Got multi-touch working

Android Processing

ak_eric

in Android Processing • 2 years ago

Was easier than I expected it to be based on what the wiki has to say about it ;)
It may not be as 'robust' as other implementations, but it will definitely track multiple points on the screen at once. I've got code and examples over on my blog:
http://www.akeric.com/blog/?p=1411

I override the parent Activity's

dispatchTouchEvent method Processing's surfaceTouchEvent and capture the passed in MotionEvent object, which has all different kinds of goodness letting you know what is going on when the user is touching the hardware.

Replies(11)

Jesse Sco..

Re: Got multi-touch working

2 years ago

Excellent Eric! Your tutorials have been a great help in understanding Android implementation to me so far - look forward to taking a look at this tomorrow.

~ J

cedrickie..

Re: Got multi-touch working

2 years ago

fantastic, these are really useful!

ak_eric

Re: Got multi-touch working

2 years ago

Glad to help. We all stand on shoulders of giants :)

ak_eric

Re: Got multi-touch working

2 years ago

With a bit more work, I have a more robust solution, find new code on my blog.

Fixes issues where drawing of graphics wasn't occurring in Processing draw() function (it now is), which caused flickering on-screen, and screwed up screengrabs. New code also tracks previous motion (and size) per event, so you can extract motion vectors from the multitouch data (for example) the same way you could do it for a mouse in 'regular Processing'.

mmix2009

Re: Got multi-touch working

2 years ago

Nice work. Very useful.

Question: how did you manage to get a clean screenshot of the four touch points?

DDMS did not work for me.

Thanks.

andres

Re: Got multi-touch working

2 years ago

You can save an image of the whole screen to the SD card by using the save() method, something like this:

save("/sdcard/screen.png")

ak_eric

Re: Got multi-touch working

2 years ago

You know DDMS screenshot is a tricky thing: While it will screengrab them, it seems to grab multiple frames and then combine it together, like the shutter speed of the grabber is slower than the refresh of the screen. Probably the only reason I can think of right now why I like my wife's iPhone more: Built in screen-shot on the phone :-S But to answer your quesiton mmix2009, based on those latest updates I published, that allowed me to make a decent screenshot (actually, the pic at the top was made with that code). Why it wouldn't work for someone else I have no idea :-S

Thanks for the tip andres.

Jesse Sco..

Re: Got multi-touch working

2 years ago

Quick Edit of the last two functions (on your first code, not your updated second...) to also return motionPressure...

void infoCircle(float x, float y, float siz, int id, float press) {
// What is drawn on sceen when touched.
float diameter = circleBaseSize * siz;
noFill();
ellipse(x, y, diameter, diameter);
fill(0,255,0);
ellipse(x, y, 8, 8);
text( ("ID:"+ id + ", " + press + ", " + int(x) + ", " + int(y) ), x-128, y-64);
}
//-----------------------------------------------------------------------------------------
// Override Processing's surfaceTouchEvent, which will intercept all
// screen touch events. This code only runs when the screen is touched.
public boolean surfaceTouchEvent(MotionEvent me) {
// Number of places on the screen being touched:
int numPointers = me.getPointerCount();
for(int i=0; i < numPointers; i++) {
int pointerId = me.getPointerId(i);
float pressureId = me.getPressure(i);
float x = me.getX(i);
float y = me.getY(i);
float siz = me.getSize(i);
infoCircle(x, y, siz, pointerId, pressureId);
}
// If you want the variables for motionX/motionY, mouseX/mouseY etc.
// to work properly, you'll need to call super.surfaceTouchEvent().
return super.surfaceTouchEvent(me);
}

ak_eric

Re: Got multi-touch working

2 years ago

I originally had put 'pressured detection' in it, but I'd only get values of 0 or 128 (If I remember the values correctly). It was basically detecting if there was no pressure, or any pressure at all, which I didn't find terribly valuable at the time. What type of values do you get back from your pressure settings? If there was some kind of range of pressure being returned, that'd be awesome, but I wasn't picking it up.

Jesse Sco..

Re: Got multi-touch working

2 years ago

Im getting between 0.3 and 0.45 ... as the Dev reference says, this will vary from device to device, based upon the calibration of the hardware...

(im on a Nexus One)...

iamtheele..

Re: Got multi-touch working

1 year ago

Hi,

Great tutorial, It helped me a lot. I have somewhat of a peculiar problem. If I use two screen inputs simultaneously, the X axis works great but the Y axis is more...weird. When both fingers are at the same Y value, It switches control!!! I assigned the first finger to a circle and the second to another circle. When both Y values are equal, the first finger controls the Y of the second circle and the second Finger controls the Y of the first circle. The X axis still works like normal. How do I get around this problem? I know I can get around it because there is a game that uses two virtual on-screen joysticks and they work independetly on my phone(like they should) .

BTW my sketch is :

public boolean surfaceTouchEvent(MotionEvent me) {
int numPointers = me.getPointerCount();
final int action = me.getAction() & MotionEvent.ACTION_MASK;
int pointerIndex = (me.getAction() & MotionEvent.ACTION_POINTER_ID_MASK)
>> MotionEvent.ACTION_POINTER_ID_SHIFT;
int pointerId = me.getPointerId(pointerIndex);
if (action == MotionEvent.ACTION_DOWN || action == MotionEvent.ACTION_POINTER_DOWN)
{
    if (pointerId == 0) {
    }
    else if (pointerId == 1) {
    }
}
else if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_POINTER_UP) {
    if (pointerId == 0) {
    }
    else if (pointerId == 1) {
    }
}
else if (action == MotionEvent.ACTION_MOVE)
{
    for (int i = 0; i<numPointers;i++)
    {
      int newId = me.getPointerId(i);
//you can get x,y positions with me.getX(i), me.getY(i)
      if (newId == 0) {
        x1 = me.getX(0);
        y1 = me.getY(0);
         circleX = x1;
          circleY = y1;
        }


    else if (newId == 1) {
      x2 = me.getX(1);
      y2 = me.getY(1);
          circleX2 = x2;
          circleY2 = y2;
        }
}
}
return super.surfaceTouchEvent(me);
}
Thank you
EDIT: I have the same problem described in this video: http://www.youtube.com/watch?feature=player_embedded&v=qzhUzq6bTPg#!