分页加载数据策略

来源：互联网发布：java 领域模型编辑：程序博客网时间：2024/05/30 04:20

1.构建一个计数的抽象基类classsA，对需要加载不同的数据类型实例化一个对象classB。

2.抽象基类开放一下接口：

typedef enum {    RequestStatusNone,    RequestStatusInProgress,    RequestStatusDone // request succeeded or failed} RequestStatus;@protocol NMPaginatorDelegate@required- (void)paginator:(id)paginator didReceiveResults:(NSArray *)results ifRefresh:(BOOL)ifRefresh;@optional- (void)paginatorDidFailToRespond:(id)paginator;- (void)paginatorDidReset:(id)paginator;@end@interface NMPaginator : NSObject {}@property (assign,nonatomic) id<NMPaginatorDelegate> delegate;@property (assign, readonly) NSInteger pageSize; // number of results per page@property (assign, nonatomic) NSInteger page; // number of pages already fetched@property (assign, readonly) NSInteger total; // total number of results@property (assign, readonly) RequestStatus requestStatus;@property (nonatomic, retain) NSMutableArray *results;- (id)initWithPageSize:(NSInteger)page_size delegate:(id<NMPaginatorDelegate>)paginatorDelegate;- (void)reset;- (BOOL)reachedLastPage;- (void)fetchFirstPage;- (void)fetchNextPage;// call these from subclass when you receive the results- (void)receivedResults:(NSMutableArray *)dataAry total:(NSInteger)totalPage ifRefresh:(BOOL)ifRefresh;- (void)failed;

抽象基类classA一个私有虚函数，方便子类重写，实现请求网络数据的功能

classA.m源文件中

#pragma mark - Sublclass methods- (void)fetchResultsWithPage:(NSInteger)page pageSize:(NSInteger)pageSize ifRefresh:(BOOL)ifRefresh{    // override this in subclass}

子类：classB.m中重写该函数

@implementation classB- (void)fetchResultsWithPage:(NSInteger)page pageSize:(NSInteger)pageSize ifRefresh:(BOOL)ifRefresh{    DataService *service = [DataService GetInstance];        [service getdate:xxx page:page pageSize:pageSize callBack:^(id service,NSMutableArray *arr,int totalNum){        [self receivedResults:arr total:totalNum ifRefresh:ifRefresh];    }];}

3.在初始化的时候启动计数调用fetchFirstPage接口获取第一页的数据

4.classB请求网络数据,得到数据传回classA，classA对数据进行处理

- (void)receivedResults:(NSMutableArray *)dataAry total:(NSInteger)totalPage ifRefresh:(BOOL)ifRefresh{    if (ifRefresh) {        if (dataAry) {            results = nil;            results = dataAry;        }    }else{        if (dataAry) {            NSMutableArray *tmpArray = [[NSMutableArray alloc] initWithCapacity:10];            [tmpArray addObjectsFromArray:results];            [tmpArray addObjectsFromArray:dataAry];            results = nil;            results = tmpArray;            tmpArray = nil;        }    }    page ++;    total = totalPage;    requestStatus = RequestStatusDone;    if (self && self.delegate) {        [self.delegate paginator:self didReceiveResults:results ifRefresh:ifRefresh];    }}

分装完成后用代理传回控制器

- (void)paginator:(id)paginator didReceiveResults:(NSArray *)results ifRefresh:(BOOL)ifRefresh;

若没有获取到网络数据，建议加载本地数据库

3.在控制器中的scrollerview的代理中调用fetchNextPage接口

#pragma mark - UIScrollView Delegate- (void)scrollViewDidScroll:(UIScrollView *)scrollView {    CGPoint offset = scrollView.contentOffset;    CGRect bounds = scrollView.bounds;    CGSize size = scrollView.contentSize;    UIEdgeInsets inset = scrollView.contentInset;    float reload_distance = 10;    if(offset.y + bounds.size.height - inset.bottom > size.height + reload_distance && ifLoadMore) {        ifLoadMore = NO;        if(![classB reachedLastPage])        {            // fetch next page of results            [classB fetchNextPage];        }    }}

0 0