ios - 使用 nsuserdefault 在 uitableviewcell 中保存图像状态

Question

我已经为这个问题苦苦挣扎了几个星期，我不好意思说，并且搜索了整个堆栈溢出和互联网，但找不到任何适合我的东西。我遇到过一些非常模糊的答案，它们说，“好吧，使用这两行代码，然后添加这两行，然后可能将其放入属性中……”到底是什么？没有人说过将代码放在哪里，也很少有人指出需要在 cellForRowAtIndexpath 中完成什么。我已经尝试了很多东西!

我只是想在我的表格 View 单元格中保存 UIImage 的状态。基本上，用户可以点击 tableview 单元格中的图像，当他们这样做时，会弹出一个 UIAlertview。他们可以选择是否使用了表格 View 中列出的交通工具类型。如果"is"，图像颜色会变为蓝色(而不是灰色)，表明他们已经使用过它。或者，他们可以通过点击“否”来取消选择图像，图像将返回其灰色状态。我希望能够使用 nsuserdefaults 保留此操作，因为只有少量信息要保存(基本上只是图像状态)。我试过的任何东西都不会保存信息。我将在下面添加我的代码，并祝愿任何能帮助我的人幸福快乐!

或者，我从自定义类中创建了运输对象。有没有办法在自定义类中设置一个 bool 值，当用户选择是或否时动态更改它，然后更新自定义类以保存信息？任何想法，将不胜感激!

主视图 Controller

@interface MainTableViewController ()
{
    NSMutableArray *selectedImages;
}


@end

@implementation MainTableViewController

-(void)viewDidLoad
{
    [super viewDidLoad];

    _transportController = [[TransportDataController alloc] init];
    self.dataSource = _transportController.populateDataSource;
    self.title = @"Transportation Types";

   selectedImages = [[[NSUserDefaults standardUserDefaults] arrayForKey:@"selected"] mutableCopy];


}


-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return _dataSource.count;
}

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"mainCell";
    TransportCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    if (cell == nil)
    {
        cell = [[TransportCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }

    Transport *transportData = [self.dataSource objectAtIndex:indexPath.row];
    cell.nameLabel.text = transportData.name;
    cell.transportImageView.image = transportData.transportImage;


    if (transportData.usedTransportIsSelected == NO)
    {
        cell.grayedImageView.image = transportData.usedTransportImage;


    }
    else if (transportData.usedTransportIsSelected == YES)
    {
        cell.grayedImageView.image = [UIImage imageNamed:@"stamp-color"];


    }


    UITapGestureRecognizer *grayedImageTouched = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(transportImageTapped:)];
    grayedImageTouched.numberOfTapsRequired = 1;
    cell.grayedImageView.tag = indexPath.row;
    [cell.grayedImageView addGestureRecognizer:grayedImageTouched];
    cell.grayedImageView.userInteractionEnabled = YES;



    return cell;
}


-(void)transportImageTapped:(UIGestureRecognizer *)gesture
{
    Transport *transportData = [self.dataSource objectAtIndex:gesture.view.tag];
    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:gesture.view.tag inSection:0];


    UIAlertController *transportAlert = [UIAlertController alertControllerWithTitle:@"Yes, it's true..." message:@"I have used this type of transport before." preferredStyle:UIAlertControllerStyleAlert];

    [transportAlert addAction:[UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction *action){

        NSLog(@"cancel");

    }]];

    [transportAlert addAction:[UIAlertAction actionWithTitle:@"Yes" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action){

        UIImage *darkImage = [UIImage imageNamed:@"stamp-color"];
        transportData.usedTransportImage = darkImage;
        transportData.usedTransportIsSelected = YES;
        [self.dataSource replaceObjectAtIndex:gesture.view.tag withObject:transportData];
        [self.tableView reloadRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationNone];

        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
        [defaults setBool:YES forKey:@"selected"];
        [defaults synchronize];

        NSLog(@"has taken this transport before");

    }]];

    [transportAlert addAction:[UIAlertAction actionWithTitle:@"No" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action){

        UIImage *grayedImage = [UIImage imageNamed:@"stamp-grayed"];
        transportData.usedTransportImage = grayedImage;
        transportData.usedTransportIsSelected = NO;
        [self.dataSource replaceObjectAtIndex:gesture.view.tag withObject:transportData];
        [self.tableView reloadRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationNone];

        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
        [defaults setBool:NO forKey:@"selected"];
        [defaults synchronize];

        NSLog(@"has not taken this transport before");

    }]];

    [self presentViewController:transportAlert animated:YES completion:nil];

}

Answer 1

修改 Transport 类对您来说可能更有意义；假设它附加了一些唯一标识符。

@interface Transport
@property (strong) id somethingThatUniquelyIdentifiesThisTransport;
@property (nonatomic) BOOL usedTransportIsSelected;
// ...
@end

@implementation Transport
- (void)setUsedTransportIsSelected:(BOOL)value {
  [[NSUserDefaults standardUserDefaults] setObject:@(value) forKey:self.somethingThatUniquelyIdentifiesThisTransport];
}

- (BOOL)usedTransportIsSelected {
  return [[[NSUserDefaults standardUserDefaults] objectForKey:self.somethingThatUniquelyIdentifiesThisTransport] boolValue];
}

// ...
@end