I want to create a simple app that draws a simple line on screen when I move my phone on the Y-axis from a start point to end point, for example from point a(0,0) to point b(0, 10) please help
demo :
You need to initialize the motion manager and then check motion.userAcceleration.y
value for an appropriate acceleration value (measured in meters / second / second).
In the example below I check for 0.05 which I've found is a fairly decent forward move of the phone. I also wait until the user slows down significantly (-Y value) before drawing. Adjusting the device MotionUpdateInterval will will determine the responsiveness of your app to changes in speed. Right now it is sampling at 1/60 seconds.
motionManager = [[CMMotionManager alloc] init];
motionManager.deviceMotionUpdateInterval = 1.0/60.0;
[motionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue currentQueue] withHandler:^(CMDeviceMotion *motion, NSError *error) {
NSLog(@"Y value is: %f", motion.userAcceleration.y);
if (motion.userAcceleration.y > 0.05) {
//a solid move forward starts
lineLength++; //increment a line length value
}
if (motion.userAcceleration.y < -0.02 && lineLength > 10) {
/*user has abruptly slowed indicating end of the move forward.
* we also make sure we have more than 10 events
*/
[self drawLine]; /* writing drawLine method
* and quartz2d path code is left to the
* op or others */
[motionManager stopDeviceMotionUpdates];
}
}];
Note this code assumes that the phone is lying flat or slightly tilted and that the user is pushing forward (away from themselves, or moving with phone) in portrait mode.