无法停止JTextFeild获取默认焦点

Question

我有一个简单的登录屏幕。我希望UserName和Password显示在第一个和第二个文本字段中，直到它们被单击。此功能正在运行。然而，当应用程序启动时，第一个文本字段始终是焦点，因此显示为"“，直到失去焦点。我试图设置一个默认按钮并请求焦点，但无济于事。该按钮看起来默认正确，但由于某种原因，它没有接收到焦点。有人知道怎么解决这个问题吗？

public class Basics implements ActionListener{

private JFrame frmBasics;
private JTextField userNameFeild;
private JTextField passwordFeild;
private JButton btnSignIn;
private JButton btnSignUp;

/**
 * Launch the application.
 */
public static void main(String[] args) {



    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                Basics window = new Basics();
                window.frmBasics.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });


}//end main

/**
 * Create the application.
 */
public Basics() {
    initialize();
}

/**
 * Initialize the contents of the frame.
 */
private void initialize() {
    frmBasics = new JFrame();
    frmBasics.setTitle("Welcome to the POOPalace!!!");
    frmBasics.setBounds(100, 100, 511, 344);
    frmBasics.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frmBasics.getContentPane().setLayout(null);

    userNameFeild = new JTextField("UserName");
    userNameFeild.setBounds(148, 79, 214, 20);
    userNameFeild.addFocusListener(new FocusedClass());
    frmBasics.getContentPane().add(userNameFeild);
    userNameFeild.setColumns(10);

    passwordFeild = new JTextField("Password");
    passwordFeild.setBounds(148, 126, 214, 20);
    passwordFeild.addFocusListener(new FocusedClass());
    frmBasics.getContentPane().add(passwordFeild);
    passwordFeild.setColumns(10);

    btnSignIn = new JButton("Sign In");
    btnSignIn.setBounds(148, 182, 89, 23);
    btnSignIn.addActionListener(this);
    frmBasics.getContentPane().add(btnSignIn);

    btnSignUp = new JButton("Sign Up");
    btnSignUp.setBounds(273, 182, 89, 23);
    btnSignUp.addActionListener(this);
    frmBasics.getContentPane().add(btnSignUp);

    //from what I've been reading these 2 lines should be the solution
    //but the request focus seems to not be working 
    frmBasics.getRootPane().setDefaultButton(btnSignIn);;
    btnSignIn.requestFocus();


}

@Override
public void actionPerformed(ActionEvent e) {

    //frmBasics.getContentPane().removeAll();
    //frmBasics.repaint();
    System.out.println(userNameFeild.getText());
    System.out.println(passwordFeild.getText());

}//actionPerformed


private class FocusedClass implements FocusListener {

    @Override
    public void focusGained(FocusEvent arg0) {

        if(arg0.getSource().equals(userNameFeild) && userNameFeild.getText().compareTo("UserName") == 0){
            userNameFeild.setText("");
            }
        if(arg0.getSource().equals(passwordFeild) && passwordFeild.getText().compareTo("Password") == 0){
            passwordFeild.setText("");
        }

    }

    @Override
    public void focusLost(FocusEvent arg0) {

        if(userNameFeild.getText().compareTo("") == 0){
            userNameFeild.setText("UserName");
        }

        if(passwordFeild.getText().compareTo("") == 0){
            passwordFeild.setText("Password");
        }

        frmBasics.getContentPane().repaint();
    }

}



}//class

Answer 1

只有在窗口布局完成后，请求焦点才起作用。我们需要在以下三种特定情况之一调用requestFocusInWindow()：

windowOpened()方法中的

1. 。EventQueue's invokeLater()中的
2. ，它将在处理所有挂起事件后运行。重写的JFrame's setVisible()方法中的
3. 。

第一个选项：

//btnSignIn.requestFocusInWindow();

frmBasics.addWindowListener(new WindowAdapter() {
    @Override
    public void windowOpened(WindowEvent e) {
        btnSignIn.requestFocusInWindow();
    }
});

还要注意的是，requestFocusInWindow()比requestFocus()更可移植。