UITableView Cell 正在重新生成

Question

我有UITableViewCell、UILabel 和UISwitch。默认情况下，所有UISwitch 都设置为关闭。

一旦我打开开关，然后滚动表格，开关值将再次设置为默认值，即关闭

下面是我使用的代码：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if(cell != nil) cell = nil;
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
    }
    if (indexPath.row == 0) {
        UILabel *lbl1 = [[UILabel alloc] initWithFrame:CGRectMake(20, 10, 100, 30)];
        lbl1.text = @"Some Text";
        [cell addSubview:lbl1];

        switch = [[UISwitch alloc] initWithFrame:CGRectMake(190, 10, 200, 30)];
        [switch setOn:NO];
        switch.tag = 1;
        [switch addTarget:self action:@selector(switchTapped:) forControlEvents:UIControlEventChanged];
        [cell addSubview:switch];
    }

}

// 下面是我的switchTapped方法：

- (void) switchTapped: (id)sender {
    UISwitch *tapSwitch = (UISwitch *)sender;

    switch (tapSwitch.tag) {
        case 1:
            if (tapSwitch.on) {
              // do something
            }
            else {
                // do something
            }
            break;
        case 2:
            if (tapSwitch.on) {
                // do something
            }
            else {
                // do something
            }
            break;
}

我在这里做错了吗？

谢谢。

Answer 1

您正在使用非常讨厌的代码，每次需要时都会重新生成单元格：

if(cell != nil) 
{
   cell = nil; 
}

if (cell == nil) 
{ 
...
}

您是否将开关的状态绑定到某个保留对象（例如，项目模型对象，其中单个单元格反映了一个项目）？

Answer 2

这就是我编写单元格绘图代码的方式：

基本上，在我的 if(cell == nil) { ... } 中，我做了所有的“initWithFrame”。除此之外，我只需设置标签文本等值。不要在 if(cell == nil) {...} 代码块之外执行 initWithFrame。

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

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:reusableCell];

    if(cell == nil)
    {        
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:reusableCell] autorelease];

        thumbnail = [[UIImageView alloc] initWithFrame:CGRectMake(5, 5, 106, 81)];

        feedTitle = [[UILabel alloc] initWithFrame:CGRectMake(116, 3, [IOSDevice screenWidth] - 140, 25)];
        postDate = [[UILabel alloc] initWithFrame:CGRectMake(116, 10, [IOSDevice screenWidth] - 140, 50)];
        description = [[UILabel alloc] initWithFrame:CGRectMake(116, 45, [IOSDevice screenWidth] - 140, 50)];

        // setting tag reminders so we can identify the element to replace
        [thumbnail setTag:1];
        [feedTitle setTag:2];
        [postDate setTag:3];
        [description setTag:4];

        [[cell contentView] addSubview:thumbnail];
        [[cell contentView] addSubview:feedTitle];
        [[cell contentView] addSubview:description];
        [[cell contentView] addSubview:postDate];

        [thumbnail release];
        [feedTitle release];
        [description release];
        [postDate release];
    }

    thumbnail = (UIImageView *)[[cell contentView] viewWithTag:1];
    feedTitle = (UILabel *)[[cell contentView] viewWithTag:2];
    postDate = (UILabel *)[[cell contentView] viewWithTag:3];
    description = (UILabel *)[[cell contentView] viewWithTag:4];

    [feedTitle setBackgroundColor:[UIColor clearColor]];
    [feedTitle setFont:[UIFont fontWithName:@"Helvetica-Bold" size:16]];
    [feedTitle setTextColor:[UIColor colorWithRed:0.215 green:0.215 blue:0.215 alpha:1.0]];

    [description setBackgroundColor:[UIColor clearColor]];
    [description setFont:[UIFont fontWithName:@"Helvetica" size:12]];
    [description setTextColor:[UIColor colorWithRed:0.328 green:0.328 blue:0.328 alpha:1.0]];
    [description setNumberOfLines:2];
    [description setLineBreakMode:UILineBreakModeWordWrap];

    [postDate setBackgroundColor:[UIColor clearColor]];
    [postDate setFont:[UIFont fontWithName:@"Helvetica" size:12]];
    [postDate setTextColor:[UIColor colorWithRed:0.707 green:0.180 blue:0.141 alpha:1.0]];

    [thumbnail setImage:[[items objectAtIndex:[indexPath row]] objectForKey:@"thumb"]];

    [feedTitle setText:[[items objectAtIndex:[indexPath row]] objectForKey:@"title"]];
    [description setText:[[items objectAtIndex:[indexPath row]] objectForKey:@"summary"]];

    // Format date
    NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease];  
    [dateFormatter setDateStyle:NSDateFormatterLongStyle];
    [dateFormatter setTimeStyle:NSDateFormatterShortStyle];

    [postDate setText:[dateFormatter stringFromDate:[[items objectAtIndex:[indexPath row]] objectForKey:@"date"]]];

    [cell setSelectionStyle:UITableViewCellSelectionStyleNone];
    [cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator];

    if([feedList contentOffset].y < -50)
    {
        shouldUpdate = TRUE;

        [activityIndicator stopAnimating];

        [feedList setContentOffset:CGPointMake(0, -30) animated:NO];
        [self loadData];

        loadingLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, -25, [IOSDevice screenWidth], 20)];
        [loadingLabel setText:@"Loading New Data"];
        [loadingLabel setTextAlignment:UITextAlignmentCenter];
        [loadingLabel setBackgroundColor:[UIColor clearColor]];
        [loadingLabel setTextColor:[UIColor colorWithRed:0.215 green:0.215 blue:0.215 alpha:1.0]];
        [loadingLabel setFont:[UIFont fontWithName:@"Helvetica-Bold" size:14]];

        reloadingSpinner = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(70, -25, 20, 20)];
        [reloadingSpinner setActivityIndicatorViewStyle:UIActivityIndicatorViewStyleGray];
        [reloadingSpinner startAnimating];
        [reloadingSpinner setHidesWhenStopped:YES];

        [feedList addSubview:reloadingSpinner];
        [feedList addSubview:loadingLabel];
    }

    return cell;
}