问题描述
所以我有一个要绘制的矩形，我想使用箭头键移动该矩形，包括对角线移动，或者允许同时按下多个键(换句话说，该移动类似于2D中的玩家移动)游戏).我试图用一个不起作用的KeyListener来做到这一点.因此，我决定转到KeyBindings，并从该网站找到一个示例: https://coderanch.com/t/606742/java/key-bindings (Rob Camick的帖子)
So I have a painted rectangle that I want to move with the arrow keys that includes diagonal movement, or rather allowance of multiple keys being pressed at the same time (In other words, movement that is similar to player movement in a 2D game). I have attempted to do this with a KeyListener, which was not working. So I decided to move to KeyBindings and I found an example from this website: https://coderanch.com/t/606742/java/key-bindings (Rob Camick's post)
我直接复制了代码，它按预期工作，除了它移动图标而不是像我想的那样绘制矩形.我试图修改代码，以便它可以移动一个绘制的矩形，但是只是失败了.这是我最近的尝试，也是可重现的最小尝试:
I directly copied the code and it works as intended, except it is moving an icon and not a painted rectangle like I want to do. I have attempted to modify the code so that it would move a painted rectangle, but was only failing. Here is my latest attempt, which is also a minimal reproducible:
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class Test extends JPanel implements ActionListener
{
public JPanel component = this;
public int x = 100;
public int y = 100;
private Timer timer;
private int keysPressed;
private InputMap inputMap;
public void addAction(String name, int keyDeltaX, int keyDeltaY, int keyCode)
{
new NavigationAction(name, keyDeltaX, keyDeltaY, keyCode);
}
// Move the component to its new location
private void handleKeyEvent(boolean pressed, int deltaX, int deltaY)
{
keysPressed += pressed ? 1 : -1;
x += deltaX;
y += deltaY;
// Start the Timer when the first key is pressed
if (keysPressed == 1)
timer.start();
// Stop the Timer when all keys have been released
if (keysPressed == 0)
timer.stop();
}
// Invoked when the Timer fires
public void actionPerformed(ActionEvent e)
{
repaint();
}
class NavigationAction extends AbstractAction implements ActionListener
{
private int keyDeltaX;
private int keyDeltaY;
private KeyStroke pressedKeyStroke;
private boolean listeningForKeyPressed;
public NavigationAction(String name, int keyDeltaX, int keyDeltaY, int keyCode)
{
super(name);
this.keyDeltaX = keyDeltaX;
this.keyDeltaY = keyDeltaY;
pressedKeyStroke = KeyStroke.getKeyStroke(keyCode, 0, false);
KeyStroke releasedKeyStroke = KeyStroke.getKeyStroke(keyCode, 0, true);
inputMap.put(pressedKeyStroke, getValue(Action.NAME));
inputMap.put(releasedKeyStroke, getValue(Action.NAME));
component.getActionMap().put(getValue(Action.NAME), this);
listeningForKeyPressed = true;
}
public void actionPerformed(ActionEvent e)
{
// While the key is held down multiple keyPress events are generated,
// we only care about the first event generated
if (listeningForKeyPressed)
{
handleKeyEvent(true, keyDeltaX, keyDeltaY);
inputMap.remove(pressedKeyStroke);
listeningForKeyPressed = false;
}
else // listening for key released
{
handleKeyEvent(false, -keyDeltaX, -keyDeltaY);
inputMap.put(pressedKeyStroke, getValue(Action.NAME));
listeningForKeyPressed = true;
}
}
}
public void paintComponent(Graphics tool) {
super.paintComponent(tool);
System.out.println(x + ", " + y);
tool.drawRect(x, y, 50, 50);
}
public Test() {}
public static void main(String[] args)
{
new Test().create();
}
public void create() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
frame.setSize(600, 600);
frame.setLocationRelativeTo( null );
frame.getContentPane().add(component);
inputMap = component.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
timer = new Timer(24, this);
timer.setInitialDelay( 0 );
addAction("Left", -3, 0, KeyEvent.VK_LEFT);
addAction("Right", 3, 0, KeyEvent.VK_RIGHT);
addAction("Up", 0, -3, KeyEvent.VK_UP);
addAction("Down", 0, 3, KeyEvent.VK_DOWN);
frame.setVisible(true);
}
}
推荐答案
好的，所以我所提供的代码存在的问题之一就是您有泄漏责任. NavigationAction 的职责不是注册键绑定或修改UI的状态.它应该只负责生成状态已更改回负责处理程序的通知.
Okay, so one of the issues I have with the code you've presented is the fact that you're leak responsibility. It's not the responsibility of the NavigationAction to register key bindings or modify the state the of UI. It should only be responsible for generating a notification that the state has changed back to a responsible handler.
这可以通过使用某种模型来实现，该模型保持某种状态，该状态由 NavigationAction 更新并由UI读取，或者按照我的选择通过委托回调.
