[英]How do I get focus for a keypress in a CardLayout?
我有一個CardLayout示例正常使用按鈕,然后嘗試將其轉換為使用按鍵。 我認為問題在於我沒有焦點,但我無法將焦點設置為框架或面板成功。 謝謝!
我從框架和所示的第一個面板嘗試了requestFocusInWindow,但這沒有幫助。 我問了frame.getFocusOwner()並返回null。 我認為CardLayout會自動將焦點放在頂部元素上,但是當我有一個按鈕時它會起作用,現在它不起作用了。
public class MyCardLayoutExample3 {
public static void main(String[] args){
MyCardLayoutExample3 game = new MyCardLayoutExample3();
game.display();
}
void display() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setSize(300, 200);
CardLayout cardLayout = new CardLayout();
frame.getContentPane().setLayout(cardLayout);
MyGamePanel3 mgp3 = new MyGamePanel3("minigame A", Color.red);
frame.getContentPane().add(mgp3);
frame.getContentPane().add(new MyGamePanel3("minigame B", Color.green));
frame.getContentPane().add(new MyGamePanel3("minigame C", Color.blue));
frame.setVisible(true);
System.out.println("owner: " + frame.getFocusOwner()); //this prints null
}
}
class MyGamePanel3 extends JPanel implements KeyListener{
MyGamePanel3(String text, Color bg){
JLabel textLabel = new JLabel(text);
this.setBackground(bg);
this.add(textLabel);
}
@Override
public void keyTyped(KeyEvent e) {}
@Override
public void keyPressed(KeyEvent e) {
System.out.println("keyPressed worked");
}
@Override
public void keyReleased(KeyEvent e) {}
}
更改為鍵綁定使示例輕松工作,感謝Abra。 盡管嘗試了上面的鏈接和許多其他鏈接,我仍然沒有讓keyListener工作。
import java.awt.CardLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.WindowConstants;
class MyGamePanel extends JPanel{
MyGamePanel(ActionListener alNext, String text, Color bg){
JButton buttonNext = new JButton("next");
buttonNext.addActionListener(alNext);
JLabel textLabel = new JLabel(text);
this.setBackground(bg);
this.add(textLabel);
this.add(buttonNext);
}
}
public class MyCardLayoutKeyBindingExample {
public static void main(String[] args){
MyCardLayoutKeyBindingExample game = new MyCardLayoutKeyBindingExample();
game.display();
}
void display() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setSize(300, 200);
CardLayout cardLayout = new CardLayout();
//frame.getContentPane().setLayout(cardLayout);
JPanel mainPanel = new JPanel(cardLayout);
frame.add(mainPanel);
ActionListener al1 = e -> cardLayout.next(mainPanel);
mainPanel.add(new MyGamePanel(al1, "minigame A", Color.red));
mainPanel.add(new MyGamePanel(al1, "minigame B", Color.green));
mainPanel.add(new MyGamePanel(al1, "minigame C", Color.blue));
mainPanel.getInputMap().put(KeyStroke.getKeyStroke("SPACE"), "space");
Action kp = new AbstractAction() {
public void actionPerformed(ActionEvent e) {
System.out.println("key pressed");
}
};
mainPanel.getActionMap().put("space", kp);
frame.setVisible(true);
}
}
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