如何在现有绘图上修复绘图

Question

我的DrawPanel出了点问题。我想做一个烤架-它应该用参数来绘制-由用户通过定义行和冒号给出。

例如，我输入3行5个冒号(:)，Swing应该绘制它。主要问题是，如果我在TextField中输入数字并按下绘制按钮，Swing会在旧格栅上绘制新格栅。此外，有时程序无法完成某些行或冒号，我不明白为什么。我已经添加了一些数字，比如rows-6，因为swing绘制的像素比他应该绘制的多了几个像素。也许你也知道这个问题的解决方案。

在这张图上你可以看到太多的线条。我用一条蓝线来表示这些线应该走多远。

​

​

DrawPanel (JPanel)

import java.awt.Graphics;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Serge Junk
 */
public class DrawPanel extends javax.swing.JPanel {

    /**
     * Creates new form DrawPanel
     * 
     */
    private int rows = 1;
    private int cols = 2;
    public DrawPanel() {
        initComponents();
    }

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

         // draw the rows
        int rowHt = (height / rows)-1;
        for (int i = 0; i <= rows; i++){
            g.drawLine(0, i * rowHt, width, i * rowHt);
        }


        // draw the columns
        int rowWid = (width / cols)-1;
        for (int i = 0; i <= cols; i++){
           g.drawLine(i * rowWid, 0, i * rowWid, height);
        }

    }

   public void setRows(int pRows){
       rows = pRows;
   }

    public void setCols(int pCols){
      cols = pCols;
   }
    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        setPreferredSize(new java.awt.Dimension(300, 200));

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 400, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 300, Short.MAX_VALUE)
        );
    }// </editor-fold>                        


    // Variables declaration - do not modify                     
    // End of variables declaration                   
}

MainFrame (JFrame)

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Serge Junk
 */
public class MainFrame extends javax.swing.JFrame {

    /**
     * Creates new form MainFrame
     */
    public MainFrame() {
        initComponents();
    }

    public void updateView()
    {
        drawPanel1.repaint();
    }
    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        drawPanel1 = new DrawPanel();
        jLabel1 = new javax.swing.JLabel();
        rowTextField = new javax.swing.JTextField();
        jLabel2 = new javax.swing.JLabel();
        colsTextField = new javax.swing.JTextField();
        drawButton = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        javax.swing.GroupLayout drawPanel1Layout = new javax.swing.GroupLayout(drawPanel1);
        drawPanel1.setLayout(drawPanel1Layout);
        drawPanel1Layout.setHorizontalGroup(
            drawPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 600, Short.MAX_VALUE)
        );
        drawPanel1Layout.setVerticalGroup(
            drawPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 200, Short.MAX_VALUE)
        );

        jLabel1.setText("Lignes");

        jLabel2.setText("Colonnes");

        drawButton.setText("Draw");
        drawButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                drawButtonActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addGroup(layout.createSequentialGroup()
                        .addContainerGap()
                        .addComponent(jLabel1)
                        .addGap(18, 18, 18)
                        .addComponent(rowTextField, javax.swing.GroupLayout.PREFERRED_SIZE, 95, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(jLabel2)
                        .addGap(18, 18, 18)
                        .addComponent(colsTextField, javax.swing.GroupLayout.PREFERRED_SIZE, 95, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(25, 25, 25)
                        .addComponent(drawButton))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(28, 28, 28)
                        .addComponent(drawPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, 600, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addContainerGap(26, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(41, 41, 41)
                .addComponent(drawPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, 200, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 14, Short.MAX_VALUE)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1)
                    .addComponent(rowTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                        .addComponent(jLabel2)
                        .addComponent(colsTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(drawButton)))
                .addContainerGap())
        );

        pack();
    }// </editor-fold>                        

    private void drawButtonActionPerformed(java.awt.event.ActionEvent evt) {                                           
        //E
        int row = Integer.valueOf(rowTextField.getText());
        int col = Integer.valueOf(colsTextField.getText());
        //T
        drawPanel1.setRows(row);
        drawPanel1.setCols(col);
        //S
        updateView();
    }                                          

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new MainFrame().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JTextField colsTextField;
    private javax.swing.JButton drawButton;
    private DrawPanel drawPanel1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JTextField rowTextField;
    // End of variables declaration                   
}

Answer 1

Netbeans把新的烤架画在了旧的烤架上。

paintComponent()方法中的第一个语句应该是：

super.paintComponent(g);

这将在您进行自定义绘制之前清除背景。

drawPanel1.setRows(row);
drawPanel1.setCols(col);
//S
updateView();

不需要使用updateView()方法。相反，setRows(...)和setCols(...)方法都应该直接调用repaint()。也就是说，当组件的属性发生更改时，组件有责任重新绘制自身。

有时程序不能完成某些行或冒号，我不明白为什么。

int rowHt = height / rows-1;

