B4A Library [Lib] Gesture Detector

Informatix · Sep 20, 2012

This library adds the detection of standard gestures (press, single-tap, double-tap, long tap, drag, scroll, fling, pinch, rotation) to B4A. Instead of using the Touch events to figure out what the user really did, now you just set 15 different listeners with one line of code and you get the gestures as events with all the useful values (scrolling distance, fling velocity, pinch variation, rotation angle...).
With this library, you can also know easily the pressure or the size of a touch event.

It works with any view.

Note: you have to create an instance of GestureDetector (with Dim) for each view you want to bind to the detector with SetOnGestureListener.

v2.2:
- Freeware.

v2.3:
- I fixed an issue with the boolean value returned by the OnTouch event with some views (e.g. ListView or ScrollView);
- I added a new demo (GD_SwipeLV);
- The OnDown event is now raised before OnDoubleTap.

v2.4:
- I fixed an issue when a view is dragged after one of the pointer is up (delta values were computed according to the pointer 0, not to the remaining pointer).

Incompatible with Android versions < 2.

Informatix · Jul 2, 2013

hookshy said:
In the example with asteroid game I found that the declaration:
code
Private ges As Gestures
\code
is not recognised .
The library GestureDetector V1.10 is activated.
I can not test the asteroid example .
Only found GestureDetector as member not Gestures.
Can you tell why ??
Thank you .

You make a confusion between the Gestures library and this one.

Informatix · Oct 28, 2013

New version 1.2 (freeware)

I added a return value to the onTouch event. If you set it to True, the event is handled by the view (it's the same behavior as before). If set to False, the event is ignored and passed down to another view under the finger.

New version 2.1 (donationware)

I added a return value to the onTouch event. If you set it to True, the event is handled by the view (it's the same behavior as before). If set to False, the event is ignored and passed down to another view under the finger.

I added two new functions: CreateMotionEvent and PassTouchEventTo. With these new functions, it's now possible to generate touch events or to pass a touch event down to another view in the activity.

I added a demo, GD_Dispatch, to illustrate these new features.

Deleted member 30048 · Oct 29, 2013

Fantastic!!!! Thanks a lot Informatix!

jalle007 · Nov 7, 2013

How to calculate left / right swipe ?

Need basic sample here

Informatix · Nov 7, 2013

jalle007 said:
How to calculate left / right swipe ?

Need basic sample here

Please read this post.

NJDude · Nov 17, 2013

Are the Freeware and Donationware libs compatible with each other?, I'm asking this because I see the events are handled differently, for example:

Donationware:

B4X:

gEvent_onTouch(Action As Int, X As Float, Y As Float, MotionEvent As Object)

Freeware:

B4X:

gEvent_onTouch(Action As Int, X As Float, Y As Float, MotionEvent As Object) As Boolean

The app crashes if the user doesn't have the "correct" lib.

Informatix · Nov 17, 2013

The two versions (1.2 and 2.1) are compatible and are always compared before release. They have the same onTouch signature. But this signature has been changed in the latest version (I added "As boolean" at the end) so you're probably comparing a former version with a new one.

NJDude · Nov 17, 2013

So users using version 2.1 will have the "As Boolean"?, if so, then it will be fine, am I correct?

Informatix · Nov 17, 2013

NJDude · Nov 17, 2013

Thank you.

kiki78 · Nov 25, 2013

Hello Informatix,

I try to use "onFling" event (Freeware 1.20 for now).
To discriminate where this event occur on screen, I try to use "getX" method of GestureDetector object with MotionEvent1 parameters.
In example give at post #50, this method take only one parameter, the MotionEvent object. Fine.
But in current version, I need to give ptrIndex.
But to obtain ptrIndex, I use getPointerIndex(ev, PID), and to obtain PID I use getPID(ev, ptrIndex) !
It bites its tail !
How to get out this infernal circle ?
Sorry if my question is trivial, but I certainly miss something...

