java - 带有背景图像和 JPanel 的 JFrame

Question

我有以下内容:

public class Frame {

public static void main(String[] args) {

    JFrame frame = new JFrame("Frame Demo");

    Panel panel = new Panel();        

    frame.add(panel);        

    frame.setBounds(250,100,800,500);
    frame.setVisible(true);
}
}

public class Panel extends JPanel {

JButton singlePlayerButton;
JButton multiPlayerButton;

BufferedImage image;

Gui gui;


public Panel() {
    gui = new Gui();
    add(gui);

    try {
        image = ImageIO.read(new File("C:\\Users\\void\\workspace\\BattleShips\\src\\Testumgebung\\background\\battleship_main.jpg"));

    } catch (IOException e) {
        e.getMessage();
        e.printStackTrace();
    }

}

public void paintComponent(Graphics g) {
    g.drawImage(image, 0, 0, this.getWidth(), this.getHeight(), null);
}


JLabel text;
JPanel mainMenuPanel;


private class Gui extends JPanel {

    public Gui() {

    setVisible(true);
    setSize(500, 300);
    setLayout(null);

    mainMenuPanel = new JPanel();

    mainMenuPanel.setLayout(null);
    mainMenuPanel.setBackground(Color.BLUE);
    mainMenuPanel.setBounds(150, 10, 200, 230);
    add(mainMenuPanel);
    mainMenuPanel.setVisible(true);


    singlePlayerButton = new JButton("Single Player");
    singlePlayerButton.setBounds(100,50 , 150, 40);

    singlePlayerButton.setVisible(true);

    mainMenuPanel.add(singlePlayerButton);

    multiPlayerButton = new JButton("Multi Player");
    multiPlayerButton.setBounds(100, 100, 150, 40);

    multiPlayerButton.setVisible(true);
    mainMenuPanel.add(multiPlayerButton);

    repaint();
}

}
}

我只想要一个带有背景图像和单人游戏等按钮的主菜单。我是否必须设置布局，或者是否可以不设置布局。我刚刚开始使用 GUI，您可以从代码中假设。提前致谢...

Answer 1

Do I have to set a Layout or is it possible without one

作为一般经验法则，是的，您应该尽可能使用布局管理器，从长远来看，它会为您节省大量工作。

根据您的代码以及我认为您想要执行的操作，我建议您查看:

• Laying Out Components Within a Container
• How to Use GridBagLayout
• How to Use CardLayout

作为补充建议:

• 不要使用 null 布局，像素完美布局是现代 UI 设计中的一种幻觉。影响组件个体尺寸的因素太多，您无法控制其中任何一个。 Swing 的设计目的是与核心的布局管理器一起工作，放弃这些将导致无穷无尽的问题和问题，您将花费越来越多的时间来尝试纠正
• 永远不要引用src，一旦程序导出，它将不存在。也尽量避免绝对路径，因为不同的计算机会将您的程序放置在不同的位置(并非所有操作系统都有驱动器号的概念)。相反，在您的情况下，您应该使用类似 getClass().getResource("/Testumgebung/background/battleship_main.jpg")
• 作为一般规则，您应该在执行任何自定义绘制之前调用 super.paintComponent。
• 为了显示背景，添加到其中的所有组件都应设为透明 (setOpaque(false))，以便背景可以显示出来。
• 将类(class)划分为职责范围。例如，Panel 应该只管理背景图像，而不应该管理任何其他内容，这意味着将 Gui 添加到 Panel作为一个单独的步骤，而不是Panel初始化的一部分

作为一个概念示例...

import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Color;
import java.awt.Composite;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Frame {

    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                Panel background = new Panel();

                JFrame frame = new JFrame("Testing");
                frame.setContentPane(background);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new Gui());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public static class Panel extends JPanel {

        BufferedImage image;

        public Panel() {
            setLayout(new BorderLayout());
            try {
                image = ImageIO.read(getClass().getResource("/Testumgebung/background/battleship_main.png"));
            } catch (IOException e) {
                e.printStackTrace();
            }

        }

        @Override
        public Dimension getPreferredSize() {
            return image == null ? super.getPreferredSize() : new Dimension(image.getWidth(), image.getHeight());
        }

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawImage(image, 0, 0, this);
        }

    }

    public static class Gui extends JPanel {

        private MainMenuPane mainMenuPane;
        private CardLayout cardLayout;

        public Gui() {

            setOpaque(false);

            setVisible(true);
            cardLayout = new CardLayout();
            setLayout(cardLayout);

            mainMenuPane = new MainMenuPane();
            // Other views

            add(mainMenuPane, "MainMenu");

            cardLayout.show(this, "MainMenu");

        }

    }

    public static class MainMenuPane extends JPanel {

        JButton singlePlayerButton;
        JButton multiPlayerButton;

        JLabel text;

        public MainMenuPane() {

            setLayout(new GridBagLayout());
            setOpaque(false);
            setBackground(Color.BLUE);

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.ipadx = 20;
            gbc.ipady = 20;

            singlePlayerButton = new JButton("Single Player");

            add(singlePlayerButton, gbc);

            multiPlayerButton = new JButton("Multi Player");

            add(multiPlayerButton, gbc);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            // This is faking transparency, so the background color
            // will be see through
            Graphics2D g2d = (Graphics2D) g.create();
            Composite old = g2d.getComposite();
            g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
            g2d.fillRect(0, 0, getWidth(), getHeight());
            g2d.setComposite(old);
        }

    }

}