In xcode 5 I am using coremotion to get the accelerometer data and then using that to move an object right/left and up/down on my screen. The right left works perfectly because the 0 center point of the x axis is straight up. However most people hold their phones at about a .-75 angle on the y axis. I would like to reset this as the 0 axis so that when tilts the phone back from this point the object moves down and when they tilt it forward from this point (toward 90 degrees) the object moves up. I have tried setting the min and max for the y center to various points but no matter what I do the object only moves in relation to the original y 0 which is straight up. Here is my code.
in view did load
self.motionManager = [[CMMotionManager alloc] init];
self.motionManager.accelerometerUpdateInterval = .05;
[self.motionManager startAccelerometerUpdatesToQueue:[NSOperationQueue currentQueue]
withHandler:^(CMAccelerometerData *accelerometerData, NSError *error) {
[self outputAccelertionData:accelerometerData.acceleration];
if(error){
NSLog(#"%#", error);
}
}];
and separate
-(void)outputAccelertionData:(CMAcceleration)acceleration
{
delta.x = acceleration.x * 10;
delta.y = acceleration.y * 10;
imageView2.center = CGPointMake(imageView2.center.x - delta.x, imageView2.center.y + delta.y);
if (imageView2.center.x < 145) {
imageView2.center = CGPointMake(145, imageView2.center.y);
}
if (imageView2.center.x > 165) {
imageView2.center = CGPointMake(165, imageView2.center.y);
}
if (imageView2.center.y < 0) {
imageView2.center = CGPointMake( imageView2.center.x,0);
}
if (imageView2.center.y >600) {
imageView2.center = CGPointMake(imageView2.center.x,600);
NSLog(#"imageViewcenter%f",imageView2.center.y);
}
}
thanks for any help.
Am developing an application to calculate the steps of the human while walking,
I did this using accelerometer but I found that it's not accurate.
So after googling this, I found that using GyroScope sensor is more accurate than the accelerometer.
Any help with a control that might do this as I didn't ever develop using GyroScope, Or a document to read more about GyroScope Sensor.
Thanks in advance for help.
-(void)addAcceleration:(UIAcceleration*)accel
{
x = accel.x;
y = accel.y;
z = accel.z;
}
-(NSString*)name
{
return #"You should not see this";
}
#end
#define kAccelerometerMinStep 5.02
#define kAccelerometerNoiseAttenuation 1.0
double Norm(double x, double y, double z)
{
return sqrt(x * x + y * y + z * z);
}
double Clamp(double v, double min, double max)
{
if(v > max)
return max;
else if(v < min)
return min;
else
return v;
}
// See http://en.wikipedia.org/wiki/Low-pass_filter for details low pass filtering
#implementation LowpassFilter
-(id)initWithSampleRate:(double)rate cutoffFrequency:(double)freq
{
self = [super init];
if(self != nil)
{
double dt = 1.0 / rate;
double RC = 1.0 / freq;
filterConstant = dt / (dt + RC);
}
return self;
}
-(void)addAcceleration:(UIAcceleration*)accel
{
double alpha = filterConstant;
if(adaptive)
{
double d = Clamp(fabs(Norm(x, y, z) - Norm(accel.x, accel.y, accel.z)) / kAccelerometerMinStep - 1.0, 0.0, 1.0);
alpha = (1.0 - d) * filterConstant / kAccelerometerNoiseAttenuation + d * filterConstant;
}
x = accel.x * alpha + x * (1.0 - alpha);
y = accel.y * alpha + y * (1.0 - alpha);
z = accel.z * alpha + z * (1.0 - alpha);
}
-(NSString*)name
{
return adaptive ? #"Adaptive Lowpass Filter" : #"Lowpass Filter";
}
#end
// See http://en.wikipedia.org/wiki/High-pass_filter for details on high pass filtering
#implementation HighpassFilter
-(id)initWithSampleRate:(double)rate cutoffFrequency:(double)freq
{
self = [super init];
if(self != nil)
{
double dt = 1.0 / rate;
double RC = 1.0 / freq;
filterConstant = RC / (dt + RC);
}
return self;
}
-(void)addAcceleration:(UIAcceleration*)accel
{
double alpha = filterConstant;
if(adaptive)
{
double d = Clamp(fabs(Norm(x, y, z) - Norm(accel.x, accel.y, accel.z)) / kAccelerometerMinStep - 1.0, 0.0, 1.0);
alpha = d * filterConstant / kAccelerometerNoiseAttenuation + (1.0 - d) * filterConstant;
}
x = alpha * (x + accel.x - lastX);
y = alpha * (y + accel.y - lastY);
z = alpha * (z + accel.z - lastZ);
lastX = accel.x;
lastY = accel.y;
lastZ = accel.z;
}
-(NSString*)name
{
return adaptive ? #"Adaptive Highpass Filter" : #"Highpass Filter";
}
Use CoreMotion FrameWork.
