Detect objects, touchesmoved and UITouch - ios

Question

I have a UIView on where i add balls with a ID. When i touch the ball with the ID 1 i draw a dashed line follows my finger.
The problem if when i move the finger to the other balls, i don't know how to detect these balls and check the ID they have. The what i need to happen is when i touch the next ball with the ID 2, the line finish draw and stay from ball 1 to ball 2, and create new one from 2 to finger, next.. 3 etc...
The code:
#import "DrawView.h"
#implementation DrawView
- (id)init
{
self = [super initWithFrame:CGRectMake(0, 0, 1024, 768)];
if (self) {
self.backgroundColor = [UIColor clearColor];
self.opaque = YES;
checkPointCircle = [[CheckPointCircle alloc] initWithPosX:315 posY:138 andNumber:1];
checkPointCircle.userInteractionEnabled = YES;
[self addSubview:checkPointCircle];
checkPointCircle = [[CheckPointCircle alloc] initWithPosX:706 posY:138 andNumber:2];
checkPointCircle.userInteractionEnabled = YES;
[self addSubview:checkPointCircle];
checkPointCircle = [[CheckPointCircle alloc] initWithPosX:315 posY:526 andNumber:3];
checkPointCircle.userInteractionEnabled = YES;
[self addSubview:checkPointCircle];
checkPointCircle = [[CheckPointCircle alloc] initWithPosX:706 posY:526 andNumber:4];
checkPointCircle.userInteractionEnabled = YES;
[self addSubview:checkPointCircle];
}
return self;
}
- (Line *)drawLine {
return drawLine;
}
- (void)setDrawLine:(Line *)line
{
drawLine = line;
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CheckPointCircle * checkTouch = (CheckPointCircle *)touch.view;
if (touch.view.class == checkPointCircle.class) {
if ([checkTouch getObjectID] == 1) {
startTouchPoint = CGPointMake([checkTouch center].x, [checkTouch center].y);
endTouchPoint = [touch locationInView:self];
}
}
self.drawLine = [[Line alloc] initWithPoint:[touch locationInView:self]];
[self setNeedsDisplay];
}
-(void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"Cancelado");
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
UITouch *secondaryTouch = (UITouch *)[[[event touchesForView:checkPointCircle] allObjects] objectAtIndex: 0];
NSLog(#"Que toco: %# ", secondaryTouch.view);
if (touch.view.class == checkPointCircle.class) {
CheckPointCircle * checkTouch = (CheckPointCircle *)touch.view;
if ([checkTouch getObjectID] == 1) {
endTouchPoint = [touch locationInView:self];
}
}
[self setNeedsDisplay];
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CheckPointCircle * checkTouch = (CheckPointCircle *)touch.view;
if (touch.view.class == checkPointCircle.class) {
if ([checkTouch getObjectID] == 1) {
endTouchPoint = [touch locationInView:self];
}
}
[self setNeedsDisplay];
}
- (void)drawRect:(CGRect)rect
{
[drawLine drawLineFrom:startTouchPoint to:endTouchPoint];
}
#end
How to detect the other balls to get the ID.
Can anybody help me?
Thanks!

Answer 1

The Apple documentation of class UIView (https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIView_Class/UIView/UIView.html#//apple_ref/occ/instm/UIView/hitTest:withEvent:) lists two methods which will determine which view contains a hit/point:
– hitTest:withEvent:
– pointInside:withEvent:
Probably hitTest will help most: Its description reads "Returns the farthest descendant of the receiver in the view hierarchy (including itself) that contains a specified point.", so it even converts coordinates as needed.
If you check [self hitTest: [touch.locationInView self] withEvent: event] (or similar, no code completion here ;-)= in your touchesMoved: method, you should be able to detect when the finger is over any of the other circles.
Hope this helps, nobi