我想默认使光标出现在JTextField“框”中。当前，我必须先将光标放在框中，然后它才会出现。这是代码。
class XYZ extends JFrame implements ActionListener {
JTextField box = new JTextField();
JButton again = new JButton("Restart");
JButton ext = new JButton("Exit");
XYZ() {
box.addActionListener(this);
again.addActionListener(this);
ext.addActionListener(this);
box.setPreferredSize(new Dimension(20,20));
box.setHorizontalAlignment(JTextField.CENTER)
JPanel s3 = new JPanel(new BorderLayout()); //This holds the 3 panels below
JPanel restart = new JPanel(new BorderLayout()); //this holds a button
JPanel leave = new JPanel(new BorderLayout()); //also holds a button
//The following holds a JLabel and the textfield
JPanel middle = new JPanel(new FlowLayout(FlowLayout.CENTER,20,0));
JLabel j2 = new JLabel("Enter your guess!");
middle.add(j2);
middle.add(box);
restart.add(again,BorderLayout.SOUTH);
leave.add(ext,BorderLayout.SOUTH);
//Adding the 3 panels to s3
s3.add(middle,BorderLayout.CENTER);
s3.add(restart,BorderLayout.WEST);
s3.add(leave,BorderLayout.EAST);
}
}
您可以通过调用来简单地请求文本字段为焦点requestFocusInWindow。一旦包含文本字段的框架可见，只需调用此方法：
box.requestFocusInWindow();
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