In app designer how do I load a previously saved array of checked-node objects that are children in the Tree?

For debugging purporses I created a simple app in App Designer with a save button, a load button and a check-box tree. Component properties below:

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure    matlab.ui.Figure
        LoadButton  matlab.ui.control.Button
        SaveButton  matlab.ui.control.Button
        Tree        matlab.ui.container.CheckBoxTree
        Node1       matlab.ui.container.TreeNode
        Under11     matlab.ui.container.TreeNode
        Under12     matlab.ui.container.TreeNode
        Under13     matlab.ui.container.TreeNode
        Node2       matlab.ui.container.TreeNode
        Under21     matlab.ui.container.TreeNode
        Under22     matlab.ui.container.TreeNode
        Under23     matlab.ui.container.TreeNode
    end

After selecting desired checked boxes in the tree (see image), the user can save the checked-nodes with the save button and the tree's check-boxes are then cleansed.

Save button function:

% Button pushed function: SaveButton
        function SaveButtonPushed(app, event)
            checked = app.Tree.CheckedNodes;
            save('data.mat', 'checked') 
            app.Tree.CheckedNodes = [];
        end

I want the user to be able to load that saved data and the tree's check-boxes be filled accordlingly after pressing the load button.

Load button function:

% Button pushed function: LoadButton
        function LoadButtonPushed(app, event)
            mfile = load('data.mat');
            app.Tree.CheckedNodes = mfile.checked;
        end

I receive the following error:

Error using matlab.ui.container.CheckBoxTree/set.CheckedNodes

'CheckedNodes' must be an empty array or an array of TreeNode objects that are children in the Tree.

As a control, I loaded the mat file in the command window and it does indeed contain an array of tree node objects that correctly correspond to children in the tree:

        >> mfile = load('data.mat')

mfile = 

  struct with fields:

    checked: [3×1 TreeNode]

>> mfile.checked

ans = 

  3×1 TreeNode array:

  TreeNode    (Under12)
  TreeNode    (Under22)
  TreeNode    (Under23)

How do I fix this error?

/Rina

Answer 1

[Swaraj]

Hi Rina,

I understand that your are not able to assign tree nodes from .mat file into "CheckedNodes".

You cannot directly assign the tree nodes into “app.tree.CheckedNodes”.

You can make use of “Tag” field inside each tree node to solve this issue.

On clicking on save button: Instead of storing the entire tree node, you can store the tag in the .mat file.

On clicking on load button: Load the .mat file and use the tag with the help of “findobj” function to get the exact handle of the tree node and then mark it as checked.

Documentation of “findobj”: Find handle objects - MATLAB (mathworks.com)

Documentation for treenode: Control tree node appearance and behavior - MATLAB (mathworks.com)

Hope it helps!!!

[Rina Blomberg]

Perfect! Thak you!