Question

原谅可能简单的问题（以及可怕的布局方法）。我已成功将输入数据写入txt文件并单击“提交”的代码关闭输入窗口，打开“菜单”，添加用户（此代码）或搜索属性（不相关）的选项。我可以毫无问题地将一组详细信息输入到txt文件中，但是当重新打开AddUser窗口时，无论输入到框中的内容是什么，都将相同的数据输入到文件中，除非程序已关闭。我认为它与在重新打开窗口之前清除一些变量有关（如尝试到底部）然而我没有运气..我该怎么办呢？感谢

AddUser.java

package assignment; 
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.util.*;
import java.io.*;
import java.lang.*;

public class AddUser extends JFrame {

    //Declare the array values

    private String[] Name;
    private String[] Username;
    private String[] Password;
    private String[] StaffID;

    public String inputStaff;
    public String inputUser;
    public String inputPass;
    public String inputID;

    static public String inputData;


    //Declare Text Fields
    public JTextField Field1;
    public JTextField Field2;
    public JTextField Field3;
    public JTextField Field4;
    public JTextField Field5;

    //Declare Labels

    private JLabel Label;
    private JLabel Label1;
    private JLabel Label2;
    private JLabel Label3;
    private JLabel Label4;
    private JLabel Label5;
    private JLabel Space1;
    private JLabel Space2;

public AddUser() {

    super("Add New Agent");     //Window Title
    setLayout(new FlowLayout(FlowLayout.LEFT));    //Set Layout Type as FlowLayout

    Label = new JLabel("Enter the Member of Staff's Details");
    Label1 = new JLabel("Staff Name");    //Label Values
    Label2 = new JLabel("Username");
    Label3 = new JLabel("Password");
    Label4 = new JLabel("Confirm Password");
    Label5 = new JLabel("Staff ID");
    Space1 = new JLabel("    ");
    Space2 = new JLabel("                                       ");

    Field1 = new JTextField (10);   //Create the Text Fields and Option Blocks & Arguments
    Field2 = new JTextField (10);
    Field3 = new JTextField (10);
    Field4 = new JTextField (10);
    Field5 = new JTextField (4);






    //Add the labels, textfields and option blocks to the JFrame

    add (Label); add(Space1); add (Label1); add (Field1); add (Label2); add (Field2); add (Label3); add (Field3); add (Label4);
    add (Field4); add (Label5); add (Field5); add (Space2);





    JButton button1 = new JButton("Submit");    //Add "Search" button to JFrame
    add (button1);

    onClick handler = new onClick();
    button1.addActionListener(handler);

    }

    private class onClick implements ActionListener{
        public void actionPerformed(ActionEvent event){

//Action to be performed

//Attempt to clear the fields

           inputStaff = ("");
           inputUser = ("");
           inputPass = ("");
           inputID = ("");




           inputStaff = Field1.getText();
           inputUser = Field2.getText();
           inputPass = Field3.getText();
           inputID = Field5.getText();

           inputData = inputStaff + " " + inputUser + " " + inputPass + " " + inputID;


           WriteFile Write = new WriteFile(); //Create instance of write-to-file

           setVisible(false);
            //Close the window on clicking submit



               }

            }


           }

写入文件代码（WriteFile.java）如下;

package assignment;

import java.io.*;

public class WriteFile{
static String data = AddUser.inputData;
BufferedWriter out;

public WriteFile(){
    try {
        out = new BufferedWriter(new FileWriter("AddUser.txt", true));

        out.write(data);

        out.newLine();

        out.close();
    }
    catch(IOException e)
    {
        System.out.println("There was a problem:" + e);

    }
}


}

Answer 1

通过这种方式来实现这一点，请考虑以下几点：

public static void WriteFile(String data){
    try {
        out = new BufferedWriter(new FileWriter("AddUser.txt", true));
        out.write(data);
        out.newLine();
        out.close();
    }
    catch(IOException e)
    {
        System.out.println("There was a problem:" + e);
    }
}

并称之为：

WriteFile.WriteFile(inputData);

我也会更改方法的名称，但我尽量让它尽可能接近原始代码。

不要以这种方式SomeClass.someField访问类的字段，并在不需要静态成员时尽量避免使用静态成员。

Answer 2

该行

static String data = AddUser.inputData;

加载类时，

仅运行一次。所有静态变量都是这种情况。（您似乎在思考“数据流编程”或电子表格，但Java不能像那样工作。或者您可能认为String对象是可更新的，但它们不是 - 它们是不可变的。）< / p>

这是在类之间实现数据传递的一种可怕方式，正如您所看到的，它不起作用。如果由于某种原因，该类恰好比它更早加载，它甚至不会工作一次。

清除JTextfields以将多个数据写入txt文件

2 个答案: