Get uitreenode expanded state

Question

I have built a UI in Matlab, displaying a tree. I used the new UI components and want to save and restore the state of the expanded/collapsed nodes. Unfortunately I could not find a way to determine the current state of a tree node. Here's a simple example:

t = uitree(uigridlayout(uifigure, [1 1]));
p = uitreenode(t, 'Text', 'Parent');
uitreenode(p, 'Text', 'Child');

How can I determine the expanded state of the parent node p?

Answer 1

You can create a cellarray containing the identifier of the nodes that have been expanded.

The cellarray will be:

• set in the TreeNodeExpanded callback that is called when the user expands a node
• reset in the TreeNodeCollapsed callback that is called when the user collapes a node

Then you can create two pushbutton:

• one to save the cellarray
• one to load it and restore the node configuration

The callback associated to the pushbutton that loads the cellarray with list of the expanded nodes:

• collapses (with the collapse function) all the node to reset the status of the tree
• loops through the cellarray and expands (with the expand function) the nodes whose identifier has been stored (and read) in the ".mat" file

The following is a possible implementation of the proposed procedure in an app.

The startupFcn callback:

• identifies the nodes present in the app
• creates a cellarray containing the identifiers of all the nodes of the tree
• sets the NodeData property of each node to an integer values that will be used as index to acces to the cellarray

The SaveTreeLeafstatusButtonPushed and LoadTreeLeafstatusButtonPushed callbacks simply save and load a ".mat" file whios name is hard written in the code; you can easily update then using the uigetfile and uiputfile functions.

The TreeNodeExpanded callback:

• gets the index of the expanded node from its NodeData property
• retrieves the identifier of the node
• sets the corresponding element of the cellarray that contains the identifier of the expanded nodes

The TreeNodeCollapsed:

• gets the index of the collapsed node from its NodeData property
• reset the corresponding element of the cellarray that contains the identifier of the expanded nodes

The comments in the code should describe the main step summarized above.

    classdef SAVE_EXPAND_TREE < matlab.apps.AppBase

   % Properties that correspond to app components
   properties (Access = public)
      save_expand_tree          matlab.ui.Figure
      Label                     matlab.ui.control.Label
      LoadTreeLeafstatusButton  matlab.ui.control.Button
      SaveTreeLeafstatusButton  matlab.ui.control.Button
      Tree                      matlab.ui.container.Tree
      Level0Node                matlab.ui.container.TreeNode
      Level_1_Node_1            matlab.ui.container.TreeNode
      Level_2_Node_1            matlab.ui.container.TreeNode
      Level_2_Node_2            matlab.ui.container.TreeNode
      Level_3_Node_1            matlab.ui.container.TreeNode
      Level_3_Node_2            matlab.ui.container.TreeNode
      Level_1_Node_2            matlab.ui.container.TreeNode
      Level_2_Node_3            matlab.ui.container.TreeNode
      Level_2_Node_4            matlab.ui.container.TreeNode
      Level_1_Node_3            matlab.ui.container.TreeNode
      Level_2_Node_5            matlab.ui.container.TreeNode
      Level_2_Node_6            matlab.ui.container.TreeNode
   end

   
   properties (Access = private)
      tree_leaf_status;    % Property in which to store the status of the tree leaves
      tree_leaf_obj_names; % Property in which tyo store the names of the tree objects
   end
   

   % Callbacks that handle component events
   methods (Access = private)

      % Code that executes after component creation
      function startupFcn(app)
         % Initialize the property in which to store the status of the tree leaves as an empty
         % cell array
         % Each element of the cellarray contains the name of a node of the tree
         % The NodeData property of each node contains an integer value. This is used as an index
         % to access the elements in the cellarray
         % Initilize the the cellarray containing the namens of the tree objects
         % Set the node idx in its NodeData property
         app_fields=fieldnames(app);
         cnt=0;
         for i=1:numel(app_fields)
            if(isa(app.(app_fields{i}),'matlab.ui.container.TreeNode'))
               cnt=cnt+1;
               app.(app_fields{i}).NodeData=cnt;
               app.tree_leaf_obj_names{app.(app_fields{i}).NodeData}=app_fields{i};
            end
         end
      end

      % Node expanded function: Tree
      function TreeNodeExpanded(app, event)
         node = event.Node;
         % Set the element of the tree_leaf_status cellarray corresponding to the index stored in
         % the NodeData property of the node that has been expanded to the name of the node itself

         % Get the idx of the expanded node
         idx=node.NodeData;
         % Set the element of the tree_leaf_status cellarray to the name of the node object
         app.tree_leaf_status{idx}=app.tree_leaf_obj_names{idx};
      end

      % Node collapsed function: Tree
      function TreeNodeCollapsed(app, event)
         node = event.Node;
         % Get the idx of the collapsed node
         idx=node.NodeData;
         % Reset the lement of the tree_leaf_status cellarray
         app.tree_leaf_status{idx}='';
      end

      % Button pushed function: SaveTreeLeafstatusButton
      function SaveTreeLeafstatusButtonPushed(app, event)
         % Get the tree_leaf_status cellarray
         tmp_tree_leaf_status=app.tree_leaf_status;
         % Save the tree_leaf_status cellarray in a ".mat" file
         save('tmp_tree_leaf_status.mat','tmp_tree_leaf_status')
      end

      % Button pushed function: LoadTreeLeafstatusButton
      function LoadTreeLeafstatusButtonPushed(app, event)
         % Check if the ".mat" file exists
         if(exist("tmp_tree_leaf_status.mat","file"))
            create_gif('tree_leaf.gif',app.save_expand_tree,1.5,0)
            app.Label.Text='Loading tmp_tree_leaf_status.mat';
            create_gif('tree_leaf.gif',app.save_expand_tree,1.5,1)
            % Load the tree_leaf_status ".mat" file
            load('tmp_tree_leaf_status.mat')
            % Collapse all the leaf of the tree
            collapse(app.Tree,'All')
            app.Label.Text='All Tree leaf collapsed before restoring the loaded status';
            create_gif('tree_leaf.gif',app.save_expand_tree,1.5,1)
            % loop through the leaf of the tree and expand those saved in the ".mat" file
            for i=1:numel(app.tree_leaf_status)
               tmp_tree_leaf_status{i};
               if(~isempty(tmp_tree_leaf_status{i}))
                  app.Label.Text=['Expanding ' tmp_tree_leaf_status{i}];
                  expand(app.(tmp_tree_leaf_status{i}))
                  create_gif('tree_leaf.gif',app.save_expand_tree,1.5,1)
               end
            end
         end
      end
   end

   % Component initialization
   methods (Access = private)

      % Create UIFigure and components
      function createComponents(app)

         % Create save_expand_tree and hide until all components are created
         app.save_expand_tree = uifigure('Visible', 'off');
         app.save_expand_tree.Position = [100 100 541 381];
         app.save_expand_tree.Name = 'Save & Restore Tree Leaft Status';

         % Create Tree
         app.Tree = uitree(app.save_expand_tree);
         app.Tree.NodeExpandedFcn = createCallbackFcn(app, @TreeNodeExpanded, true);
         app.Tree.NodeCollapsedFcn = createCallbackFcn(app, @TreeNodeCollapsed, true);
         app.Tree.Position = [22 105 279 277];

         % Create Level0Node
         app.Level0Node = uitreenode(app.Tree);
         app.Level0Node.Text = 'Level 0 Node';

         % Create Level_1_Node_1
         app.Level_1_Node_1 = uitreenode(app.Level0Node);
         app.Level_1_Node_1.Text = 'Level 1 Node 1';

         % Create Level_2_Node_1
         app.Level_2_Node_1 = uitreenode(app.Level_1_Node_1);
         app.Level_2_Node_1.Text = 'Level 2 Node 1';

         % Create Level_2_Node_2
         app.Level_2_Node_2 = uitreenode(app.Level_1_Node_1);
         app.Level_2_Node_2.Text = 'Level_2 Node 2';

         % Create Level_3_Node_1
         app.Level_3_Node_1 = uitreenode(app.Level_2_Node_2);
         app.Level_3_Node_1.Text = 'Level 3 Node 1';

         % Create Level_3_Node_2
         app.Level_3_Node_2 = uitreenode(app.Level_2_Node_2);
         app.Level_3_Node_2.Text = 'Level_3_Node_2';

         % Create Level_1_Node_2
         app.Level_1_Node_2 = uitreenode(app.Level0Node);
         app.Level_1_Node_2.Text = 'Level 1 Node 2';

         % Create Level_2_Node_3
         app.Level_2_Node_3 = uitreenode(app.Level_1_Node_2);
         app.Level_2_Node_3.Text = 'Level 2 Node 3';

         % Create Level_2_Node_4
         app.Level_2_Node_4 = uitreenode(app.Level_1_Node_2);
         app.Level_2_Node_4.Text = 'Level 2 Node 4';

         % Create Level_1_Node_3
         app.Level_1_Node_3 = uitreenode(app.Level0Node);
         app.Level_1_Node_3.Text = 'Level 1 Node 3';

         % Create Level_2_Node_5
         app.Level_2_Node_5 = uitreenode(app.Level_1_Node_3);
         app.Level_2_Node_5.Text = 'Level 2 Node 5';

         % Create Level_2_Node_6
         app.Level_2_Node_6 = uitreenode(app.Level_1_Node_3);
         app.Level_2_Node_6.Text = 'Level 2 Node 6';

         % Create SaveTreeLeafstatusButton
         app.SaveTreeLeafstatusButton = uibutton(app.save_expand_tree, 'push');
         app.SaveTreeLeafstatusButton.ButtonPushedFcn = createCallbackFcn(app, @SaveTreeLeafstatusButtonPushed, true);
         app.SaveTreeLeafstatusButton.Position = [339 289 165 33];
         app.SaveTreeLeafstatusButton.Text = 'Save Tree Leaf status';

         % Create LoadTreeLeafstatusButton
         app.LoadTreeLeafstatusButton = uibutton(app.save_expand_tree, 'push');
         app.LoadTreeLeafstatusButton.ButtonPushedFcn = createCallbackFcn(app, @LoadTreeLeafstatusButtonPushed, true);
         app.LoadTreeLeafstatusButton.Position = [339 219 165 33];
         app.LoadTreeLeafstatusButton.Text = 'Load Tree Leaf status';

         % Create Label
         app.Label = uilabel(app.save_expand_tree);
         app.Label.FontWeight = 'bold';
         app.Label.FontColor = [1 0 0];
         app.Label.Position = [22 30 482 59];
         app.Label.Text = '';

         % Show the figure after all components are created
         app.save_expand_tree.Visible = 'on';
      end
   end

   % App creation and deletion
   methods (Access = public)

      % Construct app
      function app = SAVE_EXPAND_TREE

         % Create UIFigure and components
         createComponents(app)

         % Register the app with App Designer
         registerApp(app, app.save_expand_tree)

         % Execute the startup function
         runStartupFcn(app, @startupFcn)

         if nargout == 0
            clear app
         end
      end

      % Code that executes before app deletion
      function delete(app)

         % Delete UIFigure when app is deleted
         delete(app.save_expand_tree)
      end
   end
end