#import <CoreMotion/CoreMotion.h>
self.motionManager = [[CMMotionManager alloc] init];
//Gyroscope
if([self.motionManager isGyroAvailable])
{
/* Start the gyroscope if it is not active already */
if([self.motionManager isGyroActive] == NO)
{
/* Update us 2 times a second */
[self.motionManager setGyroUpdateInterval:1.0f / 2.0f];
/* Add on a handler block object */
/* Receive the gyroscope data on this block */
[self.motionManager startGyroUpdatesToQueue:[NSOperationQueue mainQueue]
withHandler:^(CMGyroData *gyroData, NSError *error)
{
NSString *x = [[NSString alloc] initWithFormat:#"%.02f",gyroData.rotationRate.x];
self.gyro_xaxis.text = x;
NSString *y = [[NSString alloc] initWithFormat:#"%.02f",gyroData.rotationRate.y];
self.gyro_yaxis.text = y;
NSString *z = [[NSString alloc] initWithFormat:#"%.02f",gyroData.rotationRate.z];
self.gyro_zaxis.text = z;
}];
}
}
else
{
NSLog(#"Gyroscope not Available!");
}
Read this: http://developer.apple.com/library/ios/#documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/Introduction/Introduction.html
Need to use two classes: CMGyrodata and CMMotionManager
Related to your question: How to count steps using an Accelerometer?
Read that, will be a good starting point...
Hope this helps...
On an Android device, I was able to use the accelerometer to count steps without much problem, see my answer here.
I am developing a game that uses the gyroscope to keep enemies in relatively the same place, with the following code:
if([motionManager isGyroAvailable])
{
[motionManager setGyroUpdateInterval:0.05];
[motionManager startGyroUpdatesToQueue:[NSOperationQueue mainQueue]
withHandler:^(CMGyroData *gyroData, NSError *error)
{
valueX3 = gyroData.rotationRate.y* 50;
valueY3 = gyroData.rotationRate.x* 50;
int newX3 = (int)(enemyufoG.center.x +valueY3);
int newY3 = (int)(enemyufoG.center.y -valueX3);
CGPoint newCenter2 = CGPointMake(newX3, newY3);
enemyufoG.center = newCenter2;
valueX2 = gyroData.rotationRate.y* 50;
valueY2 = gyroData.rotationRate.x* 50;
int newX2 = (int)(enemyufoR.center.x +valueY2);
int newY2 = (int)(enemyufoR.center.y -valueX2);
CGPoint newCenter = CGPointMake(newX2, newY2);
enemyufoR.center = newCenter;
valueX = gyroData.rotationRate.y* 50;
valueY = gyroData.rotationRate.x* 50;
int newX = (int)(enemyAlien.center.x +valueY);
int newY = (int)(enemyAlien.center.y -valueX);
CGPoint newCenter3 = CGPointMake(newX, newY);
enemyAlien.center = newCenter3;
}];
}
Once you shoot an enemy that is in the crosshairs of the gun, it hides the UIImageView, then uses NSTimer to call a different method that shows it again. I would like to have the enemies reappear in random positions on the screen.
