I m playing with custom components in Compose Is there a way

Question

I m playing with custom components in Compose Is there a way to capture the on touch and get the X Y position thinking face

Shep Shapard · Answer

Hi there I work on pointer input gestures for Compose The underlying pointer input system is different from how Android traditionally works and right now none of the GestureDetectors produce the actual position during movement but rather that change in movement

Shep Shapard · Answer

What is it that you are actually trying to achieve slightly smiling face

Zach Klippenstein (he/him) [MOD] · Answer

I m curious how do you do hit detection for buttons and stuff then How would you write a drawing app

nglauber · Answer

< Shep Shapard> It s just a sample I want to create a custom view for a TicTacToe game So I would like to detect which square was touch on

Zach Klippenstein (he/him) [MOD] · Answer

Can you use `Clickable` for that

nglauber · Answer

Sure I can

nglauber · Answer

I can put 9 `Clickable` and I m good to go Ignore my example I just want to know how to get X Y of a touch event

Zach Klippenstein (he/him) [MOD] · Answer

I m curious now too

Shep Shapard · Answer

So given that things are still in development and in flux there is no documentation that explains how the lower level pointer input system works but you can start digging through the source of the GestureDetectors anywhere you see the us `PointerInputWrapper` I d start with PressReleasedGestureDetector to see the lower level system in action

Shep Shapard · Answer

Essentially GestureDetectors use PointerInputWrappers to observe and react to the stream of events The job of GestureDetectors is to interpret the lower level stream and eventually filter out the events that it wants to react to by consuming each event change

Shep Shapard · Answer

Right now there simply aren t any GestureDetectors that tell you the position of the of the pointer overtime I m still working through what GestureDetectors should exist and how GestureDetectors may be composed together themselves to allow simple gesture detectors to be composed together to form more complex ones

Shep Shapard · Answer

For example RawDragGestureDetector currently cares about drags and flings it doesn t know about conditions underwhich it should start It can be composed together with say TouchSlopExceededGestureDetector or LongPressGestureDetector to form a DragGestureDetector that waits for the finger to move beyond a touch slop or for a long press to occur before dragging starts

Shep Shapard · Answer

woah woah woah backing up there I think I may have jumped the gun and gone into way more detail than was necessary to address what you were looking for Still there is no GestureDetector that just says a finger clicked at x y because the most common use cases are simply was this area clicked But looking at PressReleasedGestureDetector and maybe PressIndicatorGestureDetector you should be able to design your own GestureDetector that does what you want

nglauber · Answer

thanks for the explanation < Shep Shapard> Can I expect something easy like we had in the current UI Toolkit just override `onTouch`

Shep Shapard · Answer

< nglauber> Hmm the equivalent of overriding onTouch is something like implementing a GestureDetector and using it I will try to make that easy slightly smiling face

Zach Klippenstein (he/him) [MOD] · Answer

< Shep Shapard> That s great context thanks

Foso · Answer

< nglauber> you can use the PressGestureDetector to get X Y position

nglauber · Answer

awesome thanks < Foso> wink

nglauber · Answer

Didn t work for me < Foso> confused

Shep Shapard · Answer

PressGestureDetector despite its name is actually misleadingly the wrong thing to use here It is intended to be used for something that will display press indication it has other behavior related to gesture disambiguation that will likely eventually backfire This is something else I have to improve

Shep Shapard · Answer

Also < Foso> in your example you are actually only ever getting the press location The release location isn t provided by the gesture detector

Shep Shapard · Answer

Also < nglauber> I assume you want to get the location where a pointer was released and not where it was pressed you want the Up event not the Down event correct

nglauber · Answer

For my sample I think the down press will work but it would be nice to have both

Shep Shapard · Answer

Well if you use `PressGestureDetector` it will give you coordinates for the first finger that touches on an area but it won t give you any other coordinates again until all fingers have been released and then a finger touches again thus calling onStart with the position of that finger

Shep Shapard · Answer

I still suggest digging into the lower level the lower level is where you get all of the raw events and then you can get any pointer position at any time grin