Fun with tap gesture: collapse / expand tree

[jolo2000]

Hi,

this is just a little hack to get a collapsing or expanding tree with a double tap gesture.
Thanks to the excellent design of PSTreeGraph, this feature is easy to realize.

First implement the tap gesture recognizer:

• (void) initTapGestureRecognition {
  UITapGestureRecognizer *tapDoubleGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleDoubleTap:)];
  tapDoubleGesture.numberOfTapsRequired = 2;
  [self addGestureRecognizer:tapDoubleGesture];
  [tapDoubleGesture release];
  }

With a double tap on the view, the "handleDoubleTap" function is called:

-(void)handleDoubleTap:(UITapGestureRecognizer*)gestureRecognizer {

if (gestureRecognizer.state == UIGestureRecognizerStateEnded)
{
    NSLog(@"See a tap double gesture");
    ruleOutsTreeView = [gestureRecognizer view];
    if (isCollapsed) {
        [ruleOutsTreeView expandRoot];
        isCollapsed = false;
    }
    else if (!isCollapsed) {
        [ruleOutsTreeView collapseRoot];
        isCollapsed = true;
    }
}

}

"isCollapsed" is just a local, private variable, which holds the state of the tree.
"ruleOutsTreeView" represents the "PSBaseTreeGraphView".

You can register the tap gesture recognizer in your custom tree view class, e.g. PSHTreeGraphView

• (id) initWithCoder:(NSCoder *)decoder
  {
  self = [super initWithCoder:decoder];
  if (self) {

      // Initialization code when loaded from XIB (this example)
      // init gesture recognizer
  [self initTapGestureRecognition];
  bool isCollapsed = false;
  

  }
  return self;
  }

To get the tree collapsed or expanded, I modified the functions "expandRoot()" and "collapseRoot()" of PSBaseTreeGraphView.m
E.g.:

• (void) collapseRoot
  {
  [UIView beginAnimations:@"TreeNodeExpansion" context:nil];
  [UIView setAnimationDuration:2.0];
  [UIView setAnimationBeginsFromCurrentState:YES];
  [UIView setAnimationCurve:UIViewAnimationCurveEaseOut];
  [[self rootSubtreeView] setExpanded:NO];
  [[[self rootSubtreeView] enclosingTreeGraph] layoutGraphIfNeeded];

  [UIView commitAnimations];
  }

• (void) expandRoot
  {
  [UIView beginAnimations:@"TreeNodeExpansion" context:nil];
  [UIView setAnimationDuration:2.0];
  [UIView setAnimationBeginsFromCurrentState:YES];
  [UIView setAnimationCurve:UIViewAnimationCurveEaseOut];
  [[self rootSubtreeView] setExpanded:NO]; // if not set, a collapsed subtree node will not expand
  [[self rootSubtreeView] setExpanded:YES];
  [[[self rootSubtreeView] enclosingTreeGraph] layoutGraphIfNeeded];

  [UIView commitAnimations];

}

That's all, now you have a tree collapsing or expanding with a double tap.

Have fun
Johannes