CGPoint pos = enemyAlien.center;
if ((pos.x > 254) && (pos.x < 304) && (pos.y > 140) && (pos.y < 160 && _ammoCount != 0))
{
enemyAlien.hidden = YES;
[dangerBar setProgress:dangerBar.progress-0.10];
_killCount = _killCount+3;
[killCountField setText: [NSString stringWithFormat:#"%d", _killCount]];
timer = [NSTimer scheduledTimerWithTimeInterval: 4.0
target: self
selector: #selector(showAlien)
userInfo: nil
repeats: NO];
}
- (void) showAlien {
enemyAlien.hidden = NO;
}
When I try and use enemyAlien.center = enemyAlien.center + arc4random()%100; above enemyAlien.hidden = NO, I get the following error:
'Invalid operands to binary expression ('CGPoint (aka 'struct CGPoint') and 'unsigned int').
You're trying to add an integer to a cgpoint.
try this.
enemyAlien.center = CGPointMake(enemyAlien.center.x + (arc4random()%100),enemyAlien.center.y + (arc4random()%100));
although this will only move the alien in a diagonal direction. You should probably change it to the following for a better experience.
enemyAlien.center = CGPointMake((arc4random()%SCREEN_WIDTH),(arc4random()%SCREEN_HEIGHT));
where SCREEN_WIDTH and SCREEN_HEIGHT are the dimensions of your playing field.
Ok, so I have these powerups that I want to slow/speed up the movement of the other objects in the game for a few seconds.
I have an array of objects that I have a variable called spawnInterval that gets faster and faster as the game progresses, making the ame get harder after a few mins.
But I can't really grasp how to make it so the character in the game will react differently to different objects as in when the fastPowerUp is hit by the character sprite, the spawn interval doesn't change.
And vice versa with the slowPowerUp.
the code I have at the moment is this in a move sequence method that gets called in an update method:
-
(void) updateObstacles:(ccTime)delta{
for (int i = 0; i < 20; i++) {
//int randomizer = CCRANDOM_0_1() * [obstacles count];
//NSLog(#"randomizer: %i",randomizer);
CCSprite* randomObject = [obstacles randomObject];
currentObject = [obstacles indexOfObject:randomObject];
if ([randomObject numberOfRunningActions] == 0) {
[self runObstacleMoveSequence:randomObject withTimer:delta];
break;
}
}
}
-(void) runObstacleMoveSequence:(CCSprite *)object withTimer:(ccTime)delta{
static int time;
//Slowly increase object speed
numObstaclesMoved++;
if (!slowPowerUp && !fastPowerUp) {
time += delta;
if (numObstaclesMoved % 17 == 0 && obstacleMoveDuration > 2.0f) {
obstacleMoveDuration -= 0.2f;
if (spawnInterval > 0.1f) {
[self unschedule:#selector(updateObstacles:)];
[self schedule:#selector(updateObstacles:) interval:spawnInterval];
spawnInterval-=0.1f;
NSLog(#"interval: %f",spawnInterval);
}
}
}else if (slowPowerUp && !fastPowerUp) {
if (numObstaclesMoved % 17 == 0 && obstacleMoveDuration > 2.0f) {
obstacleMoveDuration += 3.0f;
if (spawnInterval > 0.1f) {
[self unschedule:#selector(updateObstacles:)];
[self schedule:#selector(updateObstacles:) interval:spawnInterval];
spawnInterval-=0.1f;
NSLog(#"interval: %f",spawnInterval);
if (time >= (delta + 3)) {
slowPowerUp = NO;
obstacleMoveDuration -= 3.0f;
}
}
}
}else if (!slowPowerUp && fastPowerUp) {
if (numObstaclesMoved % 17 == 0 && obstacleMoveDuration > 2.0f) {
obstacleMoveDuration -= 3.0f;
if (spawnInterval > 0.1f) {
