Question

为什么在下面的代码中JFrame中的按钮没有出现？一切都很好，因为它与我正在研究的教程相同。即使我已经复制并粘贴了教程中的源代码，但它不起作用

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Insets;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JTextArea;
import javax.swing.JToolBar;
import javax.swing.SwingUtilities;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;


public class BorderLayoutExampleII extends JFrame {


    public BorderLayoutExampleII() {

        initUI();
    }

    public final void initUI() {

        JMenuBar menubar = new JMenuBar();
        JMenu file = new JMenu("File");

        menubar.add(file);
        setJMenuBar(menubar);

        JToolBar toolbar = new JToolBar();
        toolbar.setFloatable(false);

        ImageIcon exit = new ImageIcon("exit.png");
        JButton bexit = new JButton(exit);
        bexit.setBorder(new EmptyBorder(0 ,0, 0, 0));
        toolbar.add(bexit);

        add(toolbar, BorderLayout.NORTH);

        JToolBar vertical = new JToolBar(JToolBar.VERTICAL);
        vertical.setFloatable(false);
        vertical.setMargin(new Insets(10, 5, 5, 5));

        ImageIcon select = new ImageIcon("drive.png");
        ImageIcon freehand = new ImageIcon("computer.png");
        ImageIcon shapeed = new ImageIcon("printer.png");

        JButton selectb = new JButton(select);
        selectb.setBorder(new EmptyBorder(3, 0, 3, 0));

        JButton freehandb = new JButton(freehand);
        freehandb.setBorder(new EmptyBorder(3, 0, 3, 0));
        JButton shapeedb = new JButton(shapeed);
        shapeedb.setBorder(new EmptyBorder(3, 0, 3, 0));

        vertical.add(selectb);
        vertical.add(freehandb);
        vertical.add(shapeedb);

        add(vertical, BorderLayout.WEST);

        add(new JTextArea(), BorderLayout.CENTER);

        JLabel statusbar = new JLabel(" Statusbar");
        statusbar.setPreferredSize(new Dimension(-1, 22));
        statusbar.setBorder(LineBorder.createGrayLineBorder());
        add(statusbar, BorderLayout.SOUTH);

        setSize(350, 300);
        setTitle("BorderLayout");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                BorderLayoutExampleII ex = new BorderLayoutExampleII();
                ex.setVisible(true);
            }
        });
    }
}

Answer 1

检查文件exit.png是否与您的程序在同一个文件夹中。您可以通过从按钮中删除imageicon参数来确保加载图像时出现问题，如果按钮显示，则检查exit.png文件是否存在

Answer 2

看看下面的代码，我评论了所有的imageIcon并用简单的字符串替换它们，我得到了输出屏幕

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Insets;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JTextArea;
import javax.swing.JToolBar;
import javax.swing.SwingUtilities;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;

public class BorderLayoutExampleII extends JFrame {

    public BorderLayoutExampleII() {

        initUI();
    }

    public final void initUI() {

        JMenuBar menubar = new JMenuBar();
        JMenu file = new JMenu("File");

        menubar.add(file);
        setJMenuBar(menubar);

        JToolBar toolbar = new JToolBar();
        toolbar.setFloatable(false);

        // ImageIcon exit = new ImageIcon("exit.png");
        JButton bexit = new JButton("Exit");
        bexit.setBorder(new EmptyBorder(0, 0, 0, 0));
        toolbar.add(bexit);

        add(toolbar, BorderLayout.NORTH);

        JToolBar vertical = new JToolBar(JToolBar.VERTICAL);
        vertical.setFloatable(false);
        vertical.setMargin(new Insets(10, 5, 5, 5));

        // ImageIcon select = new ImageIcon("drive.png");
        // ImageIcon freehand = new ImageIcon("computer.png");
        // ImageIcon shapeed = new ImageIcon("printer.png");

        JButton selectb = new JButton("Select");
        selectb.setBorder(new EmptyBorder(3, 0, 3, 0));

        JButton freehandb = new JButton("Freehand");
        freehandb.setBorder(new EmptyBorder(3, 0, 3, 0));
        JButton shapeedb = new JButton("shapeed");
        shapeedb.setBorder(new EmptyBorder(3, 0, 3, 0));

        vertical.add(selectb);
        vertical.add(freehandb);
        vertical.add(shapeedb);

        add(vertical, BorderLayout.WEST);

        add(new JTextArea(), BorderLayout.CENTER);

        JLabel statusbar = new JLabel(" Statusbar");
        statusbar.setPreferredSize(new Dimension(-1, 22));
        statusbar.setBorder(LineBorder.createGrayLineBorder());
        add(statusbar, BorderLayout.SOUTH);

        setSize(350, 300);
        setTitle("BorderLayout");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                BorderLayoutExampleII ex = new BorderLayoutExampleII();
                ex.setVisible(true);
            }
        });
    }
}

图标没有显示在JButton中

2 个答案: