键盘没有输入任何东西的Java [英] Keyboard not inputing anything java

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本文介绍了键盘没有输入任何东西的Java的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我一直在尝试这个代码并编辑它，但它不工作。
它是假设得到一个键盘输入存储在变量c，然后比较
键盘上的键。然后，根据按下的按键，假设移动一个小方块。
键盘似乎不被识别。有人可以帮帮我吗？
请注意我是14岁，所以请不要说这是多么的简单容易，我还在学习，你能否以我可能理解的方式来写。预先感谢您 

 'package package1; 
 
 import java.awt.Color; 
 import java.awt.Graphics; 
 import java.awt.event.ActionEvent; 
 import java.awt.event.ActionListener; 
 import java.awt.event.KeyEvent; 
 import java.awt.event.KeyListener; 
 
 import javax.swing.JFrame; 
 import javax.swing.JPanel; 
 import javax.swing.Timer; 
 
 public class Class1 extends JPanel implements KeyListener，ActionListener {
 
 Timer timer = new Timer（5，this）; 
 
 //变量
 int cox = 0; 
 int spx = 0; // cox = coordinate x，spx = speedx 
 int coy = 0; 
 int spy = 0; // coy = coordinate y，spy = speedy 
 
 public void paintComponent（Graphics g）
 {
 timer.start（）; 
 
 super.paintComponent（g）; 
 g.setColor（Color.BLUE）; 
 g.fillRect（cox，coy，50，50）; 
 
 addKeyListener（this）; 
 setFocusable（true）; 
 setFocusTraversalKeysEnabled（false）; 
} 
 
 public void actionPerformed（ActionEvent e）
 {
 cox = cox + spx; 
 coy = coy + spy; 
 repaint（）; 
} 
 
 public void keyPressed（KeyEvent e）
 {
 int c = e.getKeyCode（）; 
 
 if（c == KeyEvent.VK_LEFT）
 {
 spx = -1; 
 spy = 0; 
 
 if（c == KeyEvent.VK_UP）
 {
 spx = 0; 
 spy = -1; 
 
 if（c == KeyEvent.VK_RIGHT）
 {
 spx = 1; 
 spy = 0; 
 
 if（c == KeyEvent.VK_DOWN）
 {
 spx = 0; 
 spy = 1; 
 
 
 
 $ b public void keyTyped（KeyEvent e）
 {
} 
 public void keyReleased（KeyEvent e） 
 {
 spx = 0; 
 spy = 0; 
 
 
 public static void main（String args []）
 {
 Class1 t = new Class1（）; 
 JFrame frame = new JFrame（window）; 
 frame.setSize（500,500）; 
 frame.setVisible（true）; 
 frame.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）; 
 frame.add（t）; 
 
 
 
 
解决方案

问题用你的代码：


  • KeyListeners是非常低级的结构，通常应该避免使用中的键绑定 Swing应用程序。这样做也将使得解决焦点问题困扰KeyListeners更容易，并且导致您当前的KeyListener什么都不做。如果您阅读本网站上标记为Swing和KeyListeners的大多数问题，您将会一次又一次地看到这个建议 - 因为它是真实的，而且是有效的。

  • 请理解 paintComponent（Graphics g）方法仅用于绘画 。它经常被调用，通常不受控制，因为操作系统可以诱使它被调用。
  • paintComponent 方法有一个因为它控制着你的GUI和你的GUI可能包含的任何动画的控制，所以对你的GUI的感知响应有显着的影响。如果由于任何原因而减慢的话，那么你的GUI看起来会很慢。
  • 因为这个原因，这个方法只能用于绘图，只能用于绘图和没有什么，但绘图。特别是，

    • 不要从这个方法中启动Swing Timer，

    • Don 't 从这个方法中添加KeyListeners（除非你想向GUI添加一个KeyListener 20次，这会导致无法预料的行为），






例如：

$ p $ import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.util.EnumMap;
import java.util.HashMap;
import java.util.Map;

import javax.swing。*;

@SuppressWarnings（serial）
public class Class1B extends JPanel {
private static final int PREF_W = 500;
private static final int PREF_H = PREF_W;
private static final int ANIMATION_DELAY = 15;
private static final int RECT_WIDTH = 15;
private static final Color RECT_COLOR = Color.red;
private EnumMap< Direction，Boolean> dirMap = new EnumMap<>（Direction.class）;
私人地图<整数，方向> keyToDir = new HashMap<>（）;
私人定时器animationTimer;
public int rectX;
public int rectY;

