Java KeyBindings:它是如何工作的? [英] Java KeyBindings: How does it work?
问题描述
我一直看到我应该使用键绑定而不是KeyListeners.因此，我找到了以下页面:键绑定.我仔细阅读并尝试实现它.
Action numPressed = new AbstractAction() {
public void actionPerformed(ActionEvent e) {
System.out.println("hi");
}
};
this.getInputMap().put(KeyStroke.getKeyStroke("1"), "released");
this.getActionMap().put("released", numPressed);
我决定只是看看会发生什么.这个类扩展了JPanel.之前，我使用了this.setFocusable(true).但是，当我键入"1"时，我什么也看不见.我究竟做错了什么?应该如何实现键绑定?
您的示例仅在面板具有焦点时才有效，请尝试使用getInputMap(WHEN_IN_FOCUSED_WINDOW).
您可能还会发现您的KeyStroke语句也不起作用，我建议尝试使用KeyStroke.getKeyStroke(KeyEvent.VK_1, 0, true)代替，这将为您提供一个可以响应键释放的KeyStroke对象.
已更新示例
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestKeyBindings04 {
public static void main(String[] args) {
new TestKeyBindings04();
}
public TestKeyBindings04() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_1, 0, false), "pressed");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_1, 0, true), "released");
am.put("pressed", new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("Pressed");
}
});
am.put("released", new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("released");
}
});
setFocusable(true);
requestFocusInWindow();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.dispose();
}
}
}
I keep seeing that I should use Key Bindings instead of KeyListeners. So I found this page: Key Bindings. I read through it and tried to implement it.
Action numPressed = new AbstractAction() {
public void actionPerformed(ActionEvent e) {
System.out.println("hi");
}
};
this.getInputMap().put(KeyStroke.getKeyStroke("1"), "released");
this.getActionMap().put("released", numPressed);
I decided to just see what would happen. The class this is in extends a JPanel. Earlier, I used this.setFocusable(true). However, I don't see anything happen when I type '1'. What am I doing wrong? How are Key Bindings supposed to be implemented?
Your example will only work IF the panel has focus, try using getInputMap(WHEN_IN_FOCUSED_WINDOW) instead.
You may also find that your KeyStroke statement won't work either, I'd suggest trying to use KeyStroke.getKeyStroke(KeyEvent.VK_1, 0, true) instead, which will provide you with a KeyStroke object that will respond to key releases.
Updated with example
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestKeyBindings04 {
public static void main(String[] args) {
new TestKeyBindings04();
}
public TestKeyBindings04() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_1, 0, false), "pressed");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_1, 0, true), "released");
am.put("pressed", new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("Pressed");
}
});
am.put("released", new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("released");
}
});
setFocusable(true);
requestFocusInWindow();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.dispose();
}
}
}
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