java - 在用户输入后重新绘制 JPanel(或 JFrames？)？

Question

我目前正在用 Java 编写日历。日历本身填写得非常好，月份和年份显示在其下方网格上方的 JComboBoxes 中。网格本身充满了空的 JLabel 或 JButton(针对一个月中的几天)。 JComboBoxes 链接到 ActionListeners，后者检测用户更改信息(由 System.out.print 语句确认)。但是，发生这种情况后，我找不到“重绘” JPanel 的方法。被调用的方法完全创建了一个新的 JPanel 并添加了新的 JLabels/JButtons，但在此之后 JFrame 上的任何内容都没有更新。我尝试在整个 JPanel(包括 JComboBoxes 和 BorderLayout 中其下方的网格)、仅具有网格的 JPanel 和 JFrame 上同时使用重绘和重新验证，但没有任何反应。有谁知道哪里出了问题？

// This code is within the build() method that builds the GUI.
// This method adds the centerPanel into the mainPanel

yearChoice.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent ae) {
            int i = yearChoice.getSelectedIndex();
            if (i >= 0) {
                yy = Integer.parseInt(yearChoice.getSelectedItem()
                        .toString());
                //System.out.println("Year=" + yy);
                compute();
            }
        }
    });

private void compute(){
    elements = new int[6][7];

// OMITTED is the code that determines whether a cell in the array should be an empty    
// JLabel or a JButton. This code is based on the Calendar, and does work properly,
// but I can't figure out how to get the new Month/Year to show up on a new Panel

    centerPanel = new JPanel(new GridLayout(7, 7));
    JLabel sunday = new JLabel("S"),
            monday = new JLabel("M"),
            tuesday = new JLabel("T"),
            wednesday = new JLabel("W"),
            thursday = new JLabel("Th"),
            friday = new JLabel("F"),
            saturday = new JLabel("S");

    centerPanel.add(sunday);
    centerPanel.add(monday);
    centerPanel.add(tuesday);
    centerPanel.add(wednesday);
    centerPanel.add(thursday);
    centerPanel.add(friday);
    centerPanel.add(saturday);

    for(int i = 0; i < 6; i++){
        for(int j = 0; j < 7; j++){
            if(elements[i][j] == -1){
                centerPanel.add(new JLabel(" "));
            }else{
                centerPanel.add(new JButton("" + elements[i][j]));
            }
        }

    }
    // Here is where I attempt to repaint the centerPanel for the JPanel, but it 
    // doesn't work
}

Answer 1

The method being called completely creates a new JPanel and adds in the new JLabels/JButtons, but nothing on the JFrame is updated after this happens. I have attempted using both the repaint and revalidate on the whole JPanel (which includes the JComboBoxes and the grid below it in a BorderLayout), the JPanel with only the grid, and the JFrame, but nothing happens. Does anyone have any ideas what is wrong?

1. 您为(re)validate & repaint

   调用另一个JPanel

2. 更新超出屏幕上的可见矩形，将JPanel 放到JScrollPane

3. 如果更新超出可见矩形，您可以调用 JFrame.pack()，但在这种情况下，JFrame 将更改其在屏幕上的维度

The method being called completely creates a new JPanel and adds in the new JLabels/JButtons, but nothing on the JFrame is updated after this happens.

1. 为什么要重新创建 JPanel，创建一次并使用 setVisible(false/true)

2. 不要重新创建 JPanel，将这些(两个或三个 JPanel)放到 CardLayout 中，然后任何更改都只会在 View 之间切换

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