@interface MoveView : UIView{    CGPoint startPoint;}#import "MoveView.h"@implementation MoveView- (id)initWithFrame:(CGRect)frame{    self = [super initWithFrame:frame];    if (self) {        // Initialization code        //允许用户交互        self.userInteractionEnabled = YES;    }    return self;}- (id)initWithImage:(UIImage *)image{    self = [super initWithImage:image];    if (self) {        //允许用户交互        self.userInteractionEnabled = YES;    }    return self;}- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{    //保存触摸起始点位置    CGPoint point = [[touches anyObject] locationInView:self];    startPoint = point;        //该view置于最前    [[self superview] bringSubviewToFront:self];}-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{    //计算位移=当前位置-起始位置    CGPoint point = [[touches anyObject] locationInView:self];    float dx = point.x - startPoint.x;    float dy = point.y - startPoint.y;        //计算移动后的view中心点    CGPoint newcenter = CGPointMake(self.center.x + dx, self.center.y + dy);            /* 限制用户不可将视图托出屏幕 */    float halfx = CGRectGetMidX(self.bounds);    //x坐标左边界    newcenter.x = MAX(halfx, newcenter.x);    //x坐标右边界    newcenter.x = MIN(self.superview.bounds.size.width - halfx, newcenter.x);        //y坐标同理    float halfy = CGRectGetMidY(self.bounds);    newcenter.y = MAX(halfy, newcenter.y);    newcenter.y = MIN(self.superview.bounds.size.height - halfy, newcenter.y);        //移动view    self.center = newcenter;}@end