how to set JTree "ctrl" selection mode to be always enabled

Hello,

I have a JTree that implements multi selection logic.

This works great when I do all my selections using the mouse + Ctrl key pressed. If user makes selections with the Ctrl key unpressed it breaks my logic.

I can't really see why it breaks but I think that a possible solution is to always indicate the TreeSelectionModel that the selection has been make with the Ctrl key pressed.

What would you suggest ?

From stackoverflow

• I think I've found the solution

  You will need to extend JTree and DefaultTreeSelectionModel.

  JTree relevant methods:

  /////////////////////////////////////////////////////
  /////////////////////////////////////////////////////
  /// Implement selection using "adding" only logic. //
  /////////////////////////////////////////////////////
  /////////////////////////////////////////////////////
  
  @Override
  public void setSelectionPath(TreePath path) {
  
   System.out.println("MLDebugJTree: setSelectionPath(" + path + ")");
  
   addSelectionPath(path);
  
   return;
   //super.setSelectionPath(path);
  }
  
  @Override
  public void setSelectionPaths(TreePath[] paths) {
  
   System.out.println("MLDebugJTree: setSelectionPaths(" + paths + ")");
  
   addSelectionPaths(paths);
  
   return;
  }
  
  @Override
  public void setSelectionRow(int row) {
  
   System.out.println("MLDebugJTree: setSelectionRow(" + row + ")");
  
   addSelectionRow(row);
  
   return;
   //super.setSelectionRow(row);
  }
  
  @Override
  public void setSelectionRows(int[] rows) {
  
   System.out.println("MLDebugJTree: setSelectionRows(" + rows + ")");
  
   addSelectionRows(rows);
  
   return;
   //super.setSelectionRows(rows);
  }
  

  DefaultSelectionModel relevant methods :

  package com.ml.tree2.model.impl;
  
  import javax.swing.tree.DefaultTreeSelectionModel;
  import javax.swing.tree.TreePath;
  
  public class MLTreeSelectionModel extends DefaultTreeSelectionModel {
  private static final long serialVersionUID = -4270031800448415780L;
  
  @Override
  public void addSelectionPath(TreePath path) {
   // Don't do overriding logic here because addSelectionPaths is ultimately called.
   super.addSelectionPath(path);
  }
  
  @Override
  public void addSelectionPaths(TreePath[] paths) {
   if(paths != null) {
    for(TreePath path : paths) {
  
     TreePath[] toAdd = new TreePath[1];
     toAdd[0] = path;
  
     if (isPathSelected(path)) {
      // If path has been previously selected REMOVE THE SELECTION.
      super.removeSelectionPaths(toAdd);
     } else {
      // Else we really want to add the selection...
      super.addSelectionPaths(toAdd);
     }
    }
   }
  }
  

  HTH.

  James B : @maxim - thanks, I can't upvote this enough, this saved me loads of searching!