github-MJRefresh（UI）

MJRefreshFooter
#pragma mark - 构造方法
+ (instancetype)footerWithRefreshingBlock:(MJRefreshComponentRefreshingBlock)refreshingBlock
{
MJRefreshFooter *cmp = [[self alloc] init];
cmp.refreshingBlock = refreshingBlock;
return cmp;
}
+ (instancetype)footerWithRefreshingTarget:(id)target refreshingAction:(SEL)action
{
MJRefreshFooter *cmp = [[self alloc] init];
[cmp setRefreshingTarget:target refreshingAction:action];
return cmp;
}

MJRefreshHeader
#pragma mark - 构造方法
+ (instancetype)headerWithRefreshingBlock:(MJRefreshComponentRefreshingBlock)refreshingBlock
{
MJRefreshHeader *cmp = [[self alloc] init];
cmp.refreshingBlock = refreshingBlock;
return cmp;
}
+ (instancetype)headerWithRefreshingTarget:(id)target refreshingAction:(SEL)action
{
MJRefreshHeader *cmp = [[self alloc] init];
[cmp setRefreshingTarget:target refreshingAction:action];
return cmp;
}