单例设置

+ (RootScrollView *)shareInstance;

+ (RootScrollView *)shareInstance {
    static RootScrollView *__singletion;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        __singletion=[[self alloc] initWithFrame:CGRectMake(0, 44, 320, [Globle shareInstance].globleHeight-44)];
    });
    return __singletion;
}