保存、保留和检索数组中的选定单元格

Posted 2023-03-03

【中文标题】保存、保留和检索数组中的选定单元格

【英文标题】：Saving, retaining, & retrieving selected cells in array

【发布时间】：2016-08-11 02:16:18

【问题描述】：

我已阅读每篇文章并多次尝试每种解决方案，但无法获得正确的功能。

我有一个表格视图，其中包含来自本地 JSON 文件的数据。我需要用户能够：

选择多个单元格 在选定单元格上显示复选标记 将这些选择写入数组 取消选中时删除选择

5.当用户切换视图或离开并返回表格视图、关闭和重新打开应用程序等时，使用复选标记保存/保留选择。

我已经设法让 1-4 工作，但我被困在 #5 上，无法终生解决这个问题。我已经尽我所能尝试了 NSUserDefaults。任何帮助表示赞赏。以下是当前代码。

另外，为什么我必须双击一个单元格来取消选中它？

@interface FilterViewController () <UISearchResultsUpdating>

@property (nonatomic, strong) NSArray *IngredientsArray;
@property (nonatomic, strong) UISearchController *searchController;
@property (nonatomic, strong) NSMutableArray *searchResults;
@property (nonatomic, strong) NSMutableArray *selectedCell;
@property (nonatomic, strong) NSMutableArray *selectedIngredients;
//I added this property to keep track of the selected row
@property (strong,nonatomic) NSIndexPath *selectedPath;


@end

@implementation FilterViewController 
    NSArray *_locations;





- (void)viewDidLoad 


    [super viewDidLoad];

    self.selectedIngredients = [NSMutableArray array];
     self.selectedCell = [NSMutableArray array];
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    self.lastIndexPath = [defaults objectForKey:@"lastIndexPathUsed"];



    // Create a new JSONLoader with a local file URL
    JSONLoaderIngreds *jsonLoader = [[JSONLoaderIngreds alloc] init];
    NSURL *url = [[NSBundle mainBundle] URLForResource:@"locations" withExtension:@"json"];

    // There's no transition in our storyboard to our search results tableview or navigation controller
    // so we'll have to grab it using the instantiateViewControllerWithIdentifier: method
    UINavigationController *searchResultsController = [[self storyboard] instantiateViewControllerWithIdentifier:@"FilterViewSearchResultsNavController"];

    // Our instance of UISearchController will use searchResults
    self.searchController = [[UISearchController alloc] initWithSearchResultsController:searchResultsController];

    // The searchcontroller's searchResultsUpdater property will contain our tableView.
    self.searchController.searchResultsUpdater = self;


    // create the searchBar programatically.
    self.searchController.searchBar.frame = CGRectMake(self.searchController.searchBar.frame.origin.x,
                                                       self.searchController.searchBar.frame.origin.y,
                                                       self.searchController.searchBar.frame.size.width, 44.0);

    self.tableView.tableHeaderView = self.searchController.searchBar;


    //Sets LocationsViewController as presenter for LocationDetailViewController after searxh results dsiplayed
    //and selected..  Required so searchbar doesn't show in detailsview after segue, and instead, default nav
    //controller back button displays.
    self.definesPresentationContext = true;





    // Load the data on a background queue...
    // As we are using a local file it's not really necessary, but if we were connecting to an online URL then we'd need it
    //NSString *ingreds = [dict objectForKey:@"ingredients"]
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^
        _locations = [jsonLoader ingredientsFromJSONFile:url];
        // Now that we have the data, reload the table data on the main UI thread
        [self.tableView performSelectorOnMainThread:@selector(reloadData) withObject:nil waitUntilDone:YES];

        );



// Just before showing the LocationViewController, set the selected Location object
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender 
    LocationsViewController *vc = segue.destinationViewController;
    NSIndexPath *indexPath = [self.tableView indexPathForCell:sender];
    vc.location = [_locations objectAtIndex:indexPath.row];



- (void)didReceiveMemoryWarning 
    [super didReceiveMemoryWarning];


- (void)viewWillAppear:(BOOL)animated

    //I added this if clause to select the row that was last selected
    if (self.selectedPath != nil) 
        [self.tableView selectRowAtIndexPath:self.selectedPath animated:NO scrollPosition:UITableViewScrollPositionNone];
    



