java - Action和ActionMap-向我解释此行为

我有一个Action

SampleAction a = new SampleAction("foo", null);

然后，将其添加到Button和ActionMap中

JButton b = new JButton(a);
b.getActionMap().put("bar", a);
b.getInputMap().put(KeyStroke.getKeyStroke("F1"), "bar");

我在动作中放了一个痕迹（System.out.println("Action [" + e.getActionCommand() + "] performed!");）。当我用鼠标按下按钮时

Action [foo] performed!

但是当我使用F1时，它显示：

Action [null] performed!

为什么？

class SampleAction extends AbstractAction
{
    public SampleAction(String text, Icon icon) {
        super(text, icon);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("Action [" + e.getActionCommand() + "] performed!");
    }
}

最佳答案

除非我有误解，否则应通过getActionCommand在JButton实例上调用ae.getSource()，而在getActionCommand()上调用ActionEvent的位置：

  SampleAction a = new SampleAction("foo", null);

  JButton b = new JButton(a);
  b.getActionMap().put("bar", a);
  b.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke("F1"), "bar");

class SampleAction extends AbstractAction
{
    public SampleAction(String text, Icon icon) {
    super(text, icon);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
    System.out.println("Action [" + ((JButton)e.getSource()).getActionCommand() + "] performed!");
    }
}

更新：

感谢@Kleopatra，这可能是更好的方法：

SampleAction a = new SampleAction("foo", null);

JButton b = new JButton(a);
b.getActionMap().put("bar", a);
b.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke("F1"), "bar");

 class SampleAction extends AbstractAction {

        public SampleAction(String text, Icon icon) {
            super(text, icon);

            putValue(Action.ACTION_COMMAND_KEY, text);//'foo' will be printed when button clicekd/F1 pressed
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            System.out.println("Action [" + e.getActionCommand() + "] performed!");
        }
    }