如何将关键侦听器添加到 JFrame？

【问题标题】：How to add Key Listener to JFrame?如何将关键侦听器添加到 JFrame？
【发布时间】：2016-06-02 00:53:26
【问题描述】：

我正在尝试用我的按键控制火箭动画并尝试使用 KeyListener 方法，但是，我的程序对我的按键没有反应。我尝试将 keylistener 添加到我的 JFrame 但它没有调用它，因为 JFrame 是一个单独的静态方法。如果你运行它，你将没有图像，但是如果你运行，请用矩形替换。你能告诉我的错误吗？提前致谢。

这是我的代码：

import java.awt.*;
import hsa.Console;
import javax.imageio.*;
import java.io.*;

import java.awt.Graphics;
import java.awt.Color;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyListener;
import java.awt.event.KeyEvent;

import javax.swing.*;
import javax.swing.JPanel;
import javax.swing.JFrame;
import javax.swing.Timer;

import java.util.Arrays;

public class MA_RocketLauncher extends JPanel implements ActionListener, KeyListener
{

    static Console c;

    //***********************************Main Program*********************************

    public static void main (String[] args)
    {

        c = new Console (27, 85);

        MainProgram ();

    }

    //********************************JFrame******************************************

    public static void JFrame()
    {

        JFrame jf = new JFrame();

        MA_RocketLauncher r = new MA_RocketLauncher();

        jf.setSize(692, 542);
        jf.setTitle("Rocket Launcher");
        jf.setVisible(true);
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setResizable(false);
        jf.add(r);

    }

    //********************************All Methods*************************************

    public static void MainProgram ()
    {

        //IntroMessage();
        //Password();

        JFrame ();

    }

    //***********************************Timer****************************************

    Timer t = new Timer(12, this);

    int y = 240, velY = 0, y2 = 300, velY2 = 0, x = 20, velX = 0, x2 = -5, velX2 = 0, y3 = -5, velY3 = 0,
        y4 = -5, velY4 = 0;

    //*********************************Rocket*****************************************

    public void paintComponent (Graphics c)
    {  

        super.paintComponent (c);

        Color darkGrey = new Color (32, 32, 32);

        c.setColor (darkGrey);
        c.fillRect (0, 0, 700, 550);

        c.setColor (Color.black);
        c.drawRect (18, 0, 639, 379);

        Image picture3 = loadImage ("Canada.png");
        c.drawImage (picture3, 19, 1, null);

        Font f2 = new Font ("Monaco", Font.BOLD, 20);

        c.setColor (Color.white);
        c.setFont (f2);

        c.drawString ("LIVE VIEW", 550, 25);

        Font f = new Font ("Courier New", Font.BOLD, 30);

        c.setColor (Color.red);
        c.setFont (f);

        c.drawString ("Status: ", 30, 420);

        c.setColor (Color.green);

        c.drawString ("        Launching!", 30, 420);

        Font f3 = new Font ("Courier New", Font.BOLD, 25);

        c.setFont (f3);

        c.drawString ("Clearance Level 1 Achieved", 30, 460);
        c.drawString ("ETA: 30 seconds", 30, 500);

        Image picture2 = loadImage ("circle_flag_us_america_united_states-512.png");
        c.drawImage (picture2, 627, 475, null);

        Font f1 = new Font ("Courier New", Font.BOLD, 12);

        c.setColor (Color.green);
        c.setFont (f1);

        c.drawString ("Property of the United States government", 340, 490);
        c.drawString ("Confidential Information", 450, 505);

        Image picture4 = loadImage ("RocketUp.png");

        c.drawImage (picture4, 100, y, null);
        c.drawImage (picture4, 500, y, null);

        t.start ();

        addKeyListener(this);

        setFocusable(true);

        setFocusTraversalKeysEnabled(false);

        if (y < -130)
        {

            c.setColor (darkGrey);
            c.fillRect (0, 0, 700, 550);

            c.setColor (Color.black);
            c.drawRect (18, 0, 639, 379);

