Question

我读过创建索引的最佳方法（uitableview侧面的az）是设置一个nsdictionaries数组，其中每个字典对应一个部分，而rowValue键包含一个数组行。

NSDictionary
    headerTitle => ‘A’
    rowValues => {”Aardvark”, “Ape”, “Aquaman”}
NSDictionary
    headerTitle => ‘B’
    rowValues => {”Bat”, “Boot”, “Bubbles”} etc

但是如何从所有行标题的数组中创建 - {“Aardvark”，“Ape”，“Aquaman”，“Bat”，“Boot”，“Bubbles”，“Cat”，“Cabbage”等等......}

Answer 1

我最近有一个类似的目标，这就是我解决它的方式。这个优于Robin解决方案的优势在于它根据数组的内容动态创建索引标题数组，并且不包含空白部分的索引（加上它更清晰一些）。

我创建了一个NSMutableDictionary类别，它将一组数据作为参数返回NSMutableDictionary（我们称之为indexDictionary，它应该是一个实例变量）：

// if your data is static, you can call this in `viewDidLoad`
indexDictionary = [NSMutableDictionary createDictionaryForSectionIndex:arrayOfStrings];

类别方法：

@implementation NSMutableDictionary (DictionaryForSectionIndex)

+(NSMutableDictionary *)createDictionaryForSectionIndex:(NSArray *)array
{
    NSMutableDictionary *dict = [NSMutableDictionary dictionary];
    for (char firstChar = 'a'; firstChar <= 'z'; firstChar++)
    {
        //NSPredicates are fast
        NSString *firstCharacter = [NSString stringWithFormat:@"%c", firstChar];
        NSArray *content = [array filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"SELF beginswith[cd] %@", firstCharacter]];
        NSMutableArray *mutableContent = [NSMutableArray arrayWithArray:content];

        if ([mutableContent count] > 0)
        {
            NSString *key = [firstCharacter uppercaseString];
            [dict setObject:mutableContent forKey:key];
            NSLog(@"%@: %u", key, [mutableContent count]);
        }
    }

    return dict;
}

@end

/*

**Input:** 
{"Aardvark", "Cabbage", "Boot", "Eggs", "Ape", "Aquaman", "Elephant", "Cat", "Bat", "Bubbles"}

**Output:**
NSMutableDictionary
    key => 'A'
    object => {"Aardvark", "Ape", "Aquaman"}

    key => 'B'
    object => {"Bat", "Boot", "Bubbles"}

    key => 'C'
    object => {"Cat", "Cabbage"}

    key => 'E'
    object => {"Elephant", "Eggs"}

*/

然后我创建一个NSArray实例变量来排序和存储来自indexDictionary的所有键：

// this line should follow the creation of `indexDictionary`

sortedKeys = [[indexDictionary allKeys] sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];

// Output, in this case, is {'A', 'B', 'C', 'E'}

您现在拥有了为表设置索引所需的一切。实现以下方法（如果某些事情不能自我解释，请告诉我）：

//this code assumes `sortedKeys` is not empty

#pragma mark - UITableViewDataSource

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return ([sortedKeys count]);
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    NSString *key = [sortedKeys objectAtIndex:section];
    return [[indexDictionary valueForKey:key] count];
}


-(NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    return ([sortedKeys objectAtIndex:section]);
}


-(NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView
{
    return sortedKeys;
}


-(NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index
{
    return index;
}


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    // preceding code...

    NSString *key = [sortedKeys objectAtIndex:indexPath.section];
    NSArray *array = [indexDictionary objectForKey:key];
    NSString *yourString = [array objectAtIndex:indexPath.row];

    cell.textLabel.text = yourString;

    // following code...
}

结果是一个带有索引的表，该索引跳过没有关联数据的字母。

Answer 2

#pragma mark -
#pragma mark View lifecycle
- (void)viewDidLoad
{
    [super viewDidLoad];
    NSMutableArray *temp = [[NSMutableArray alloc] init];
    NSMutableArray *temp2 = [[NSMutableArray alloc] init];
    for(int i = 0; i < tableListArray.count; i++)
    {
        NSString *string = [tableListArray objectAtIndex:i];
        NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
        [dict setObject:string forKey:@"Name"];
        [dict setObject:[NSNumber numberWithInt:i] forKey:@"ID"];
        NSString *firstString = [string substringToIndex:1];
        if([temp2 containsObject:firstString] == NO || temp2.count == 0)
        {
            if(temp2.count != 0)
            {
                [temp addObject:temp2];
                [temp2 release];
                temp2 = [[NSMutableArray alloc] init];
            }
            [temp2 addObject:firstString];
        }
        [temp2 addObject:dict];
        [dict release];
    }
    [temp addObject:temp2];
    detailListArray = [[NSArray alloc] initWithArray:temp];
    [temp release];
    [temp2 release];
}

