java如何缩短此KeyListener代码

Question

我用这段代码来检测用户何时按下程序中的箭头键。我需要哪个箭头键被按下发送到一个方法，它将处理它，并做它需要做的事情。这是可行的，但问题是我的代码太长而且重复，我相信有办法缩短它。我可以传递整数0-3而不是字符串，如果这样做更容易的话。这是我现在的代码：

getRootPane().getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
    KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), "left"); 
getRootPane().getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
    KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0), "right");
getRootPane().getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
    KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), "up");
getRootPane().getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
    KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), "down");
getRootPane().getActionMap().put("left", new AbstractAction(){
    public void actionPerformed(ActionEvent e)
    {
        close("left");
    }
});
getRootPane().getActionMap().put("right", new AbstractAction(){
    public void actionPerformed(ActionEvent e)
    {
        close("right");
    }
});
getRootPane().getActionMap().put("up", new AbstractAction(){
    public void actionPerformed(ActionEvent e)
    {
        close("up");
    }
});
getRootPane().getActionMap().put("down", new AbstractAction(){
    public void actionPerformed(ActionEvent e)
    {
        close("down");
    }
});

Answer 1

创建一个内部类，该类扩展AbstractAction并可以获取字符串参数

像这样的

private class CloseAction extends AbstractAction {
    private final String action;
    public CloseAction(String anAction) {
        action = anAction;
    }

    public void actionPerformed(ActionEvent e) {
        close(action);
    }
}

然后：

getRootPane().getActionMap().put("up", new CloseAction("up"));

Answer 2

将通用功能抽象为一种方法：

private void mapKey(String keyStroke, final String command) {
    Action action = new AbstractAction() {
        public void actionPerformed(ActionEvent e) {
            close(command);
        }
    };
    getRootPane().getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW)
        .put(KeyStroke.getKeyStroke(keyStroke), action);
    getRootPane().getActionMap()
        .put(action, action);
}

然后你可以做：

mapKey("LEFT",  "left");
mapKey("RIGHT", "right");
mapKey("UP",    "up");
mapKey("DOWN",  "down");