[self unschedule:#selector(updateObstacles:)];
[self schedule:#selector(updateObstacles:) interval:spawnInterval];
spawnInterval-=0.1f;
NSLog(#"interval: %f",spawnInterval);
if (time >= (delta + 3)) {
fastPowerUp = NO;
obstacleMoveDuration += 3.0f;
}
}
}
}
CGSize screenSize = [[CCDirector sharedDirector]winSize];
CGPoint aboveScreenPosition = CGPointMake(object.position.x, screenSize.height - object.position.y);
int rotations = (CCRANDOM_0_1()*3) * 360;
float duration = (CCRANDOM_0_1()*5.0f) + 8.0f;
CCMoveTo* move = [CCMoveTo actionWithDuration:obstacleMoveDuration position:aboveScreenPosition];
CCRotateTo* rotate = [CCRotateBy actionWithDuration:duration angle:rotations];
CCSpawn* moveRotate = [CCSpawn actions: move, rotate, nil];
CCCallFuncN* call = [CCCallFuncN actionWithTarget:self selector:#selector(objectAboveScreen:)];
CCSequence* sequence = [CCSequence actions:moveRotate, call, nil];
[object runAction:sequence];
if (time >= (delta + 3)) {
fastPowerUp = NO;
}
}
-(void) objectAboveScreen:(id) sender{
//make sure sender is actually of the right class
NSAssert([sender isKindOfClass:[CCSprite class]], #"sender is not a CCSprite!");
CCSprite* obstacle = (CCSprite*)sender;
//move the back to the bottom of the screen
CGPoint pos = obstacle.position;
CGSize screenSize = [[CCDirector sharedDirector]winSize];
pos.y = (-screenSize.height - [obstacle texture].contentSize.height);
pos.x = CCRANDOM_0_1() * screenSize.width;
obstacle.position = pos;
}
I really just don't know where to go from here... Should I make the powerUps a different class? If so, how would I implement something like this? I really hate trying to ask for someone to solve my question, but I really just can't rack my brain around this and I'm rather new... if it were explained to me, then I know I would be able to implement it in future games on my own...
Thanks in advance, and let me know if more information is needed...
I'd do something like
in the .h file
float speedModifier;
-(void)resetPowerUp;
in the .m
-(void)resetPowerUp
{
speedModifier = 1;
}
wherever you are initializing the level
[self resetPowerUp];
upon collision with powerup:
speedModifier = 2;
[self performSelector:#selector(resetPowerUp) withObject:nil afterDelay:5];
then wherever you are moving whatever it is which speed should be effected by the powerup mode, multiply the speed of the animation (or divide the duration it takes for it to get wherever it's going) by speedModified
hope that helps
Regarding iPhone Map Kit cluster pinpoints:
I have 1000's of marks that I want to show on the map but it's just too many to handle so I want to cluster them.
Are there frameworks available or proof of concepts? That this is possible or is already been done?
You can use REVClusterMap to cluster
Note: This is a commercial product I'm affiliated with, but it solves this very problem.
I solved this problem in few of my apps and decided to extract it into a reusable framework. It's called Superpin and it is an (commercial, license costs $149) iOS Framework that internally uses quadtrees for annotation storage and performs grid-based clustering. The algorithm is quite fast, the included sample app is showing airports of the world (more than 30k+ annotations) and it's running quite smooth on an 3G iPhone.