$ b $ public class1B（）{
for（方向dir：Direction.values（））{
dirMap.put（dir，Boolean.FALSE）;
}
keyToDir.put（KeyEvent.VK_UP，Direction.UP）;
keyToDir.put（KeyEvent.VK_DOWN，Direction.DOWN）;
keyToDir.put（KeyEvent.VK_LEFT，Direction.LEFT）;
keyToDir.put（KeyEvent.VK_RIGHT，Direction.RIGHT）;
setKeyBindings（）;

animationTimer = new Timer（ANIMATION_DELAY，new AnimationListener（））;
animationTimer.start（）;

$ b @Override
public Dimension getPreferredSize（）{
return new Dimension（PREF_W，PREF_H）;
}

@Override
保护void paintComponent（Graphics g）{
super.paintComponent（g）;
g.setColor（RECT_COLOR）;
g.fillRect（rectX，rectY，RECT_WIDTH，RECT_WIDTH）;
}

private void setKeyBindings（）{
int condition = WHEN_IN_FOCUSED_WINDOW;
final InputMap inputMap = getInputMap（condition）;
final ActionMap actionMap = getActionMap（）;
boolean [] keyPressed = {true，false};
for（Integer keyCode：keyToDir.keySet（））{
Direction dir = keyToDir.get（keyCode）;
for（boolean onKeyPress：keyPressed）{
boolean onKeyRelease =！onKeyPress;
KeyStroke keyStroke = KeyStroke.getKeyStroke（keyCode，0，
onKeyRelease）;
Object key = keyStroke.toString（）;
inputMap.put（keyStroke，key）;
actionMap.put（key，new KeyBindingsAction（dir，onKeyPress））;



$ b private class KeyBindingsAction extends AbstractAction {
private Direction dir;
boolean按下;

public KeyBindingsAction（方向dir，boolean按下）{
this.dir = dir;
this.pressed =按下;

$ b @Override
public void actionPerformed（ActionEvent evt）{
dirMap.put（dir，pressed）;


$ b private class AnimationListener implements ActionListener {
@Override
public void actionPerformed（ActionEvent evt）{
boolean repaint = false ; （dirMap.get（dir））{
rectX + = dir.getIncrX（）;
（方向dir：Direction.values（））
rectY + = dir.getIncrY（）;
repaint = true;


if（repaint）{
repaint（）;



$ b private static void createAndShowGui（）{
Class1B mainPanel = new Class1B（）;

JFrame frame = new JFrame（Class1B）;
frame.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;
frame.getContentPane（）。add（mainPanel）;
frame.pack（）;
frame.setLocationByPlatform（true）;
frame.setVisible（true）;


public static void main（String [] args）{
SwingUtilities.invokeLater（new Runnable（）{
public void run（）{
createAndShowGui（）;
}
}）;


$ b $ enum方向{
UP（0，-1），DOWN（0,1），LEFT（-1,0），RIGHT 1,0）;
private int incrX;
private int incrY;

私有方向（int incrX，int incrY）{
this.incrX = incrX;
this.incrY = incrY;
}

public int getIncrX（）{
return incrX;
}

public int getIncrY（）{
return incrY;
}
}


i have been trying this code and editing it but it doesnt work. it is suppose to get a keyboard input store it in the variable "c" and then compare that to keys on the keyboard. Then it is suppose to move a little square depending the key pressed. The keyboard doesnt seem to be recognised. Can someone please help me? Please be aware i am 14 so please dont say how simple and easy it is, i am still learning and could you also write it in a way i am likely to understand. Thank you in advance

'package package1;

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

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

public class Class1 extends JPanel implements KeyListener, ActionListener{

Timer timer = new Timer(5, this);

//variables    
int cox = 0;
int spx = 0;  //cox = coordinates x, spx = speedx
int coy = 0;
int spy = 0;  //coy = coordinates y, spy = speedy

public void paintComponent(Graphics g)
{
    timer.start();

    super.paintComponent(g);
    g.setColor(Color.BLUE);     
    g.fillRect(cox, coy, 50, 50);

    addKeyListener(this);
    setFocusable(true);
    setFocusTraversalKeysEnabled(false);
}

public void actionPerformed(ActionEvent e)
{
    cox = cox + spx;
    coy = coy + spy;
    repaint();
}

public void keyPressed(KeyEvent e)
{
    int c = e.getKeyCode();

    if(c == KeyEvent.VK_LEFT)
    {
        spx = -1;
        spy = 0;
    }
    if(c == KeyEvent.VK_UP)
    {
        spx = 0;
        spy = -1;
    }
    if(c == KeyEvent.VK_RIGHT)
    {
        spx = 1;
        spy = 0;
    }
    if(c == KeyEvent.VK_DOWN)
    {
        spx = 0;
        spy = 1;
    }

}

public void keyTyped(KeyEvent e)
{
}
public void keyReleased(KeyEvent e)
{
    spx = 0;
    spy = 0;
}

public static void main(String args[])
{
    Class1 t = new Class1();
    JFrame frame = new JFrame("window");
    frame.setSize(500,500);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.add(t);
}
}

