How do I load hierarchical data from a database into a tree view

问题

I have a database table with data and need to load the fields into a TTreeView object.

The line:

ItemTree.Items.AddChild(nil, CurrentField_Text);

simply adds a node to the top level.

How can I specify a point to insert it in?

Please note that while looping through the data from the table, I may (for example) insert 3 top level items and then the 4th element is actually the child of node 2.

How can I specify this?

回答1:

This is some code lifted directly from a program of mine which inserts values taken from a query into a treeview.

 tv.items.clear;
 with qCustTree do  // this is the query which 'feeds' the treeview
  try
   close;
   params[0].asinteger:= qCustWithCallsID.asinteger;
   open;
   tv.items.BeginUpdate;
  while not eof do
   begin
    father:= fieldbyname ('father').asinteger;
    if father = 0
     then node:= nil
     else node:= FindANode (father);
    lastnode:= tv.Items.AddChildObject (node, fieldbyname ('curdate').asstring,
                                        pointer (fieldbyname ('id').asinteger));
    next
   end;
  finally
   tv.items.endupdate;
   tv.fullexpand;
   tv.Selected:= tv.Items[0];
   tvchange (nil, tv.Selected);
  end;

If the 'father' field of the returned tuple is 0, then a new parent node is opened on the tree, otherwise a new child node is opened.

回答2:

Use the parent node instead of nil in the call to AddChild, so that the child is added to the parent node:

ParentNode := ItemTree.Items.AddChild(nil, 'Parent');
ItemTree.Items.AddChild(ParentNode, 'Child node');

来源：https://stackoverflow.com/questions/13225429/how-do-i-load-hierarchical-data-from-a-database-into-a-tree-view

标签

treeview

lazarus