MouseListener / KeyListener无法正常工作（JPanel） [英] MouseListener/KeyListener not working (JPanel)

问题描述

我正在做一个涉及JPanel中的鼠标和关键监听器的小项目。不幸的是，当我使用鼠标/键盘时，没有一个方法被调用。之前我曾使用过JPanels / JFrame / JApplet和JComponents。代码段如下所示：

I'm doing a little project that involves the mouse and key listeners in JPanel. Unfortunately, none of the methods are called when I use the mouse/keyboard. I have worked with JPanels/JFrame/JApplet and JComponents before. The code snippets are shown below:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.io.File;
import java.io.PrintWriter;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import java.util.Scanner;

public class Hello extends JPanel implements KeyListener, MouseListener{
    JPanel panel = new JPanel();
    JFrame frame = new JFrame();
    public Hello(){
        addKeyListener(this);
        addMouseListener(this);
    }
    public static void main(String [] args){
        Hello play = new Hello();
        play.setPanel();
    }
    public void setPanel(){
        panel.setLayout(null);
        frame.add(panel);
        frame.setLayout(null);
        panel.setBounds(0,0,100,100);
        frame.setVisible(true);
        panel.setVisible(true);
        panel.setFocusable(true);
        frame.setSize(100,100);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    public void keyTyped(KeyEvent evt){
        System.out.println("keytyped");
    }
    public void keyPressed(KeyEvent evt){
        System.out.print("keypressed");
    }
    public void keyReleased(KeyEvent evt){
        System.out.println("keyreleased");
    }
    public void mousePressed(MouseEvent evt){
        System.out.println("mousepressed");
    }
    public void mouseReleased(MouseEvent evt){
        System.out.println("mousereleased");
    }
    public void mouseClicked(MouseEvent evt){
        System.out.println("mouseclicked");
    }
    public void mouseEntered(MouseEvent evt){
        System.out.println("mousenentered");
    }
    public void mouseExited(MouseEvent evt){
        System.out.println("mouseexited");
    }
}

非主题：我一直收到错误
您的帖子似乎包含未正确格式化为代码的代码。请使用代码工具栏按钮或CTRL + K键盘快捷键将所有代码缩进4个空格。有关更多编辑帮助，请单击[？]工具栏图标。
我不知道如何解决它。有时候我把所有内容都放在代码中但仍然无法提交。

Off topic: I keep getting the error Your post appears to contain code that is not properly formatted as code. Please indent all code by 4 spaces using the code toolbar button or the CTRL+K keyboard shortcut. For more editing help, click the [?] toolbar icon. I have no idea how to fix it. Sometimes I put everything in code and it still won't submit.

推荐答案

看看 JFrame的Java KeyListener没有响应？。

您需要为每个 JComponent KeyListener 和 MouseListener $ c>你想收听：

You need to register your KeyListener and MouseListener for every JComponent you want to listen to:

public Hello() {
    addKeyListener(this);
    addMouseListener(this);
    panel.addKeyListener(this);
    panel.addMouseListener(this);
    frame.addKeyListener(this);
    frame.addMouseListener(this);
}

修改：

键和鼠标事件仅从当时具有焦点的 JComponent 中触发。因此，似乎一致认为KeyBindings可能对KeyListeners有利。然而，这两者都有它们的应用，所以这里没有硬性规定。阅读如何编写关键监听器和'如何编写密钥绑定'和'你'得到要点。

Key and mouse events are only fired from the JComponent which has focus at the time. Because of this there seems to be a consensus that KeyBindings may be favorable to KeyListeners. The two have their applications, however, and so there is no hard and fast rule here. Have a read of 'How to Write a Key Listener' and 'How to Write a Key Binding' and you'll get the gist.

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