java - 设置 Swing BorderLayout 侧面板的最小宽度

Question

我了解 BorderLayout 的某些部分 - 例如，EAST/WEST(或 BEGINNING_OF_LINE/END_OF_LINE)面板组件保持一个宽度，其长度随着窗口的长度而拉伸(stretch)。

我想在西侧放置一个面板，它本身具有多个组件 - 在本例中是一个按钮面板和一个按钮控制的 JList。我想为该 JList 中的字符串分配最小宽度，但某些东西(可能是 BorderLayout)阻止我设置最小或首选宽度。

当我运行下面的代码时，左侧面板中的列表对于“LongNameGame 3”来说足够宽，但这只是因为我在渲染列表之前添加了字符串。我想设置该 JList 的宽度以容纳我选择的宽度的字符串。稍后我会将其放入 ScrollPane 中以处理比这更宽的字符串，但这是一个不同的问题。

通过向其他布局管理器推荐我并不能回答我的问题——如果可能的话，我想知道如何使用 BorderLayout 来做到这一点。

package comm;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.util.Vector;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.border.Border;

public class BLPlay
{
  public static void main(String ... arguments)
  {
    JFrame frame = buildLoungeFrame();
    frame.setVisible(true);
  }
  private static JFrame buildLoungeFrame()
  {
    JFrame loungeFrame = new JFrame("BLPlay");
    loungeFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    loungeFrame.setLayout(new BorderLayout(10,10));

    // left panel is another BorderLayout panel with buttons and a list of games
    JPanel gameListControlPanel = new JPanel(new BorderLayout());

    Border innerBorder = BorderFactory.createLineBorder(Color.BLACK, 2);
    Border outerBorder = BorderFactory.createEmptyBorder(3,3,3,3);
    gameListControlPanel.setBorder(BorderFactory.createCompoundBorder(outerBorder, innerBorder));

    String[] gamePanelButtonLabels = { "New", "Join", "Leave", "End" };
    JPanel gamePanelButtons = new JPanel(new GridLayout(gamePanelButtonLabels.length,1));
    addButtons(gamePanelButtons, gamePanelButtonLabels);
    JPanel gamePanelButtonsContainerPanel = new JPanel();
    gamePanelButtonsContainerPanel.add(gamePanelButtons);
    gameListControlPanel.add(gamePanelButtonsContainerPanel, BorderLayout.WEST);

    Vector<String> gameList = new Vector<>();
    gameList.add("Game 1");
    gameList.add("Game 2");
    gameList.add("LongNameGame 3");

    JList<String> gameJList = new JList<>(gameList);
    JPanel gameListPanel = new JPanel(new FlowLayout());
    gameListPanel.setMinimumSize(new Dimension(600,600));   // <-- has no effect
    gameListPanel.add(gameJList);
    gameListControlPanel.add(gameListPanel, BorderLayout.EAST);

    loungeFrame.add(gameListControlPanel, BorderLayout.WEST);

    // center panel in the lounge is for chat messages; it has a separate border layout,
    // center for accumulated messages, bottom for entering messages
    JPanel chatMessagePanel = new JPanel(new BorderLayout());
//    Border chatMessagePanelBorder = BorderFactory.createEmptyBorder(7,7,7,7);
//    chatMessagePanel.setBorder(chatMessagePanelBorder);

    JTextArea chatMessages = new JTextArea();
    chatMessagePanel.add(chatMessages, BorderLayout.CENTER);
    // debug
    chatMessages.append("message one\n");
    chatMessages.append("message two\n");
    chatMessages.append("message three\n");

    // and lower panel is for entering one's own chat messages
    JPanel chatMessageEntryPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));
    JTextField chatMessageEntryField = new JTextField(35);
    JButton chatMessageEntryButton = new JButton("Enter");
    chatMessageEntryPanel.add(chatMessageEntryField);
    chatMessageEntryPanel.add(chatMessageEntryButton);
    chatMessagePanel.add(chatMessageEntryPanel, BorderLayout.SOUTH);

    loungeFrame.add(chatMessagePanel, BorderLayout.CENTER);

    loungeFrame.pack();    

    return loungeFrame;
  }

  private static void addButtons(JPanel panel, String ... labels)
  {
    for (String label : labels)
    {
      JButton button = new JButton(label);
      panel.add(button);
    }
  }

}

Answer 1

为 JList 提供一个足够宽的原型(prototype)单元格值以显示您需要的内容。例如，

gameJList.setPrototypeCellValue("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");

原型(prototype)值(此处为 String，因为列表已声明为 JList<String> )用于设置列表的首选大小，但不会显示在 JList 中。您可以根据需要使用尽可能大或小的列表。另外，请务必在水平维度中出于相同目的设置可见行数:

gameJList.setVisibleRowCount(20);  // for example