Question

似乎无法让扫描程序将JTextField的用户输入与文本文件相匹配。例如：搜索员工编号1121并查看其身份。数字＆amp;文本文件中的名称

更新：完整代码，下面有更改

public class custSearch extends JFrame{
private static final long serialVersionUID = 1L;
public JTextField userInput;

// Declaring Window Name, Size & Functions
public custSearch(){
    super ("Customer Records");
    setSize(630,250);
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    //NumberFormat integerFieldFormatter = NumberFormat.getIntegerInstance();
    //integerFieldFormatter.setGroupingUsed(false);

// Declaring JPanels & New FlowLayouts  
    JPanel p1 = new JPanel();
    p1.setLayout(new FlowLayout(-2));

// Declaring JLabels    
    JLabel cs = new JLabel("Search Phone Number:"); 

// Declaring JButtons
    JButton sb1 = new JButton("Search");

// Declaring JFormattedTextFields
    //JFormattedTextField cNumber = new JFormattedTextField(integerFieldFormatter);
    //cNumber.setColumns(7);
    JTextField cNumber = new JTextField();
    cNumber.setColumns(7);

// Declaring JPanel Layout
    p1.add(cs);
    p1.add(cNumber);
    p1.add(sb1);
    add(p1, BorderLayout.NORTH);

    //Create File & Save Details
    //sb.addActionListener(new ActionListener() {

        //@Override
    //  public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub

    //      File file = new File("Customers.txt");
    //      try{
    //      if(file.exists()==false){
    //              file.createNewFile();
    //      }
    //      PrintWriter pw = new PrintWriter(new FileWriter(file, true));
    //      pw.println(cNumber.getText());
    //      pw.close();
    //      }catch(IOException e1){
    //          JOptionPane.showMessageDialog(null,"<html>Customer File Could Not Be Created<p>Make Sure Program Has File Write Perssions");
    //      }

    //}
    //});
    sb1.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            try(Scanner sc = new Scanner(new File("Customers.txt"))) {
                while(sc.hasNextInt()) {
                    int cNumber = sc.nextInt();
                    if(cNumber == Integer.parseInt(userInput.getText()))
                        JOptionPane.showMessageDialog(null, "Customer Found" + cNumber);
                    break;
                }
            }
            catch(IOException e1) {
                    JOptionPane.showMessageDialog(null,"Error");

            }

        }

    });
}
}

获取此错误

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at custSearch$1.actionPerformed(custSearch.java:83)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

很难找出您提供的代码的问题。你能提供全班和你遇到的错误吗？您似乎也在if语句中使用了赋值运算符：

if(sc = cNumber);

if语句的正确形式是：

if() {

}

或：

if()
    only one line allowed;

并且您似乎将Scanner分配给int变量。 cNumber包含你的下一个标记，所以我猜你要做的就是做

之类的事情

if(cNumber == 1121) etc..

如果你说有

private JTextField userInput;

您的actionPerformed（）必须可见，然后您可以执行以下操作：

if(cNumber == Integer.parseInt(userInput.getText())) {
     JOptionPane.showMessageDialog(null, "Customer Found" + cNumber);
}

所以尝试写下这样的东西：

      @Override
        public void actionPerformed(ActionEvent e) {
            try(Scanner sc = new Scanner(new File("Customers.txt"))) {
                while(sc.hasNextInt()) {
                    int cNumber = sc.nextInt();
                    if(cNumber == Integer.parseInt(userInput.getText()))
                        JOptionPane.showMessageDialog(null, "Customer Found" + cNumber);
                }
            }
            catch(IOException e1) {
                    JOptionPane.showMessageDialog(null,"Error");
            }

更新尝试创建类似代码：很抱歉，您的代码很难理解，因为我没有其他组件，例如它继承的类，所以我创建的是一个简单的版本你可能需要，对不起，我有点匆忙，所以如果你有任何问题可以随便问我，我无法评论它！基本上它可以满足您的需求，只需确保将Customer.txt放在与src文件夹相同的文件夹中。

所以这是：

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JTextField;

public class Test extends JFrame implements ActionListener {

    private static final long serialVersionUID = 1L;

    private JTextField numberTextField;
    private JButton submitButton;

    public Test() {
        setTitle("Get Phone Number");
        setLayout(new FlowLayout());
        setSize(600, 300);
        setResizable(true);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create TextField, Label and Button
        add(new JLabel("Search Phone Number:"));
        numberTextField = new JTextField(10);
        add(numberTextField);
        submitButton = new JButton("Search");
        add(submitButton);

        //Adding action listener to the button
        submitButton.addActionListener(this);

        setVisible(true);
        pack();
    }

    public static void main(String[] args) {
        new Test();
    }

    public void findNumber(String path, int number) {
        File file = new File(path);

        try {
            Scanner sc = new Scanner(file);

            while(sc.hasNextInt()) {
                int i = sc.nextInt();
                if(i == number) {
                    JOptionPane.showMessageDialog(null, "Phone Number: " + number + " is found!");
                    break;
                }
                else {
                    if(!sc.hasNextInt()) {
                        JOptionPane.showMessageDialog(null, "Sorry  phone number: " + number + " is not found!");
                        break;
                    }
                    continue;
                }
            }
        }
        catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        findNumber("Customers.txt", Integer.parseInt(numberTextField.getText()));
    }
}

无法获取JTextField用户输入以搜索文本文件

1 个答案: