}

#import <UIKit/UIKit.h> 
 
@interface GragView : UIImageView 
{ 
    CGPoint startPoint; 
} 
@end 

#import "GragView.h" 
 
@implementation GragView 
 
- (id)initWithFrame:(CGRect)frame 
{ 
    self = [super initWithFrame:frame]; 
    if (self) { 
        // Initialization code 
        //允許用戶交互 
        self.userInteractionEnabled = YES; 
    } 
    return self; 
} 
 
- (id)initWithImage:(UIImage *)image 
{ 
    self = [super initWithImage:image]; 
    if (self) { 
        //允許用戶交互 
        self.userInteractionEnabled = YES; 
    } 
    return self; 
} 
 
- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    //保存觸摸起始點位置 
    CGPoint point = [[touches anyObject] locationInView:self]; 
    startPoint = point; 
     
    //該view置于最前 
    [[self superview] bringSubviewToFront:self]; 
} 
 
-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    //計算位移=當前位置-起始位置 
    CGPoint point = [[touches anyObject] locationInView:self]; 
    float dx = point.x - startPoint.x; 
    float dy = point.y - startPoint.y; 
     
    //計算移動后的view中心點 
    CGPoint newcenter = CGPointMake(self.center.x + dx, self.center.y + dy); 
     
     
    /* 限制用戶不可將視圖托出屏幕 */ 
    float halfx = CGRectGetMidX(self.bounds); 
    //x坐標左邊界 
    newcenter.x = MAX(halfx, newcenter.x); 
    //x坐標右邊界 
    newcenter.x = MIN(self.superview.bounds.size.width - halfx, newcenter.x); 
     
    //y坐標同理 
    float halfy = CGRectGetMidY(self.bounds); 
    newcenter.y = MAX(halfy, newcenter.y); 
    newcenter.y = MIN(self.superview.bounds.size.height - halfy, newcenter.y); 
     
    //移動view 
    self.center = newcenter; 
} 
 
/* 
// Only override drawRect: if you perform custom drawing. 
// An empty implementation adversely affects performance during animation. 
- (void)drawRect:(CGRect)rect 
{ 
    // Drawing code 
} 
*/ 
 
@end