Comparison of touch coordinates
Is it possible to compare touch coordinates made by users in UIView to one repository in plist or txt format? The argument looks like this:
if (user touch coordinate == touch coordinate stored in plist or text)
then
(do something)
else
(do something)
If possible, in what format should I write the coordinates in the list and how to link it inside the program?
Thanks in advance and sorry if you find my question a little noobie.
source to share
Not sure if there is a one line solution.
On a UITouch instance, the method locationInView:
returns a CGPoint structure (x and y coordinates, both floats). This way, you can store the x and y coordinates in your plist and then compare them with your current x and y coordinates.
EDIT: Also, when comparing coordinates, you probably want to use the distance between two points to determine when you have a hit.
EDIT: Below is a sample code to load and write to a property list where the values are based on NSDictionary:
- (NSMutableDictionary *)loadDictionaryFromPList: (NSString *)plistName
{
NSString *plistPath = [[NSBundle mainBundle] pathForResource:plistName ofType:@"plist"];
NSDictionary *immutableDictionary = [NSDictionary dictionaryWithContentsOfFile: plistPath];
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithDictionary: immutableDictionary];
return mutableDictionary;
}
- (void)saveDictionary: (NSDictionary *)mySettings toPList: (NSString *)plistName
{
NSString *plistPath = [[NSBundle mainBundle] pathForResource:plistName ofType:@"plist"];
[mySettings writeToFile: plistPath atomically: YES];
}
Method for calculating distance between two UITouches locations:
-(CGFloat) distanceBetween: (CGPoint) point1 and: (CGPoint)point2
{
CGFloat dx = point2.x - point1.x;
CGFloat dy = point2.y - point1.y;
return sqrt(dx*dx + dy*dy );
}
And finally, the code that uses the values in the property list to determine if the user is in a previous location:
CGPoint currentTouchLocation = [currentTouch locationInView:self];
// Lookup last Touch location from plist, and handle case when current Touch matches it:
NSMutableDictionary *mySettings = [self loadDictionaryFromPList: @"MySettings"];
NSNumber *lastXCoordinate = [mySettings objectForKey:@"lastXCoordinate"];
NSNumber *lastYCoordinate = [mySettings objectForKey:@"lastYCoordinate"];
if (lastXCoordinate && lastYCoordinate)
{
CGPoint lastTouchLocation = CGPointMake([lastXCoordinate floatValue], [lastYCoordinate floatValue]);
CGFloat distanceBetweenTouches = [self distanceBetween: currentTouchLocation and: lastTouchLocation];
if (distanceBetweenTouches < 25) // 25 is just an example
{
// Handle case where current touch is close enough to "hit" previous one
NSLog(@"You got a hit!");
}
}
// Save current touch location to property list:
[mySettings setValue: [NSNumber numberWithFloat: currentTouchLocation.x] forKey: @"lastXCoordinate"];
[mySettings setValue: [NSNumber numberWithFloat: currentTouchLocation.y] forKey: @"lastYCoordinate"];
[self saveDictionary:mySettings toPList: @"MySettings"];
source to share
The features you are probably looking for are NSStringFromCGPoint()
and CGPointFromString()
.
But the two touch coordinates will almost certainly never be accurate. You almost never compare CGFloats
to ==
, let alone what you get from analog input like finger touch. You need to compare if they are "close enough". See this blog for a good example of how to measure the distance between two points. You want this result to be less than some value (epsilon or "small number") that suits your purpose.
source to share