ruby-****@sourc*****
ruby-****@sourc*****
2003年 10月 21日 (火) 03:36:34 JST
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URL = http://ruby-gnome2.sourceforge.jp/?tips_lazy_treeview
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=Creating a "lazy" TreeView
- In some applications, populating an entire tree of data to be displayed by a Gtk::TreeView can be expensive to do all at once. Thankfully it is possible to write a function to populate child rows as they are expanded. The trick is to get the row expander to appear without any real child rows. The easiest way to achieve this is to create a "dummy" row which contains no data.
+ In some applications, populating an entire tree of data to be displayed by a Gtk::TreeView can be expensive to do all at once. Thankfully it is possible to create a signal handler that populates child rows as they are expanded. The trick is to get the row expander to appear without any real child rows. The easiest way to achieve this is to create a "dummy" row which contains no data.
For example, let's create a simple TreeStore, and add a single row to it.
model = Gtk::TreeStore.new(String)
view = Gtk::TreeView.new(model)
column = Gtk::TreeViewColumn.new("Example column",
Gtk::CellRendererText.new, {:text => 1})
iter = store.append(nil)
iter[0] = 'Parent row'
store.append(iter) # DUMMY CHILD
- Then we can create a "row-expanded" handler which checks whether the first child row contains a real value, and if not appends the real data.
+ Then we can create a "row-expanded" handler which checks whether the first child row contains a real value; if it doesn't, we will append the actual data.
view.signal_connect("row-expanded") do |self, iter, path|
child = iter.first_child
if (! child[0])
new_child = store.append(iter)
new_child[0] = 'Child row'
store.remove(child) # REMOVE DUMMY CHILD
end
end
The order here is important. If you remove the dummy child before you append real data, the row will end up with no children and it will never expand.
((<Masao>)) wrote a simple file tree browser that demonstrates a practical use of this technique: {{attach_anchor("fileview.rb")}}