java - Swing - windowStateChanged 事件问题

Question

我有一个 JFrame，在调整窗口大小时或更改窗口状态时，某些元素(目前只有一个)必须手动居中在 contentPane 上。调整大小事件 (componentResized) 工作正常，但 windowStateChanged 事件导致问题，因为它似乎没有正确地“更新”contentPane 的新大小 - 它保留了以前的值。这可以通过简单地打印在 contentPane 上调用的 getSize 的结果来看出。

居中是通过以编程方式更改组件的约束(使用 putConstraint、SpringLayout)来完成的。问题是该方法中使用的 getWidth 返回“错误”值，这会导致组件不居中。 也许这里需要另一个监听器？

附加信息:带有 WindowBuilder 的 Eclipse、Linux Mint 15

欢迎任何类型的建议。

addWindowStateListener(new WindowStateListener()
{
    public void windowStateChanged(WindowEvent e)
    {
        System.out.println(contentPane.getSize()); // returns old size
        tfArrayPanelCenter();
    }
});

public void tfArrayPanelCenter()
{
    int padding = (contentPane.getWidth()
            - tfArrayPanel.getPreferredSize().width - HGAP) / 2;
    sl_contentPane.putConstraint(SpringLayout.WEST, tfArrayPanel, padding,
            SpringLayout.WEST, contentPane);
}

根据要求，我发布了更多代码 - 一个简单的刽子手游戏。我认为 JFrame 构造函数应该足够了(其他东西是非 GUI 的):

/**
 * Create the frame.
 */
public MainWindow()
{
    addWindowStateListener(new WindowStateListener()
    {
        // no "@Override" was generated but it is the same with it
        public void windowStateChanged(WindowEvent e)
        {
            System.out.println("EVENT: " + contentPane.getSize() + ", "
                    + getExtendedState() + ", " + e.getOldState()); // amusingly, states are actually correct - interchanging between 0 (Frame.NORMAL) and 6 (Frame.MAXIMIZED_BOTH) when I maximize and "unmaximize"
            tfArrayPanelCenter();
        }
    });
    addComponentListener(new ComponentAdapter()
    {
        @Override
        public void componentResized(ComponentEvent e)
        {
            tfArrayPanelCenter();
        }
    });
    setTitle("Hangman");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 790, 620);
    setLocationRelativeTo(null);
    GameMechanics.setMainWindow(this);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    setContentPane(contentPane);
    sl_contentPane = new SpringLayout(); // I've declared this as a field, it is normally generated as a local variable
    contentPane.setLayout(sl_contentPane);

    newGame = new JButton("New Game");
    newGame.addMouseListener(new MouseAdapter()
    {
        @Override
        public void mouseClicked(MouseEvent e)
        {
            newGame.setVisible(false);
            lblGame.setVisible(true);
            lblGame.setBtnHintStatus(true);
            lblGame.setLblTriesLeftCountText(Integer
                    .toString(GameMechanics.TRIES));
            lblGame.paint(triesLeft);
            inputChars = new ArrayList<Character>();
            GameMechanics.loadWord();
            initControls(GameMechanics.getGuessingWord().length());
            lblTest.setText(GameMechanics.getGuessingWord().toUpperCase());
        }
    });
    newGame.setFont(new Font("Tempus Sans ITC", Font.BOLD, 12));
    sl_contentPane.putConstraint(SpringLayout.NORTH, newGame, 10,
            SpringLayout.NORTH, contentPane);
    sl_contentPane.putConstraint(SpringLayout.WEST, newGame, 10,
            SpringLayout.WEST, contentPane);
    newGame.setPreferredSize(new Dimension(100, 40));
    newGame.setFocusPainted(false);
    contentPane.add(newGame);

    tfArrayPanel = new JPanel();
    sl_contentPane.putConstraint(SpringLayout.SOUTH, tfArrayPanel, -10,
            SpringLayout.SOUTH, contentPane);
    sl_contentPane.putConstraint(SpringLayout.WEST, tfArrayPanel, 400,
            SpringLayout.WEST, contentPane);
    contentPane.add(tfArrayPanel);
    tfArrayPanel.setLayout(new FlowLayout(FlowLayout.CENTER, HGAP, VGAP));

    lblTest = new JLabel("New label");
    sl_contentPane.putConstraint(SpringLayout.NORTH, lblTest, 15,
            SpringLayout.NORTH, contentPane);
    sl_contentPane.putConstraint(SpringLayout.WEST, lblTest, 416,
            SpringLayout.WEST, contentPane);
    contentPane.add(lblTest);

    lblGame = new GameLabels(); // custom JPanel imported into the Palette and used from there on the MainWindow
    sl_contentPane.putConstraint(SpringLayout.SOUTH, lblGame, -60,
            SpringLayout.SOUTH, contentPane);
    sl_contentPane.putConstraint(SpringLayout.WEST, lblGame, 10,
            SpringLayout.WEST, contentPane);
    lblGame.setPreferredSize(new Dimension(315, 130));
    lblGame.setLayout(null);
    lblGame.setVisible(false);
    lblGame.setMainWindow(this);
    contentPane.add(lblGame);
}

Answer 1

"Any kind of advice is appreciated."

不确定它是否完全符合您的要求，但如果您只想让一组组件始终居中(无论包含框架的大小如何)，正如评论指出的那样，您可以将所有内容包装在 GridBagLayout

import java.awt.GridBagLayout;
import javax.swing.*;
import javax.swing.border.TitledBorder;

public class CenteringWithGridBag {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable(){
            public void run() {
                JPanel gridBagPanel = new JPanel(new GridBagLayout());
                gridBagPanel.setBorder(new TitledBorder("JPanel with GridBagLayout"));

                JPanel innerPanel = new JPanel();
                innerPanel.setBorder(new TitledBorder("JPanel Wrap"));
                innerPanel.add(new JButton("Button"));
                gridBagPanel.add(innerPanel);

                JFrame frame = new JFrame("GridBagLayout Test");
                frame.add(gridBagPanel);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
}