myview.m

This is an example applications that shows how to handle multiple touches at the same time on the iP

	return theView;
}


// Releases necessary resources. 
- (void)dealloc
{
	// Release each of the subviews
	[firstPieceView release];
	[secondPieceView release];
	[thirdPieceView release];
	// Release the labels
	[touchInfoText release];
	[touchPhaseText release];
	[super dealloc];	
}

#pragma mark -
#pragma mark === Touch handling  ===
#pragma mark

// Handles the start of a touch
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    NSUInteger numTaps = [[touches anyObject] tapCount];
	touchPhaseText.text = @"Phase: Touches began";
	touchInfoText.text = @"";
	if(numTaps >= 2) {
		touchInfoText.text = [NSString stringWithFormat:@"%d taps",numTaps]; 
		if ((numTaps == 2) && (self.piecesOnTop)) {
			// A double tap positions the three pieces in a diagonal.
			// The user will want to double tap when two or more pieces are on top of each other
			if (firstPieceView.center.x == secondPieceView.center.x)
				secondPieceView.center = CGPointMake(firstPieceView.center.x -45, firstPieceView.center.y -45);		
			if (firstPieceView.center.x == thirdPieceView.center.x)
				thirdPieceView.center  = CGPointMake(firstPieceView.center.x +45, firstPieceView.center.y +45);	
			if (secondPieceView.center.x == thirdPieceView.center.x)
				thirdPieceView.center  = CGPointMake(secondPieceView.center.x +45, secondPieceView.center.y +45);
			touchInstructionsText.text = @"";
		}
	} else {
		touchTrackingText.text = @"";
	}
	// Enumerate through all the touch objects.
	NSUInteger touchCount = 0;
	for (UITouch *touch in touches) {
	    // Send to the dispatch method, which will make sure the appropriate subview is acted upon
		[self dispatchFirstTouchAtPoint:[touch locationInView:self] forEvent:nil];
		touchCount++;  
	}	
}

/*
 Checks to see which view, or views, the point is in and then calls a method to perform the opening animation,
 which  makes the piece slightly larger, as if it is being picked up by the user.
*/
-(void) dispatchFirstTouchAtPoint:(CGPoint)touchPoint forEvent:(UIEvent *)event
{
	if (CGRectContainsPoint([firstPieceView frame], touchPoint)) {
		[self animateFirstTouchAtPoint:touchPoint forView:firstPieceView];
	}
	if (CGRectContainsPoint([secondPieceView frame], touchPoint)) {
		[self animateFirstTouchAtPoint:touchPoint forView:secondPieceView];
	} 
	if (CGRectContainsPoint([thirdPieceView frame], touchPoint)) {
		[self animateFirstTouchAtPoint:touchPoint forView:thirdPieceView];
	}
	
}

// Handles the continuation of a touch.
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{  

	NSUInteger touchCount = 0;
	touchPhaseText.text = @"Phase: Touches moved";
	// Enumerates through all touch objects
   for (UITouch *touch in touches){
		// Send to the dispatch method, which will make sure the appropriate subview is acted upon
	 	[self dispatchTouchEvent:[touch view] toPosition:[touch locationInView:self]];
	    touchCount++;
	}
	
	// When multiple touches, report the number of touches. 
	if (touchCount > 1) {
		touchTrackingText.text = [NSString stringWithFormat:@"Tracking %d touches", touchCount];
	} else {
		touchTrackingText.text = [NSString stringWithFormat:@"Tracking 1 touch", touchCount];
	}
}

/*
 Checks to see which view, or views, the point is in and then sets the center of each moved view to the new postion.
 If views are directly on top of each other, they move together.
*/
-(void) dispatchTouchEvent:(UIView *)theView toPosition:(CGPoint)position
{
	// Check to see which view, or views,  the point is in and then move to that position.
	if (CGRectContainsPoint([firstPieceView frame], position)) {
        firstPieceView.center = position;
	} 
	if (CGRectContainsPoint([secondPieceView frame], position)) {
        secondPieceView.center = position;
	} 
	if (CGRectContainsPoint([thirdPieceView frame], position)) {
		thirdPieceView.center = position;
	}
}

// Handles the end of a touch event.
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    touchPhaseText.text = @"Phase: Touches ended";
    // Enumerates through all touch object
    for (UITouch *touch in touches){
		// Sends to the dispatch method, which will make sure the appropriate subview is acted upon
		[self dispatchTouchEndEvent:[touch view] toPosition:[touch locationInView:self]];
	}
}

/*
 Checks to see which view, or views,  the point is in and then calls a method to perform the closing animation,
 which is to return the piece to its original size, as if it is being put down by the user.
*/
-(void) dispatchTouchEndEvent:(UIView *)theView toPosition:(CGPoint)position
{   
	// Check to see which view, or views,  the point is in and then animate to that position.
	if (CGRectContainsPoint([firstPieceView frame], position)) {
        [self animateView:firstPieceView toPosition: position];
	} 
	if (CGRectContainsPoint([secondPieceView frame], position)) {
        [self animateView:secondPieceView toPosition: position];
	} 
	if (CGRectContainsPoint([thirdPieceView frame], position)) {
		[self animateView:thirdPieceView toPosition: position];
	}
	// If one piece obscures another, display a message so the user can move the pieces apart
	if (((firstPieceView.center.x == secondPieceView.center.x) && (firstPieceView.center.y == secondPieceView.center.y)) ||
		((secondPieceView.center.x  == thirdPieceView.center.x ) && (secondPieceView.center.y  == thirdPieceView.center.y)) ||
		((firstPieceView.center.x  == thirdPieceView.center.x ) && (firstPieceView.center.y  == thirdPieceView.center.y))){
		touchInstructionsText.text = @"Double tap the background to move the pieces apart.";
		self.piecesOnTop = YES;
	} else {
		self.piecesOnTop = NO;
	}
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
	touchPhaseText.text = @"Phase: Touches cancelled";
    // Enumerates through all touch object
    for (UITouch *touch in touches){
		// Sends to the dispatch method, which will make sure the appropriate subview is acted upon
		[self dispatchTouchEndEvent:[touch view] toPosition:[touch locationInView:self]];
	}
}

#pragma mark -
#pragma mark === Animating subviews ===
#pragma mark

// Scales up a view slightly which makes the piece slightly larger, as if it is being picked up by the user.
- (void)animateFirstTouchAtPoint:(CGPoint)touchPoint forView:(UIImageView *)theView 
{
	// Pulse the view by scaling up, then move the view to under the finger.
	NSValue *touchPointValue = [[NSValue valueWithCGPoint:touchPoint] retain];
	[UIView beginAnimations:nil context:touchPointValue];
	[UIView setAnimationDuration:GROW_ANIMATION_DURATION_SECONDS];
	CGAffineTransform transform = CGAffineTransformMakeScale(1.2, 1.2);
	theView.transform = transform;
	[UIView commitAnimations];
}

// Scales down the view and moves it to the new position. 
- (void)animateView:(UIImageView *)theView toPosition:(CGPoint) thePosition
{
	[UIView beginAnimations:nil context:NULL];
	[UIView setAnimationDuration:SHRINK_ANIMATION_DURATION_SECONDS];
	// Set the center to the final postion
	theView.center = thePosition;
	// Set the transform back to the identity, thus undoing the previous scaling effect.
	theView.transform = CGAffineTransformIdentity;
	[UIView commitAnimations];	
}


@end