在Java中制作一条数字线以显示一个点，getWidth（）和getHeight（）无法正确校准位置

所以我想制作一个数字线类，我可以用它来显示沿着一个轴的单个点，但是我希望它能够响应它现在所在的容器的大小，并改变它的大小。不幸的是，我无法正确使用getWidth（）和getHeight（）来获取所需的数字行。这是我迄今为止编写的代码：

import javax.swing.*;
import java.awt.*;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;

public class NumberLine extends JPanel {
    private int value;
    private Color green1 = new Color(32, 77, 2);

@Override
public void paintComponent(Graphics g)
{
    Graphics2D g2 = (Graphics2D) g;
    int maxXValue = getWidth();
    int maxYValue = getHeight();
    Line2D.Float xline = new Line2D.Float((float) maxXValue/6, (float) maxYValue/2, (float) maxXValue * (5/6), (float) maxYValue/2);
    Line2D.Float yline = new Line2D.Float( (float) maxXValue/ 2, (float) maxYValue * (9/20), (float) maxXValue/2, (float) maxYValue *(11/20));
    g2.draw(xline);
    g2.draw(yline);
    Ellipse2D.Float cir = new Ellipse2D.Float((float) (maxXValue/10 + (8 * value/1000) * (maxXValue)), (float) (maxYValue/2), 10F, 10F );
    g2.setColor(green1);
    g2.fill(cir);
}


public NumberLine(int val0) {
    value = val0;
}

public static void main(String[] args) {
    JFrame frame = new JFrame();
    frame.setSize(150,100);
    NumberLine num = new NumberLine(5);
    frame.setContentPane(num);
    frame.setVisible(true);

}
}

理想情况下，我想要这样的东西，如果我要做的话

NumberLine num = new NumberLine(5);

我会得到这样的东西：

相反，我得到的是：

---

我认为你的问题是一个基本的几何问题。如果要使圆在直线内居中，则需要从其位置减去一半宽度和高度。就是这样：

Ellipse2D.Float cir = new Ellipse2D.Float(
        (float) (maxXValue / 10 + (8 * value / 1000) * (maxXValue)) - 5,
        (float) (maxYValue / 2) - 5, 10F, 10F);

此外，您正在进行整数除法，这将返回0个您不需要的值。改变

Line2D.Float yline = new Line2D.Float((float) maxXValue / 2, (float) maxYValue * (9 / 20),
        (float) maxXValue / 2, (float) maxYValue * (11 / 20));

到

无关问题：

• 不要忘记调用super的paintComponent方法：

  @Override
  public void paintComponent(Graphics g) {
      super.paintComponent(g); // !! don't forget this!
  

• 并避免在程序中使用“神奇”数字，因为它们会使调试变得困难

• 使用渲染提示平滑图形2D图形：

  // rendering hints to smooth out your drawing
  g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
       RenderingHints.VALUE_ANTIALIAS_ON);
  

• 在EDT上启动Swing GUI：

  SwingUtilities.invokeLater(() -> {
      JFrame frame = new JFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  

例如，类似于：

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Stroke;
import javax.swing.JPanel;

public @SuppressWarnings("serial")
class NumberLine3 extends JPanel {
    private static final double X_GAP = 1.0 / 20.0;
    private static final double MAJOR_TIC_HT = 0.4;
    private static final int PREF_W = 600;
    private static final int PREF_H = 50;
    private static final Stroke MAIN_STROKE = new BasicStroke(5f);
    private static final Stroke MAJOR_TIC_STOKE = new BasicStroke(3f);
    private static final int CIRCLE_WIDTH = 20;
    private static final Color VALUE_COLOR = new Color(32, 230, 2);
    private int maxX;
    private int majorTickCount;
    private int minorTicksPerMajor;
    private double value;

    public NumberLine3(int maxX, int majorTickCount, int minorTicksPerMajor, double value) {
        this.maxX = maxX;
        this.majorTickCount = majorTickCount;
        this.minorTicksPerMajor = minorTicksPerMajor;
        this.value = value;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;

