Java-JFrame根本不顯示其內容

Question

我的第一篇文章。 我是計算機科學專業第一年的學生。

我只是在為任務分配一個基本的GUI，由於某種原因，我一生都看不到它，我已經創建了一個JFrame，當從Register按鈕調用該類時，Register Class的實例顯示為完全空白登錄類中的操作偵聽器...

我還有一個單獨的主類，其中包含Main方法並調用Login Class。 登錄類JFrame可以正常工作，並且如上所述，只有在“登錄類”的“注冊”按鈕操作偵聽器中調用“注冊類”時，才會出現問題。 該程序中的所有其他JFrame也可以正常工作。

我試圖直接從主體調用Register Class，並且它具有相同的問題，盡管我試圖將其簡化為最基本的形式，除了空白的未着色JFrame之外，它仍然不顯示任何內容。

這是代碼（未完成，但按原樣工作）。 我為我的馬虎而道歉，但是我是一個完整的初學者。

誰能看到這是怎么回事？

提前致謝！

    package guitest;

    import java.awt.Color;
    import java.awt.Component;
    import java.awt.FlowLayout;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.io.BufferedWriter;
    import java.io.FileWriter;
    import java.awt.event.*;
    import java.io.*;
    import javax.swing.*;

    public class Register extends JFrame{

        JButton regSubmit = new JButton("Submit");

        JTextField email = new JTextField();
        JTextField name = new JTextField();
        JTextField Address1 = new JTextField();
        JTextField Address2 = new JTextField();

        JPasswordField password1 = new JPasswordField();
        JPasswordField password2 = new JPasswordField();

        String nameTxt = email.getText();
        String passTxt = password1.getText();
        String info = "";

        FlowLayout layout1 = new FlowLayout();    

        public void Reg(){
            this.setTitle("La Volpe Registration");
            this.setLayout(layout1);    
            this.add(Address1);
            this.add(Address2);
            this.add(email);
            this.add(password1);
            this.add(password2);
            this.add(name);
            this.add(regSubmit);
            this.getContentPane().setBackground(Color.green);
            this.setSize(370, 160);

            regSubmit.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent evt) {
                    regSubmitActionPerformed(evt);
                }

                private void regSubmitActionPerformed(java.awt.event.ActionEvent evt) { 

                String name = email.getText();
                String pass = password1.getText();
                String info = "";

                System.out.println("registering...");

                boolean eof;

                try{
                    // Create file
                    FileWriter file = new FileWriter("\\regdata.txt");
                    BufferedWriter out = new BufferedWriter(file);
                    out.write("\n"+nameTxt+", "+passTxt);
                }

                catch (Exception e){
                }   
            }   
        });
        this.setVisible(true);
    }    
}

---

和鏈接到它的類...

---

package guitest;

    import java.awt.Color;
    import java.awt.Component;
    import java.awt.FlowLayout;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.io.BufferedWriter;
    import java.io.FileWriter;
    import java.awt.event.*;
    import java.io.*;
    import javax.swing.*;

    /**
    * @author david
    */

    public class Login {

    JFrame loginFrame = new JFrame();
    Register reg3 = new Register();

    JButton submit = new JButton("Submit");
    JButton clear = new JButton("Clear");
    JButton register = new JButton ("Register with Us");

    JPasswordField pass = new JPasswordField(20);
    JTextField email = new JTextField(20);
    JLabel em = new JLabel("Email Address: ");
    JLabel pw = new JLabel("Password: ");

    String pathname;
    String line;
    String [] records = new String [1000];
    int count = 0;

    FlowLayout layout1 = new FlowLayout();

        public Login(){

            //Adds Email label and text field
            loginFrame.add(em);
            loginFrame.add(email);

            //Adds password label and field
            loginFrame.add(pw);
            loginFrame.add(pass);

            //Adds buttons
            loginFrame.add(submit);
            loginFrame.add(clear);
            loginFrame.add(register);

            loginFrame.getContentPane().setBackground(Color.green);

            loginFrame.setLayout(layout1);

            loginFrame.setSize(370, 160);

            loginFrame.setTitle("La Volpe - Login");

            submit.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent evt) {
                    submitActionPerformed(evt);    
                }            

                private void submitActionPerformed(java.awt.event.ActionEvent evt){                                         
                String emailadd = email.getText();
                String password = pass.getText();
                pathname = "\\regdata.txt";

                boolean eof;

                try{
                    FileReader file = new FileReader(pathname);
                    BufferedReader buff = new BufferedReader(file);

                    eof = false; // set the eof boolean to false

                        while (!eof){
                        line = buff.readLine();
                        if (line == null){ // test to see if the end of file has been reached
                        eof = true;  // if the end of file has been found set the eof Boolean to true
                        }
                        else{ 
                        // end of file not reached so move the contents of the line to the records
                        //array
                        records[count] = line;
                        count ++;
                        System.out.println(line);  // print out the new line input for error checking
                        }
                    }    
                    buff.close();
                }
                catch (IOException e){
                    System.out.println("Error --  "+ e.toString());
                }

                boolean notTrue = false;

                for (int i = 0; i < count; i++) {       
                    if ((!notTrue)&&((emailadd + "," + password).equals(records[i]))) {
                        FoodSelectionMain loggedIn = new FoodSelectionMain();
                        loggedIn.setVisible(true);
                    } 
                }
                if (!notTrue){
                    JOptionPane.showInputDialog("Please check your login "
                    + "and try again. If you are a new user, please "
                    + "register by pressing the 'REGISTER' button");
                }
            }   

        }); 

        // TODO add your handling code here:


        clear.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                clearActionPerformed(evt);
            }

            public void clearActionPerformed(java.awt.event.ActionEvent evt){
                email.setText(null);
                pass.setText(null);
            }

        }); 
        register.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                registerActionPerformed(evt);
            }

            public void registerActionPerformed(java.awt.event.ActionEvent evt){
                reg3.setVisible(true);
                    System.out.println("Register pressed");
            }
        });
        loginFrame.setVisible(true);
    }
}

Answer 1

嘗試這樣做，在Register類中，將Reg（）中的構造函數名稱更正為Register（）。

在構建gui應用之前，請牢記這幾項准則

1. 創建容器子類的對象。

2. 將容器中包含的所有組件視為實例變量。

3. 在方法的構造函數外部設置這些實例變量和事件處理（即setComponent（），setHandler（）。etc），但從構造函數執行這些方法調用。

4. 現在主要用於...

。

EventQueue.invokeLater(new Runnable() {

    public void run() {
        Myframe f = new Myframe();
        f.setVisible(true);
    }
}