Java KeyListener切换JPanel后未响应 [英] Java KeyListener not responding after switching JPanels
问题描述
当我在JPanels之间切换时,KeyListener没有响应(由于未获得焦点)而出现问题.
I got a problem with the KeyListener not responding(due to not gaining focus) when I switch between JPanels.
我有Google,并且知道要解决此问题,我需要使用KeyBindings,但我不喜欢KeyBindings.所以我想知道,还有其他方法吗?
I have Google'd this and know that to fix this problem I need to use KeyBindings, but I don't like KeyBindings. So I was wondering, is there any other way?
这是JPanel的初始化代码,它的KeyListener没有响应:
Here is the init code of the JPanel that has an unresponsive KeyListener:
public void init()
{
setFocusable(true);
requestFocusInWindow();
requestFocus();
addMouseListener(new MouseInput());
addMouseMotionListener(new MouseInput());
addMouseWheelListener(new MouseInput());
addKeyListener(new KeyInput(p));
t = new Timer(10, this);
t.start();
}
如有需要,随时询问更多代码示例!
Feel free to ask for more code samples if you need to!
推荐答案
有问题的解决方案是在JPanel
上调用requestFocusInWindow()
以确保其将焦点放在KeyListener
/KeyAdapter
上,仅应调用添加Componnet之后(尽管为了确保我的组件具有焦点,我在通过revalidate()
和repaint()
刷新JFrame
之后调用了它)例如:
The hacky solution is to call requestFocusInWindow()
on the JPanel
to make sure it has focus for KeyListener
/KeyAdapter
this should only be called after the Componnet has been added (though to be sure my component has focus I called it after the JFrame
is refreshed via revalidate()
and repaint()
) for example:
public class MyUI {
//will switch to the gamepanel by removing all components from the frame and adding GamePanel
public void switchToGamePanel() {
frame.getContentPane().removeAll();
GamePanel gp = new GamePanel();//keylistener/keyadapter was added to Jpanel here
frame.add(gp);//add component. we could call requestFocusInWindow() after this but to be 98% sure it works lets call after refreshing JFrame
//refresh JFrame
frame.pack();
frame.revalidate();
frame.repaint();
gp.requestFocusInWindow();
}
}
class GamePanel extends JPanel {
public GamePanel() {
//initiate Jpanel and Keylistener/adapter
}
}
但是您应该使用Swing KeyBinding
(+ 1到@Reimeus注释).
However you should use Swing KeyBinding
s (+1 to @Reimeus comment).
请在此处阅读以熟悉它们:
Have a read here to get familiar with them:
现在,您已经阅读了让我们展示另一个示例来帮助阐明(尽管Oracle做得很好)
Now that you have read that lets show another example to help clarify (though Oracle did a good job)
如果我们想将KeyBinding
添加到某个JComponent
,即JButton
for Esc ,则可以执行以下操作:
If we wanted to add a KeyBinding
to a certain JComponent
i.e JButton
for Esc you would do:
void addKeyBinding(JComponent jc) {
jc.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_ESCAPE, 0, false), "esc pressed");
jc.getActionMap().put("esc pressed", new AbstractAction() {
@Override
public void actionPerformed(ActionEvent ae) {
System.out.println("Esc pressed");
}
});
jc.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_ESCAPE, 0, true), "esc released");
jc.getActionMap().put("esc released", new AbstractAction() {
@Override
public void actionPerformed(ActionEvent ae) {
System.out.println("Esc released");
}
});
}
上面的方法将被称为:
JButton b=..;//create an instance of component which is swing
addKeyBinding(b);//add keybinding to the component
请注意:
1)您不需要同时使用KeyBindings
,我只是演示了如何获取不同的键状态并使用Keybindings
适当地执行操作.
1) You would not need both KeyBindings
, I just showed how to get different key state and act appropriately using Keybindings
.
2)此方法将添加一个Keybinding
,只要按下 Esc 且组件位于具有焦点的窗口中,就会激活该Keybinding
,您可以通过指定另一个
2) This method will add a Keybinding
which will be activated as long as Esc is pressed and the component is in the window which has focus, you can change this by specifying another InputMap
i.e:
jc.getInputMap(JComponent.WHEN_FOCUSED).put(..);//will only activated when component has focus
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