how to capture GestureDetector for onScaleUpdate and onScaleEnd

[mars000]

Hi
I'm trying to capture a pinch to zoom action by using GestureDector as per below,
I can confirm it first onDoubleTap but not for onLongPress, onScaleUpdae or onScaleEnd.
Is it something I'd doing wrong ?
any help would be much appreciated.

child: GestureDetector(
                child: LineChart(
                  // showAvg ? avgData() : mainData(),
                  mainData(),
                ),
                onDoubleTap: () {
                  print(
                      '61-[line_chart_sample2.dart] onDoubleTap gesture triggered');   // this fires! and i get print statemt when I doubletap
                },
                onLongPress: () {
                  print(
                      '61-[line_chart_sample2.dart] onLongPress gesture triggered');  // this does not fire
                },
                onScaleUpdate: (details) {
                  print(
                      '61-[line_chart_sample2.dart] onScaleUpdate details = $details'); // this does not fire
                },
                onScaleEnd: (ScaleEndDetails details) {
                  print(
                      '61-[line_chart_sample2.dart] onScaleUpdate details = $details'); // this does not fire
                },
              ),

[dLogicC]

Hi I'm trying to capture a pinch to zoom action by using GestureDector as per below, I can confirm it first onDoubleTap but not for onLongPress, onScaleUpdae or onScaleEnd. Is it something I'd doing wrong ? any help would be much appreciated.

child: GestureDetector(
                child: LineChart(
                  // showAvg ? avgData() : mainData(),
                  mainData(),
                ),
                onDoubleTap: () {
                  print(
                      '61-[line_chart_sample2.dart] onDoubleTap gesture triggered');   // this fires! and i get print statemt when I doubletap
                },
                onLongPress: () {
                  print(
                      '61-[line_chart_sample2.dart] onLongPress gesture triggered');  // this does not fire
                },
                onScaleUpdate: (details) {
                  print(
                      '61-[line_chart_sample2.dart] onScaleUpdate details = $details'); // this does not fire
                },
                onScaleEnd: (ScaleEndDetails details) {
                  print(
                      '61-[line_chart_sample2.dart] onScaleUpdate details = $details'); // this does not fire
                },
              ),

Hi, did you find a solution? I have the same problem.

[mars000]

I found if you enable gestures in FL_CHART then it traps all gesture messages and does not process or pass through all gestures :-(
If I disabled handleBuiltInTouches: true, i.e. set to false then my GestureDetector would capture the gestures. Its not ideal but a crude workaround. Perhaps someone else has a more elegant approach ?

[dLogicC]

I found the same solution.
I think a better approach is to edit the "RenderBaseChart" class in the "render_base_chart.dart" file in order to catch the scale event.
Were you able to get a good pinch-to-zoom effect?

[mars000]

I like your idea - much neater.
I did not actually implement code to pinch-to-zoom...in the end I just implemented a simple slider below graph that dynamically adjusted zoom factor of graph .... was neater and fingers get in the way in viewing the graph on a small screen i found :-)

[imaNNeo]

Can you please tell me what you want to do?
Are you looking for a zoom feature?
If yes, please follow this issue: #71

[mars000]

That’s correct. Or at least pass through that gesture as at preeent it’s not passed through

…

On Mon, 16 Jan 2023 at 00:55, Iman Khoshabi ***@***.***> wrote: Can you please tell me what you want to do? Are you looking for a zoom feature? — Reply to this email directly, view it on GitHub <#1183 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEURLD77QQ3U7CCSRCT64VLWSP6UVANCNFSM6AAAAAARWB2TSI> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[imaNNeo]

Okay so let's only talk about the gesture here.
For the scroll feature you can follow the mentioned issue.

[mars000]

Sorry @imaNNeo what do you mean by the statement “mentioned issue” ?
Is there anyway you can pass through the pinch zoom gesture so I can write the code to process it…from my understanding this is not passed through therefore I am unable to react to it.

[imaNNeo]

I meant #71
There are some workarounds introduced by people

[TNorbury]

Hello, I created a fork with a proposed solution (see commit here). Basically it replaces pan gestures with scale gestures. Scale gestures are a superset of pan gestures (source), so I think that's a safe swap as developers will just be able to check the number of pointers being used to determine if they want to pan or scale.

In my code, which now has pinch to zoom and horizontal panning, my LineTouchData.touchCallback now looks like this:

case FlScaleUpdateEvent:
  {
    event = event as FlScaleUpdateEvent;
    if (event.details.pointerCount == 1) {
      chartController.onHorizontalDrag(
            context,
            deltaX: event.details.focalPointDelta.dx,
          );
    } else {
      chartController.onScale(scaleDetails: event.details);
    }
  }

My fork is just a hacked together version that works for my app's needs, but more than happy to work with you @imaNNeo to make it something that could be merged in

[TNorbury]

Here's an example of how it works, I currently use: long press, tap, and scale to achieve this

[extrame]

I tested the solution of @TNorbury , It work only on PanGestureRecognizer disabled.