如何获取扩展 JPanel 以显示在另一个 classes JPanel 中的 class 实例？

Question

incomePanel 显示在 IncomeAndSpendingPanel 内部，但如果我将所有 incomePanel 代码移动到它自己的 class（就像我对 SpendingPanel 和 TransactionAdder 所做的那样）并尝试以这种方式将它们添加到 IncomeAndSpendingPanel，则不会显示任何内容。我只是想清理我的代码并将其分成不同的部分。

public class IncomeAndSpendingPanel extends JPanel {

    private ColorX cx = new ColorX();
    DefaultTableModel incomeTableModel;
    DefaultTableModel spendingTableModel;


    private String[] incomeColumnHeadings = {"Date","Description","Amount"};
    private String[] spendingColumnHeadings = {"Date","Description","Amount","Category"};

    Border empty = BorderFactory.createEmptyBorder(10, 10, 10, 10);
    Border blackLine = BorderFactory.createLineBorder(Color.black);
    CompoundBorder line = new CompoundBorder(empty, blackLine);

    public IncomeAndSpendingPanel() {

        setLayout(new BorderLayout());
        add(new TransactionAdder(), BorderLayout.NORTH);
        add(new SpendingPanel(), BorderLayout.EAST);


        JPanel incomePanel;
        Border incomePanelBorder = BorderFactory.createTitledBorder(line, "INCOME");
        JTable incomeTransactionInputTable;


        incomePanel = new JPanel(new GridLayout());

        incomePanel.setBorder(incomePanelBorder);

        incomeTableModel = new DefaultTableModel(50, incomeColumnHeadings.length);
        incomeTableModel.setColumnIdentifiers(incomeColumnHeadings);

        incomeTransactionInputTable = new JTable(incomeTableModel);
        incomeTransactionInputTable.getColumnModel().getColumn(0).setPreferredWidth(1);
        incomeTransactionInputTable.getColumnModel().getColumn(1).setPreferredWidth(200);
        incomeTransactionInputTable.getColumnModel().getColumn(2).setPreferredWidth(10);

        incomePanel.add(new JScrollPane(incomeTransactionInputTable));

        add(incomePanel, BorderLayout.CENTER);
    }

这是我为 TransactionAdder 构建的 class，当我尝试将它添加到 IncomeAndSpendingPanel 时没有任何显示，我已经尝试创建一个 TransactionAdder transactionAdder = new TransactionAdder();然后像这样添加 TransactionAdder 的实例

add(transactionAdder, BorderLayout.NORTH);

但是收入和支出面板上也没有任何显示

public class TransactionAdder extends JPanel {

    DefaultTableModel model3;
    DefaultTableModel model4;

    private String[] incomeColumnHeadings = {"Date","Description","Amount"};
    private String[] spendingColumnHeadings = {"Date","Description","Amount","Category"};

    Border empty = BorderFactory.createEmptyBorder(10, 10, 10, 10);
    Border blackLine = BorderFactory.createLineBorder(Color.black);
    CompoundBorder line = new CompoundBorder(empty, blackLine);

    JTable incomeTransactionTable;
    JTable spendingTransactionTable;
    JPanel transactionAdderPanel;
    Border transactionAdderPanelBorder = BorderFactory.createTitledBorder(line, "ADD TRANSACTION");
    JScrollPane jScrollPane;
    JScrollPane jScrollPane1;

    public TransactionAdder() {

        transactionAdderPanel = new JPanel(new GridLayout());

        transactionAdderPanel.setBorder(transactionAdderPanelBorder);

        model3 = new DefaultTableModel(1, incomeColumnHeadings.length);
        model3.setColumnIdentifiers(incomeColumnHeadings);
        model4 = new DefaultTableModel(1, spendingColumnHeadings.length);
        model4.setColumnIdentifiers(spendingColumnHeadings);

        transactionAdderPanel.add(new JButton("Add New Income"));

        incomeTransactionTable = new JTable(model3);
        jScrollPane = new JScrollPane(incomeTransactionTable);
        jScrollPane.setPreferredSize(new Dimension(300, 38));
        transactionAdderPanel.add(jScrollPane);

        transactionAdderPanel.add(new JButton("Add New Spending"));

        spendingTransactionTable = new JTable(model4);
        jScrollPane1 = new JScrollPane(spendingTransactionTable);
        jScrollPane1.setPreferredSize(new Dimension(300, 38));
        transactionAdderPanel.add(jScrollPane1);



    }
}

Answer 1

这里有很多话要说...首先，您可能需要使用 JFrame，因此请阅读有关顶级容器的信息 here。

此外，由于您正在使用继承，因此您肯定需要将所有这些基本 class 方法调用移动到一个方法中，并且仅使用构造函数来初始化实例变量。如果你不这样做，你可能会在创建任何 JPanel 对象时遇到各种问题，因为你在初始化期间有可覆盖的方法调用。

但是，当您添加 incomePanel 和 TransactionAdder

您从未设置过其中任何一个.setVisible(true)
您从未将 IncomeAndSpendingPanel 设置为 .setVisible(true)
您从未将 IncomeAndSpendingPanel 设置为任何大小（使用 Dimension class）
您从未使用过容器hierarchy

请将它们包含在 JFrame 中并将您的代码更改为更像这样：

class IncomeAndSpendingPanel extends JFrame
{
   //Instance variables

   public IncomeAndSpendingPanel()
   {
     //initialize instance variables
     createAndShowGui();
   }

   private void createAndShowGui()
   {
     //Your code
     this.setVisible(true);
   }

如何获取扩展 JPanel 以显示在另一个 classes JPanel 中的 class 实例？

How do I get an instance of a class that extends a JPanel to display in another classes JPanel?

java

swing

jpanel