Java Swing : components not added to JPanel with JScrollPane

Question

这段代码只是一个愚蠢的例子，我需要理解它才能解决我正在处理的另一个项目的一个更大的问题:如您所见，在 for 循环中，应该将 23 个按钮添加到 JPanel。由于它们无法一起显示，我决定添加一个 JScrollPane，但发生了一件奇怪的事情:只显示了 19 个，我不明白为什么。大小矩阵有 1 列 23 行，所以它是正确的。你知道为什么会这样吗？谢谢

package proveGUI;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ScrollPaneConstants;

import layout.TableLayout;

public class Main {

  public static void main(String argv[]) {

      JFrame jframe = new JFrame("Protocollo UTL");
      //jframe.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
      jframe.setSize(1200, 450);

      JPanel body = new JPanel();
      double[][] size = {
              {0.05},
              {0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05,0.05}

      };

      body.setLayout(new TableLayout(size));

      for(int i=0; i<22; i++) {
          body.add(new JButton(String.valueOf(i)), "0,"+String.valueOf(i));
      }

      JScrollPane scrollPane = new JScrollPane(body,
              ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
              ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);

      jframe.add(scrollPane);
      jframe.setVisible(true);

  }

}

Answer 1

问题源于您使用的尺寸值介于 0.00 和 1.00 之间。这些被解释为相对大小/百分比，在本例中为 5%。这就是为什么它只显示 20 行(包括 0 到 19)。尝试改用“50.0”，问题就会消失。或者使用 TableLayout.PREFERRED。