[英]Java KeyListener not responding after switching JPanels
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。
我已经用过Google,并且知道要解决此问题,我需要使用KeyBindings,但是我不喜欢KeyBindings。 所以我想知道,还有其他方法吗?
这是具有不响应的KeyListener的JPanel的初始化代码:
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();
}
如果需要,请随时请求更多代码示例!
hacky解决方案是在JPanel
上调用requestFocusInWindow()
以确保它具有KeyListener
/ KeyAdapter
焦点,只有在添加Componnet之后才应调用它(尽管要确保我的组件具有焦点,所以刷新JFrame
之后我会调用它)通过revalidate()
和repaint()
),例如:
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)。
在这里阅读以熟悉它们:
现在,您已经阅读了让我们展示另一个示例来帮助阐明的内容(尽管Oracle做得很好)
如果我们想将KeyBinding
添加到某个JComponent
即Esc的 JButton
,则可以执行以下操作:
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)您不需要两个KeyBindings
,我只是演示了如何获取不同的键状态并使用Keybindings
适当地操作。
2)此方法将添加一个Keybinding
,只要按下Esc并且该组件位于具有焦点的窗口中,就可以激活它,您可以通过指定另一个InputMap
来更改它,即:
jc.getInputMap(JComponent.WHEN_FOCUSED).put(..);//will only activated when component has focus
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