试图画板

Question

我有一个带有if语句的paintComponent。在每种情况下，应在面板上显示正方形。什么都没有出现。

 @Override
public void paintComponent(Graphics g) {

    //for loop to draw current board
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j <= columns; j++) {

            if (board[i][j] == '.') {
                g.setColor(Color.black);
                g.drawRect((xSize / 5) * i, (ySize / 6) * j, 50, 50);
            }

            if (board[i][j] == '#') {
                g.setColor(Color.magenta);
                g.drawRect((xSize / 5) * i, (ySize / 6) * j, 50, 50);
            }

            if (board[i][j] == '%') {
                g.setColor(Color.orange);
                g.drawRect((xSize / 5) * i, (ySize / 6) * j, 50, 50);
            }

            if (board[i][j] == '@') {
                g.setColor(Color.pink);
                g.drawRect((xSize / 5) * i, (ySize / 6) * j, 50, 50);
            }

        }
    }

}//end of paint component

Answer 1

你有两个问题，

1. 您不应使用幻数，使用您可用的变量。

   g.fillRect(xSize * i, ySize * j, xSize, ySize);
   

2. 不要过度循环列。您应该始终使用<，因为数组从零开始编制索引。

   for (int j = 0; j < columns; j++) {
   



工作示例

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

public class DrawPanel extends JPanel {
    private static final long serialVersionUID = 568117316148341762L;

    private int columns;
    private int rows;
    private int xSize;
    private int ySize;
    private char[][] board;

    public DrawPanel(int columns, int rows, int xSize, int ySize) {
        super();

        this.columns = columns;
        this.rows = rows;
        this.xSize = xSize;
        this.ySize = ySize;
        this.board = new char[rows][columns];

        this.setPreferredSize(new Dimension(columns * xSize, rows * ySize));

        setRandomTiles();
    }

    private void setRandomTiles() {
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                board[i][j] = randTile();
            }
        }
    }

    private char randTile() {
        switch ((int) (Math.random() * 4)) {
            case 0: return '.';
            case 1: return '#';
            case 2: return '%';
            case 3: return '@';
            default: return ' ';
        }
    }

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

        // for loop to draw current board
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                switch (board[i][j]) {
                    case '.':
                        g.setColor(Color.BLACK);
                        break;
                    case '#':
                        g.setColor(Color.MAGENTA);
                        break;
                    case '%':
                        g.setColor(Color.ORANGE);
                        break;
                    case '@':
                        g.setColor(Color.PINK);
                        break;
                }

                g.fillRect(xSize * i, ySize * j, xSize, ySize);
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame f = new JFrame("Draw Panel");
                DrawPanel p = new DrawPanel(30, 30, 10, 10);

                f.setContentPane(p);
                f.pack();
                f.setLocationRelativeTo(null);
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setVisible(true);
            }
        });
    }
}

您可以使用BufferedReader从文件加载电路板。

import java.awt.*;
import java.io.BufferedReader;
import java.io.*;
import javax.swing.*;

public class DrawPanel extends JPanel {
    private static final long serialVersionUID = 568117316148341762L;

    private int cols;
    private int rows;
    private int xSize;
    private int ySize;
    private char[][] board;

    public DrawPanel(int rows, int cols, int xSize, int ySize) {
        super();

        this.rows = rows;
        this.cols = cols;
        this.xSize = xSize;
        this.ySize = ySize;
        this.board = new char[rows][cols];

        init();
        initRandomTiles();
    }

    public DrawPanel(String filename) {
        super();

        try {
            loadBoard(filename);
            init();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    protected void init() {
        this.setPreferredSize(new Dimension(cols * xSize, rows * ySize));
    }

    private void loadBoard(String filename) throws IOException {
        InputStream is = this.getClass().getClassLoader().getResourceAsStream(filename);
        BufferedReader br = new BufferedReader(new InputStreamReader(is, "UTF-8"));

        String[] metadata = br.readLine().split("\\s+");

        this.rows = Integer.parseInt(metadata[0], 10);
        this.cols = Integer.parseInt(metadata[1], 10);
        this.xSize = Integer.parseInt(metadata[2], 10);
        this.ySize = Integer.parseInt(metadata[3], 10);
        this.board = new char[rows][cols];

        int row = 0;
        String line = null;
        while ((line = br.readLine()) != null) {
            board[row++] = line.trim().toCharArray();
        }
    }

    private void initRandomTiles() {
        for (int row = 0; row < rows; row++) {
            for (int col = 0; col < cols; col++) {
                board[row][col] = randTile();
            }
        }
    }

    private char randTile() {
        switch ((int) (Math.random() * 4)) {
            case 0: return '.';
            case 1: return '#';
            case 2: return '%';
            case 3: return '@';
            default: return ' ';
        }
    }

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

        for (int row = 0; row < rows; row++) {
            for (int col = 0; col < cols; col++) {
                switch (board[row][col]) {
                    case '.':
                        g.setColor(Color.BLACK);
                        break;
                    case '#':
                        g.setColor(Color.MAGENTA);
                        break;
                    case '%':
                        g.setColor(Color.ORANGE);
                        break;
                    case '@':
                        g.setColor(Color.PINK);
                        break;
                }

                g.fillRect(xSize * col, ySize * row, xSize, ySize);
            }
        }

        g.dispose();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame f = new JFrame("Draw Panel");
                DrawPanel p = new DrawPanel("resources/board.txt");

                f.setContentPane(p);
                f.pack();
                f.setLocationRelativeTo(null);
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setVisible(true);
            }
        });
    }
}

board.txt

13 19 10 10
...................
.%#######%##@####%.
.#...............#.
.@...............#.
.#...............#.
.#...............#.
.%...............%.
.#...............#.
.#...............#.
.#...............@.
.#...............#.
.%####@##%#######%.
...................