        // rendering hints to smooth out your drawing
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        Graphics2D g2b = (Graphics2D) g2.create(); // so we can change stroke without problems
        g2b.setStroke(MAIN_STROKE);
        int x1 = (int) xValueToScreen(-maxX);
        int y1 = getHeight() / 2;
        int x2 = (int) xValueToScreen(maxX);
        int y2 = y1;
        g2b.drawLine(x1, y1, x2, y2);
        g2b.setStroke(MAJOR_TIC_STOKE);
        for (int i = 0; i <= 2 * majorTickCount; i++) {
            double xVal = ((double) i * maxX) / majorTickCount - maxX;
            x1 = (int) xValueToScreen(xVal);
            x2 = x1;
            double dY1 = getHeight() * (1 - MAJOR_TIC_HT) / 2.0;
            if (i == majorTickCount) {
                dY1 = 0.5 * dY1;
            }
            double dY2 = getHeight() - dY1;
            g2b.drawLine(x1, (int) dY1, x2, (int) dY2);
        }
        g2b.dispose();

        g2.setColor(VALUE_COLOR);
        x1 = (int) (xValueToScreen(value) - CIRCLE_WIDTH / 2.0);
        y1 = (int) (getHeight() - CIRCLE_WIDTH) / 2;
        g2.fillOval(x1, y1, CIRCLE_WIDTH, CIRCLE_WIDTH);
    }

    private double xValueToScreen(double xValue) {
        double gap = getWidth() * X_GAP;
        double scale = (double) (getWidth() - 2 * gap) / (2 * maxX);
        return (xValue + maxX) * scale + gap;
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }

    public double getValue() {
        return value;
    }

    public void setValue(double value) {
        this.value = value;
        repaint();
    }

    public int getMaxX() {
        return maxX;
    }

    public int getMajorTickCount() {
        return majorTickCount;
    }

    public int getMinorTicksPerMajor() {
        return minorTicksPerMajor;
    }
}

---

我认为你的问题是一个基本的几何学问题。如果要使圆在直线内居中，则需要从其位置减去一半宽度和高度。就是这样：

Ellipse2D.Float cir = new Ellipse2D.Float(
        (float) (maxXValue / 10 + (8 * value / 1000) * (maxXValue)) - 5,
        (float) (maxYValue / 2) - 5, 10F, 10F);

此外，您正在进行整数除法，这将返回0个您不需要的值。改变

Line2D.Float yline = new Line2D.Float((float) maxXValue / 2, (float) maxYValue * (9 / 20),
        (float) maxXValue / 2, (float) maxYValue * (11 / 20));

到

无关问题：

• 不要忘记调用super的paintComponent方法：

  @Override
  public void paintComponent(Graphics g) {
      super.paintComponent(g); // !! don't forget this!
  

• 并避免在程序中使用“神奇”数字，因为它们会使调试变得困难

• 使用渲染提示平滑图形2D图形：

  // rendering hints to smooth out your drawing
  g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
       RenderingHints.VALUE_ANTIALIAS_ON);
  

• 在EDT上启动Swing GUI：

  SwingUtilities.invokeLater(() -> {
      JFrame frame = new JFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  

例如，类似于：

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Stroke;
import javax.swing.JPanel;

public @SuppressWarnings("serial")
class NumberLine3 extends JPanel {
    private static final double X_GAP = 1.0 / 20.0;
    private static final double MAJOR_TIC_HT = 0.4;
    private static final int PREF_W = 600;
    private static final int PREF_H = 50;
    private static final Stroke MAIN_STROKE = new BasicStroke(5f);
    private static final Stroke MAJOR_TIC_STOKE = new BasicStroke(3f);
    private static final int CIRCLE_WIDTH = 20;
    private static final Color VALUE_COLOR = new Color(32, 230, 2);
    private int maxX;
    private int majorTickCount;
    private int minorTicksPerMajor;
    private double value;

    public NumberLine3(int maxX, int majorTickCount, int minorTicksPerMajor, double value) {
        this.maxX = maxX;
        this.majorTickCount = majorTickCount;
        this.minorTicksPerMajor = minorTicksPerMajor;
        this.value = value;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;

