更改JFrame的面板“禁用”插入新Panel的inputMap [英] Changing the Panels of a JFrame "disable" the inputMap of the new Panel inserted

问题描述

问题描述：我有一个JFrame，在这个JFrame里面有一个带有按钮的JPanel，当我按下按钮一个动作监听器用一个新的JPanel来改变当前的JPanel，其中包含其他两个JPanel，一个inputMap，当用户按下上键时，两者都会有一些东西。问题是：当我用新的更改JPanel时，up键不会执行任何操作。

Description of the problem: I have a JFrame, inside this JFrame there is a JPanel with a button, when I press the button an action listener change the current JPanel with a new JPanel, which contains other two JPanels, those two have an inputMap that when the user press the key "up" make something on both of them. The problem is: when I change the JPanel with the new one the "up" key won't do anything.

这是代码：是一个SSCCE，所以你只需要复制并粘贴即可看到它的作用。

Here is the code: is a SSCCE, so you just have to copy and paste to see what it does.

这个修改后的代码来自另一个有时候解决的问题。 如何使两个JPanels听同一个事件？
（代码在我选择的答案中）。

This modified code comes from another question that I "solved" sometimes ago. How to make two JPanels listen to the same event? (the code is in the answer that I selected).

import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.util.Arrays;
import java.util.List;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.KeyStroke;

public class TwoPanelsTest extends JFrame {

private static MyPanel one = new MyPanel("One");
private static MyPanel two = new MyPanel("Two");
private static List<MyPanel> list = Arrays.asList(one, two);
private PanelsController panelsController;

public TwoPanelsTest() {
    super("TwoPanelsTest");
    panelsController= new PanelsController(this);
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    this.setSize(400,400);
    this.setLocationRelativeTo(null);
    this.setVisible(true);
}

private static class MyPanel extends JPanel {

    private String string = " will be updated though its action.";
    private Action action = new UpdateAction(this);
    private String name;
    private JLabel label;

    public MyPanel(String name) {
        this.name = name;
        this.label = new JLabel(name + string, JLabel.CENTER);
        this.setLayout(new GridLayout());
        this.setFocusable(true);
        this.add(label);
    }

    public Action getAction() {
        return action;
    }

    private void update() {
        label.setText(name + ": " + System.nanoTime());
    }

    private static class UpdateAction extends AbstractAction {

        private MyPanel panel;

        public UpdateAction(MyPanel panel) {
            this.panel = panel;
        }

        @Override
        public void actionPerformed(ActionEvent ae) {
            panel.update();
        }
    }
}//MyPanel

private static class ButtonPanel extends JPanel{
    private JButton button ;
    private PanelsController panelsController;

    public ButtonPanel(PanelsController panelsController){
        this.panelsController=panelsController;

        button = new JButton("Button");
        button.setActionCommand("buttonPressed");
        button.addActionListener(this.panelsController);
        this.setFocusable(true);
        add(button);
    }
}//ButtonPanel

private static class PanelsController implements ActionListener {

    private TwoPanelsTest twoPanelsTest;

    public PanelsController(TwoPanelsTest twoPanelsTest){
        this.twoPanelsTest=twoPanelsTest;
        this.twoPanelsTest.getContentPane().add(new ButtonPanel(this));
    }

    @Override
    public void actionPerformed(ActionEvent ae) {
        if (ae.getActionCommand().equals("buttonPressed")){
            twoPanelsTest.getContentPane().removeAll();
            twoPanelsTest.getContentPane().invalidate();

            JPanel panel = new JPanel(new GridLayout(0, 1, 10, 10));
            panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
            panel.add(one);
            panel.add(two);
            panel.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT)
            .put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), "up");
            panel.getActionMap().put("up", new AbstractAction() {

                @Override
                public void actionPerformed(ActionEvent e) {
                    for (MyPanel panel : list) {
                        panel.getAction().actionPerformed(e);
                    }
                }
            });
            twoPanelsTest.getContentPane().add(panel);
            twoPanelsTest.validate();
            twoPanelsTest.repaint();
        }
    }//ActionPerformed

}//PanelsController

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {

        @Override
        public void run() {
            TwoPanelsTest t = new TwoPanelsTest();
        }
    });
}
}

推荐答案

，它很简单 - 如果你有这两个面板没有任何组件，并希望他们听热键使用：

Well, its pretty simple - if you have those two panels without any components inside and want them to listen the hotkey use:

panel.getInputMap ( JComponent.WHEN_IN_FOCUSED_WINDOW )
     .put ( KeyStroke.getKeyStroke ( KeyEvent.VK_UP, 0 ), "up" );

JComponent.WHEN_IN_FOCUSED_WINDOW而不是JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT。

JComponent.WHEN_IN_FOCUSED_WINDOW instead of JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT.

否则，您需要将重点放在面板中，以便能够捕获关键事件。

Otherwise you need to have somthing focused inside the panel so it could catch the key events.

顺便说一句，还有另一种方式来监听内部的全局热键Java应用程序窗口：

By the way, there is also another way to listen global hotkeys inside Java application windows:

Toolkit.getDefaultToolkit ().addAWTEventListener ( new AWTEventListener ()
{
    public void eventDispatched ( AWTEvent event )
    {
        // All application key events will be passed here
    }
}, AWTEvent.KEY_EVENT_MASK );

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