Java Swing - Repaint() 无法正常工作

我从以下位置获取程序这个话题 https://stackoverflow.com/questions/8693342/drawing-a-simple-line-graph-in-java。我尝试在实时模式下编辑点。我将 MouseMotionListener 添加到构造函数中，并编写一些基本函数来接近鼠标点并编辑该点。当我在构造函数中得到 (x,y) 点时，repaint()工作起来很奇怪。当我得到 (x,y) 点时paintComponent, repaint()根本不起作用。所以，这是在构造函数和中获取 (x,y) 的图像paintComponent。我的错误在哪里？

package simplegrapher2;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Stroke;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import static java.lang.Math.sqrt;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class SimpleGrapher2 extends JPanel {

    private int width = 800;
    private int heigth = 400;
    private int padding = 25;
    private int labelPadding = 25;
    private Color lineColor = new Color(44, 102, 230, 180);
    private Color pointColor = new Color(100, 100, 100, 180);
    private Color gridColor = new Color(200, 200, 200, 200);
    private static final Stroke GRAPH_STROKE = new BasicStroke(2f);
    private int pointWidth = 4;
    private int numberYDivisions = 10;
    private List<Double> scores;
    private static double serieX = 0;
    public List<Point2D.Double> graphPoints;

    public SimpleGrapher2(List<Double> scores) {
        this.scores = scores;
        addMouseMotionListener(new MouseMotionListener() {
            @Override
            public void mouseDragged(MouseEvent me) {
                double x = me.getX();
                double y = me.getY();
                findNearPoint(x, y);
                editSerie(x, y);
                revalidate();
                repaint();
            }

            @Override
            public void mouseMoved(MouseEvent me) {}
        });

        double xScale = ((double) getWidth() - (2 * padding) - labelPadding) / (scores.size() - 1);
        double yScale = ((double) getHeight() - 2 * padding - labelPadding) / (getMaxScore() - getMinScore());

        graphPoints = new ArrayList<>();
        for (int i = 0; i < scores.size(); i++) {
            double x1 = (double) (i * xScale + padding + labelPadding);
            double y1 = (double) ((getMaxScore() - scores.get(i)) * yScale + padding);
            graphPoints.add(new Point2D.Double(x1, y1));
        }
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        /*double xScale = ((double) getWidth() - (2 * padding) - labelPadding) / (scores.size() - 1);
        double yScale = ((double) getHeight() - 2 * padding - labelPadding) / (getMaxScore() - getMinScore());

        graphPoints = new ArrayList<>();
        for (int i = 0; i < scores.size(); i++) {
            double x1 = (double) (i * xScale + padding + labelPadding);
            double y1 = (double) ((getMaxScore() - scores.get(i)) * yScale + padding);
            graphPoints.add(new Point2D.Double(x1, y1));
        }*/

        // draw white background
        g2.setColor(Color.WHITE);
        g2.fillRect(padding + labelPadding, padding, getWidth() - (2 * padding) - labelPadding, getHeight() - 2 * padding - labelPadding);
        g2.setColor(Color.BLACK);

        // create hatch marks and grid lines for y axis.
        for (int i = 0; i < numberYDivisions + 1; i++) {
            int x0 = padding + labelPadding;
            int x1 = pointWidth + padding + labelPadding;
            int y0 = getHeight() - ((i * (getHeight() - padding * 2 - labelPadding)) / numberYDivisions + padding + labelPadding);
            int y1 = y0;
            if (scores.size() > 0) {
                g2.setColor(gridColor);
                g2.drawLine(padding + labelPadding + 1 + pointWidth, y0, getWidth() - padding, y1);
                g2.setColor(Color.BLACK);
                String yLabel = ((int) ((getMinScore() + (getMaxScore() - getMinScore()) * ((i * 1.0) / numberYDivisions)) * 100)) / 100.0 + "";
                FontMetrics metrics = g2.getFontMetrics();
                int labelWidth = metrics.stringWidth(yLabel);
                g2.drawString(yLabel, x0 - labelWidth - 5, y0 + (metrics.getHeight() / 2) - 3);
            }
            g2.drawLine(x0, y0, x1, y1);
        }

        // and for x axis
        for (int i = 0; i < scores.size(); i++) {
            if (scores.size() > 1) {
                int x0 = i * (getWidth() - padding * 2 - labelPadding) / (scores.size() - 1) + padding + labelPadding;
                int x1 = x0;
                int y0 = getHeight() - padding - labelPadding;
                int y1 = y0 - pointWidth;
                if ((i % ((int) ((scores.size() / 20.0)) + 1)) == 0) {
                    g2.setColor(gridColor);
                    g2.drawLine(x0, getHeight() - padding - labelPadding - 1 - pointWidth, x1, padding);
                    g2.setColor(Color.BLACK);
                    String xLabel = i + "";
                    FontMetrics metrics = g2.getFontMetrics();
                    int labelWidth = metrics.stringWidth(xLabel);
                    g2.drawString(xLabel, x0 - labelWidth / 2, y0 + metrics.getHeight() + 3);
                }
                g2.drawLine(x0, y0, x1, y1);
            }
        }

