循环遍历 JPanel 中的嵌套字段

Question

我已经制作了 2 个类，第一个是制作 JTextFields，第二个是把这些 JTextFields 注入到 JPanel 中。我正在尝试将 .setText 设置为每个 JTextField 但很简单

    for (Field f: fields) {
    f.setValue("my text");
    }

不起作用 - 它仅将文本设置为一个 JPanel 中的 JTextFields。由于每个 JTextField 都有唯一的 fieldID，您能告诉我如何为它们设置文本（setValue）吗？这些值需要在循环之外设置，使用 ActionListener。

public class Field {

    JTextField field = new JTextField();
    static int fieldID = 0;
    private String text;
    public Field() {
        fieldID++;
    }

    public String getValue() {
        return field.getText();
    }

    public void setValue(String text) {
        field.setText(text);
    }
} 

public class Frame extends JFrame {

public Frame() {
    Field[] fields = new Field[9];
    JPanel[] corePane = new JPanel[9];
    JPanel frontPane = new JPanel();
    frontPane.setLayout(new GridLayout(3, 3));

    for (int i = 0; i < corePane.length; i++) {
        corePane[i] = new JPanel();
        for (int j = 0; j < 9; j++) {
            fields[j] = new Field();
            corePane[i].add(fields[j].field);
        }
        corePane[i].setLayout(new GridLayout(3, 3));
        frontPane.add(corePane[i]);
    }

    setLayout(new BorderLayout());
    setSize(300, 300);
    getContentPane().add(frontPane, BorderLayout.CENTER);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);
}

public static void main(String args[]) {
    SwingUtilities.invokeLater(Frame::new);
}
}

Answer 1

所以，你的fields 可能需要是一个二维数组，例如

Field[][] fields = new Field[9][9];

这样，您可以访问给定面板（第一维）的字段（第二维），即fields[pane][field]。

显然，在您的for-loop 中，您需要正确初始化字段的数组，例如fields[i] = new Field[9]；

这可能会使您的代码看起来更像...

public class Field {

    JTextField field = new JTextField();
    static int fieldID = 0;
    private String text;

    public Field() {
        fieldID++;
    }

    public String getValue() {
        return field.getText();
    }

    public void setValue(String text) {
        field.setText(text);
    }
}

public class Frame extends JFrame {

    public Frame() {
        Field[][] fields = new Field[9][9];
        JPanel[] corePane = new JPanel[9];
        JPanel frontPane = new JPanel();
        frontPane.setLayout(new GridLayout(3, 3));

        for (int i = 0; i < corePane.length; i++) {
            corePane[i] = new JPanel();
            fields[i] = new Field[9];
            for (int j = 0; j < 9; j++) {
                fields[i][j] = new Field();
                corePane[i].add(fields[i][j].field);
            }
            corePane[i].setLayout(new GridLayout(3, 3));
            frontPane.add(corePane[i]);
        }

        setLayout(new BorderLayout());
        setSize(300, 300);
        getContentPane().add(frontPane, BorderLayout.CENTER);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
    }

    public static void main(String args[]) {
        SwingUtilities.invokeLater(Frame::new);
    }
}

现在，static的一句话

static int fieldID = 0;

意味着Field 的每个实例都将具有相同的fieldID，无论您将其更改为什么。对我来说（根据你所说的），以这种方式使用static 是没有意义的

有替代方案，可能会提供更好和更可重用的解决方案

Answer 2

作为@MadProgrammer 解决方案的替代方案，我可以为您提供一些有用的方法，可以帮助您解决这些任务而无需声明任何数组。

/**
 * Searches for all children of the given component which are instances of the given class.
 *
 * @param aRoot start object for search. May not be null.
 * @param aClass class to search. May not be null.
 * @param <E> class of component.
 * @return list of all children of the given component which are instances of the given class. Never null.
 */
public static <E> List<E> getAllChildrenOfClass(Container aRoot, Class<E> aClass) {
    return getAllChildrenOfClass(aRoot, aClass, e -> true);
}

/**
 * Searches for all children of the given component which are instances of the given class and satisfies the given condition.
 *
 * @param aRoot start object for search. May not be null.
 * @param aClass class to search. May not be null.
 * @param condition condition to be satisfied. May not be null.
 * @param <E> class of component.
 * @return list of all children of the given component which are instances of the given class. Never null.
 */
public static <E> List<E> getAllChildrenOfClass(Container aRoot, Class<E> aClass, Predicate<E> condition) {
    final List<E> result = new ArrayList<>();
    final Component[] children = aRoot.getComponents();
    for (final Component c : children) {
        if (aClass.isInstance(c) && condition.test(aClass.cast(c))) {
            result.add(aClass.cast(c));
        }
        if (c instanceof Container) {
            result.addAll(getAllChildrenOfClass((Container) c, aClass, condition));
        }
    }
    return result;
}

现在您可以为所有文本字段设置文本。

getAllChildrenOfClass(getContentPane(), JTextField.class).forEach(tf -> tf.setText("My text"));