Hi Dianne, I estimate the time lag from touch to event reception at around 200ms. It's most obvious in quick drag or fling type motions where the UI's response to the touch event is very obviously out of sync with your finger. Unfortunately it does seem that the delay is roughly in line with how the rest of the device feels. So it looks like I'm stuck with that performance, at least on this particular device.
Hi Richard, Thanks for the suggestion, I think I've read those same threads. In this case we have plenty of time to draw frames as fast as we get events, it's just that we're getting the events a fair bit behind the actual touch from the finger. This kind of stuff is only really obvious when you want something on screen to track a long running touch. Try one of the air hockey games for example, you'll see that the paddle lags the touch on screen by as much as 40-50 pixels at times (at least on my phone). That doesn't appear to be the fault of the game developer, but rather a built in lag generated by the phone hardware/drivers (accordingly Dianne). Thanks for the suggestions, Matt On Oct 18, 3:44 am, RichardC <[email protected]> wrote: > Try putting a short sleep into your onTouchEvent handler, about 16ms > is good. If I remember correctly (from previous posts in this forum) > your app is getting hammered by all the Touch events, they are coming > much more frequently than the maximum possible screen refresh/redraw > rate. > > -- > RichardC > > On Oct 18, 4:56 am, Dianne Hackborn <[email protected]> wrote: > > > > > The move event you receive contains as close as possible to the most recent > > location (it is retrieved immediately before dispatching to the app). > > You don't say how much lag you are seeing, so it is hard to offer advice -- > > is it more laggy than in other standard parts of the UI like list views? Is > > it the same? If it is the same, this is probably just a lower-level > > characteristic of the device -- there can be a lot of filtering/processing > > going on in the touch firmware to generate clean points, for example. > > > If the lag you are seeing is worse than the rest of the UI, it most likely > > is an issue in your app, unrelated to the simple dispatching code here. > > Perhaps some part of the drawing is very slow, etc. You could try > > profiling it to see what is going on. > > > On Sat, Oct 17, 2009 at 8:04 PM, Matt Hall <[email protected]> wrote: > > > > Hi everyone, > > > > I noticed when developing on an HTC Magic (G2) that when moving your > > > finger on the screen the location of the touch events trail your > > > finger pretty significantly. To test this I wrote a very simple app > > > that just draws a rectangle where you're touching. Even in this simple > > > case the rectangle can trail the finger on screen by a fair amount. > > > Here's the View that handles the touches and draws the rectangle: > > > > public class TouchTestView extends View { > > > private float x; > > > private float y; > > > private Paint paint = new Paint(); > > > public static final int SIZE = 40; > > > > public TouchTestView(Context context) { > > > super(context); > > > paint.setColor(Color.RED); > > > } > > > > �...@override > > > public boolean onTouchEvent(MotionEvent event) { > > > switch (event.getAction()) { > > > case MotionEvent.ACTION_DOWN: > > > x = event.getX(); > > > y = event.getY(); > > > invalidate(); > > > return true; > > > case MotionEvent.ACTION_MOVE: > > > x = event.getX(); > > > y = event.getY(); > > > invalidate(); > > > return true; > > > case MotionEvent.ACTION_UP: > > > x = -1; > > > y = -1; > > > invalidate(); > > > return true; > > > } > > > return super.onTouchEvent(event); > > > } > > > > �...@override > > > protected void onDraw(Canvas canvas) { > > > canvas.drawRect(x - SIZE, y - SIZE, x + SIZE, y + SIZE, > > > paint); > > > } > > > } > > > > So my question is: Is there a significant built in time delay between > > > the generation of the touch event and it's reception in the running > > > activity? If so, is there any tricks or methods to get those events in > > > a faster or more direct way? In our application the delay is causing > > > some pretty unfortunate performance results. > > > > Thanks for any advice or help, > > > Matt > > > -- > > Dianne Hackborn > > Android framework engineer > > [email protected] > > > Note: please don't send private questions to me, as I don't have time to > > provide private support, and so won't reply to such e-mails. All such > > questions should be posted on public forums, where I and others can see and > > answer them. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -~----------~----~----~----~------~----~------~--~---
