touchimageview_private.m

iphone app 中的多点触摸实例

#import "TouchImageView_Private.h"

@implementation UITouch (TouchSorting)

- (NSComparisonResult)compareAddress:(id)obj
{
    if ((void *)self < (void *)obj) {
        return NSOrderedAscending;
    } else if ((void *)self == (void *)obj) {
        return NSOrderedSame;
    } else {
        return NSOrderedDescending;
    }
}

@end

@implementation TouchImageView (Private)

- (CGAffineTransform)incrementalTransformWithTouches:(NSSet *)touches
{
    NSArray *sortedTouches = [[touches allObjects] sortedArrayUsingSelector:@selector(compareAddress:)];
    NSInteger numTouches = [sortedTouches count];
    
	// No touches
	if (numTouches == 0) {
        return CGAffineTransformIdentity;
    }

	// Single touch
	if (numTouches == 1) {
        UITouch *touch = [sortedTouches objectAtIndex:0];
        CGPoint beginPoint = *(CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch);
        CGPoint currentPoint = [touch locationInView:self.superview];
		return CGAffineTransformMakeTranslation(currentPoint.x - beginPoint.x, currentPoint.y - beginPoint.y);
	}

	// If two or more touches, go with the first two (sorted by address)
	UITouch *touch1 = [sortedTouches objectAtIndex:0];
	UITouch *touch2 = [sortedTouches objectAtIndex:1];

    CGPoint beginPoint1 = *(CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch1);
    CGPoint currentPoint1 = [touch1 locationInView:self.superview];
    CGPoint beginPoint2 = *(CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch2);
    CGPoint currentPoint2 = [touch2 locationInView:self.superview];

	double layerX = self.center.x;
	double layerY = self.center.y;
	
	double x1 = beginPoint1.x - layerX;
	double y1 = beginPoint1.y - layerY;
	double x2 = beginPoint2.x - layerX;
	double y2 = beginPoint2.y - layerY;
	double x3 = currentPoint1.x - layerX;
	double y3 = currentPoint1.y - layerY;
	double x4 = currentPoint2.x - layerX;
	double y4 = currentPoint2.y - layerY;
	
	// Solve the system:
	//   [a b t1, -b a t2, 0 0 1] * [x1, y1, 1] = [x3, y3, 1]
	//   [a b t1, -b a t2, 0 0 1] * [x2, y2, 1] = [x4, y4, 1]
	
	double D = (y1-y2)*(y1-y2) + (x1-x2)*(x1-x2);
	if (D < 0.1) {
        return CGAffineTransformMakeTranslation(x3-x1, y3-y1);
    }

	double a = (y1-y2)*(y3-y4) + (x1-x2)*(x3-x4);
	double b = (y1-y2)*(x3-x4) - (x1-x2)*(y3-y4);
	double tx = (y1*x2 - x1*y2)*(y4-y3) - (x1*x2 + y1*y2)*(x3+x4) + x3*(y2*y2 + x2*x2) + x4*(y1*y1 + x1*x1);
	double ty = (x1*x2 + y1*y2)*(-y4-y3) + (y1*x2 - x1*y2)*(x3-x4) + y3*(y2*y2 + x2*x2) + y4*(y1*y1 + x1*x1);
	
    return CGAffineTransformMake(a/D, -b/D, b/D, a/D, tx/D, ty/D);
}

- (void)updateOriginalTransformForTouches:(NSSet *)touches
{
    if ([touches count] > 0) {
        CGAffineTransform incrementalTransform = [self incrementalTransformWithTouches:touches];
        self.transform = CGAffineTransformConcat(originalTransform, incrementalTransform);
        originalTransform = self.transform;
    }
}

- (void)cacheBeginPointForTouches:(NSSet *)touches
{
    if ([touches count] > 0) {
        for (UITouch *touch in touches) {
            CGPoint *point = (CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch);
            if (point == NULL) {
                point = (CGPoint *)malloc(sizeof(CGPoint));
                CFDictionarySetValue(touchBeginPoints, touch, point);
            }
            *point = [touch locationInView:self.superview];
        }
    }
}

- (void)removeTouchesFromCache:(NSSet *)touches
{
    for (UITouch *touch in touches) {
        CGPoint *point = (CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch);
        if (point != NULL) {
            free((void *)CFDictionaryGetValue(touchBeginPoints, touch));
            CFDictionaryRemoveValue(touchBeginPoints, touch);
        }
    }
}

@end