设置 JList 以填充其所添加到的组件的整个大小
下面是我创建 JList 的代码。当它在独立的 JFrame 中创建时，JList 会填充整个框架。但是，当我将其创建为 JPanel 并将其添加到 JFrame 时，它没有填充组件的大小，为什么？
public class ListBranchesInterface extends JPanel {
private Library theLibrary; // reference to back end
private ArrayList<LibraryBranch> branches;
private DefaultListModel dlm;
private JList list;
private JScrollPane scroll;
public ListBranchesInterface(Library theLibrary) {
this.theLibrary = theLibrary;
branches = new ArrayList<LibraryBranch>();
branches.addAll(theLibrary.getLibraryBranches());
Iterator<LibraryBranch> iter = branches.iterator();
dlm = new DefaultListModel();
while (iter.hasNext()) {
dlm.addElement(iter.next().toString());
}
list = new JList(dlm); // create a JList from the default list model
scroll = new JScrollPane(list, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); // add a scroll pane
// to the JList
add(scroll);
setVisible(true);
}
below is my code for creating the JList. When it is created in a standalone JFrame the JList fills the entire frame. However, when I create it as a JPanel and add it to the JFrame it is not filling the size of the component, Why?
public class ListBranchesInterface extends JPanel {
private Library theLibrary; // reference to back end
private ArrayList<LibraryBranch> branches;
private DefaultListModel dlm;
private JList list;
private JScrollPane scroll;
public ListBranchesInterface(Library theLibrary) {
this.theLibrary = theLibrary;
branches = new ArrayList<LibraryBranch>();
branches.addAll(theLibrary.getLibraryBranches());
Iterator<LibraryBranch> iter = branches.iterator();
dlm = new DefaultListModel();
while (iter.hasNext()) {
dlm.addElement(iter.next().toString());
}
list = new JList(dlm); // create a JList from the default list model
scroll = new JScrollPane(list, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); // add a scroll pane
// to the JList
add(scroll);
setVisible(true);
}
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因为
JFrame的 内容窗格 的默认布局管理器是BorderLayout，直接添加到它会填充整个可用空间（即中心) 框架的内容窗格。另一方面，JPanel的默认布局管理器是FlowLayout。 FlowLayout 类将组件排成一行，并按其首选大小调整大小。因此，将JList添加到JPanel不会填充整个可用空间。Because the default layout manager of a
JFrame's content pane isBorderLayoutand adding directly to it would fill the entire available space (i.e., center) of the frame's content pane. On the other hand, the default layout manager of aJPanelisFlowLayout. TheFlowLayoutclass puts components in a row, sized at their preferred size. So adding theJListto aJPanelwould not fill the entire available space.我从@kavka 得到了答案......事实是更改边框布局。
From @kavka I derived the answer... The fact is Change to Border Layout.