e857. enabling an action.txt

这里面包含了一百多个JAVA源文件

Actions can be bound to many different kinds of components. When an action is enabled or disabled, components that are bound to that action may automatically alter its display to match the enabled state of the action. This example creates three components: a button, a text component, and a menu item - - all bound to the same action. When the action is disabled, the button and menu item will appear disabled and the text component will not be able to invoke the action. 
    JFrame frame = new JFrame();
    
    // Button
    JButton button = new JButton(action);
    
    // Text Component
    JTextField textfield = new JTextField();
    textfield.getInputMap(JComponent.WHEN_FOCUSED).put(
        KeyStroke.getKeyStroke("F2"), action.getValue(Action.NAME));
    textfield.getActionMap().put(action.getValue(Action.NAME), action);
    
    // Menu Item
    JMenuBar menuBar = new JMenuBar();
    JMenu menu = new JMenu("Menu Label");
    menu.add(new JMenuItem(action));
    menuBar.add(menu);
    frame.setJMenuBar(menuBar);
    
    // The action
    public Action action = new AbstractAction("Action Name") {
        public void actionPerformed(ActionEvent evt) {
            // Perform action
        }
    };