Java Swing gridbaglayout无法填充完整框架

我正在尝试构建类似于JProgressBar的组件,该组件将显示三个状态而不是两个状态,如here所示.

我通过将三个JLabel组件(具有三种不同的背景颜色)添加到具有设置为GridBagLayout的面板中来构建此组件.我已经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在于,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,并且在面板的末端看到了黑色条纹,如here所示.

我也尝试设置gbc.fill和gbc.anchor参数,但仍然无法正常工作.

对此问题的任何帮助将不胜感激！谢谢 ：)

解决方法:

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

然后,当然可以通过以下方式设置面板的布局：

panel.selLayout(new MyLayout(panel));

标签：gridbaglayout,swing,layout-manager,java
来源： https://codeday.me/bug/20191109/2011894.html