一键连续运动? [英] Continuous movement with a single key press?
问题描述
我正在尝试用Java编写一个程序，该程序涉及通过一次按键使对象不断移动.想想吃豆子，在其中按下一次，吃豆子继续上升直到您按下另一个键.如果可能的话，我想保持代码简单.我原来的动作(一键=一次动作)是这样的:
I'm trying to make a program in java that involves making an object move constantly from a single key press. Think Pacman, where you press up once and Pacman continues to go up until you press another key. I want to keep the code simple if possible. My original movement (one keypress = one movement) is like this:
public class AL extends KeyAdapter {
public void keyPressed(KeyEvent e){
int keyCode = e.getKeyCode();
if(keyCode == e.VK_A){
x -= 5;
}
if(keyCode == e.VK_D){
x += 5;
}
if(keyCode == e.VK_W){
y -= 5;
}
if(keyCode == e.VK_S){
y += 5;
}
}
值中的x和y是椭圆的位置.这完美地工作了，但是我希望它只按一次键就可以继续运动，而不是必须按住它才能使运动继续进行.我尝试了一个带有布尔参数的while循环，该布尔参数在true时移动，而在false时不移动，但是一旦我激活该循环，它就会冻结程序.这是这段代码的示例:
The x and y in values are the position of an oval. This works perfectly, but I want it to keep moving after I press the key only once, instead of having to hold it to keep the movement going. I tried a while loop with a boolean parameter that moves while true and doesn't while false, but as soon as I activate the loop, it freezes the program. Here's an example of that bit of code:
public void keyPressed(KeyEvent e){
int keyCode = e.getKeyCode();
if(keyCode == e.VK_LEFT && moveL==false){
moveL=true;
moveR=false;
moveU=false;
moveD=false;
while(moveL){
x--;
}
}
请帮我解决这个问题，我已经尝试了好几天了.感谢您提供的任何帮助.谢谢.
Please help me figure this out, I've been trying and looking around for days now. I appreciate any help you guys can give. Thanks.
推荐答案
基本概念围绕"delta"或"change"值的概念展开.然后，通过将该状态值递增或递减，将其应用于您要更改的状态.
The basic concept revolves around this idea of a "delta" or "change" value. This value is then applied to the state you want to change by either incrementing or decrementing the state value by it.
由于Swing的性质，您不能阻止事件调度线程，否则最终将阻止处理传入事件(例如绘画和按键事件).
Because of the nature of Swing, you can't block the Event Dispatching Thread, otherwise you end up preventing from processing incoming events (such as paint and key events).
同样，您永远不要尝试从EDT以外的任何线程更新任何UI组件(或可能影响UI的状态变量).
Equally, you should never try and update any UI component (or state variable that might effect the UI) from any thread other then the EDT.
虽然有一些技巧可以满足这些要求，但最简单的方法是使用javax.swing.Timer，它会在EDT中定期触发actionPerformed事件.
While there are tricks you can apply to facilitate these requirements, the simplest is to use a javax.swing.Timer, which triggers a actionPerformed event on a regular bases within the EDT.
发生这种情况时，您可以按规定的数量更新"所有元素并重新粉刷屏幕.
When this occurs you "update" all the elements by the prescribed amount and repaint the screen.
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class PacManTest {
public static void main(String[] args) {
new PacManTest();
}
public PacManTest() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new MazePane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class PacMan {
private int x;
private int y;
private int deltaX;
private int deltaY;
private BufferedImage sprite;
public PacMan() {
try {
sprite = ImageIO.read(new File("PacMan.png"));
} catch (IOException ex) {
ex.printStackTrace();
}
}
public void move(int x, int y) {
deltaX = x;
deltaY = y;
}
public void update(MazePane pane) {
x += deltaX;
y += deltaY;
if (x + sprite.getWidth() > pane.getWidth()) {
x = pane.getWidth() - sprite.getWidth();
} else if (x < 0) {
x = 0;
}
if (y + sprite.getHeight() > pane.getHeight()) {
y = pane.getHeight() - sprite.getHeight();
} else if (y < 0) {
y = 0;
}
}
public void paint(MazePane pane, Graphics2D g2d) {
Graphics2D g = (Graphics2D) g2d.create();
float angle = 0;
if (deltaX != 0) {
angle = deltaX > 0 ? 0 : 180;
} else if (deltaY != 0) {
angle = deltaY > 0 ? 90 : 270;
}
AffineTransform t = new AffineTransform();
t.translate(x, y);
t.rotate(Math.toRadians(angle), sprite.getWidth() / 2, sprite.getHeight() / 2);
g.setTransform(t);
g.drawImage(sprite, 0, 0, pane);
g.dispose();
}
}
public class MazePane extends JPanel {
private PacMan pacMan;
public MazePane() {
pacMan = new PacMan();
Timer timer = new Timer(40, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
pacMan.update(MazePane.this);
repaint();
}
});
timer.start();
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), "left");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0), "right");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), "up");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), "down");
am.put("left", new MoveAction(pacMan, -4, 0));
am.put("right", new MoveAction(pacMan, 4, 0));
am.put("up", new MoveAction(pacMan, 0, -4));
am.put("down", new MoveAction(pacMan, 0, 4));
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
pacMan.paint(this, g2d);
g2d.dispose();
}
public class MoveAction extends AbstractAction {
private int deltaX;
private int deltaY;
private PacMan pacMan;
public MoveAction(PacMan pacMan, int deltaX, int deltaY) {
this.deltaX = deltaX;
this.deltaY = deltaY;
this.pacMan = pacMan;
}
@Override
public void actionPerformed(ActionEvent e) {
pacMan.move(deltaX, deltaY);
}
}
}
}
我还建议您花时间学习关键字绑定，KeyListener存在焦点问题，这些键绑定可以解决...
I would also recommend that you take the time to learn about Key Bindings, KeyListener suffer from focus issues, which key bindings are capable of addressing...
这篇关于一键连续运动?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！
