Java Swing 的 KeyListener 和同时按下的多个键
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原文地址: http://stackoverflow.com/questions/2623995/
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Swing's KeyListener and multiple keys pressed at the same time
提问by Maksim Skurydzin
is there any conventional way in swing of tracking down the events, when two keyboard keys are pressed at the same time? I have a couple of ideas e.g. remembering the key and event generation time so that we could in a consecutive event handler invocation check the time difference between these two events and decide, whether it's a two-button event or not. But it looks like a kludge.
当同时按下两个键盘键时，是否有任何传统的跟踪事件的摆动方式？我有一些想法，例如记住键和事件生成时间，以便我们可以在连续的事件处理程序调用中检查这两个事件之间的时间差并决定它是否是两个按钮的事件。但它看起来像一团糟。
采纳答案by Ben S
Use a collection to remember which keys are currently pressed and check to see if more than one key is pressed every time a key is pressed.
使用集合来记住当前按下了哪些键，并检查每次按下一个键时是否按下了多个键。
class MultiKeyPressListener implements KeyListener {
// Set of currently pressed keys
private final Set<Integer> pressedKeys = new HashSet<>();
@Override
public synchronized void keyPressed(KeyEvent e) {
pressed.add(e.getKeyCode());
Point offset = new Point();
if (!pressedKeys.isEmpty()) {
for (Iterator<Integer> it = pressedKeys.iterator(); it.hasNext();) {
switch (it.next()) {
case KeyEvent.VK_W:
case KeyEvent.VK_UP:
offset.y = -1;
break;
case KeyEvent.VK_A:
case KeyEvent.VK_LEFT:
offset.x = -1;
break;
case KeyEvent.VK_S:
case KeyEvent.VK_DOWN:
offset.y = 1;
break;
case KeyEvent.VK_D:
case KeyEvent.VK_RIGHT:
offset.x = 1;
break;
}
}
}
System.out.println(offset); // Do something with the offset.
}
@Override
public synchronized void keyReleased(KeyEvent e) {
pressedKeys.remove(e.getKeyCode());
}
@Override
public void keyTyped(KeyEvent e) { /* Not used */ }
}
回答by Eyal Schneider
The KeyListener interface allows detecting key pressing and releasing separately. Therefore, you can maintain a set of "active keys", i.e. keys which have been pressed but not released yet.
KeyListener 接口允许分别检测按键按下和释放。因此，您可以维护一组“活动键”，即已按下但尚未释放的键。
回答by res
If after 7 years I tried to do this (just to see if it is possible), someone else might as well...
如果 7 年后我尝试这样做（只是为了看看是否可能），其他人也可能......
The code below controls the movement with 8 axis direction, explanation in the comments. But basically, the KeyListenerjust define where it is possible to move, then a Threadwill combine the possible destinations and move the JLabel.
下面的代码控制8轴方向的运动，注释中说明。但基本上，KeyListener只需定义可以移动的位置，然后 aThread将组合可能的目的地并移动JLabel.
package tests;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class Move8Axis extends JFrame {
private static final long serialVersionUID = 7722803326073073681L;
private boolean left = false;
private boolean up = false;
private boolean down = false;
private boolean right = false;
private JLabel lbl = new JLabel("#");
public Move8Axis() {
// Just setting up the window and objects
setSize(400, 400);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
lbl.setBounds(100, 100, 20, 20);
add(lbl);
setLocationRelativeTo(null);
// Key listener, will not move the JLabel, just set where to
addKeyListener(new KeyListener() {
@Override
public void keyTyped(KeyEvent e) {}
@Override
public void keyReleased(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_LEFT) left = false;
if (e.getKeyCode() == KeyEvent.VK_RIGHT) right = false;
if (e.getKeyCode() == KeyEvent.VK_UP) up = false;
if (e.getKeyCode() == KeyEvent.VK_DOWN) down = false;
}
@Override
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_LEFT) left = true;
if (e.getKeyCode() == KeyEvent.VK_RIGHT) right = true;
if (e.getKeyCode() == KeyEvent.VK_UP) up = true;
if (e.getKeyCode() == KeyEvent.VK_DOWN) down = true;
}
});
// This thread will read the 4 variables left/right/up/down at every 30 milliseconds
// It will check the combination of keys (left and up, right and down, just left, just up...)
// And move the label 3 pixels
new Thread(new Runnable() {
@Override
public void run() {
try {
while (true) {
if (left && up) {
lbl.setBounds(lbl.getX() - 3, lbl.getY() - 3, 20, 20);
} else if (left && down) {
lbl.setBounds(lbl.getX() - 3, lbl.getY() + 3, 20, 20);
} else if (right && up) {
lbl.setBounds(lbl.getX() + 3, lbl.getY() - 3, 20, 20);
} else if (right && down) {
lbl.setBounds(lbl.getX() + 3, lbl.getY() + 3, 20, 20);
} else if (left) {
lbl.setBounds(lbl.getX() - 3, lbl.getY(), 20, 20);
} else if (up) {
lbl.setBounds(lbl.getX(), lbl.getY() - 3, 20, 20);
} else if (right) {
lbl.setBounds(lbl.getX() + 3, lbl.getY(), 20, 20);
} else if (down) {
lbl.setBounds(lbl.getX(), lbl.getY() + 3, 20, 20);
}
Thread.sleep(30);
}
} catch (Exception ex) {
ex.printStackTrace();
System.exit(0);
}
}
}).start();
}
public static void main(String[] args) {
new Move8Axis();
}
}