        // rendering hints to smooth out your drawing
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        Graphics2D g2b = (Graphics2D) g2.create(); // so we can change stroke without problems
        g2b.setStroke(MAIN_STROKE);
        int x1 = (int) xValueToScreen(-maxX);
        int y1 = getHeight() / 2;
        int x2 = (int) xValueToScreen(maxX);
        int y2 = y1;
        g2b.drawLine(x1, y1, x2, y2);
        g2b.setStroke(MAJOR_TIC_STOKE);
        for (int i = 0; i <= 2 * majorTickCount; i++) {
            double xVal = ((double) i * maxX) / majorTickCount - maxX;
            x1 = (int) xValueToScreen(xVal);
            x2 = x1;
            double dY1 = getHeight() * (1 - MAJOR_TIC_HT) / 2.0;
            if (i == majorTickCount) {
                dY1 = 0.5 * dY1;
            }
            double dY2 = getHeight() - dY1;
            g2b.drawLine(x1, (int) dY1, x2, (int) dY2);
        }
        g2b.dispose();

        g2.setColor(VALUE_COLOR);
        x1 = (int) (xValueToScreen(value) - CIRCLE_WIDTH / 2.0);
        y1 = (int) (getHeight() - CIRCLE_WIDTH) / 2;
        g2.fillOval(x1, y1, CIRCLE_WIDTH, CIRCLE_WIDTH);
    }

    private double xValueToScreen(double xValue) {
        double gap = getWidth() * X_GAP;
        double scale = (double) (getWidth() - 2 * gap) / (2 * maxX);
        return (xValue + maxX) * scale + gap;
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }

    public double getValue() {
        return value;
    }

    public void setValue(double value) {
        this.value = value;
        repaint();
    }

    public int getMaxX() {
        return maxX;
    }

    public int getMajorTickCount() {
        return majorTickCount;
    }

    public int getMinorTicksPerMajor() {
        return minorTicksPerMajor;
    }
}

---

谢谢你的回答。问题不是圆的位置，而是直线的位置。我想要一条在中间的水平线，而不是现在的左边，我画的垂直线甚至不在屏幕上。关于你的其他观点，我还有几个问题，什么是EDT？那么，什么是神奇的数字？虽然不必太担心这些神奇的数字，但这听起来像是我可以轻松搜索的东西。@Jenniferl3:啊，我的错。请显示一个更好的ASCII图像或您正试图完成的任务的真实图像。@JenniferHL3:EDT=事件调度线程。主Swing线程，负责关键Swing操作，包括绘制和与用户交互。请参阅：了解更多信息。@JenniferHL3:您正在进行整除运算，如果底部分母大于分子，整除运算将返回0。用双除法或浮除法代替。谢谢。我在原始问题中添加了我希望该程序生成的新图像。理想情况下，轴应位于JFrame的中心。谢谢您的回答。问题不是圆的位置，而是直线的位置。我想要一条在中间的水平线，而不是现在的左边，我画的垂直线甚至不在屏幕上。关于你的其他观点，我还有几个问题，什么是EDT？那么，什么是神奇的数字？虽然不必太担心这些神奇的数字，但这听起来像是我可以轻松搜索的东西。@Jenniferl3:啊，我的错。请显示一个更好的ASCII图像或您正试图完成的任务的真实图像。@JenniferHL3:EDT=事件调度线程。主Swing线程，负责关键Swing操作，包括绘制和与用户交互。请参阅：了解更多信息。@JenniferHL3:您正在进行整除运算，如果底部分母大于分子，整除运算将返回0。用双除法或浮除法代替。谢谢。我在原始问题中添加了我希望该程序生成的新图像。理想情况下，该轴应位于JFrame的中心。请参阅对答案的编辑请参阅对答案的编辑