如何制作(keyPressed)KeyListener? [英] How do I make a (keyPressed) KeyListener?
问题描述
我正在尝试编写一个非常简单的程序,该程序允许您使用箭头键控制精灵并在屏幕上移动.据我了解,要做到这一点,我需要一个keyPressed()
KeyListener
.我相信我是根据Java Doc正确执行此操作的,但是当我按指定的键时,它不会返回正确的输出.有人可以告诉我我的代码有什么问题吗,如果可能,请提供此类用法的简单示例?谢谢!
Im trying to write a very simple program that allows you to control a sprite with arrow keys and move around the screen. From what I understand, to do this I need a keyPressed()
KeyListener
. I believe Im doing this correctly based on the Java Doc but its not returning the correct output when I press the designated key. Can someone please tell me what is wrong with my code, and if possible, provide a simple example of the usage of this class? Thanks!
(注意,代码未完成)
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
public class Display extends JPanel implements ActionListener, KeyListener {
Display() {
// super();
loadImages();
initTimer();
this.addKeyListener(this);
}
BufferedImage sprite;
Timer timer;
int up = 0;
public void loadImages() {
File spriteImage = new File("Pacman_sprite.png");
try {
sprite = ImageIO.read(spriteImage);
} catch (IOException e) {
System.out.println("Sprite import failed");
}
}
public void initTimer() {
timer = new Timer(100, this);
timer.start();
this.addKeyListener(this);
}
@Override
public void keyTyped(KeyEvent e) {
}
@Override
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
System.out.println("Key press registered"); //does not print this?
if (key == KeyEvent.VK_UP) {
System.out.println("sucess"); // does not print this?
up++;
repaint();
}
}
@Override
public void keyReleased(KeyEvent e) {
System.out.println("release");
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
setBackground(Color.WHITE);
Graphics2D g2d = (Graphics2D) g;
g2d.drawImage(sprite, 500, 500 + up, null);
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
repaint();
}
}
可能在这里找到了答案.我将密钥处理代码移到了一个名为KeyHandler的新类中,然后将以下两行添加到了构造函数中:
May have found the answer here. I moved the key handling code to a new class called KeyHandler then added these two lines to the constructor:
addKeyListener(new KeyHandler());
setFocusable(true);
现在看来工作正常(至少在检测何时按下了向上键.我的图形没有.)
It now appears to be working just fine (sort of, at least it is detecting when the up key is hit. My graphics aren't.)
推荐答案
您没有将侦听器添加到JPanel
.
You are not adding the listener to the JPanel
.
注意:我建议您更改设计.现在,Display
类既是JPanel
又是Listener
(在我看来这没有意义).
Note: I would suggest you to change your design. Right now, Display
class is both a JPanel
and a Listener
(which doesn't make sense in my opinion).
但是要在代码中添加侦听器,请执行以下操作,
But to add the listener in your code do something like,
this.addKeyListener(this); // This looks awkward right. That's why you should change the design.
在您的构造函数中.
这篇关于如何制作(keyPressed)KeyListener?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!