This could be achieved through the use of some kind of model, which maintains the some kind of state, which is updated by the NavigationAction and read by the UI or, as I've chosen to do, via a delegation callback.
另一个问题是，当用户释放密钥时会发生什么?另一个问题是，您如何处理重复按键的延迟(即，当您按住键时，第一个按键事件和重复按键事件之间的延迟很小)?
Another issue is, what happens when the user releases the key? Another issue is, how do you deal with the delay in repeated key press (ie when you hold the key down, there is a small delay between the first key event and the repeating key events)?
我们可以通过简单地改变思维方式来处理这些问题.而不是使用 NavigationAction 确定什么".如果发生这种情况，应该使用它来告诉我们的用户界面何时"发生了什么事.在这种情况下，方向键已被按下或释放.
We can deal with these things through a simple change in mind set. Instead of using the NavigationAction to determine "what" should happen, it should be used to tell our UI "when" something has happened. In this a directional key has been pressed or released.
我们不是直接对击键做出反应，而是添加"或添加"了.或删除"状态模型的方向，并允许Swing Timer 相应地更新UI的状态，这通常会更快，更流畅.
Instead of reacting to key stroke directly, we either "add" or "remove" the direction from a state model and allow the Swing Timer to update the state of the UI accordingly, this will generally be faster and smoother.
它也具有去耦逻辑的副作用，因为您不再需要关心如何"操作.状态发生了变化，只有状态发生了变化，然后您就可以决定要如何对它做出反应.
It also has the side effect of decoupling logic, as you no longer need to care about "how" the state was changed, only that it was and you can then decide how you want to react to it.
这种方法通常在游戏引擎中普遍使用(以某种形式或另一种形式).
This approach is generally commonly used (in some form or another) in gaming engines.
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.util.HashSet;
import java.util.Set;
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;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
JFrame frame = new JFrame();
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public interface KeyActionHandler {
public void keyActionPerformed(Direction direction, boolean pressed);
}
public enum Direction {
LEFT, RIGHT, DOWN, UP;
}
class NavigationAction extends AbstractAction implements ActionListener {
private KeyActionHandler keyActionHandler;
private Direction direction;
private Boolean pressed;
public NavigationAction(Direction direction, boolean pressed, KeyActionHandler keyActionHandler) {
this.direction = direction;
this.pressed = pressed;
this.keyActionHandler = keyActionHandler;
}
public void actionPerformed(ActionEvent e) {
keyActionHandler.keyActionPerformed(direction, pressed);
}
}
public class TestPane extends JPanel implements ActionListener, KeyActionHandler {
private int xDelta = 0;
private int yDelta = 0;
public int x = 100;
public int y = 100;
private Timer timer;
public TestPane() {
timer = new Timer(24, this);
InputMap inputMap = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap actionMap = getActionMap();
inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, false), "Pressed-Left");
inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, false), "Pressed-Right");
inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, false), "Pressed-Up");
inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, false), "Pressed-Down");
actionMap.put("Pressed-Left", new NavigationAction(Direction.LEFT, true, this));
actionMap.put("Pressed-Right", new NavigationAction(Direction.RIGHT, true, this));
actionMap.put("Pressed-Up", new NavigationAction(Direction.UP, true, this));
actionMap.put("Pressed-Down", new NavigationAction(Direction.DOWN, true, this));
inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, true), "Released-Left");
inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, true), "Released-Right");
inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, true), "Released-Up");
inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, true), "Released-Down");
actionMap.put("Released-Left", new NavigationAction(Direction.LEFT, false, this));
actionMap.put("Released-Right", new NavigationAction(Direction.RIGHT, false, this));
actionMap.put("Released-Up", new NavigationAction(Direction.UP, false, this));
actionMap.put("Released-Down", new NavigationAction(Direction.DOWN, false, this));
}
@Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
@Override
public void addNotify() {
super.addNotify();
timer.start();
}
@Override
public void removeNotify() {
super.removeNotify();
timer.stop();
}
private Set<Direction> directions = new HashSet<>();
// Invoked when the Timer fires
@Override
public void actionPerformed(ActionEvent e) {
if (directions.contains(Direction.LEFT)) {
x -= 3;
} else if (directions.contains(Direction.RIGHT)) {
x += 3;
}
if (directions.contains(Direction.UP)) {
y -= 3;
} else if (directions.contains(Direction.DOWN)) {
y += 3;
}
repaint();
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawRect(x, y, 50, 50);
}
@Override
public void keyActionPerformed(Direction direction, boolean pressed) {
if (pressed) {
directions.add(direction);
} else {
directions.remove(direction);
}
}
}
}
这只是解决同一问题的另一种方法；)
This is just one more approach to solve the same problem ;)
这篇关于按键绑定多个按键不起作用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！