使用公式时要明确，这样我们才能确切地知道您想要什么，而不是依赖于编译器。所以你应该使用：

int rowHt = (height / rows) - 1;

不要害怕为你的参数创建变量：

//g.drawLine(i * rowWid, 0, i * rowWid, height-5);
int xOffset = i * rowWidth;
int yEnd = height - 5;
g.drawLine(xOffset, 0, xOffset, yEnd);

这样，您就可以轻松地添加调试代码，以准确地查看用于绘制直线的值：

System.out.println(xOffset + " : " + yEnd);

现在，您应该能够确定您的逻辑是否正确。

Answer 2

因此，正如camickr建议的那样，您不应该将任何隐藏变量添加到分区或行/高或cols /宽度，因为这是维护的噩梦。远离神奇的价值观！

DrawPanel.paintComponent必须做一些事情。

1. 不要忘记调用super()！
2. 您需要确定线条粗细，以便知道要偏移多少。
3. 将单位保留为浮点值，直到您需要将其设置为integers.
4. Dispose。

此外，您不希望在它们的声明中设置实例变量，而是通过某种构造函数来设置。

另外，我添加了另外两个字段来控制线条宽度和颜色，如下所示。我还重新设计了布局，以便从代码维护的角度来看，它实际上是可读的。

​

​

​

​

跑步者

package question58310987;

import javax.swing.*;

public class Runner {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new MainFrame();

                setLookAndFeel(frame);

                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setVisible(true);
            }
        });
    }

    private static void setLookAndFeel(JFrame frame) {
        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
            SwingUtilities.updateComponentTreeUI(frame);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (UnsupportedLookAndFeelException e) {
            e.printStackTrace();
        }
    }
}

DrawPanel

package question58310987;

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

public class DrawPanel extends JPanel {
    private static final long serialVersionUID = 1889951852010548809L;

    private int rows;
    private int cols;
    private int thickness;
    private Color fgColor;
    private Color bgColor;

    private boolean dirty;
    private Stroke strokeRef;

    public DrawPanel() {
        this(3, 3);
    }

    public DrawPanel(int rows, int cols) {
        this(rows, cols, 1, Color.BLACK, null);
    }

    public DrawPanel(int rows, int cols, int thickness, Color fgColor, Color bgColor) {
        super();
        this.rows = rows;
        this.cols = cols;
        this.thickness = thickness;
        this.fgColor = fgColor;
        this.bgColor = bgColor;

        this.dirty = true; // initialized as true
    }

    private float getStrokeThickness(Graphics2D g2d) {
        Stroke stroke = g2d.getStroke();

        if (stroke instanceof BasicStroke) {
            return ((BasicStroke) stroke).getLineWidth();
        }

        return 1.0f;
    }

    /**
     * Re-evaluates the state of the properties.
     */
    protected void commitProperties(Graphics2D g2d) {
        if (dirty) {
            strokeRef = new BasicStroke(this.thickness);
            dirty = false;
        }
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        Graphics2D g2d = (Graphics2D) g;

        commitProperties(g2d);

        g2d.setStroke(strokeRef);

        float lineSize = getStrokeThickness(g2d); // Calculate line thickness
        float halfStroke = lineSize > 2.0f ? lineSize / 2.0f : 1.0f;
        int width = this.getWidth();
        int height = this.getHeight();
        int maxWidth = (int) (width - halfStroke);
        int maxHeight = (int) (height - halfStroke);
        float yOffset = (((float) maxHeight - halfStroke) / (rows));
        float xOffset = (((float) maxWidth - halfStroke) / (cols));

        if (bgColor != null) {
            g2d.setColor(bgColor);
            g2d.fillRect(0, 0, getWidth(), getHeight());
        }

        g2d.setColor(fgColor);

        // Draw the horizontal lines
        for (int row = 0; row < rows; row++) {
            int y = (int) (row * yOffset + halfStroke);
            g2d.drawLine((int) halfStroke, y, maxWidth, y);
        }
        g2d.drawLine((int) halfStroke, maxHeight, maxWidth, maxHeight); // Draw the final horizontal line

        // Draw the vertical lines
        for (int col = 0; col < cols; col++) {
            int x = (int) (col * xOffset + halfStroke);
            g2d.drawLine(x, (int) halfStroke, x, maxHeight);
        }
        g2d.drawLine(maxWidth, (int) halfStroke, maxWidth, maxHeight); // Draw the final vertical line

        g2d.dispose(); // Clear changes
    }

    public String getFgColorHex() {
        return String.format("#%02X%02X%02X", fgColor.getRed(), fgColor.getGreen(), fgColor.getBlue());
    }

    public int getRows() {
        return rows;
    }

    public void setRows(int rows) {
        this.rows = rows;
    }

    public int getCols() {
        return cols;
    }

    public void setCols(int cols) {
        this.cols = cols;
    }

    public int getThickness() {
        return thickness;
    }

    public void setThickness(int thickness) {
        this.thickness = thickness;
        this.dirty = true;
    }

    public Color getFgColor() {
        return fgColor;
    }

    public void setFgColor(Color fgColor) {
        this.fgColor = fgColor;
    }

    public Color getBgColor() {
        return bgColor;
    }

    public void setBgColor(Color bgColor) {
        this.bgColor = bgColor;
    }
}

MainFrame

package question58310987;