            Image picture5 = loadImage ("Sky.png");

            c.drawImage (picture5, 19, 1, null);

            Image picture6 = loadImage ("RocketUpMedium.png");

            c.drawImage (picture6, 100, y2, null);
            c.drawImage (picture6, 500, y2, null);

            c.setColor (Color.white);
            c.setFont (f2);

            c.drawString ("LIVE VIEW", 550, 25);

            c.setColor (Color.red);
            c.setFont (f);

            c.drawString ("Status: ", 30, 420);

            c.setColor (Color.green);

            c.drawString ("        Launched!", 30, 420);

            c.setFont (f3);

            c.drawString ("Clearance Level 2 Achieved", 30, 460);
            c.drawString ("ETA: 20 seconds", 30, 500);

            c.drawImage (picture2, 627, 475, null);

            c.setColor (Color.green);
            c.setFont (f1);

            c.drawString ("Property of the United States government", 340, 490);
            c.drawString ("Confidential Information", 450, 505);

            if (y2 < -130)
            {

                c.setColor (darkGrey);
                c.fillRect (0, 0, 700, 550);

                c.setColor (Color.black);
                c.drawRect (18, 0, 639, 379);

                c.setFont (f2);
                c.setColor (Color.white);

                c.drawString ("LIVE VIEW", 550, 25);

                c.setColor (Color.red);
                c.setFont (f);

                c.drawString ("Status: ", 30, 420);

                c.setColor (Color.green);

                c.drawString ("        En Route!", 30, 420);

                c.setFont (f3);

                c.drawString ("Clearance Level 3 Achieved", 30, 460);
                c.drawString ("ETA: 10 seconds", 30, 500);

                c.drawImage (picture2, 627, 475, null);

                c.setColor (Color.green);
                c.setFont (f1);

                c.drawString ("Property of the United States government", 340, 490);
                c.drawString ("Confidential Information", 450, 505);

                Image picture7 = loadImage ("Space.jpg");

                c.drawImage (picture7, 19, 1, null);

                c.setFont (f2);
                c.setColor (Color.white);

                c.drawString ("LIVE VIEW", 550, 25);

                Image picture8 = loadImage ("Earth.png");

                c.drawImage (picture8, 19, 1, null);

                Image picture9 = loadImage ("RocketRightSmall.png");

                c.drawImage (picture9, x, 100, null);
                c.drawImage (picture9, x, 200, null);

                c.setColor (darkGrey);
                c.fillRect (658, 0, 40, 379);

                if (x > 658)
                {

                    c.setColor (darkGrey);
                    c.fillRect (0, 0, 700, 550);

                    c.setColor (Color.black);
                    c.drawRect (18, 0, 639, 379);

                    c.drawImage (picture7, 19, 1, null);

                    c.setFont (f2);
                    c.setColor (Color.white);

                    c.drawString ("LIVE VIEW", 550, 25);

                    c.setColor (Color.red);
                    c.setFont (f);

                    c.drawString ("Status: ", 30, 420);

                    c.setColor (Color.green);

                    c.drawString ("        Arriving!", 30, 420);

                    c.setFont (f3);

                    c.drawString ("Clearance Level 4 Achieved", 30, 460);
                    c.drawString ("ETA: 5 seconds", 30, 500);

                    c.drawImage (picture2, 627, 475, null);

                    c.setColor (Color.green);
                    c.setFont (f1);

                    c.drawString ("Property of the United States government", 340, 490);
                    c.drawString ("Confidential Information", 450, 505);

                    Image picture10 = loadImage ("Moon.png");

                    c.drawImage (picture10, 400, 100, null);

                    c.drawImage (picture9, x2, 100, null);
                    c.drawImage (picture9, x2, 200, null);

                    c.setColor (darkGrey);
                    c.fillRect (0, 0, 19, 379);

                    if (x2 > 450)
                    {

                        c.setColor (darkGrey);
                        c.fillRect (0, 0, 700, 550);

