swing.JPanel;

public class SimpleBarChart extends JPanel {

    private double[] value;
    private String[] languages;
    private String title;

    public SimpleBarChart(double[] val, String[] lang, String t) {
        languages = lang;
        value = val;
        title = t;
    }

    @Override
    public void paintComponent(Graphics graphics) {
        super.paintComponent(graphics);
        if (value == null || value.length == 0) {
            return;
        }
        double minValue = 0;
        double maxValue = 0;
        for (int i = 0; i < value.length; i++) {
            if (minValue > value[i]) {
                minValue = value[i];
            }
            if (maxValue < value[i]) {
                maxValue = value[i];
            }
        }
        Dimension dim = getSize();
        int clientWidth = dim.width;
        int clientHeight = dim.height;
        int barWidth = clientWidth / value.length;
        Font titleFont = new Font("Book Antiqua", Font.BOLD, 15);
        FontMetrics titleFontMetrics = graphics.getFontMetrics(titleFont);
        Font labelFont = new Font("Book Antiqua", Font.PLAIN, 10);
        FontMetrics labelFontMetrics = graphics.getFontMetrics(labelFont);
        int titleWidth = titleFontMetrics.stringWidth(title);
        int q = titleFontMetrics.getAscent();
        int p = (clientWidth - titleWidth) / 2;
        graphics.setFont(titleFont);
        graphics.drawString(title, p, q);
        int top = titleFontMetrics.getHeight();
        int bottom = labelFontMetrics.getHeight();
        if (maxValue == minValue) {
            return;
        }
        double scale = (clientHeight - top - bottom) / (maxValue - minValue);
        q = clientHeight - labelFontMetrics.getDescent();
        graphics.setFont(labelFont);
        for (int j = 0; j < value.length; j++) {
            int valueP = j * barWidth + 1;
            int valueQ = top;
            int height = (int) (value[j] * scale);
            if (value[j] >= 0) {
                valueQ += (int) ((maxValue - value[j]) * scale);
            } else {
                valueQ += (int) (maxValue * scale);
                height = -height;
            }
            graphics.setColor(Color.blue);
            graphics.fillRect(valueP, valueQ, barWidth - 2, height);
            graphics.setColor(Color.black);
            graphics.drawRect(valueP, valueQ, barWidth - 2, height);
            int labelWidth = labelFontMetrics.stringWidth(languages[j]);
            p = j * barWidth + (barWidth - labelWidth) / 2;
            graphics.drawString(languages[j], p, q);
        }
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setSize(350, 300);
        double[] value = new double[5];
        String[] languages = new String[5];
        value[0] = 1;
        languages[0] = "Visual Basic";

        value[1] = 2;
        languages[1] = "PHP";

        value[2] = 3;
        languages[2] = "C++";

        value[3] = 4;
        languages[3] = "C";

        value[4] = 5;
        languages[4] = "Java";
        frame.getContentPane().add(new SimpleBarChart(value, languages,
                "Programming Languages"));

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

<小时/>

另请参阅JFreeChart如果您不介意使用外部库。

您可能需要通过@trashGod 获得的示例:example及其 source code .