如何在iphone中实现图片的放大（不使用多点触控：即两个手指拉开）

#import <UIKit/UIKit.h>

#define IMAGE_VIEW_1	100
#define	IMAGE_VIEW_2	101

#define BIGRECT CGRectMake(0.0f, 0.0f, 320.0f, 435.0f)
#define SMALLRECT CGRectMake(130.0f, 187.0f, 60.0f, 60.0f) 

@interface ToggleView: UIView
{
	BOOL isOne;
}
@end

@implementation ToggleView

- (id) initWithFrame: (CGRect) aFrame;
{
	self = [super initWithFrame:aFrame];

	// Load both views, make them non-interactive
	UIImageView *imgView1 = [[UIImageView alloc] initWithFrame:BIGRECT];
	imgView1.image = [UIImage imageNamed:@"one.png"];
	imgView1.userInteractionEnabled = NO;
	imgView1.tag = IMAGE_VIEW_1;

	UIImageView *imgView2 = [[UIImageView alloc] initWithFrame:SMALLRECT];
	imgView2.image = [UIImage imageNamed:@"two.png"];
	imgView2.userInteractionEnabled = NO;
	imgView2.tag = IMAGE_VIEW_2;

	// image 1 is in front of image 2 to begin
	[self addSubview:imgView2];
	[self addSubview:imgView1]; 
	isOne = YES;

	[imgView1 release];
	[imgView2 release];

	return self;
}

- (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event
{
	// Determine which view occupies which role
	UIImageView *big = (UIImageView *)[self viewWithTag: (isOne ? IMAGE_VIEW_1 : IMAGE_VIEW_2)];
	UIImageView *little = (UIImageView *)[self viewWithTag: (isOne ? IMAGE_VIEW_2 : IMAGE_VIEW_1)];
	isOne = !isOne;

	// Pack all the changes into the animation block
	CGContextRef context = UIGraphicsGetCurrentContext();
	[UIView beginAnimations:nil context:context];
	[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
	[UIView setAnimationDuration:1.0];

	[big setFrame:SMALLRECT];
	[big setAlpha:0.5];
	[little setFrame:BIGRECT];
	[little setAlpha:1.0];

	[UIView commitAnimations];

	// Hide the shrunken "big" image.
	[big setAlpha:0.0f];
	[[big superview] bringSubviewToFront:big];
}
@end

@interface HelloController : UIViewController
@end

@implementation HelloController
- (void)loadView
{
	ToggleView *contentView = [[ToggleView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
	contentView.backgroundColor = [UIColor whiteColor];
	self.view = contentView;
    [contentView release];
}
@end


@interface SampleAppDelegate : NSObject <UIApplicationDelegate> 
@end

@implementation SampleAppDelegate
- (void)applicationDidFinishLaunching:(UIApplication *)application {
	UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
	HelloController *hello = [[HelloController alloc] init];
	[window addSubview:hello.view];
	[window makeKeyAndVisible];
}
@end

int main(int argc, char *argv[])
{
	NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	int retVal = UIApplicationMain(argc, argv, nil, @"SampleAppDelegate");
	[pool release];
	return retVal;
}