让java显示超过1个.add()

Question

我已经开始学习基本的 Java，并想重写我曾经用 PHP 编写的游戏地图生成器。我已经让它的一部分工作正常（这只是开始），但是每当我想显示 2 件事（使用 .add()）时，它只会显示其中之一。这是我的代码；

public static void main(String[] args) {
    JFrame m1 = new JFrame();
    Container con = m1.getContentPane();
    Color c = new Color(16, 174, 0);
    con.setBackground(c);
    m1.setSize(mapWidth, mapHeight);
    m1.setTitle("ThomasMosey's Map Generator"); // Window Title
    m1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    m1.add(new User());
    m1.add(new Grid());
    m1.setVisible(true);
}

这只是代码的一部分，但我想知道我在 .add 那里做错了什么。

先感谢您。

---

这是完整的代码；

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JComponent;
import javax.swing.JFrame;

public class Map extends JFrame {
    public static int mapWidth = 576; // The Map's Width
    public static int mapHeight = 598; // The Map's Height
    public static int userX = 1;
    public static int userY = 1;
    private static final long serialVersionUID = 1L;
    public static void main(String[] args) {
        JFrame m1 = new JFrame();
        Container con = m1.getContentPane();
        Color c = new Color(16, 174, 0);
        con.setBackground(c);
        m1.setSize(mapWidth, mapHeight);
        m1.setTitle("ThomasMosey's Map Generator"); // Window Title
        m1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        con.add(new User(), BorderLayout.NORTH);
        con.add(new Grid(), BorderLayout.CENTER);
        m1.setVisible(true);
    }
}
// The Grid system
class Grid extends JComponent {
    private static final long serialVersionUID = 1L;
    public void paint(Graphics g) {
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        Color gridColor = new Color(0, 84, 12);
        g2.setColor(gridColor);
        int i;
        int i2;
        for(i = 50; i <= Map.mapWidth; i += 51) {
            g2.drawLine(0, i, Map.mapWidth, i);
        }
        for(i2 = 50; i2 <= Map.mapHeight; i2 += 51) {
            g2.drawLine(i2, 0, i2, Map.mapHeight);
        }
    }
}
// Drawing the Grid but lower down to give a significant difference to check whether or not it's actually drawing on the JFrame
class User extends JComponent {
    private static final long serialVersionUID = 1L;
    public void paint(Graphics g2) {
        Graphics2D g22 = (Graphics2D) g2;
        g22.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        Color gridColor = new Color(0, 84, 12);
        g22.setColor(gridColor);
        int i22;
        for(i22 = 50; i22 <= 6000; i22 += 53) {
            g22.drawLine(0, i22, Map.mapWidth, i22+1);
        }
    }
}

Answer 1

1. 内容窗格的默认布局是 BorderLayout。
2. 将组件添加到不受约束的边框布局中，最终会出现在 CENTER 中。
3. 边框布局的每一部分只能出现一个组件。

---

所以请尝试这个。

m1.add(new User(), BorderLayout.NORTH);
m1.add(new Grid(), BorderLayout.CENTER);

---

部分问题是自定义组件的默认首选大小为 0x0。尝试这个变体。

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

public class Map extends JFrame {
    public static int mapWidth = 576; // The Map's Width
    public static int mapHeight = 598; // The Map's Height
    public static int userX = 1;
    public static int userY = 1;
    private static final long serialVersionUID = 1L;
    public static void main(String[] args) {
        JFrame m1 = new JFrame();
        Container con = m1.getContentPane();
        Color c = new Color(16, 174, 0);
        con.setBackground(c);
        // bad form - pack() instead
        //m1.setSize(mapWidth, mapHeight);
        m1.setTitle("ThomasMosey's Map Generator"); // Window Title
        m1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        User user = new User();
        user.setPreferredSize(new Dimension(300,300));
        con.add(user, BorderLayout.NORTH);
        Grid grid = new Grid();
        grid.setPreferredSize(new Dimension(600,600));
        con.add(grid, BorderLayout.CENTER);
        m1.pack();
        m1.setVisible(true);
    }
}
// The Grid system
class Grid extends JComponent {
    private static final long serialVersionUID = 1L;
    public void paintComponent(Graphics g) {
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        Color gridColor = new Color(0, 84, 12);
        g2.setColor(gridColor);
        int i;
        int i2;
        for(i = 50; i <= Map.mapWidth; i += 51) {
            g2.drawLine(0, i, Map.mapWidth, i);
        }
        for(i2 = 50; i2 <= Map.mapHeight; i2 += 51) {
            g2.drawLine(i2, 0, i2, Map.mapHeight);
        }
    }
}
// Drawing the Grid but lower down to give a significant difference to check whether or not it's actually drawing on the JFrame
class User extends JComponent {
    private static final long serialVersionUID = 1L;
    public void paintComponent(Graphics g2) {
        Graphics2D g22 = (Graphics2D) g2;
        g22.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        Color gridColor = new Color(0, 84, 12);
        g22.setColor(gridColor);
        int i22;
        for(i22 = 50; i22 <= 6000; i22 += 53) {
            g22.drawLine(0, i22, Map.mapWidth, i22+1);
        }
    }
}

Answer 2

JFrame 的当前布局是 BorderLayout，您将在中心添加这两个组件。尝试改变布局。

Container con = m1.getContentPane();
con.setLayout(new FlowLayout());

或

m1.add(new User(),BorderLayout.NORTH);
m1.add(new Grid(),BorderLayout.CENTER);

编辑：您必须重写 User 的 setPreferredSize() 方法。

class User extends JComponent {
  public java.awt.Dimension getPreferredSize() { 
    return new java.awt.Dimension(100,100);
  }
}

Answer 3

AFAIR，默认情况下，JFrame 的内容窗格仅接受单个子项。你必须
设置并配置一些布局以拥有多个子布局