Multitouch Madness
Entry posted by Josh ·
2,673 views
I've implemented multitouch input on iOS, and gave Aria the information he needs to do the same for Android devices. Multitouch is an interesting input method. Each "touch" has a beginning, some movement, and an end. To handle multiple touches, they need to be persistent; you need to keep track of which touch is which. This is a little weird if you're coming from a mouse and keyboard paradigm.
On iOS, you have a pointer to a UITouch object, and on Android it's a jObject object (I think). I opted to make touches correspond to fingers...the first touch is touch 0, the second is 1, and so on. I set it to handle up to five touch inputs simultaneously. (Interestingly, there doesn't seem to be any limit on the number of touches a device can handle at once. At least, I tried ten, and ran out of fingers to test any further.)
Touches emit an event which you can get through the event queue, or you can supply an event callback hook. Alternatively, you can just call GetTouchDown(), GetTouchHit(), GetTouchX(), etc., which work the same as mouse input. The only difference is you need to supply an index for the finger number.
To implement zooming, I just checked to see if finger 0 and 1 are touched, then found the distance between the two fingers. I'll have to write some detailed tutorials about this, but until then here's my code:
while (PeekEvent())
{
Event event = WaitEvent();
Print(event.Debug());
switch (event.id)
{
case EVENT_KEY_DOWN:
if ((event.data)==KEY_ESCAPE)
{
return false;
}
break;
case EVENT_WINDOW_CLOSE:
if (window==event.source) return false;
break;
case EVENT_TOUCH_UP:
numTouches--;
break;
case EVENT_TOUCH_DOWN:
numTouches++;
Print("Event.data = "+String(event.data));
Print("Event.X = "+String(event.x));
Print("Event.Y = "+String(event.y));
Print("");
touchposition[event.data].x = event.x;
touchposition[event.data].y = event.y;
dx = touchposition[0].x - touchposition[1].x;
dy = touchposition[0].y - touchposition[1].y;
touchdistance = sqrt(dx*dx+dy*dy);
break;
case EVENT_TOUCH_MOVE:
if (event.data==0)
{
if (numTouches==3) camera->Move(-(event.x - touchposition[0].x)*0.01,(event.y - touchposition[0].y)*0.01,0);
touchposition[0].x = event.x;
touchposition[0].y = event.y;
dx = touchposition[0].x - touchposition[1].x;
dy = touchposition[0].y - touchposition[1].y;
d = sqrt(dx*dx+dy*dy);
if (numTouches==2) camera->Move(0,0,-(touchdistance - d)*0.01);
touchdistance = d;
//Print(touchdistance);
}
if (event.data==1)
{
touchposition[1].x = event.x;
touchposition[1].y = event.y;
dx = touchposition[0].x - touchposition[1].x;
dy = touchposition[0].y - touchposition[1].y;
d = sqrt(dx*dx+dy*dy);
if (numTouches==2) camera->Move(0,0,-(touchdistance - d)*0.01);
touchdistance = d;
// Print(touchdistance);
}
break;
}
}
And here's the result in action:
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