Question

我有一个简单的应用程序，显示由平铺图像组成的图片（名为u1，u2，...，u16.jpg）。现在我想添加一些事件，这样我只有在点击适当的按钮时才能显示这些图像。我已经尝试过自己做了，但它没有用。我在哪里做错了什么？

原始代码：

import java.awt.GridLayout;
import javax.swing.*;
import javax.swing.border.BevelBorder;

public class Tiles_2 {

    public static void main(String[] args) {
        final JFrame f = new JFrame("Usmiech");
        JPanel panel = new JPanel(new GridLayout(4, 4, 3, 3));
        JLabel l = new JLabel();

        for (int i = 1; i < 17; i++) {
            String path = "u"+ i+".jpg";
            l = new JLabel(new ImageIcon(path));
            l.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
            panel.add(l);
        }

        f.setContentPane(panel);
        f.setSize(300, 300);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
    }
}

新代码：

import java.awt.GridLayout;
import javax.swing.*;
import javax.swing.border.BevelBorder;
import java.awt.event.*;

public class Zad_8_1 implements ActionListener {

    public void actionPerformed(ActionEvent e) {
        JButton b = (JButton)(e.getSource());
        String i = b.getText();
        b = new JButton(new ImageIcon("u"+i+".jpg"));
    }

    public static void main(String[] args) {
        final JFrame f = new JFrame("Smile");
        JPanel panel = new JPanel(new GridLayout(4, 4, 3, 3));
        JButton l = null;

        for (int i = 1; i < 17; i++) {
            String path = "u"+ i+".jpg";
            l = new JButton(""+i);
            l.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
            l.setSize(53,53);
            panel.add(l);
        }

        f.setContentPane(panel);
        f.setSize(300, 300);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
    }
}

这应该是这样的： this http://img535.imageshack.us/img535/3129/lab8a.jpg

Answer 1

尝试注册按钮以收听如下事件：

 for (int i = 1; i < 17; i++) {
        String path = "u"+ i+".jpg";
        l = new JButton(""+i);
        l.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
        l.setSize(53,53);
        l.addActionListener(this);
        panel.add(l);
    }

Answer 2

您应该只重置图标，而不是重新分配b JButton的新实例：

b.setIcon(new ImageIcon("u"+i+".jpg"));

（看看通过引用传递/通过Java中的值概念传递，well explained here）

最重要的是，您需要遵循Vincent的建议并实际注册所有按钮ActionListener

l.addActionListener(this);

Answer 3

b = new JButton(new ImageIcon("u"+i+".jpg"));

创建一个新按钮并不会使按钮只是位于内存中，因为它尚未添加到GUI中。

简单的解决方案是重置图标：

b.setIcon( new ImageIcon(...) );

Answer 4

您需要使用构造函数来添加事件侦听器。

import java.awt.GridLayout;
import javax.swing.*;
import javax.swing.border.BevelBorder;
import java.awt.event.*;
import java.awt.*;

public class Demo {

    public static void main(String args[]) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                render("Window");
            }
        });
    }

    public static void render(String s){
        JFrame f = new JFrame("Smile");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Pane pan = new Pane();
        f.add(pan);
        f.setSize(300,300);
        f.setVisible(true);
    }
}

    class Pane extends JPanel implements ActionListener {

        Pane(){
            setLayout(new GridLayout(4, 4, 3, 3));
            JButton l = null;
            for (int i = 1; i < 17; i++) {
                l = new JButton(""+i);
                l.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
                l.addActionListener(this);
                l.setSize(53,53);
                add(l);
            }
        }

    public void actionPerformed(ActionEvent e) {
        JButton b = (JButton)(e.getSource());
        String i = b.getText();
        b.setIcon(new ImageIcon("u"+i+".jpg"));
    }
    }

从事件监听器开始

4 个答案: