Java swing gridbaglayout 没有填满整个框架

Question

我正在尝试构建一个类似于 JProgressBar 的组件，它将显示三种状态而不是如图所示的两种状态 here。

我通过将三个 JLabel 组件（具有三种不同的背景颜色）添加到布局设置为 GridBagLayout 的面板来构建它。我为这些标签分配了相应的权重，以便根据父面板的大小调整它们的大小。下面是相应的示例代码：

public class CustomProgressBar {

  public static void main(String[] args) {

    JFrame frame = new JFrame("test");

    JPanel panel = new JPanel();

    double firstLabelWeight = 0.10d;
    double secondLabelWeight = 0.20d;
    double thirdLabelWeight = 1d - firstLabelWeight - secondLabelWeight;

    JLabel firstLabel = new JLabel();
    firstLabel.setOpaque(true);
    firstLabel.setBackground(Color.GREEN);

    JLabel secondLabel = new JLabel();
    secondLabel.setOpaque(true);
    secondLabel.setBackground(Color.YELLOW);

    JLabel thirdLabel = new JLabel();
    thirdLabel.setOpaque(true);
    thirdLabel.setBackground(Color.RED);

    panel.setLayout(new GridBagLayout());
    GridBagConstraints gbc = new GridBagConstraints();
    gbc.fill = GridBagConstraints.BOTH;

    gbc.weightx = firstLabelWeight;
    gbc.weighty = 1d;
    panel.add(firstLabel, gbc);

    gbc.weightx = secondLabelWeight;
    gbc.weighty = 1d;
    panel.add(secondLabel, gbc);

    gbc.weightx = thirdLabelWeight;
    gbc.weighty = 1d;
    panel.add(thirdLabel, gbc);

    panel.setBackground(Color.BLACK);
    panel.setPreferredSize(new Dimension(157, 50));

    frame.add(panel);
    frame.setVisible(true);
    frame.pack();

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }
}

现在这种方法的问题是，当我尝试调整 JFrame 的大小时，上面的三个标签没有填满父面板中的完整水平 space，我们看到如图所示的面板 here。

我也试过设置gbc.fill和gbc.anchor参数，但还是不行。

非常感谢任何解决此问题的帮助！谢谢 :)

Answer 1

为了克服舍入问题，您可以通过这种方式覆盖面板的布局：

class MyLayout extends GridBagLayout
{
  private Component owner;

  public MyLayout(Component owner)
  {
    this.owner = owner;
  }

  @Override
  protected void adjustForGravity(GridBagConstraints constraints,
                                  Rectangle          rect)
  {
    // Adjust position and width of first (GREEN) label if necessary
    if ((rect.x > 0) && (rect.x <= 2))
    {
      rect.width += rect.x;
      rect.x = 0;
    }

    // Adjust width of last (RED) label if necessary
    int gap = owner.getWidth() - rect.x - rect.width;
    if ((gap > 0) && (gap <= 2))
      rect.width += gap;
  }

} // class MyLayout

那当然是这样设置面板的布局了：

panel.selLayout(new MyLayout(panel));

Answer 2

如果您构建 GridBagConstraints 提供负面 Insets，这将不会显示基础 Panel。变化如下

GridBagConstraints gbc = new GridBagConstraints(-1, -1, 1, 1, 0, 0, 10, 0, new Insets(-1, -1, -1, -1), 0, 0);

更新示例：

public class CustomProgressBar {

public static void main(String[] args) {

    JFrame frame = new JFrame("test");

    JPanel panel = new JPanel();

    double firstLabelWeight = 0.10d;
    double secondLabelWeight = 0.20d;
    double thirdLabelWeight = 1d - firstLabelWeight - secondLabelWeight;

    JLabel firstLabel = new JLabel();
    firstLabel.setOpaque(true);
    firstLabel.setBackground(Color.GREEN);

    JLabel secondLabel = new JLabel();
    secondLabel.setOpaque(true);
    secondLabel.setBackground(Color.YELLOW);

    JLabel thirdLabel = new JLabel();
    thirdLabel.setOpaque(true);
    thirdLabel.setBackground(Color.RED);

    panel.setLayout(new GridBagLayout());

    GridBagConstraints gbc = new GridBagConstraints(-1, -1, 1, 1, 0, 0, 10, 0, new Insets(-1, -1, -1, -1), 0, 0);

    gbc.fill = GridBagConstraints.BOTH;

    gbc.weightx = firstLabelWeight;
    gbc.weighty = 1d;
    panel.add(firstLabel, gbc);

    gbc.weightx = secondLabelWeight;
    gbc.weighty = 1d;
    panel.add(secondLabel, gbc);

    gbc.weightx = thirdLabelWeight;
    gbc.weighty = 1d;
    panel.add(thirdLabel, gbc);

    panel.setBackground(Color.BLACK);
    panel.setPreferredSize(new Dimension(157, 50));

    frame.add(panel);
    frame.setVisible(true);
    frame.pack();

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 }
}

输出：

Java swing gridbaglayout 没有填满整个框架

Java swing gridbaglayout does not fill complete frame

java

swing

layout-manager

gridbaglayout