        // create x and y axes 
        g2.drawLine(padding + labelPadding, getHeight() - padding - labelPadding, padding + labelPadding, padding);
        g2.drawLine(padding + labelPadding, getHeight() - padding - labelPadding, getWidth() - padding, getHeight() - padding - labelPadding);

        Stroke oldStroke = g2.getStroke();
        g2.setColor(lineColor);
        g2.setStroke(GRAPH_STROKE);
        for (int i = 0; i < graphPoints.size() - 1; i++) {
            double x1 = graphPoints.get(i).x;
            double y1 = graphPoints.get(i).y;
            double x2 = graphPoints.get(i + 1).x;
            double y2 = graphPoints.get(i + 1).y;
            g2.draw(new Line2D.Double(x1, y1, x2, y2));
        }

        g2.setStroke(oldStroke);
        g2.setColor(pointColor);
        for (int i = 0; i < graphPoints.size(); i++) {
            double x = graphPoints.get(i).x - pointWidth / 2;
            double y = graphPoints.get(i).y - pointWidth / 2;
            int ovalW = pointWidth;
            int ovalH = pointWidth;
            //g2.fillOval(x, y, ovalW, ovalH);
        }
    }

    public void findNearPoint(double x, double y) {
        double delta = 0;
        for (int j = 0; j < graphPoints.size(); j++) {
            double sx = graphPoints.get(j).x;
            double sy = graphPoints.get(j).y;
            double root = sqrt((x-sx)*(x-sx) + (y-sy)*(y-sy));
            if (j == 0) {
                delta = root;
                serieX = sx;
            }
            else if (root < delta) {
                serieX = sx;
                delta = root;
            }
        }
    }

    public void editSerie(double x, double y) {
        double tmpSerieX = serieX;
        int ind = 0;
        for (int i = 0; i < graphPoints.size(); i++) {
            if (graphPoints.get(i).x == tmpSerieX) {
                ind = i;
            }
        }
        graphPoints.remove(ind);
        graphPoints.add(ind, new Point2D.Double(x, y));
        serieX = x;
    }

    private double getMinScore() {
        double minScore = Double.MAX_VALUE;
        for (Double score : scores) {
            minScore = Math.min(minScore, score);
        }
        return minScore;
    }

    private double getMaxScore() {
        double maxScore = Double.MIN_VALUE;
        for (Double score : scores) {
            maxScore = Math.max(maxScore, score);
        }
        return maxScore;
    }

    public void setScores(List<Double> scores) {
        this.scores = scores;
        invalidate();
        this.repaint();
    }

    public List<Double> getScores() {
        return scores;
    }

    private static void createAndShowGui() {
        List<Double> scores = new ArrayList<>();
        Random random = new Random();
        int maxDataPoints = 40;
        int maxScore = 10;
        for (int i = 0; i < maxDataPoints; i++) {
            scores.add((double) random.nextDouble() * maxScore);
        }
        SimpleGrapher2 mainPanel = new SimpleGrapher2(scores);
        mainPanel.setPreferredSize(new Dimension(800, 600));
        JFrame frame = new JFrame("DrawGraph");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

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

当您计算时，问题出在您的构造函数中x/yScale...

public SimpleGrapher2(List<Double> scores) {
    //...
    double xScale = ((double) getWidth() - (2 * padding) - labelPadding) / (scores.size() - 1);
    double yScale = ((double) getHeight() - 2 * padding - labelPadding) / (getMaxScore() - getMinScore());
    //...
}

在构建组件时，组件的大小为0x0。在计算点之前，您需要等到组件以某种有意义的方式调整大小......

这也是有问题的，因为当组件首次在屏幕上实现时，可能会快速连续地多次调整其大小。

我过去所做的是使用 SwingTimer设置为较小的延迟以允许在较小的时间范围内多次调整组件的大小。当一切都安顿下来之后Timer将触发，您可以执行所需的操作，例如...

public SimpleGrapher2(List<Double> scores) {
    //...
    addComponentListener(new ComponentAdapter() {

        private Timer initTimer = new Timer(200, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                initTimer.stop();
                double xScale = ((double) getWidth() - (2 * padding) - labelPadding) / (scores.size() - 1);
                double yScale = ((double) getHeight() - 2 * padding - labelPadding) / (getMaxScore() - getMinScore());

                graphPoints = new ArrayList<>();
                for (int i = 0; i < scores.size(); i++) {
                    double x1 = (double) (i * xScale + padding + labelPadding);
                    double y1 = (double) ((getMaxScore() - scores.get(i)) * yScale + padding);
                    graphPoints.add(new Point2D.Double(x1, y1));
                }
                repaint();
            }
        });

        @Override
        public void componentResized(ComponentEvent e) {
            if (graphPoints == null) {
                initTimer.restart();
            }
        }

    });

}

这一切所做的就是等待，直到计时器之间compoentResized事件超过 200 毫秒（您可以使用此值使其更接近您想要的值，但我发现大约 250 毫秒是合理的延迟）

您将需要更正paintComponent允许graphPoints been null以及。