對於JTextField，如何設置其他類的文本？

Question

我環顧了其他線程，找不到有效的解決方案。

我的程序讀取一個文件，將每個單詞分成一行，然后存儲在數組中。 如果要搜索的是array [0]，那么我想將數組輸出到其對應的文本字段中。

我試圖通過僅設置1個文本字段（ID文本字段）的文本來測試它，但是該文本字段沒有填充文本。 到目前為止，這是我的代碼：

GUI-StudentUI

public class StudentUI extends javax.swing.JFrame {

/**
 * Creates new form StudentUI
 */
public StudentUI() {
    initComponents();
    saveBtn.setVisible(false);
}

final String FILENAME = "Students.txt";

private void initComponents() {

    searchTxt = new javax.swing.JTextField();
    idLbl = new javax.swing.JLabel();
    titleLbl = new javax.swing.JLabel();
    forenameLbl = new javax.swing.JLabel();
    surnameLbl = new javax.swing.JLabel();
    address1Lbl = new javax.swing.JLabel();
    address2Lbl = new javax.swing.JLabel();
    postcodeLbl = new javax.swing.JLabel();
    numberLbl = new javax.swing.JLabel();
    birthLbl = new javax.swing.JLabel();
    idTxt = new javax.swing.JTextField();
    forenameTxt = new javax.swing.JTextField();
    surnameTxt = new javax.swing.JTextField();
    address1Txt = new javax.swing.JTextField();
    address2Txt = new javax.swing.JTextField();
    postcodeTxt = new javax.swing.JTextField();
    numberTxt = new javax.swing.JTextField();
    birthTxt = new javax.swing.JTextField();
    searchBtn = new javax.swing.JButton();
    searchLbl = new javax.swing.JLabel();
    titleCombo = new javax.swing.JComboBox<>();
    addBtn = new javax.swing.JButton();
    editBtn = new javax.swing.JButton();
    deleteBtn = new javax.swing.JButton();
    saveBtn = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    idLbl.setText("ID");

    titleLbl.setText("Title");

    forenameLbl.setText("Forename");

    surnameLbl.setText("Surname");

    address1Lbl.setText("Address 1");

    address2Lbl.setText("Address 2");

    postcodeLbl.setText(" Postcode");

    numberLbl.setText("Phone Number");

    birthLbl.setText("Date of Birth (DD/MM/YYYY)");

    searchBtn.setText("Search");
    searchBtn.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            searchBtnActionPerformed(evt);
        }
    });


public void setTextField(JTextField jTF, String value) {
    jTF.setText(value);
}

private void searchBtnActionPerformed(java.awt.event.ActionEvent evt) {                                          
    int count = Search.totalLines(FILENAME);
    Search.linear(FILENAME, count, searchTxt.getText());
}                                         

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new StudentUI().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JButton addBtn;
private javax.swing.JLabel address1Lbl;
private javax.swing.JTextField address1Txt;
private javax.swing.JLabel address2Lbl;
private javax.swing.JTextField address2Txt;
private javax.swing.JLabel birthLbl;
private javax.swing.JTextField birthTxt;
private javax.swing.JButton deleteBtn;
private javax.swing.JButton editBtn;
private javax.swing.JLabel forenameLbl;
private javax.swing.JTextField forenameTxt;
private javax.swing.JLabel idLbl;
private javax.swing.JTextField idTxt;
private javax.swing.JLabel numberLbl;
private javax.swing.JTextField numberTxt;
private javax.swing.JLabel postcodeLbl;
private javax.swing.JTextField postcodeTxt;
private javax.swing.JButton saveBtn;
private javax.swing.JButton searchBtn;
private javax.swing.JLabel searchLbl;
private javax.swing.JTextField searchTxt;
private javax.swing.JLabel surnameLbl;
private javax.swing.JTextField surnameTxt;
private javax.swing.JComboBox<String> titleCombo;
private javax.swing.JLabel titleLbl;
// End of variables declaration                   
}

搜索類別

public class Search {

public static int totalLines(String filename) {
    int n = 0;
    String currentLine;
    try {
        FileReader fr = new FileReader(filename);
        BufferedReader br = new BufferedReader(fr);
        while ((currentLine = br.readLine()) != null) {
            n = n + 1;
        }

    } catch (Exception e) {

    }

    return n;
}

public static void linear(String filename, int lines, String searchItem) {
    String currentLine;

    try {
        FileReader fr = new FileReader(filename);
        BufferedReader br = new BufferedReader(fr);
        while ((currentLine = br.readLine()) != null) {
            String[] array = new String[lines];
            array = currentLine.split(",");
            if (array[0].equals(searchItem)) {
                StudentUI student = new StudentUI();
                student.setTextField(student.idTxt, array[0]);
            }
        }

    } catch (Exception e) {

    }
}

}

Answer 1

您在（A）遇到了一個大問題：

public static void linear(String filename, int lines, String searchItem) {
    String currentLine;

    try {
        FileReader fr = new FileReader(filename);
        BufferedReader br = new BufferedReader(fr);
        while ((currentLine = br.readLine()) != null) {
            String[] array = new String[lines];
            array = currentLine.split(",");
            if (array[0].equals(searchItem)) {
                StudentUI student = new StudentUI();  // ****** (A) ******
                student.setTextField(student.idTxt, array[0]);
            }
        }

    } catch (Exception e) {
        // ****** (B) ******
    }
}

您正在創建一個new StudentUI()對象-一個新的對象，該對象與已經顯示的StudentUI完全不同，因此設置其JTextField的狀態將對當前顯示的StudentUI對象無效。

一個錯誤的解決方案是將JTextField變量設置為靜態-不要這樣做，因為這樣做會把OOP嬰兒和洗澡水一起扔掉。

更好的解決方案是將對當前顯示的 StudentUI對象的引用傳遞給他的方法，以便您可以更改感興趣的對象的狀態。

---

（B）中的另一個問題-不要以這種方式忽略異常，因為這樣做，如果您的代碼崩潰了，您將不知道為什么。

---

因此，解決此問題的一種方法是為線性方法提供一個StudentUI參數：

public static void linear(StudentUI student, String filename, int lines, String searchItem) {

    String currentLine;

    try {
        FileReader fr = new FileReader(filename);
        BufferedReader br = new BufferedReader(fr);
        while ((currentLine = br.readLine()) != null) {
            String[] array = new String[lines];
            array = currentLine.split(",");
            if (array[0].equals(searchItem)) {
                //  StudentUI student = new StudentUI();  // ****** (A) ******
                student.setTextField(student.idTxt, array[0]);
            }
        }

    } catch (Exception e) {
        e.printStacktrace();  // ****** (B) *******
    }
}

然后調用它，通過this入法作為第一個參數。

另外，請注意，我現在正在打印異常的堆棧跟蹤，以便我可以查看是否/何時引發異常，導致異常的原因和位置。