java - 当我尝试在框架上添加多个组件时，Swing 显示白色框

Question

我正在开发 java swing 应用程序。我尝试在我的主 JFrame 上添加 2 个 JPanel。

我的主要 JPanel 类:

public class DrawingPanel extends JPanel {
    //mouse variables here
    //Point mPt = new Point(0,0);

    public DrawingPanel() {
        setBackground(COLOURBACK);
        MyMouseListener ml = new MyMouseListener();
        addMouseListener(ml);
    }

    public Dimension getPreferredSize() {
    return new Dimension(width, height);
    }
....
....
....
}

当我添加为主框架上的唯一组件时，

工作正常。但是当我尝试在框架上添加另一个 JPanel 时，我的 DrawingPanel 显示为小白框。

private void createAndShowGUI()
    {
        DrawingPanel panel = new DrawingPanel();


        JFrame frame = new JFrame("Hex Testing 4");
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        Container content = frame.getContentPane();
        JPanel aggregationFrame = new JPanel(new GridBagLayout());
        aggregationFrame.add(panel);
        aggregationFrame.add(new JLabel("Enter username:"));
        content.add(aggregationFrame);
        //this.add(panel);  -- cannot be done in a static context
        //for hexes in the FLAT orientation, the height of a 10x10 grid is 1.1764 * the width. (from h / (s+t))
        frame.setSize( (int)(SCRSIZE/1.23), SCRSIZE);
        frame.setResizable(false);
        frame.setLocationRelativeTo( null );
        frame.setVisible(true);
    }

看起来像这样

我尝试按照 JPanel appears as a small white box 中的建议将 getPreferredSize() 方法添加到 DrawingPanel问题但效果不佳。

你能帮我解决这个问题吗？

更新:

我已经更改了布局，现在我看到了 JPanel 的一半。我认为问题与 JPanel 和 JFrame 的固定大小有关。会调查一下。

Answer 1

所以，我采用了你的断章取义的代码，拼凑了一个可运行的变体并且......没有任何问题。这表明问题出在您未向我们展示的代码中的某个位置。不要发布不完整代码的“片段”，这会引发更多问题，而是发布 Minimal, Complete, and Verifiable example ，可以编译并运行，它演示了您遇到的问题

一个运行并工作的示例...

import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Test {

  public static void main(String[] args) {
    new Test();
  }

  public Test() {
    EventQueue.invokeLater(new Runnable() {
      @Override
      public void run() {
        DrawingPanel panel = new DrawingPanel();

        JFrame frame = new JFrame("Hex Testing 4");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Container content = frame.getContentPane();
        JPanel aggregationFrame = new JPanel(new GridBagLayout());
        aggregationFrame.add(panel);
        aggregationFrame.add(new JLabel("Enter username:"));
        content.add(aggregationFrame);
        //this.add(panel);  -- cannot be done in a static context
        //for hexes in the FLAT orientation, the height of a 10x10 grid is 1.1764 * the width. (from h / (s+t))
        frame.pack();
        //frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
      }
    });
  }

  public class DrawingPanel extends JPanel {
    //mouse variables here
    //Point mPt = new Point(0,0);

    private int width = 200;
    private int height = 200;

    public DrawingPanel() {
      setBackground(Color.BLACK);
//    MyMouseListener ml = new MyMouseListener();
//    addMouseListener(ml);
    }

    public Dimension getPreferredSize() {
      return new Dimension(width, height);
    }
  }

}