Java swing gridbaglayout未填充整个框架

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

我通过将三个JLabel组件（具有三种不同的背景色）添加到布局设置为GridBagLayout的面板中来实现这一点。我为这些标签指定了相应的权重，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充父面板中的整个水平空间，我们看到面板末端的黑色条带，如图所示

我也尝试过设置gbc.fill和gbc.anchor参数，但仍然不起作用

---

非常感谢您对这个问题的任何帮助！谢谢：）

为了克服舍入问题，您可以通过以下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

panel.selLayout(new MyLayout(panel));

---

如果构建

GridBagConstraints

以提供负

插入

，则不会显示底层

面板

。变化如下

GridBagConstraints gbc=新的GridBagConstraints（-1，-1,1,0,0,10,0，新插入（-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：

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);
 }
}

---

这似乎是一个取整问题。将初始宽度设置为160时，左侧或右侧没有黑色条。它们在缓慢调整大小时出现/消失。黑色条纹是由于舍入错误造成的。父面板的宽度始终为整数像素。当将它们分发到特定组件时，布局管理器会得到一些额外的像素，它不知道放在哪里。这就是GridBagLayout的工作原理。如果这对您来说是一个严重的问题，您将不得不覆盖GridBagLayout。看看它处理的是您遇到的类似问题。@MatheM相关链接确实解决了我的问题。更简单的方法是：创建默认约束“gbc=new GridBagConstraints（）”，然后只设置水平插入“gbc.Insets=new Insets（0，-1，0，-1）”。虽然这种方法很简单，可以填充整个面板，但当其中一个标签必须填充整个面板时，会出现问题。例如，在上面的示例中，将第一个和第二个标签的重量设为零，应使用红色的第三个标签填充整个面板，但我们在开始处看到一条绿色。