#pragma mark -
#pragma mark Table view data source
- (NSInteger)tableView:(UITableView *)tableView 
sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index
{
    int i = 0;
    for(NSArray *array in detailListArray)
    {
        NSString *string = [array objectAtIndex:0];
        if([string compare:title] == NSOrderedSame)
            break;
        i++;
    }
    return i;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return detailListArray.count;
}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    NSArray *array = [detailListArray objectAtIndex:section];
    return [array objectAtIndex:0];
}

- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView 
{
    NSMutableArray *titleArray = [NSMutableArray array];
    [titleArray addObject:@"A"];
    [titleArray addObject:@"B"];
    [titleArray addObject:@"C"];
    [titleArray addObject:@"D"];
    [titleArray addObject:@"E"];
    [titleArray addObject:@"F"];
    [titleArray addObject:@"G"];
    [titleArray addObject:@"H"];
    [titleArray addObject:@"I"];
    [titleArray addObject:@"J"];
    [titleArray addObject:@"K"];
    [titleArray addObject:@"L"];
    [titleArray addObject:@"M"];
    [titleArray addObject:@"N"];
    [titleArray addObject:@"O"];
    [titleArray addObject:@"P"];
    [titleArray addObject:@"Q"];
    [titleArray addObject:@"R"];
    [titleArray addObject:@"S"];
    [titleArray addObject:@"T"];
    [titleArray addObject:@"U"];
    [titleArray addObject:@"V"];
    [titleArray addObject:@"W"];
    [titleArray addObject:@"X"];
    [titleArray addObject:@"Y"];
    [titleArray addObject:@"Z"];
    return titleArray;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    NSArray *array = [detailListArray objectAtIndex:section];
    return (array.count - 1);
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault
                                                    reuseIdentifier:@"CELL"] autorelease];
    NSArray *array = [detailListArray objectAtIndex:indexPath.section];
    NSDictionary *dict = [array objectAtIndex:indexPath.row + 1];
    cell.textLabel.text = [dict objectForKey:@"Name"];
    return cell;
}

#pragma mark -
#pragma mark Table view delegate
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSArray *array = [detailListArray objectAtIndex:indexPath.section];
    NSDictionary *dict = [array objectAtIndex:indexPath.row + 1];
    int entryID = [[dict objectForKey:@"ID"] intValue];
     // Do what ever you want to do with the selected row here....
}

这是我在最近的一个项目中使用过的代码。

Answer 3

我正在开发一个项目，我需要针对同一问题的动态解决方案，所以我找到了这个只返回可用部分的字典的解决方案。希望它对某人有所帮助。

-(NSMutableDictionary *)getSortedDataWithArray:(NSArray *)dataArray{
  NSMutableDictionary *allDataDictionary = [[NSMutableDictionary alloc]init];

  for(int i = 0 ; i< dataArray.count ;i++){

    NSString *currentStr = [[[dataArray objectAtIndex:i] substringToIndex:1] uppercaseString];
    NSArray *allKeysArray = allDataDictionary.allKeys;

    if([allKeysArray containsObject:currentStr]){
        NSMutableArray *currentArray = [[NSMutableArray alloc] initWithArray:[allDataDictionary valueForKey:currentStr]];
        [currentArray addObject:[dataArray objectAtIndex:i]];
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF beginswith[c] %@" ,currentStr];
        NSArray *finalArray = [currentArray filteredArrayUsingPredicate:predicate];
        [allDataDictionary setValue:finalArray forKey:currentStr];
    }
    else{
        NSMutableArray *finalArray = [[NSMutableArray alloc] initWithObjects:[dataArray objectAtIndex:i], nil];

        [allDataDictionary setValue:finalArray forKey:currentStr];
    }
  }
 return allDataDictionary;
}

从NSArray为UITableView创建索引

3 个答案: