Java Swing : Show pressed button when using corresponding keyboard button

Question

我正在使用 Java 使用 Swing 编写一个程序，并使用包含箭头键的 GUI。方向键对应键盘上的方向键。

当我按下键盘上的向上箭头键时，我希望 GUI 上的向上箭头键显示为已按下。在我松开箭头键之前，它应该显示它仍在被按下，并且在松开时它也应该松开。

到目前为止我的代码片段(仅用于向上按钮)，我认为在显示被按下类别中这是完全错误的:

...
if (e.getKeyCode() == KeyEvent.VK_UP) {
                    actionArrowUp();
                    JButton buttonUp = (JButton) mainTab.getComponent(4);
                    buttonUp.setSelected(true);
                }
...
@Override
public void keyReleased(KeyEvent e) { 
            if (e.getKeyCode() == KeyEvent.VK_UP)
                actionArrowUpRelease();
                buttonUp.setSelected(true);

Answer 1

使用 keyBindings(正如@trashgod 已经提到的那样)是的方法。获得与通过空格/输入激活按钮(当它被聚焦时)完全相同的视觉行为

• 实现委托(delegate)给为按下/释放注册的按钮的默认操作的操作
• 需要绑定(bind)到按键的按下和释放来模拟
• 在 WHEN_ANCESTOR 类型的 inputMap 中安装到按钮父级的绑定(bind)

在代码中:

// the delegating  action
public static class SimulateButtonAction extends AbstractAction {

    AbstractButton button;

    public SimulateButtonAction(AbstractButton model, String fire) {
        super(fire);
        this.button = model;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        Action delegate = button.getActionMap().get(getName());
        delegate.actionPerformed(new ActionEvent(button, 
                ActionEvent.ACTION_PERFORMED, getName()));
    }

    public String getName() {
        return (String) getValue(Action.NAME);
    }

}

// example usage
JComponent content = new JPanel(new GridLayout(0, 5));
Action log = new AbstractAction() {

    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("triggered: " + ((AbstractButton) e.getSource()).getText());
    }

};
String pressed = "pressed";
String released = "released";
ActionMap actionMap = content.getActionMap();
InputMap inputMap = content.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT);
String[] arrows = {"UP", "DOWN", "LEFT", "RIGHT"};
for (int i = 0; i < arrows.length; i++) {
    JButton button = new JButton(log);
    button.setAction(log);
    button.setText(arrows[i]);
    content.add(button);
    // simulate pressed
    String pressedKey = pressed + arrows[i];
    inputMap.put(KeyStroke.getKeyStroke(arrows[i]), pressedKey);
    actionMap.put(pressedKey, new SimulateButtonAction(button, pressed));
    String releasedKey = released + arrows[i];
    inputMap.put(KeyStroke.getKeyStroke(released + " " +arrows[i]), releasedKey);
    actionMap.put(releasedKey, new SimulateButtonAction(button, released));
}