GridBagLayout忽略由于固定大小的JPanel引起的权重分布

Question

我的UI分为两个面板，让我们称之为 NormalPanel 和 SpecialPanel 。 NormalPanel 应占用水平空间的25％， SpecialPanel 占另外75％。为实现这一点，我使用了

gridBagLayout.columnWeights = new double[] { 1, 3 };

结果：

我遇到的问题是由于 specialPanel 的属性。它是一个包含固定大小Panel的JScrollPane。这意味着只要JFrame变得足够大以显示整个固定大小的面板，它就会忽略重量分布，只显示整个面板。

问题：

如何阻止这种情况发生？

我用来创建示例的代码：

public MyWindow() {

    GridBagLayout gbLayout = new GridBagLayout();
    // This makes the first row take 100% of the space (We only have one row)
    gbLayout.rowWeights = new double[] { 1 };
    // This makes the second column take up 3 times as much space as the first
    gbLayout.columnWeights = new double[] { 1, 3 };

    GridBagConstraints gbc = new GridBagConstraints();
    gbc.fill = gbc.BOTH;
    gbc.weightx = 1;
    gbc.weighty = 1;

    // Initialize the panels
    normalPanel = new JPanel();
    normalPanel.setBackground(Color.red);
    specialPanel = new SpecialPanel();
    contentPanel = new JPanel(gbLayout);

    gbc.gridx = 0;
    gbc.gridy = 0;
    contentPanel.add(normalPanel, gbc);

    gbc.gridx = 1;
    gbc.gridy = 0;
    contentPanel.add(specialPanel, gbc);

    setContentPane(contentPanel);
    setSize(1280, 720);
    setMinimumSize(new Dimension(1280, 720));
    setVisible(true);
}

public static void main(String[] args) {
    MyWindow window = new MyWindow();
}

/**
 * 
 * This panel has a ScrollPan which is displaying a fixed sized panel.
 *
 */
public class SpecialPanel extends JPanel {

    private JScrollPane scrollPane;
    private JPanel scrollPaneView;
    private JPanel fixedSizePanel;

    public SpecialPanel() {
        fixedSizePanel = new JPanel();
        fixedSizePanel.setPreferredSize(new Dimension(1280,720));
        fixedSizePanel.setMaximumSize(new Dimension(1280,720));
        fixedSizePanel.setMinimumSize(new Dimension(1280,720));
        fixedSizePanel.setBackground(Color.blue);

        scrollPaneView = new JPanel(new FlowLayout());
        scrollPaneView.add(fixedSizePanel);

        scrollPane = new JScrollPane(scrollPaneView);
        scrollPane.setHorizontalScrollBarPolicy(scrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        scrollPane.setVerticalScrollBarPolicy(scrollPane.VERTICAL_SCROLLBAR_AS_NEEDED); 

        this.setLayout(new GridLayout(1,1));
        this.add(scrollPane);
    }
}

}

Answer 1

GridBagLayout是...... 违反直觉的以及它分配空间的方式。它首先“询问”组件他们想要的大小，并给他们那个空间，只有在那之后才是基于权重分配的剩余空间。

要解决此问题，请扩展您要添加到GridBagLayout的面板，并覆盖它们的getPrefferedSize()方法。

@Override
public Dimension getPreferredSize() {
    return new Dimension();
}

现在，面板将“告诉”他们不需要任何空间的布局，因此布局将根据权重分配所有空间。