如何滚动到JTable中的最后一行 [英] How to scroll to last row in a JTable
问题描述
我试图以新数据记录添加到最后的方式使用 JTable 。奇怪的是滚动条不会到达表的末尾;相反，它总是显示从最后一秒开始的第二个。有什么办法告诉滚动条总是到表的末尾？
I am trying to use JTable in the way where new data record are added to the end. The strange thing is the scroll bar does not go to the end of the table; instead, it always shows the second from the last. Any way to tell the scroll bar to always go to the end of the table?
以下是我的代码的一部分：
Here is part of my code:
table.scrollRectToVisible(table.getCellRect(table.getRowCount()-1, 0, true));
推荐答案
我刚遇到这个问题 - 实际上什么都没有这行代码错了;问题在于你执行它。
I just ran into this problem - there is actually nothing wrong with that line of code; the problem lies in when you execute it.
如果你像我一样，在操作TableModel（甚至通过 invokeLater ）或使用
If you're, like me, trying to execute it immediately after manipulating the TableModel (even via invokeLater) or by using a TableModelListener, you'll get the problem you're describing. The problem is that while the model has been updated with the new data (table.getRowCount() is simply a pass-through to the getRowCount() method on your TableModel), the JTable component visually has not.
当你在前面描述的地方执行那行代码时，你实际上是想告诉 JScrollPane （ JTable。 scrollRectToVisible 将任何操作推迟到可以提供滚动行为的父级，例如 JScrollPane ），以滚动到所附 JTable 组件的末尾。它拒绝这样做，而是滚动到 JTable 组件的当前末尾。
When you execute that line of code in the previously described places, you're actually trying to tell the JScrollPane (JTable.scrollRectToVisible defers any action to a parent that can provide scrolling behaviour, e.g. JScrollPane) to scroll beyond the end of the enclosed JTable component. It refuses to do that, and instead scrolls to the current end of the JTable component instead.
稍后， JTable 组件可视化地更新自身，并将新添加的行添加到之前滚动到的行的下方。您可以通过添加一个独立于添加新行的代码执行它的按钮来验证该行代码的工作原理，例如
At some point later, the JTable component updates itself visually, and adds the newly added row underneath the row scrolled to earlier. You can verify that that line of code works by adding a button that executes it independently of the code that adds new rows, e.g.
private JTable _table = new JTable();
...
JButton b = new JButton("Force scroll to bottom");
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
_table.scrollRectToVisible(_table.getCellRect(_table.getRowCount()-1, 0, true));
}
});
this.add(b);
此问题的解决方案有点间接，但在我的测试中确实可靠。因为问题在于视觉方面的问题，所以我决定将 ComponentListener 挂钩，其中包括 componentResized 方法。无论何时添加或删除行， JTable 都会调整大小，即使由于 JScrollPane的视口而无法直观地看到它。因此，只需在该侦听器方法中运行该行代码，事情就会按预期运行。
The solution to this problem is a little indirect, but does work reliably in my testing. Because the issue lies in the visual side of things, I decided to hook into the ComponentListener instead, which provides, among other things, a componentResized method. Whenever a row is added or removed, the JTable resizes, even if it cannot be seen visually due to the JScrollPane's viewport. Therefore just run that line of code in that listener method, and things will work as expected.
private JTable _table = new JTable();
...
_table.addComponentListener(new ComponentAdapter() {
public void componentResized(ComponentEvent e) {
_table.scrollRectToVisible(_table.getCellRect(_table.getRowCount()-1, 0, true));
}
});
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