java 当框架太小而无法显示所有 JList 时，如何让滚动条出现在 JList 上？
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How to get scrollbar to appear on a JList when the frame is too small to show all of the JList?
提问by idungotnosn
I want to make a scrollbar appear on a JList whenever the frame is resized to be too small for the List itself. So far, this is the code I have. Run it, resize the frame, and notice how no scrollbar ever appears on the JList.
我想让一个滚动条出现在 JList 上，只要框架被调整到对于 List 本身来说太小了。到目前为止，这是我拥有的代码。运行它，调整框架的大小，并注意 JList 上从未出现滚动条。
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
public class JListScroll extends JPanel{
JScrollPane listScrollPane;
public JListScroll() {
String[] stringArray = {"Testing","This","Stuff"};
JList<String> rowList = new JList<String>(stringArray);
listScrollPane = new JScrollPane();
listScrollPane.getViewport().setView(rowList);
this.setSize(new Dimension(75,200));
this.add(listScrollPane);
this.doLayout();
}
public static void main(String[] args){
JFrame frame = new JFrame();
JListScroll scrollPanel = new JListScroll();
frame.add(scrollPanel);
frame.setVisible(true);
frame.setSize(new Dimension(75,300));
}
}
Notice how there is a JScrollPane added, but no scroll bar appears on the list when the window gets really small. This is what I want to fix.
请注意添加了 JScrollPane 的方式，但是当窗口变得非常小时，列表中不会出现滚动条。这就是我想要修复的。
Thanks in advance!
提前致谢！
回答by mKorbel
JPanel has implemented FlowLayout
FlowLayout accepting only PreferredSize (in your case hardcoded by setSize)
FlowLayout isn't designated, not implemented any resize JComponents (layed by FlowLayout) together with container, JComponent isn't resizable, stays as it is
don't want to commenting something about your code posted here, see differencies, quite good low level
JPanel 已经实现了 FlowLayout
FlowLayout 仅接受 PreferredSize（在您的情况下由 setSize 硬编码）
FlowLayout 未指定，未与容器一起实现任何调整大小的 JComponents（由 FlowLayout 放置），JComponent 不可调整大小，保持原样
不想评论有关您在此处发布的代码的内容，请查看差异，相当不错的低级
import java.awt.BorderLayout;
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
public class JListScroll {
private JFrame frame = new JFrame();
private JPanel panel = new JPanel();
private JScrollPane listScrollPane = new JScrollPane();
private String[] stringArray = {"Testing", "This", "Stuff"};
private JList rowList = new JList(stringArray);
public JListScroll() {
rowList.setVisibleRowCount(2);
listScrollPane.setViewportView(rowList);
panel.setLayout(new BorderLayout());
panel.add(listScrollPane);
frame.add(panel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // EDIT
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
JListScroll jListScroll = new JListScroll();
}
});
}
}
回答by ddmps
You can force the visibility of the (vertical) scroll bar with the method listScrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS)
您可以使用该方法强制（垂直）滚动条的可见性 listScrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS)