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

public class MainFrame extends JFrame {
    private static final long serialVersionUID = -2796976952328960949L;
    private static final String DEFAULT_APP_TITLE = "Main Frame";

    private DrawPanel drawPanel;

    private JLabel rowLabel;
    private JTextField rowTextField;

    private JLabel colLabel;
    private JTextField colTextField;

    private JLabel thicknessLabel;
    private JTextField thicknessTextField;

    private JLabel colorLabel;
    private JTextField colorTextField;

    private JButton drawButton;

    public MainFrame() {
        this(DEFAULT_APP_TITLE);
    }

    public MainFrame(String title) {
        super(title);

        initialize();
        addChildren();
    }

    protected void initialize() {
        drawPanel = new DrawPanel();
        drawPanel.setThickness(6);
        drawPanel.setFgColor(Color.BLUE);
        drawPanel.setPreferredSize(new Dimension(600, 200));

        rowLabel = new JLabel("Rows");
        rowTextField = new JTextField(Integer.toString(drawPanel.getRows()), 3);

        colLabel = new JLabel("Columns");
        colTextField = new JTextField(Integer.toString(drawPanel.getCols()), 3);

        thicknessLabel = new JLabel("Thickness");
        thicknessTextField = new JTextField(Integer.toString(drawPanel.getThickness()), 3);

        colorLabel = new JLabel("Color");
        colorTextField = new JTextField(drawPanel.getFgColorHex(), 6);

        drawButton = new JButton("Draw");
        drawButton.addActionListener(evt -> drawButtonActionPerformed(evt));
    }

    protected void addChildren() {
        GridBagLayout verticalLayout = new GridBagLayout();
        GridBagConstraints gbc = new GridBagConstraints();

        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.insets = new Insets(16, 16, 16, 16); // top, left, bottom, right

        getContentPane().setLayout(verticalLayout);
        getContentPane().add(drawPanel, gbc);

        FlowLayout horizontalLayout = new FlowLayout();
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(horizontalLayout);

        buttonPanel.add(rowLabel);
        buttonPanel.add(rowTextField);
        buttonPanel.add(Box.createHorizontalStrut(30));

        buttonPanel.add(colLabel);
        buttonPanel.add(colTextField);
        buttonPanel.add(Box.createHorizontalStrut(30));

        buttonPanel.add(thicknessLabel);
        buttonPanel.add(thicknessTextField);
        buttonPanel.add(Box.createHorizontalStrut(30));

        buttonPanel.add(colorLabel);
        buttonPanel.add(colorTextField);
        buttonPanel.add(Box.createHorizontalStrut(30));

        buttonPanel.add(drawButton);

        gbc.gridx = 0;
        gbc.gridy = 1;
        gbc.insets = new Insets(0, 16, 16, 16); // top, left, bottom, right

        getContentPane().add(buttonPanel, gbc);
    }

    private void drawButtonActionPerformed(ActionEvent evt) {
        int row = Integer.valueOf(rowTextField.getText().trim());
        int col = Integer.valueOf(colTextField.getText().trim());
        int thickness = Integer.valueOf(thicknessTextField.getText().trim());
        String colorHex = colorTextField.getText().trim();

        drawPanel.setRows(row);
        drawPanel.setCols(col);
        drawPanel.setThickness(thickness);
        drawPanel.setFgColor(hexToColor(colorHex));

        this.updateView();
    }

    public void updateView() {
        drawPanel.repaint();
    }

    /**
     * Supports both #FF0000 and #F00 formats.
     * 
     * @param hex a hexadecimal color value from #000000 -> #FFFFFF
     * @return
     */
    public static final Color hexToColor(String hex) {
        if (hex.startsWith("#")) {
            hex = hex.replace("#", "");
        }
        if (hex.length() == 3) {
            hex = splicePad(hex, 2);
        }
        int v = Integer.parseInt(hex, 16);
        int r = (v & 0xFF0000) >> 16;
        int g = (v & 0xFF00) >> 8;
        int b = (v & 0xFF);
        return new Color(r, g, b);
    }

    /**
     * Splices each character after itself n-number of times. 
     */
    public static final String splicePad(String str, final int repeat) {
        StringBuffer buff = new StringBuffer();

        for (char ch : str.toCharArray()) {
            for (int i = 0; i < repeat; i++) {
                buff.append(ch);
            }
        }

        return buff.toString();
    }
}