#pragma mark - Table View Controller Methods

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath 

     self.selectedPath = indexPath;
    NSString *Ingredient = [_locations objectAtIndex:indexPath.row];
    UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
    if([self isRowSelectedOnTableView:tableView atIndexPath:indexPath])
        [self.selectedCell removeObject:indexPath];
        [self.selectedIngredients removeObject:Ingredient];
        cell.accessoryType = UITableViewCellAccessoryNone;
     else 
        [self.selectedCell addObject:indexPath];
        [self.selectedIngredients addObject:Ingredient];
        cell.accessoryType = UITableViewCellAccessoryCheckmark;
    
    NSLog(@"***************Selected Ingredients**************** %@", self.selectedIngredients);
    NSUserDefaults *userdefaults = [NSUserDefaults standardUserDefaults];
    [userdefaults setObject:[NSString stringWithFormat:@"%ld",(long)indexPath.section] forKey:@"lastIndexPathUsed"];
    [userdefaults synchronize];




-(BOOL)isRowSelectedOnTableView:(UITableView *)tableView atIndexPath:(NSIndexPath *)indexPath

    return ([self.selectedCell containsObject:indexPath]) ? YES : NO;




- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
    static NSString *unifiedID = @"FilterCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:unifiedID];

    if (!cell) 
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:unifiedID];
    

    cell.textLabel.text = [_locations objectAtIndex:indexPath.row];
    cell.imageView.image = [UIImage imageNamed:@"ingredientsicon3232.png"];

    //if the indexPath was found among the selected ones, set the checkmark on the cell
    cell.accessoryType = ([self isRowSelectedOnTableView:tableView atIndexPath:indexPath]) ? UITableViewCellAccessoryCheckmark : UITableViewCellAccessoryNone;
    return cell;






- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section 
    return [_locations count];

更新：

我设法按照建议更改了代码，使用下面的更新代码将选择保存到 NSUserDefaults 中的数组，但我仍然无法弄清楚保存/调用复选标记所需的 cellForRowAtIndexPath 代码。

如何编写 cellForRowAtIndexPath 代码来调用复选标记？

使用此代码将选择保存到数组：

ViewDidLoad 代码：

_selections = [NSMutableArray arrayWithArray:(NSArray *)[[NSUserDefaults standardUserDefaults] objectForKey:@"selections"]];
    if(_selections == nil)
        _selections = [[NSMutableArray alloc] init];
    

didSelectRowAtIndexPath 代码：

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath 

    UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];

    
    if ([_selections containsObject: cell.textLabel.text] == NO)
        [_selections addObject:cell.textLabel.text];
        cell.accessoryType = UITableViewCellAccessoryCheckmark;
     else 
        [_selections removeObject:cell.textLabel.text];
        cell.accessoryType = UITableViewCellAccessoryNone;
    
    NSLog(@"***************Selected Ingredients**************** %@", _selections);
    NSUserDefaults *userdefaults = [NSUserDefaults standardUserDefaults];

    [userdefaults setObject:_selections forKey:@"selections"];
    [userdefaults synchronize];
    NSLog(@"-------------NSUserDefaults------------%@", [[NSUserDefaults standardUserDefaults] dictionaryRepresentation])

【参考方案1】：

您的解决方案非常简单。

首先，您需要将一组选定的索引路径保存到您的用户默认对象，而不仅仅是最后一次选定的路径。 每当用户选择或取消选择一行时。从同一个数组中添加和删除对象并将其保存回您的用户默认值。 在您的cellForRowAtIndexPath 中，检查您的索引路径是否存在于用户默认值保存的数组中。如果存在，请选择带有复选标记的行，否则保持原样。

希望这会有所帮助。

【讨论】：

我想我明白了，但你能展示一下如何在代码中完成吗？我尝试了几种不同的方法，但无法开始工作。仍然在学习。谢谢。

我现在正在旅行。可能在几个小时后我可以给你看一个例子，但现在你应该尝试这三个步骤，你会明白的。这一点都不难。试一试吧。

按照您的指示，我设法将选择保存到存储在用户默认值中的数组中，但我无法找出保留复选标记的代码。能否提供代码示例？

你能分享你在用户默认值中保存数组的代码吗？

查看相关更新。任何帮助表示赞赏。

【参考方案2】：

我认为与其使用indexPath，不如直接使用数据本身，添加Bool 属性以指示Ingredient 类中的选择，然后将整个数组保存在@987654324 @，这样更正确，因为您的数据可以更改，导致您保存的选择indexPath不再正确