解决方案

Problems with your code:

  • KeyListeners are very low-level constructs, and in general should be avoided in favor of key bindings in most Swing applications. Doing this will also make it much easier to solve focus issues that plague KeyListeners, and which is causing your current KeyListener to do nothing whatsoever. If you read most questions on this site tagged with Swing and KeyListeners, you'll see this advice time and again -- because it's true, and it works.
  • Please understand that the paintComponent(Graphics g) method is for painting only. It is frequently called, often out of your control, since the OS can induce it to be called.
  • The paintComponent method has a significant influence on the perceived responsiveness of your GUI, since it is in control of drawing your GUI and any animations that your GUI might contain. If it is slowed for any reason, your GUI will seem slow.
  • For this reason, this method should be used for drawing and only drawing and nothing but drawing. Specifically,
    • Don't start your Swing Timer from within this method,
    • Don't add KeyListeners from within this method (unless you want to add a KeyListener 20 times to the GUI which will result in wildly unpredictable behavior),
    • Don't change the state of any of your objects from within this method.

For example:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.util.EnumMap;
import java.util.HashMap;
import java.util.Map;

import javax.swing.*;

@SuppressWarnings("serial")
public class Class1B extends JPanel {   
   private static final int PREF_W = 500;
   private static final int PREF_H = PREF_W;
   private static final int ANIMATION_DELAY = 15;
   private static final int RECT_WIDTH = 15;
   private static final Color RECT_COLOR = Color.red;
   private EnumMap<Direction, Boolean> dirMap = new EnumMap<>(Direction.class);
   private Map<Integer, Direction> keyToDir = new HashMap<>();
   private Timer animationTimer;
   public int rectX;
   public int rectY;


   public Class1B() {
      for (Direction dir : Direction.values()) {
         dirMap.put(dir, Boolean.FALSE);
      }
      keyToDir.put(KeyEvent.VK_UP, Direction.UP);
      keyToDir.put(KeyEvent.VK_DOWN, Direction.DOWN);
      keyToDir.put(KeyEvent.VK_LEFT, Direction.LEFT);
      keyToDir.put(KeyEvent.VK_RIGHT, Direction.RIGHT);
      setKeyBindings();

      animationTimer = new Timer(ANIMATION_DELAY, new AnimationListener());
      animationTimer.start();
   }

   @Override
   public Dimension getPreferredSize() {
      return new Dimension(PREF_W, PREF_H);
   }

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      g.setColor(RECT_COLOR);
      g.fillRect(rectX, rectY, RECT_WIDTH, RECT_WIDTH);
   }

   private void setKeyBindings() {
      int condition = WHEN_IN_FOCUSED_WINDOW;
      final InputMap inputMap = getInputMap(condition);
      final ActionMap actionMap = getActionMap();
      boolean[] keyPressed = { true, false };
      for (Integer keyCode : keyToDir.keySet()) {
         Direction dir = keyToDir.get(keyCode);
         for (boolean onKeyPress : keyPressed) {
            boolean onKeyRelease = !onKeyPress;
            KeyStroke keyStroke = KeyStroke.getKeyStroke(keyCode, 0,
                  onKeyRelease);
            Object key = keyStroke.toString();
            inputMap.put(keyStroke, key);
            actionMap.put(key, new KeyBindingsAction(dir, onKeyPress));
         }
      }
   }

   private class KeyBindingsAction extends AbstractAction {
      private Direction dir;
      boolean pressed;

      public KeyBindingsAction(Direction dir, boolean pressed) {
         this.dir = dir;
         this.pressed = pressed;
      }

      @Override
      public void actionPerformed(ActionEvent evt) {
         dirMap.put(dir, pressed);
      }
   }

   private class AnimationListener implements ActionListener {
      @Override
      public void actionPerformed(ActionEvent evt) {
         boolean repaint = false;
         for (Direction dir : Direction.values()) {
            if (dirMap.get(dir)) {
               rectX += dir.getIncrX();
               rectY += dir.getIncrY();
               repaint = true;
            }
         }
         if (repaint) {
            repaint();
         }
      }
   }

   private static void createAndShowGui() {
      Class1B mainPanel = new Class1B();

      JFrame frame = new JFrame("Class1B");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

enum Direction {
   UP(0, -1), DOWN(0, 1), LEFT(-1, 0), RIGHT(1, 0);
   private int incrX;
   private int incrY;

   private Direction(int incrX, int incrY) {
      this.incrX = incrX;
      this.incrY = incrY;
   }

   public int getIncrX() {
      return incrX;
   }

   public int getIncrY() {
      return incrY;
   }
}

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