直到您选择它，JTextArea才会显示

Question

My code creates a basic Sign Up screen, but the JTextArea objTE1 does not show up until you select where the text would be.

import java.awt.*;
import javax.swing.*;
public class SignUpScreen extends Frame
{
    SignUpScreen()
    {
        super("No Layout Manager");
        setLayout(null);
        setTitle("Sign Up");
        setSize(400,700);
        show();
    }
    public static void main(String[] args)
    {
        Frame objFrame;
        JTextArea objTE1;

        JCheckBox objCheckMail;
        JCheckBox objCheckEmail;
        JCheckBox objCheckPhone;

        Button objButtonFinish;
        Button objButtonCancel;

        TextField objEnterEmail;
        TextField objEnterAdress;
        TextField objEnterPhone;
        TextField objEnterUsername;
        TextField objEnterPassword;
        TextField objConfirmPassword;


        objFrame = new SignUpScreen();
        objTE1 = new JTextArea();
        objCheckMail = new JCheckBox("Mail Notifications");
        objCheckEmail = new JCheckBox("Email Notifications");
        objCheckPhone = new JCheckBox("Text Notifications");

        objButtonFinish = new Button("Sign Up");
        objButtonCancel = new Button("Cancel");

        objEnterEmail = new TextField("Enter Email",0);
        objEnterAdress = new TextField("Enter Adress",0);
        objEnterPhone = new TextField("Enter Phone Number",0);
        objEnterUsername = new TextField("Enter Username",0);
        objEnterPassword = new TextField("Enter Password",0);
        objConfirmPassword = new TextField("Confirm Password",0);

        Font pagehead = new Font("Verdana", Font.BOLD, 24);
        objTE1.setFont(pagehead);
        objTE1.setForeground(Color.BLUE);

        objTE1.setText("     Sign up for the\nWatermelone Mail List");
        objTE1.setEditable(false);
            objTE1.setVisible(true);


        objTE1.setBounds(50, 75, 300, 70);

        objCheckMail.setBounds(100,450,200,50);
        objCheckEmail.setBounds(100,500,200,50);
        objCheckPhone.setBounds(100,550,200,50);

        objEnterEmail.setBounds(100,150,150,20);
        objEnterAdress.setBounds(100,200,200,20);
        objEnterPhone.setBounds(100,250,200,20);
        objEnterUsername.setBounds(100,300,200,20);
        objEnterPassword.setBounds(100,350,200,20);
        objConfirmPassword.setBounds(100,400,200,20);

        objButtonFinish.setBounds(50,600,120,60);
        objButtonCancel.setBounds(220,600,120,60);


        objFrame.add(objTE1);

        objFrame.add(objEnterEmail);

        objFrame.add(objButtonFinish);
        objFrame.add(objButtonCancel);

        objFrame.add(objEnterUsername);
        objFrame.add(objEnterPassword);
        objFrame.add(objConfirmPassword);
        objFrame.add(objEnterAdress);
        objFrame.add(objEnterPhone);

        objFrame.add(objCheckMail);
        objFrame.add(objCheckPhone);
        objFrame.add(objCheckEmail);
    }
}

Answer 1

1. Don't use a "null layout". Swing was designed to be used with layout managers.
2. Use new JTextArea(5, 30); when creating a text area. That is specify the rows/columns for the text area.
3. Don't use AWT components in a Swing application. Swing components start with a "J", JButton, JTextField, JFrame.
4. Don't use show() . The proper method is setVisible(true)
5. Create your GUI components on the Event Dispatch Thread (EDT) .
6. The setVisible(true) needs to be done AFTER all the components have been added to the frame.

I suggest you read the section from the Swing tutorial on Using Layout Managers for some examples of using layout managers and on to use the EDT .