iOS - [UITableView reloadData] 重新加载，但不删除旧单元格？

Posted 2023-02-27

技术标签:

【中文标题】iOS - [UITableView reloadData] 重新加载，但不删除旧单元格？【英文标题】：iOS - [UITableView reloadData] reloads, but not removes old cells? 【发布时间】：2014-03-05 21:49:37 【问题描述】：

这很奇怪，我知道，但我的 [UITableView reloadData] 没有删除旧单元格，如下所示：

你看到的混乱发生在我点击+按钮后，回来并再次更改值。加号按钮将 navigationController 推到另一个控制器上，当我点击 back 按钮 回来并更改了值后，这就是我所看到的。这怎么可能？？我使用了一个自定义视图（从 UIView 子类化），它是作为带有 UILabel 的 UIStepper 创建的。这是自定义 UIView 的代码、controller.m 和 .h-.m 文件。

controller.m

@interface ViewController ()
@property NSString *docsDir;
@property sqlite3 *DB;
@property NSArray *dirPaths;
@property NSString* databasePath;
@property (strong, nonatomic) IBOutlet UITableView *tableView;
@property BOOL isCreatedBefore;
@property NSArray *theList;
@end

@implementation ViewController
@synthesize docsDir;
@synthesize DB;
@synthesize dirPaths;
@synthesize databasePath;
- (void)viewDidLoad

    [super viewDidLoad];
    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    docsDir = [dirPaths objectAtIndex:0];
    databasePath = [[NSString alloc] initWithString: [docsDir stringByAppendingPathComponent: [NSString stringWithFormat:@"database.db"]]];

    [self createDatabase];
    self.theList = [self readAllEntries];


-(void) viewWillAppear:(BOOL)animated
    self.theList = [self readAllEntries];
    [self.tableView reloadData];


- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView

    return 1;


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section

    return [self.theList count];


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
   SeriesObject * obj = [self.theList objectAtIndex:indexPath.row];
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cellocan"];
    UILabel *nameLabel = (UILabel *)[cell.contentView viewWithTag:1];
    [nameLabel setText:obj.name];

    CounterView *seasonCounter = [[CounterView alloc] initWithX:220 WithY:28 WithName:obj.name withCount:obj.session withCustomTag:indexPath.row];
    seasonCounter.tag = 2;
    CounterView *episodeCounter = [[CounterView alloc] initWithX:268 WithY:28 WithName:obj.name withCount:obj.episode withCustomTag:indexPath.row];
    episodeCounter.tag = 4;

    [cell.contentView addSubview:seasonCounter];
    [cell.contentView addSubview:episodeCounter];

    return cell;



- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath 
    // Return YES if you want the specified item to be editable.
    return YES;


// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath 
    if (editingStyle == UITableViewCellEditingStyleDelete) 
        SeriesObject *obj = [self.theList objectAtIndex:indexPath.row];
        [self deleteEntryWithID:obj.idd];

        self.theList = [self readAllEntries];
        [self.tableView reloadData];
    

-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
    return 88;




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

    [tableView deselectRowAtIndexPath:indexPath animated:YES];



______and more about reading from database or deleting; not about the view. (this is a very simple app, as a free time hobby; so I didn't spend time to follow MVC)

CounterView.h

@interface CounterView : UIView
@property NSString* name;
@property NSInteger count;
@property UILabel *label;
@property NSInteger customTag;

- (id)initWithX:(CGFloat)xPoint WithY:(CGFloat)yPoint WithName:(NSString*)newName withCount:(NSInteger)newCount withCustomTag:(NSInteger)newTag;
@end

CounterView.m

@interface CounterView()

@property NSString *docsDir;
@property sqlite3 *DB;
@property NSArray *dirPaths;
@property NSString* databasePath;

@end


@implementation CounterView

@synthesize docsDir;
@synthesize DB;
@synthesize dirPaths;
@synthesize databasePath;

- (id)initWithX:(CGFloat)xPoint WithY:(CGFloat)yPoint WithName:(NSString*)newName withCount:(NSInteger)newCount withCustomTag:(NSInteger)newTag

    self = [super initWithFrame:CGRectMake(xPoint, yPoint, 24, 52)];
    if (self) 
        self.customTag = newTag;
        self.count = newCount;
        self.name = newName;

        UIButton *btnUp = [[UIButton alloc] initWithFrame:CGRectMake(3, 2, 18, 12)];
        [btnUp setImage:[UIImage imageNamed:@"top.png"] forState:UIControlStateNormal];
        [btnUp addTarget:self action:@selector(increaseValue) forControlEvents:UIControlEventTouchUpInside];
        UIButton *btnDown = [[UIButton alloc] initWithFrame:CGRectMake(3, 38, 18, 12)];
        [btnDown setImage:[UIImage imageNamed:@"bottom.png"] forState:UIControlStateNormal];
        [btnDown addTarget:self action:@selector(decreaseValue) forControlEvents:UIControlEventTouchUpInside];
        self.label = [[UILabel alloc] initWithFrame:CGRectMake(0, 14, 24, 24)];
        [self.label setText:[NSString stringWithFormat:@"%ld", (long)self.count]];
        self.label.textAlignment = NSTextAlignmentCenter;

        [self addSubview:btnUp];
        [self addSubview:btnDown];
        [self addSubview:self.label];
    
    return self;


- (void)addTarget:(id)target action:(SEL)action forControlEvents:(UIControlEvents)controlEvents




-(void) increaseValue
    self.count++;
    [self.label setText:[NSString stringWithFormat:@"%ld", (long)self.count]];

-(void) decreaseValue
    self.count--;
    [self.label setText:[NSString stringWithFormat:@"%ld", (long)self.count]];


____and some more database codes too..

【问题讨论】：

【参考方案1】：

在您的cellForRowAtIndexPath: 中，您每次都添加一个子视图。 UITableView 重用单元格，因此当您重新加载时，您会得到一个“脏”单元格。您需要检查视图是否已经存在。如果是这样，请修改视图而不是添加视图。谷歌“UITableViewCell viewWithTag”查看一些示例代码。

【讨论】：

我以前用过。所以每次都会发生，但由于内容稳定，我从来没有意识到。谢谢.. @Esq 模式已经写了几百遍了，很容易找到。【参考方案2】：

- (void)prepareForReuse

    //remove your subviews here 
    [self.subViewToRemove removeFromSuperView];

【讨论】：

【参考方案3】：

我建议您创建一个从 UITableViewCell 派生的自定义单元格类，并让它包含您的自定义 CounterView 实例。在这种情况下，您不需要每次都在 cellForRowAtIndexPath 中添加子视图（这会导致您遇到问题），而是可以传递它所需的任何值。

【讨论】：

【参考方案4】：

经过一些修改，在 cellForRowAtIndexpath: 方法中使用它解决了所有问题。谢谢大家。