iphone shaking code

mek · September 2008

iphone shaking code

ive looked around quite a bit, and can't seem to find any examples of code to perform an action if the iphone is shaken

has anyone been able to successfully do this? if so how
i would imagine you would monitor the accelerometer for changes in x,y,and,z

maybe?


- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
	const float earthquake = 1.5;
	static BOOL shakeme;
	BOOL shake = FALSE;
	
	if (shakeme) return;
	beenhere = TRUE;
	if (acceleration.x > earthquake || acceleration.x < (-1* earthquake))
		shake = TRUE;
	if (acceleration.y > earthquake || acceleration.y < (-1* earthquake))
		shake = TRUE;
	if (acceleration.z > earthquake || acceleration.z < (-1* earthquake))
		shake = TRUE;
	if (shake) { /* perform action here */ }
 
        shakeme = false;
}

so if the action that you wanted to perform was to pull a random object/data from a sqlite3 database, it would be some rand code that randomized the Primary key, and whatever that value is ...send that data to the view or a label or imagecontroller

i dunno

any ideas?

pfhorte · September 2008

This is what I do for a left to right shake.

- (void)accelerometer:(UIAccelerometer*)accelerometer didAccelerate:(UIAcceleration*)acceleration;
{

++frameNum;
if (acceleration.x > shakeLimit && shakeLeft == NO)
{
lastFrameFullRight = frameNum;
shakeLeft = YES;
if (lastFrameFullRight - lastFrameFullLeft < 15) // a shake
{
if (++numChanges > 3)
{
[self erase];
numChanges = 0;
}
}
else
numChanges = 0;
}
if (acceleration.x < -shakeLimit && shakeLeft == YES)
{
lastFrameFullLeft = frameNum;
shakeLeft = NO;
if (lastFrameFullLeft - lastFrameFullRight < 15) // a shake
{
if (++numChanges > 3)
{
[self erase];
numChanges = 0;
}
}
else
numChanges = 0;
}
}

db3d · September 2008

Check out how LightsOn did it. Most of it is on LightsOnApplication.m

Essentially calculating if the distance from the last point was above a certain threshold. The distance is calculated by:

#define DIST(X, Y, Z) sqrtf(((X)*(X))+((Y)*(Y))+((Z)*(Z)));

And used in:

dist = DIST(x - old_x, y - old_y, z - old_z);

pfhorte · September 2008

That does not detect a shake, only a large singe movement.
My code detects several large movements, first one way, then another and also the frequency of the movement.
Shake too slow, and its NOT a shake. Shake only once and its NOT a shake.

mek · October 2008

thank you so much for that

narendar · March 2009

hi can you please tell
what values you assigned for the variables at starting ...for

lastFrameFullRight , frameNum, shakeLimit.

Of course it is simple Question i am asking ....can you post it with total code.

thansk,
naren

DenVog · March 2009

mek;20614 said:
ive looked around quite a bit, and can't seem to find any examples of code to perform an action if the iphone is shaken

There is some sample code from the Beginning iPhone Development book that covers this. As I recall, it's Chapter 15 "ShakeandBreak" example. You can download the code even if you don't have the book, but I recommend the book if you're new to iPhone Dev.

London_iPhone_Dev · November 2009

Is there any way of getting this in javascript form? I'm using phoneGap.

Thanks in advance.

johnathon · November 2009

Use the new motionEnded method in 3.0. Your view (or viewController) has to be first responder to recieve shake events.
This should do it :


-(BOOL)canBecomeFirstResponder {
    return YES;
}

-(void)viewDidAppear:(BOOL)animated {

    [self becomeFirstResponder];
}

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
	if (event.type == UIEventSubtypeMotionShake) {
            //It has sheked

	}
}

Hokie · February 2010

Personally I have tried out the - (void)motionEnded...method and found the response time to be rather slow.

What I am trying to do is detect a fast shake vs. a slow shake and write a message. The project compiles, and if you shake below the 1.5 acceleration threshold I setup the labels says "Slow" as it is suppose to. Speed up the shake and it shows "Fast." THE PROBLEM is if I slow the shake back down the label doesn't change. What I have is as follows:

- (void)accelerometer : (UIAccelerometer *)accelerometer
didAccelerate : (UIAcceleration *)acceleration {

static NSInteger shakeCount = 0;
static NSDate *shakeStart;

NSDate *now = [[NSDate alloc] init];
NSDate *checkDate = [[NSDate alloc] initWithTimeInterval: 2.0f sinceDate:shakeStart];

if ([now compare:checkDate]== NSOrderedDescending || shakeStart == nil) {

shakeCount = 0;
[shakeStart release];
shakeStart = [[NSDate alloc] init];
}

[now release];
[checkDate release];

// Shake is too fast
if (acceleration.y > AccelerationThreshold) {
shakeCount++;

if (shakeCount > 4) {
myLabel.text = [NSString stringWithFormat:@"To Fast %i", shakeCount];
NSLog(@"To Fast");
shakeCount = 0;
shakeStart == nil;
[shakeStart release];
shakeStart = [[NSDate alloc] init];
// shakeCheckComplete = YES;
}

}

// Shake is slow
if (acceleration.y < AccelerationThreshold && acceleration.y > 0.5) {

shakeCount++;

if (shakeCount > 5) {
myLabel.text = [NSString stringWithFormat:@"Slow %i", shakeCount];
NSLog(@"Slow");
shakeCount = 0;
shakeStart == nil;
[shakeStart release];
shakeStart = [[NSDate alloc] init];
}
}

}

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