MJRefresh 封装

MJRefresh是很好用的一个刷新控件，但是如果在每个ViewController中都加入如下代码

self.tableView.header = [MJRefreshNormalHeader headerWithRefreshingBlock:^{
   //Call this Block When enter the refresh status automatically 
}];

self.tableView.mj_footer = [MJRefreshAutoNormalFooter footerWithRefreshingBlock:^{
    //Call this Block When enter the refresh status automatically
}];

代码复用性不高，而且每个ViewController 在加载更多的时候还要管理Page
所以想一个办法对MJRefresh进行二次封装，在使用的时候方便调用。

MJRefresh 支持TableView，CollectionView，Scrollview，很容易联想到TableView，CollectionView都是继续Scrollview，那我们写一个Scrollview的Category是不是就可以

接下来我们需要考虑两个问题，Category是不可以直接添加属性的，那我们怎么添加Page和刷新Block这两个属性。相信都知道用RunTime 关联属性不就可以了。

所以我们在Category中声明属性

typedef void(^RefreshBlock)(NSInteger pageIndex);
typedef void(^LoadMoreBlock)(NSInteger pageIndex);

@interface UIScrollView()

/**页码*/
@property (assign, nonatomic) NSInteger pageIndex;
/**下拉时候触发的block*/
@property (nonatomic, copy) RefreshBlock refreshBlock;
/**上拉时候触发的block*/
@property (nonatomic, copy) LoadMoreBlock loadMoreBlock;

@end

然后用RunTime添加属性

static void *pagaIndexKey = &pagaIndexKey;
- (void)setPageIndex:(NSInteger)pageIndex{
    objc_setAssociatedObject(self, &pagaIndexKey, @(pageIndex), OBJC_ASSOCIATION_ASSIGN);
}

- (NSInteger)pageIndex
{
    return [objc_getAssociatedObject(self, &pagaIndexKey) integerValue];
}

static void *RefreshBlockKey = &RefreshBlockKey;
- (void)setRefreshBlock:(void (^)(void))RefreshBlock{
    objc_setAssociatedObject(self, &RefreshBlockKey, RefreshBlock, OBJC_ASSOCIATION_COPY);
}

- (RefreshBlock)refreshBlock
{
    return objc_getAssociatedObject(self, &RefreshBlockKey);
}

static void *LoadMoreBlockKey = &LoadMoreBlockKey;
- (void)setLoadMoreBlock:(LoadMoreBlock)loadMoreBlock{
    objc_setAssociatedObject(self, &LoadMoreBlockKey, loadMoreBlock, OBJC_ASSOCIATION_COPY);
}

- (LoadMoreBlock)loadMoreBlock
{
    return objc_getAssociatedObject(self, &LoadMoreBlockKey);
}

接下来就是添加两个刷新和加载更多的方法

- (void)addHeaderWithHeaderWithBeginRefresh:(BOOL)beginRefresh animation:(BOOL)animation refreshBlock:(void(^)(NSInteger pageIndex))refreshBlock{

    __weak typeof(self) weakSelf = self;
    self.refreshBlock = refreshBlock;
    
    MJRefreshNormalHeader * header = [MJRefreshNormalHeader headerWithRefreshingBlock:^{
        [weakSelf resetPageNum];
    
        if (weakSelf.refreshBlock) {
            weakSelf.refreshBlock(weakSelf.pageIndex);
        }
        [weakSelf endHeaderRefresh];
    }];
    
    if (beginRefresh && animation) {
        //有动画的刷新
        [self beginHeaderRefresh];
    }else if (beginRefresh && !animation){
        //刷新，但是没有动画
        [self.mj_header executeRefreshingCallback];
    }
    
    header.mj_h = 70.0;
    self.mj_header = header;
}

- (void)addFooterWithWithHeaderWithAutomaticallyRefresh:(BOOL)automaticallyRefresh loadMoreBlock:(void(^)(NSInteger pageIndex))loadMoreBlock{
    
    self.loadMoreBlock = loadMoreBlock;
    
    if (automaticallyRefresh) {
        MJRefreshAutoNormalFooter * footer = [MJRefreshAutoNormalFooter footerWithRefreshingBlock:^{
             self.pageIndex += 1;
            if (self.loadMoreBlock) {
                self.loadMoreBlock(self.pageIndex);
            }
            [self endFooterRefresh];
        }];
        
        footer.automaticallyRefresh = automaticallyRefresh;
        
        footer.stateLabel.font = [UIFont systemFontOfSize:13.0];
        footer.stateLabel.textColor = [UIColor colorWithWhite:0.400 alpha:1.000];
        [footer setTitle:@"加载中…" forState:MJRefreshStateRefreshing];
        [footer setTitle:@"这是我的底线啦~" forState:MJRefreshStateNoMoreData];
        
        self.mj_footer = footer;
    }
    else{
        MJRefreshBackNormalFooter * footer = [MJRefreshBackNormalFooter footerWithRefreshingBlock:^{
             self.pageIndex += 1;
            if (self.loadMoreBlock) {
                self.loadMoreBlock(self.pageIndex);
            }
            [self endFooterRefresh];
        }];
        
        footer.stateLabel.font = [UIFont systemFontOfSize:13.0];
        footer.stateLabel.textColor = [UIColor colorWithWhite:0.400 alpha:1.000];
        [footer setTitle:@"加载中…" forState:MJRefreshStateRefreshing];
        [footer setTitle:@"这是我的底线啦~" forState:MJRefreshStateNoMoreData];
        
        self.mj_footer = footer;
    }
   
}

-(void)beginHeaderRefresh {
    
    [self resetPageNum];
    [self.mj_header beginRefreshing];
}

- (void)resetPageNum {
    self.pageIndex = 0;
}

- (void)resetNoMoreData {
    
    [self.mj_footer resetNoMoreData];
}

-(void)endHeaderRefresh {
    
    [self.mj_header endRefreshing];
    [self resetNoMoreData];
}

-(void)endFooterRefresh {
    [self.mj_footer endRefreshing];
}

调用,是不是很简单，都不需要单独管理Page

  [self.tableView addHeaderWithHeaderWithBeginRefresh:YES animation:YES refreshBlock:^(NSInteger pageIndex) {
        NSLog(@"pageIndex:%zd",pageIndex);
    }];
    
    [self.tableView addFooterWithWithHeaderWithAutomaticallyRefresh:NO loadMoreBlock:^(NSInteger pageIndex) {
        NSLog(@"pageIndex:%zd",pageIndex);
    }];

Demo 地址:https://github.com/destinyzhao/MJRefreshEX