This might be a bit like using a chainsaw to mow the lawn, but here is an excerpt from Algorithms in a Nutshell
Creating a KD-Tree...
public class KDFactory {
// Known comparators for partitioning points along dimensional axes.
private static Comparator<IMultiPoint> comparators[ ] ;
// Recursively construct KDTree using median method on input points.
public static KDTree generate (IMultiPoint [ ] points) {
if (points. length == 0) { return null; }
// median will be the root.
int maxD = points[ 0] . dimensionality( );
KDTree tree = new KDTree(maxD) ;
// Make dimensional comparators that compare points by ith dimension
comparators = new Comparator[ maxD+1] ;
for (int i = 1; i <= maxD; i++) {
comparators[ i] = new DimensionalComparator(i) ;
}
tree. setRoot(generate (1, maxD, points, 0, points. length-1) ) ;
return tree;
}
// generate the node for the d-th dimension (1 <= d <= maxD)
// for points[ left, right]
private static DimensionalNode generate (int d, int maxD,
IMultiPoint points[ ] ,
int left, int right) {
// Handle the easy cases first
if (right < left) { return null; }
if (right == left) { return new DimensionalNode (d, points[ left] ) ; }
// Order the array[ left, right] so the mth element will be the median
// and the elements prior to it will all be <=, though they won' t
// necessarily be sorted; similarly, the elements after will all be >=
int m = 1+(right-left) /2;
Selection. select(points, m, left, right, comparators[ d] ) ;
// Median point on this dimension becomes the parent
DimensionalNode dm = new DimensionalNode (d, points[ left+m-1] ) ;
// update to the next dimension, or reset back to 1
if (++d > maxD) { d = 1; }
// recursively compute left and right sub-trees, which translate
// into ' below' and ' above' for n-dimensions.
dm. setBelow(maxD, generate (d, maxD, points, left, left+m-2) ) ;
dm. setAbove(maxD, generate (d, maxD, points, left+m, right) ) ;
return dm;
}
}
Finding nearest neighbors best: O(log n) worst O(n)
// method in KDTree
public IMultiPoint nearest (IMultiPoint target) {
if (root == null) return null;
// find parent node to which target would have been inserted. This is our
// best shot at locating closest point; compute best distance guess so far
DimensionalNode parent = parent(target) ;
IMultiPoint result = parent. point;
double smallest = target. distance(result) ;
// now start back at the root, and check all rectangles that potentially
// overlap this smallest distance. If better one is found, return it.
double best[ ] = new double[ ] { smallest };
double raw[ ] = target. raw( );
IMultiPoint betterOne = root. nearest (raw, best) ;
if (betterOne ! = null) { return betterOne; }
return result;
}
// method in DimensionalNode. min[ 0] contains best computed shortest distance.
IMultiPoint nearest (double[ ] rawTarget, double min[ ] ) {
// Update minimum if we are closer.
IMultiPoint result = null;
// If shorter, update minimum
double d = shorter(rawTarget, min[ 0] ) ;
if (d >= 0 && d < min[ 0] ) {
min[ 0] = d;
result = point;
}
// determine if we must dive into the subtrees by computing direct
// perpendicular distance to the axis along which node separates
// the plane. If d is smaller than the current smallest distance,
// we could "bleed" over the plane so we must check both.
double dp = Math. abs(coord - rawTarget[ dimension-1] ) ;
IMultiPoint newResult = null;
if (dp < min[ 0] ) {
// must dive into both. Return closest one.
if (above ! = null) {
newResult = above. nearest (rawTarget, min) ;
if (newResult ! = null) { result = newResult; }
}
if (below ! = null) {
newResult = below. nearest(rawTarget, min) ;
if (newResult ! = null) { result = newResult; }
}
} else {
// only need to go in one! Determine which one now.
if (rawTarget[ dimension-1] < coord) {
if (below ! = null) {
newResult = below. nearest (rawTarget, min) ;
}
} else {
if (above ! = null) {
newResult = above. nearest (rawTarget, min) ;
}
}
// Use smaller result, if found.
if (newResult ! = null) { return newResult; }
}
return result;
}
More on KD-Trees at Wikipedia
I tried the others suggested here, and I also found OCMapView which has worked the best.
Its free and allows for easy grouping of annotations, which is what I needed. Its a bit newer & more updated than Revolver and to me is easier to implement.