Regards

Informatix · Nov 25, 2013

kiki78 said:
Hello Informatix,

I try to use "onFling" event (Freeware 1.20 for now).
To discriminate where this event occur on screen, I try to use "getX" method of GestureDetector object with MotionEvent1 parameters.
In example give at post #50, this method take only one parameter, the MotionEvent object. Fine.
But in current version, I need to give ptrIndex.
But to obtain ptrIndex, I use getPointerIndex(ev, PID), and to obtain PID I use getPID(ev, ptrIndex) !
It bites its tail !
How to get out this infernal circle ?
Sorry if my question is trivial, but I certainly miss something...

Regards

0 is the first pointer.

kiki78 · Nov 26, 2013

Thank you Informatix,

I have found that first pointer is 0. But if I have multiple point I need to now which one to use.
So my question is why I need to pass ptrIndex to getX method, as it seem's it's embedded in MotionEvent object ?

Regards

Informatix · Nov 26, 2013

The motion event contains data for each pointer. So there's a X value for each pointer. How can I return the right value of X if I don't know the pointer?
You get the pointer id and pointer index of each pointer after the first with the event onPointerDown.
Did you look at my Paint example? It shows how to manage many pointers.

kiki78 · Nov 26, 2013

So sorry to disturb you...
I expect I obtain one fling event for each pointer, but not test it .
I will carefully reread your Paint example and make test.
Thank you Informatix for your patience.

Regards

b4auser1 · Nov 27, 2013

Hello, Informatix

B4X:

I use
    Private m_clsCheckListAll As ClsCheckList

to show data in

    Dim scvAll As ScrollView
Sub Activity_Create(FirstTime As Boolean)
    Activity.LoadLayout(sACTIVITY_NAME)

    m_clsGestureDetector.SetOnGestureListener(scvAll, "Gesture")
  
End Sub

and try to detect left/right swipe using

B4X:

Sub Gesture_onFling(velocityX As Float, velocityY As Float, MotionEvent1 As Object, MotionEvent2 As Object)
Log ("Fling")
Log ("velocityX: " & velocityX)
Log ("velocityY: " & velocityY)
Log ("MotionEvent1: " & MotionEvent1)
Log ("MotionEvent2: " & MotionEvent2)
'    Dim iWidth As Int = m_clsGestureDetector.getX(MotionEvent1, 0) - m_clsGestureDetector.getX(MotionEvent2, 0)
'   
'    If (iWidth) > 100 Then
'        RightSwipe
'    Else If ((iWidth) < -100) Then
'        LeftSwipe
'    End If
   
End Sub

but

MotionEvent1: null

as Log shows:

B4X:

Fling
velocityX: -220.43174743652344
velocityY: -29.126550674438477
MotionEvent1: null
MotionEvent2: MotionEvent { action=ACTION_UP, id[0]=0, x[0]=589.51404, y[0]=760.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x80000000, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=122598, downTime=122293, deviceId=0, source=0x1002 }

How to get MotionEvent1 to be not null ?

b4auser1 · Nov 28, 2013

I resolved my problem above, using transparent panel over scvAll
with

B4X:

m_clsGestureDetector.SetOnGestureListener(pnlScvAllGD, "Gesture")

and

B4X:

Sub Gesture_onTouch(Action AsInt, X AsFloat, Y AsFloat, MotionEvent AsObject) AsBoolean
  'Return True 'True = Handle this touch event, False = Ignore it
  Return m_clsGestureDetector.PassTouchEventTo(MotionEvent, scvAll)
End Sub

TheMightySwe · Nov 29, 2013

Hi again,

Do you have a Moneybookers/Skrill account? Just hate to use Cards on the web and I don't have a Paypal account? I like to donate a few $$$ for this library.

/ TMS

Informatix · Nov 29, 2013

TheMightySwe said:
Hi again,

Do you have a Moneybookers/Skrill account? Just hate to use Cards on the web and I don't have a Paypal account? I like to donate a few $$$ for this library.

/ TMS

Are you Trevor from NZ?

tchart · Dec 2, 2013

Informatix said:
Are you Trevor from NZ?

Informatix, no Im Trevor from NZ

Also, I'd just like to say how impressed I am with your library. Well worth the donation for anybody thinking about it.

B4A Library [Lib] Gesture Detector

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