当从另一个JFrame遍历时，键侦听器在一个JFrame中不起作用

Question

我有两节课。

一个扩展canvas并在内部创建一个jframe，将canvas添加到该jframe，并添加另一个keyadapter类以接收键事件。我也有主要的函数来测试代码。当从main运行时，表单将显示并接收关键事件。

现在我创建了另一个扩展jframe并实现keylistener以接收这种形式的事件的类。

在第二个类中完成功能后，我想关闭第二个表单并显示第一个表单。当从第二个类中的键事件函数显示它时，第一个类的键侦听器不工作。

请看一下我的代码并告诉我如何纠正我的问题。感谢您的时间和宝贵的建议。

第1类

public class Test extends Canvas {

private JFrame container;

public Test() {

    container = new JFrame("Space Invaders");
    JPanel panel = (JPanel) container.getContentPane();
    panel.setPreferredSize(new Dimension(screenSize.width, screenSize.height));
    panel.setLayout(null);
    setBounds(0, 0, screenSize.width, screenSize.height);
    panel.add(this);
    container.pack();
    container.setResizable(false);
    container.setVisible(true);

    try {

        addKeyListener(new KeyInputHandler(this));
    } catch (Exception e) {
        e.printStackTrace();
    }
    requestFocus();
}

private class KeyInputHandler extends KeyAdapter {

public void keyPressed(KeyEvent e) {
    //Some Action
}
public void keyReleased(KeyEvent e) {
    //Some Action
}
public void keyTyped(KeyEvent e) {
    //Some Action
}
}

public static void main(String args[]){
    //Running this canvas here works perfectly with all added keylisteners
}
}

public class Sample extends JFrame implements KeyListener {

public Sample() {
    init();
    this.setSize(100, 100);
    this.setVisible(true);
    Sample.this.dispose();
            // Created a window here and doing some operation and finally redirecting
            // to the previous test window. Even now the test window works perfectly
            // with all keylisteners
    new Test();
}

public static void main(String[] args) {
    new Sample();

}

private void init() {
    addKeyListener(this);
}

@Override
public void keyTyped(KeyEvent e) {

}

@Override
public void keyPressed(KeyEvent e) {
    removeKeyListener(this);
    Sample.this.dispose();
            // But when calling the previous Test window here, the window 
            // gets displayed but the keylistener is not added to the 
            // window. No keys are detected in test window.
    new Test();
}

@Override
public void keyReleased(KeyEvent e) {

}
}

Answer 1

简单的不要使用keylistener/keyadapter，它用于AWT组件，并且与Swing一起使用时有已知的焦点问题。

通过setFocusable(true)确保组件可聚焦，并在添加组件/组件可见后调用RequestFocusInWindown()来解决这些问题。

而是使用keybindings进行Swing。

public static void addKeyBindings(JComponent jc) {
    jc.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_D, 0, false), "D pressed");
    jc.getActionMap().put("D pressed", new AbstractAction() {
        @Override
        public void actionPerformed(ActionEvent ae) {
            System.out.println("D pressed");
        }
    });

    jc.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_D, 0, true), "D released");
    jc.getActionMap().put("D released", new AbstractAction() {
        @Override
        public void actionPerformed(ActionEvent ae) {
            System.out.println("D released");
        }
    });
}

我们将此方法称为：

JPanel ourPanel=new JPanel();

...

addKeyBindings(ourPanel);//adds keybindings to the panel

有关守则的其他建议

>

始终通过SwingUtilities.Invokelater(Runnable r)块在事件调度线程上创建和操作Swing组件