A proof of concept is the Offline Maps app "OffMaps" ;)
http://itunes.apple.com/us/app/offmaps/id313854422?mt=8
I recently had to implement annotation clustering with MapKit. The solutions mentioned above are good, depending on your use case. I ended up going with FBAnnotationClustering (Objective-C) because it was free, and had lots of stars and few issues on github:
https://github.com/infinum/FBAnnotationClustering
The app I was working on was very map-centric, so it made sense to translate FBAnnotationClustering into Swift. Here's a blog post on the approach, which includes a link to the sample project on github.
http://ribl.co/blog/2015/05/28/map-clustering-with-swift-how-we-implemented-it-into-the-ribl-ios-app/
Inspired by WWDC 2011 video, this code works very well for me. Maybe not the fastest of all proposed here but it's for free and it's definitely the simplest.
It basically use 2 maps. One is hidden and hold every single annotation (allAnnotationMapView in my code). One is visible and show only the clusters or the annotations if single (mapView in my code).
- (void)didZoom:(UIGestureRecognizer*)gestureRecognizer {
if (gestureRecognizer.state == UIGestureRecognizerStateEnded){
[self updateVisibleAnnotations];
}
}
- (void)updateVisibleAnnotations {
static float marginFactor = 2.0f;
static float bucketSize = 50.0f;
MKMapRect visibleMapRect = [self.mapView visibleMapRect];
MKMapRect adjustedVisibleMapRect = MKMapRectInset(visibleMapRect, -marginFactor * visibleMapRect.size.width, -marginFactor * visibleMapRect.size.height);
CLLocationCoordinate2D leftCoordinate = [self.mapView convertPoint:CGPointZero toCoordinateFromView:self.view];
CLLocationCoordinate2D rightCoordinate = [self.mapView convertPoint:CGPointMake(bucketSize, 0) toCoordinateFromView:self.view];
double gridSize = MKMapPointForCoordinate(rightCoordinate).x - MKMapPointForCoordinate(leftCoordinate).x;
MKMapRect gridMapRect = MKMapRectMake(0, 0, gridSize, gridSize);
double startX = floor(MKMapRectGetMinX(adjustedVisibleMapRect) / gridSize) * gridSize;
double startY = floor(MKMapRectGetMinY(adjustedVisibleMapRect) / gridSize) * gridSize;
double endX = floor(MKMapRectGetMaxX(adjustedVisibleMapRect) / gridSize) * gridSize;
double endY = floor(MKMapRectGetMaxY(adjustedVisibleMapRect) / gridSize) * gridSize;
gridMapRect.origin.y = startY;
while(MKMapRectGetMinY(gridMapRect) <= endY) {
gridMapRect.origin.x = startX;
while (MKMapRectGetMinX(gridMapRect) <= endX) {
NSSet *allAnnotationsInBucket = [self.allAnnotationMapView annotationsInMapRect:gridMapRect];
NSSet *visibleAnnotationsInBucket = [self.mapView annotationsInMapRect:gridMapRect];
NSMutableSet *filteredAnnotationsInBucket = [[allAnnotationsInBucket objectsPassingTest:^BOOL(id obj, BOOL *stop) {
BOOL isPointMapItem = [obj isKindOfClass:[PointMapItem class]];
BOOL shouldBeMerged = NO;
if (isPointMapItem) {
PointMapItem *pointItem = (PointMapItem *)obj;
shouldBeMerged = pointItem.shouldBeMerged;
}
return shouldBeMerged;
}] mutableCopy];
NSSet *notMergedAnnotationsInBucket = [allAnnotationsInBucket objectsPassingTest:^BOOL(id obj, BOOL *stop) {
BOOL isPointMapItem = [obj isKindOfClass:[PointMapItem class]];
BOOL shouldBeMerged = NO;
if (isPointMapItem) {
PointMapItem *pointItem = (PointMapItem *)obj;
shouldBeMerged = pointItem.shouldBeMerged;
}
return isPointMapItem && !shouldBeMerged;
}];
for (PointMapItem *item in notMergedAnnotationsInBucket) {
[self.mapView addAnnotation:item];
}
if(filteredAnnotationsInBucket.count > 0) {
PointMapItem *annotationForGrid = (PointMapItem *)[self annotationInGrid:gridMapRect usingAnnotations:filteredAnnotationsInBucket];
[filteredAnnotationsInBucket removeObject:annotationForGrid];
annotationForGrid.containedAnnotations = [filteredAnnotationsInBucket allObjects];
[self.mapView addAnnotation:annotationForGrid];
//force reload of the image because it's not done if annotationForGrid is already present in the bucket!!