                        c.setColor (Color.black);
                        c.drawRect (18, 0, 639, 379);

                        c.drawImage (picture7, 19, 1, null);

                        c.setFont (f2);
                        c.setColor (Color.white);

                        c.drawString ("LIVE VIEW", 550, 25);

                        Image picture11 = loadImage ("MoonBig.png");

                        c.drawImage (picture11, 150, 250, null);

                        c.setColor (darkGrey);
                        c.fillRect (0, 380, 700, 170);

                        c.drawImage (picture2, 627, 475, null);

                        c.setColor (Color.green);
                        c.setFont (f1);

                        c.drawString ("Property of the United States government", 340, 490);
                        c.drawString ("Confidential Information", 450, 505);

                        c.setColor (Color.red);
                        c.setFont (f);

                        c.drawString ("Status: ", 30, 420);

                        c.setColor (Color.green);

                        c.drawString ("        Landing!", 30, 420);

                        c.setFont (f3);

                        c.drawString ("Clearance Level 5 Achieved", 30, 460);
                        c.drawString ("ETA: 2.5 seconds", 30, 500);

                        c.drawImage (picture6, 290, y3, null);
                        c.drawImage (picture6, 390, y3, null);

                        if (y3 > 290)
                        {

                            c.setColor (darkGrey);
                            c.fillRect (0, 0, 700, 550);

                            c.setColor (Color.black);
                            c.drawRect (18, 0, 639, 379);

                            Image picture12 = loadImage ("MoonSurface.jpg");
                            c.drawImage (picture12, 19, 1, null);

                            c.setFont (f2);
                            c.setColor (Color.white);

                            c.drawString ("LIVE VIEW", 550, 25);

                            c.drawImage (picture2, 627, 475, null);

                            c.setColor (Color.green);
                            c.setFont (f1);

                            c.drawString ("Property of the United States government", 340, 490);
                            c.drawString ("Confidential Information", 450, 505);

                            c.setColor (Color.red);
                            c.setFont (f);

                            c.drawString ("Status: ", 30, 420);

                            c.setColor (Color.green);

                            c.drawString ("        Taxi!", 30, 420);

                            c.setFont (f3);

                            c.drawString ("Clearance Level 6 Achieved", 30, 460);
                            c.drawString ("ETA: 1 second", 30, 500);

                            c.drawImage (picture4, 100, y4, null);
                            c.drawImage (picture4, 500, y4, null);

                            if (y4 > 260)
                            {

                                c.setColor (darkGrey);
                                c.fillRect (0, 0, 700, 550);

                                c.setColor (Color.black);
                                c.drawRect (18, 0, 639, 379);

                                c.drawImage (picture12, 19, 1, null);

                                c.setFont (f2);
                                c.setColor (Color.white);

                                c.drawString ("LIVE VIEW", 550, 25);

                                c.drawImage (picture2, 627, 475, null);

                                c.setColor (Color.green);
                                c.setFont (f1);

                                c.drawString ("Property of the United States government", 340, 490);
                                c.drawString ("Confidential Information", 450, 505);

                                c.setColor (Color.red);
                                c.setFont (f);

                                c.drawString ("Status: ", 30, 420);

                                c.setColor (Color.green);

                                c.drawString ("        Landed!", 30, 420);

                                c.setFont (f3);

                                c.drawString ("Clearance Level 7 Achieved", 30, 460);
                                c.drawString ("ETA: 0 seconds", 30, 500);

                                c.drawImage (picture4, 100, 260, null);
                                c.drawImage (picture4, 500, 260, null);

                                c.setColor(Color.green);

                                Font f4 = new Font ("Monaco", Font.BOLD, 100);
                                c.setFont(f4);

                                c.drawString("SUCCESS", 90, 200);

                            }

                        }

                    }

                }

            }

        }

    }   

    //********************************Action Listener Method**************************

    public void actionPerformed (ActionEvent e)
    {

        if (y < -130)
        {
            y2 = y2 - velY2;

            if (y2 < -130)
            {
                x = x + velX;

                if (x > 658)
                {

                    x2 = x2 + velX2;

                    if (x2 > 450)
                    {

                        y3 = y3 + velY3;

