UITableView 索引的设置

if (_indexCollation == nil) {

_indexCollation = [UILocalizedIndexedCollation currentCollation];

}

NSArray *localTracks = [NSArray array];

//查找本地音乐

NSEntityDescription * trEty = [NSEntityDescription entityForName:@"Track" inManagedObjectContext:ShareAppDelegate.managedObjectContext];

NSFetchRequest *frq = [[NSFetchRequest alloc]init];

[frq setEntity:trEty];

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"beAdded == %@",[NSNumber numberWithBool:YES]];

[frq setPredicate:predicate];

localTracks =[ShareAppDelegate.managedObjectContext executeFetchRequest:frq error:nil];

//每个索引下的数组

NSMutableArray *newLocalTracks = [[NSMutableArray alloc] initWithCapacity:[[_indexCollation sectionTitles] count]];

for (int i = 0; i < [[_indexCollation sectionTitles] count]; i ++) {

NSMutableArray *array2 = [[NSMutableArray alloc] initWithCapacity:1];

[newLocalTracks addObject:array2];

}

for (Track *track in localTracks) {

//判断这个数据应该处于本地索引的那个序列下

NSInteger index = [_indexCollation sectionForObject:track collationStringSelector:@selector(trackTitle)];

NSMutableArray *array = [newLocalTracks objectAtIndex:index];

[array addObject:track];

__tracksCount ++;

}

//处理结果：将结果中统计数为0的结果对应的索引去掉。

for (int i = 0; i < [[_indexCollation sectionTitles] count]; i++) {

NSMutableArray *array = [newLocalTracks objectAtIndex:i];

if (array.count > 0) {

//获得排序结果

NSArray *sortedarray = [_indexCollation sortedArrayFromArray:array collationStringSelector:@selector(trackTitle)];

//替换原来数组

[newLocalTracks replaceObjectAtIndex:i withObject:sortedarray];

}

}

//删选没有内容的array 删除；加载数据到table，重新生成新的曲目数组及索引数组

NSMutableArray *newLocalTracks1 = [NSMutableArray array];

NSMutableArray *newIndexArray = [NSMutableArray array];

for (NSMutableArray *array in newLocalTracks)

{

if ([array count] > 0) {

[newLocalTracks1 addObject:array];

[newIndexArray addObject:[[_indexCollation sectionTitles] objectAtIndex:[newLocalTracks indexOfObject:array]]];

}

}

_tracksArray = [NSMutableArray arrayWithArray:newLocalTracks1];

_indexArray = [NSMutableArray arrayWithArray:newIndexArray];

dispatch_async(dispatch_get_main_queue(), ^{

[_table reloadData];

});

/* 返回索引数组 */

- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView

{

return _indexArray;

}