MKAnnotationView* annotationView = [self.mapView viewForAnnotation:annotationForGrid];
NSString *imageName = [AnnotationsViewUtils imageNameForItem:annotationForGrid selected:NO];
UILabel *countLabel = [[UILabel alloc] initWithFrame:CGRectMake(15, 2, 8, 8)];
[countLabel setFont:[UIFont fontWithName:POINT_FONT_NAME size:10]];
[countLabel setTextColor:[UIColor whiteColor]];
[annotationView addSubview:countLabel];
imageName = [AnnotationsViewUtils imageNameForItem:annotationForGrid selected:NO];
annotationView.image = [UIImage imageNamed:imageName];
if (filteredAnnotationsInBucket.count > 0){
[self.mapView deselectAnnotation:annotationForGrid animated:NO];
}
for (PointMapItem *annotation in filteredAnnotationsInBucket) {
[self.mapView deselectAnnotation:annotation animated:NO];
annotation.clusterAnnotation = annotationForGrid;
annotation.containedAnnotations = nil;
if ([visibleAnnotationsInBucket containsObject:annotation]) {
CLLocationCoordinate2D actualCoordinate = annotation.coordinate;
[UIView animateWithDuration:0.3 animations:^{
annotation.coordinate = annotation.clusterAnnotation.coordinate;
} completion:^(BOOL finished) {
annotation.coordinate = actualCoordinate;
[self.mapView removeAnnotation:annotation];
}];
}
}
}
gridMapRect.origin.x += gridSize;
}
gridMapRect.origin.y += gridSize;
}
}
- (id<MKAnnotation>)annotationInGrid:(MKMapRect)gridMapRect usingAnnotations:(NSSet *)annotations {
NSSet *visibleAnnotationsInBucket = [self.mapView annotationsInMapRect:gridMapRect];
NSSet *annotationsForGridSet = [annotations objectsPassingTest:^BOOL(id obj, BOOL *stop) {
BOOL returnValue = ([visibleAnnotationsInBucket containsObject:obj]);
if (returnValue) {
*stop = YES;
}
return returnValue;
}];
if (annotationsForGridSet.count != 0) {
return [annotationsForGridSet anyObject];
}
MKMapPoint centerMapPoint = MKMapPointMake(MKMapRectGetMinX(gridMapRect), MKMapRectGetMidY(gridMapRect));
NSArray *sortedAnnotations = [[annotations allObjects] sortedArrayUsingComparator:^(id obj1, id obj2) {
MKMapPoint mapPoint1 = MKMapPointForCoordinate(((id<MKAnnotation>)obj1).coordinate);
MKMapPoint mapPoint2 = MKMapPointForCoordinate(((id<MKAnnotation>)obj2).coordinate);
CLLocationDistance distance1 = MKMetersBetweenMapPoints(mapPoint1, centerMapPoint);
CLLocationDistance distance2 = MKMetersBetweenMapPoints(mapPoint2, centerMapPoint);
if (distance1 < distance2) {
return NSOrderedAscending;
}
else if (distance1 > distance2) {
return NSOrderedDescending;
}
return NSOrderedSame;
}];
return [sortedAnnotations objectAtIndex:0];
}
I think Foto Brisko (iTunes link) does this.
I do not think there is a Cocoa Touch framework for it.