Using TreeField , expand or collapse a Tree in Blackberry?

Question

I have drawn a tree structure using TreeField in Blackberry now . The root node consists of 15 nodes and every node has its corresponding child nodes and on running the application , all the node comes as expanded . I need only a particular node to be expanded and all the others as collapsed .

I have tried using the following method from apis .

myTree.setDefaultExpanded(false);

and

myTree.setExpanded(1, true);

but does not seem to have any effect so far on the tree . All nodes comes as expanded on launching the application .

Answer 1

If you look at the documentation for TreeField, you'll see that setDefaultExpanded() must be called before you add the nodes, not just before they are displayed:

setDefaultExpanded

public void setDefaultExpanded(boolean expanded)

      Sets the default expansion state for future node allocations.

So, to modify the TreeField example, you'd do something like this:

   public TreeFieldDemoScreen()
   {             
      setTitle("Tree Field Demo");

      String fieldOne =  new String("Parent folder 1");
      String fieldTwo =  new String("Parent folder 2");
      String fieldThree =  new String("Sub-folder 1");
      String fieldFour =  new String("Sub-folder 2");

      TreeCallback myCallback = new TreeCallback();
      TreeField myTree = new TreeField(myCallback, Field.FOCUSABLE);
      myTree.setDefaultExpanded(false);
      
      int node1 = myTree.addChildNode(0, fieldOne);
      int node2 = myTree.addChildNode(0, fieldTwo);
      int node3 = myTree.addChildNode(node2, fieldThree);
      int node4 = myTree.addChildNode(node3, fieldFour);

      add(myTree);
   }