                        if (y3 > 290)
                        {

                            y4 = y4 + velY4;

                        }

                    }

                }

            }

        }

        y = y - velY;

        repaint();

    }

    //******************************Key Listener Method*******************************

    public void keyPressed (KeyEvent e)
    {

        int c = e.getKeyCode();

        if (c == KeyEvent.VK_LEFT)
        {

            velX = -1;

            velX2 = -1;

            velY = 0;

            velY2 = 0;

            velY3 = 0;

            velY4 = 0;

        }

        if (c == KeyEvent.VK_UP)
        {

            velY = -1;

            velY2 = -1;

            velY3 = -1;

            velY4 = -1;

            velX = 0;

            velX2 = 0;

        }

        if (c == KeyEvent.VK_RIGHT)
        {

            velX = +1;

            velX2 = +1;

            velY = 0;

            velY2 = 0;

            velY3 = 0;

            velY4 = 0;

        }

        if (c == KeyEvent.VK_DOWN)
        {

            velY = +1;

            velY2 = +1;

            velY3 = +1;

            velY4 = +1;

            velX = 0;

            velX2 = 0;

        }

    }

    public void keyTyped(KeyEvent e){}

    public void keyReleased(KeyEvent e){}

    //********************************Image Loader Method*****************************

    public static Image loadImage (String name)
    {

        Image img = null;

        try
        {

            img = ImageIO.read (new File (name));

        }

        catch (IOException e)
        {

        }

        return img;

    }

【问题讨论】：

    标签： java swing jframe keylistener


    【解决方案1】：

    paintComponent(...) 只能用于绘画。它不应该：

    1. 读取图片文件
    2. 设置面板属性：setFocusable(..), setFocusKeysEnabled(...)
    3. 向面板添加监听器：addKeyListener(...)

    以上所有代码在构造函数中都应该是 ONCE。

    每次 repaint() 完成时都会调用 paintComponent() 方法，因此您不想继续阅读图像或添加侦听器。

    您发布的代码太多，无法查看。当您遇到问题时，发布正确的SSCCE 来说明问题。

    侦听器不起作用的通常原因是面板没有焦点。

    常见的解决方案是使用Key Bindings，而不是KeyListener。阅读 HOw to Use Key Bindings 上的 Swing 教程部分了解更多信息。

    【讨论】：

      【解决方案2】：

      所以我做错了将计时器和关键命令放在疼痛组件中，所以我所要做的就是创建一个公共类并将我的命令放在那里。我还从主程序中加载了图像，并在绘图组件中调用它们，如上述答案所述。

      这是我工作代码的一部分：

          import java.awt.*;
    import hsa.Console;
    import javax.imageio.*;
    import java.io.*;

    import java.awt.Graphics;
    import java.awt.Color;

    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.awt.event.KeyListener;
    import java.awt.event.KeyEvent;

    import javax.swing.*;
    import javax.swing.JPanel;
    import javax.swing.JFrame;
    import javax.swing.Timer;

    import java.util.Arrays;

    public class MA_RocketLauncher extends JPanel implements ActionListener, KeyListener
    {

        static Console c;

        //***********************************Main Program*********************************

        public static void main (String[] args)
        {

            c = new Console (27, 85);

            MainProgram ();

        }

        //********************************JFrame******************************************

        public static void JFrame()
        {

            JFrame jf = new JFrame();

            MA_RocketLauncher r = new MA_RocketLauncher();

            jf.setSize(692, 542);
            jf.setTitle("Rocket Launcher");
            jf.setVisible(true);
            jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            jf.setResizable(false);
            jf.add(r);

        }

        //********************************All Methods*************************************

        public static void MainProgram ()
        {

            //IntroMessage();
            //Password();

            JFrame ();

        }

        //***********************************Timer****************************************

