在简单的绘图程序方面，我只是试图了解基础知识。我有一个绘制矩形的程序，然后让我向任何方向移动它。我用一个线程来顺利行动。然而，令我困扰的是，如果我按下三个键并释放其中两个，程序将无法检测到第三个，从而使矩形保持静止。
我在这里要求的太多了，还是硬件相关？我有一个非常便宜的键盘。
如果您想乘车，这是完整的计划。
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Boxxy extends JFrame implements Runnable{
int xPos, yPos, xDir, yDir;
MyPanel panel;
ImageIcon ii;
Image i;
public Boxxy() {
setSize(400,400);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
panel = new MyPanel();
add(panel);
setVisible(true);
}
class MyPanel extends JPanel {
private static final long serialVersionUID = 1L;
private int squareX = 0;
private int squareY = 0;
private int squareW = 20;
private int squareH = 20;
private MyPanel() {
setFocusable(true);
addKeyListener(new KeyAdapter() {
public void keyPressed(KeyEvent e) {
switch (e.getKeyCode()) {
case (KeyEvent.VK_UP): setyDir(-1);
break;
case (KeyEvent.VK_DOWN): setyDir(1);
break;
case (KeyEvent.VK_LEFT): setxDir(-1);
break;
case (KeyEvent.VK_RIGHT): setxDir(1);
break;
}
}
public void keyReleased(KeyEvent e) {
switch (e.getKeyCode()) {
case (KeyEvent.VK_UP): setyDir(0);
break;
case (KeyEvent.VK_DOWN): setyDir(0);
break;
case (KeyEvent.VK_LEFT): setxDir(0);
break;
case (KeyEvent.VK_RIGHT): setxDir(0);
break;
}
}
});
}
private void repaintSquare(int x, int y) {
int OFFSET = 1;
if ((squareX!=x) || (squareY!=y)) {
repaint(squareX,squareY,squareW+OFFSET,squareH+OFFSET);
squareX=x;
squareY=y;
repaint(squareX,squareY,squareW+OFFSET,squareH+OFFSET);
}
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.RED);
g.fillRect(squareX,squareY,squareW,squareH);
}
}
private void move() {
panel.repaintSquare(xPos, yPos);
xPos += xDir;
yPos += yDir;
}
private void setxDir(int x) {
this.xDir = x;
}
private void setyDir(int y) {
this.yDir = y;
}
public static void main(String[] args) {
Thread t = new Thread(new Boxxy());
t.start();
}
@Override
public void run() {
try {
while(true) {
move();
Thread.sleep(5);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
答案 0 :(得分：1)
正如在类似问题中所讨论的那样，不要使用KeyListener，而是使用Key Bindings。 Swing Timer可用于重复移动精灵。
修改
例如：
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.*;
import java.util.EnumMap;
import javax.swing.*;
@SuppressWarnings("serial")
public class Boxxy2 extends JPanel {
private static final int PREF_W = 400;
private static final int PREF_H = PREF_W;
private static final int SQUARE_W = 20;
private static final String PRESSED = "pressed";
private static final String RELEASED = "released";
public static final int MOVE_SCALE = 1;
private static final int TIMER_DELAY = 5;
private int squareX = 0;
private int squareY = 0;
private int squareW = SQUARE_W;
private int squareH = SQUARE_W;
private EnumMap<Direction, Boolean> dirMap = new EnumMap<>(Direction.class);
public Boxxy2() {
setupKeyBinding();
new Timer(TIMER_DELAY, new TimerListener()).start();
}
private void setupKeyBinding() {
int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
InputMap inMap = getInputMap(condition);
ActionMap actMap = getActionMap();
// this uses an enum of Direction that holds ints for the arrow keys
for (Direction direction : Direction.values()) {
dirMap.put(direction, Boolean.FALSE);
int key = direction.getKey();
String name = direction.name();
KeyStroke keyPressed = KeyStroke.getKeyStroke(key, 0, false);
KeyStroke keyReleased = KeyStroke.getKeyStroke(key, 0, true);
// add the key bindings for arrow key and shift-arrow key
inMap.put(keyPressed, name + PRESSED);
inMap.put(keyReleased, name + RELEASED);
actMap.put(name + PRESSED, new MyKeyAction(this, direction, true));
actMap.put(name + RELEASED, new MyKeyAction(this, direction, false));
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.RED);
g.fillRect(squareX, squareY, squareW, squareH);
}
private static void createAndShowGui() {
Boxxy2 mainPanel = new Boxxy2();
JFrame frame = new JFrame("Boxxy2");
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();
}
});
}
private class TimerListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
for (Direction dir : dirMap.keySet()) {
if (dirMap.get(dir)) {
squareX += MOVE_SCALE * dir.getRight();
squareY += MOVE_SCALE * dir.getDown();
}
}
repaint();
}
}
public void setMovement(Direction direction, boolean keyPressed) {
dirMap.put(direction, keyPressed);
}
}
enum Direction {
UP(KeyEvent.VK_UP, 0, -1), DOWN(KeyEvent.VK_DOWN, 0, 1), LEFT(KeyEvent.VK_LEFT, -1, 0), RIGHT(KeyEvent.VK_RIGHT, 1, 0);
private int key;
private int right;
private int down;
private Direction(int key, int right, int down) {
this.key = key;
this.right = right;
this.down = down;
}
public int getKey() {
return key;
}
public int getRight() {
return right;
}
public int getDown() {
return down;
}
}
// Actions for the key binding
@SuppressWarnings("serial")
class MyKeyAction extends AbstractAction {
private Boxxy2 boxxy2;
private Direction direction;
private boolean keyPressed;
public MyKeyAction(Boxxy2 boxxy2, Direction direction, boolean keyPressed) {
this.boxxy2 = boxxy2;
this.direction = direction;
this.keyPressed = keyPressed;
}
@Override
public void actionPerformed(ActionEvent e) {
boxxy2.setMovement(direction, keyPressed);
}
}