如何使用用户的iPod库艺术家索引UITableView？

Question

我想在我的应用程序中获取并索引所有iPod库艺术家,就像音乐应用程序一样.我遇到的问题是我不知道解决这个问题的最佳方法是什么.有帮助吗？

Answer 1

让我们为你的UITableViewController班级命名LibraryArtistsBrowserTableViewController

1.准备

接口文件LibraryArtistsBrowserTableViewController.h将包含以下变量:

@interface LibraryArtistsBrowserTableViewController : UITableViewController 

@property (nonatomic, strong) MPMediaQuery *artistsQuery;
@property (nonatomic, strong) NSArray *artistsArray,*sectionedArtistsArray;
@property (nonatomic, strong) UILocalizedIndexedCollation *collation;

- (NSArray *)partitionObjects:(NSArray *)array collationStringSelector:(SEL)selector;

@end

2.索引

在您的实现文件LibraryArtistsBrowserTableViewController.m中,将以下代码放在您的viewDidLoad方法中:

- (void)viewDidLoad
{
    [super viewDidLoad];

    //Make a query for artists
    self.artistsQuery = [MPMediaQuery artistsQuery];
    //Group by Album Artist
    [self.artistsQuery setGroupingType:MPMediaGroupingAlbumArtist];
    //Grab the "MPMediaItemCollection"s and store it in "artistsArray"
    self.artistsArray = [self.artistsQuery collections];

    //We then populate an array "artists" with the individual "MPMediaItem"s that self.artistsArray` contains
    NSMutableArray *artists = [NSMutableArray array];

    for (MPMediaItemCollection *artist in artistsArray) {
        //Grab the individual MPMediaItem representing the collection
        MPMediaItem *representativeItem = [artist representativeItem];
        //Store it in the "artists" array
        [artists addObject:representativeItem];
    }
    //We then index the "artists" array and store individual sections (which will be the alphabet letter and a numbers section), all containing the corresponding MPMediaItems
    self.sectionedArtistsArray = [self partitionObjects:artists collationStringSelector:@selector(albumArtist)];    
}

下面定义了用于对项进行分区的函数,将其放在实现文件的某处:

- (NSArray *)partitionObjects:(NSArray *)array collationStringSelector:(SEL)selector
{
    self.collation = [UILocalizedIndexedCollation currentCollation];
    NSInteger sectionCount = [[collation sectionTitles] count];
    NSMutableArray *unsortedSections = [NSMutableArray arrayWithCapacity:sectionCount];
    for(int i = 0; i < sectionCount; i++)
        [unsortedSections addObject:[NSMutableArray array]];

    for (id object in array)
    {
        NSInteger index = [self.collation sectionForObject:object collationStringSelector:selector];
        [[unsortedSections objectAtIndex:index] addObject:object];
    }
    NSMutableArray *sections = [NSMutableArray arrayWithCapacity:sectionCount];
    for (NSMutableArray *section in unsortedSections)
        [sections addObject:[self.collation sortedArrayFromArray:section collationStringSelector:selector]];

    return sections;
}

然后,我们确保视图控制器知道每个部分中有多少部分和行,以及每个部分的标题(索引字母/数字):

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
    return [[self.collation sectionTitles] objectAtIndex:section];
}

- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView {
    return [self.collation sectionIndexTitles];
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return [[self.collation sectionTitles] count];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [[self.sectionedArtistsArray objectAtIndex:section] count];
}

3.显示艺术家

然后我们按如下方式展示艺术家:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
    }
    //We grab the MPMediaItem at the nth indexPath.row corresponding to the current section (or letter/number)
    MPMediaItem *temp = [[self.sectionedArtistsArray objectAtIndex:indexPath.section] objectAtIndex:indexPath.row];
    //Title the current cell with the Album artist
    cell.textLabel.text = [temp valueForProperty:MPMediaItemPropertyAlbumArtist];

    return cell;
}

你应该好好去.我唯一的问题是它无法逃脱标点符号(撇号等)和'''艺术家的前缀.除此之外它工作得很好.