        Timer t = new Timer(10, this);

        int y = 240, velY = 0, y2 = 300, velY2 = 0, x = 20, velX = 0, x2 = -5, velX2 = 0, y3 = -5, velY3 = 0,
            y4 = -5, velY4 = 0;

        public MA_RocketLauncher()
        {

            t.start ();

            addKeyListener(this);

            setFocusable(true);

            setFocusTraversalKeysEnabled(false);

        }

        //**********************************Images****************************************

        Image picture2 = loadImage ("circle_flag_us_america_united_states-512.png");

        Image picture3 = loadImage ("Canada.png");

        Image picture4 = loadImage ("RocketUp.png");

        Image picture5 = loadImage ("Sky.png");

        Image picture6 = loadImage ("RocketUpMedium.png");

        Image picture7 = loadImage ("Space.jpg");

        Image picture8 = loadImage ("Earth.png");

        Image picture9 = loadImage ("RocketRightSmall.png");

        Image picture10 = loadImage ("Moon.png");

        Image picture11 = loadImage ("MoonBig.png");

        Image picture12 = loadImage ("MoonSurface.jpg");

        //*********************************Rocket*****************************************

        public void paintComponent (Graphics c)
        {  

            super.paintComponent (c);

            //Graphics

        }   

        //********************************Action Listener Method**************************

        public void actionPerformed (ActionEvent e)
        {

            if (y < -130)
            {
                y2 = y2 - velY2;

                if (y2 < -130)
                {
                    x = x + velX;

                    if (x > 658)
                    {

                        x2 = x2 + velX2;

                        if (x2 > 450)
                        {

                            y3 = y3 + velY3;

                            if (y3 > 290)
                            {

                                y4 = y4 + velY4;

                            }

                        }

                    }

                }

            }

            y = y - velY;

            repaint();

        }

        //******************************Key Listener Method*******************************

        public void keyPressed (KeyEvent e)
        {

            int c = e.getKeyCode();

            if (c == KeyEvent.VK_LEFT)
            {

                velX = -1;

                velX2 = -1;

            }

            if (c == KeyEvent.VK_UP)
            {

                if (y < -130)
                {

                    y = -1000;

                }

                else 
                {

                    velY = 1;

                }

                if (y2 < -130)
                {

                    y2 = -1000;

                }

                else
                {

                    velY2 = 1;

                }

                velY3 = -1;

                velY4 = -1;

            }

            if (c == KeyEvent.VK_RIGHT)
            {

                velX = +1;

                velX2 = +1;

            }

            if (c == KeyEvent.VK_DOWN)
            {

                velY = -1;

                velY2 = -1;

                velY3 = +1;

                velY4 = +1;

            }

        }

        public void keyTyped(KeyEvent e){}

        //*****************************Key Released Method********************************

        public void keyReleased(KeyEvent e)
        {

            velX = 0;

            velX2 = 0;

            velY = 0;

            velY2 = 0;

            velY3 = 0;

            velY4 = 0;

        }
}

      【讨论】：

      • So what I was doing wrong was putting the timer and key commands inside the pain component - 这正是另一个答案告诉你不要做的事情。所以另一个答案给了你解决问题的方法。那么为什么你不接受这个答案，因为它为你提供了解决问题所需的信息？
      猜你喜欢
      • 1970-01-01
      • 2013-06-29
      • 1970-01-01
      • 1970-01-01
      • 2021-08-10
      • 2017-04-06
      • 2016-08-21
      • 2022-08-03
      • 1970-01-01
      相关资源
      最近更新 更多
      热门标签
      Java Python linux javascript Mysql C# Docker 算法 前端 SpringBoot Redis Vue spring 设计模式 .net core .net kubernetes c++ 数据库 数据结构 大数据 js 机器学习 微服务 Android Go 程序员 面试 JVM ASP.net core 云原生 人工智能 后端 PHP git CSS golang k8s Nginx Django mybatis 深度学习 多线程 React 架构 devops 爬虫 云计算 Spring Boot LeetCode