iOS UITableView 正在绘制奇怪的单元格

Question

我有一个 UITableView，它应该只在第一部分第一行显示一个 UISwitch，但由于某种原因，开关显示在第四部分。此外，每当打开/关闭开关时，一个新的 UISwitch 就会出现在另一个单元格中。它的行为非常奇怪。任何帮助将不胜感激。

代码:

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

    PrettyTableViewCell *cell = [tableViewdequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {

        cell = [[PrettyTableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier];
        cell.tableViewBackgroundColor = tableView.backgroundColor;
    }

    [cell prepareForTableView:tableView indexPath:indexPath];
    cell.cornerRadius = 10;

    if (indexPath.section == 0) {
        if (indexPath.row == 0) {
            cell.textLabel.text = @"Push Notifications";
            pushNotificationSwitch = [[UISwitch alloc] init];
            pushNotificationSwitch.on = pushSwitchState;
            cell.accessoryView = pushNotificationSwitch;
            [pushNotificationSwitch addTarget:self action:@selector(pushSwitch:) forControlEvents:UIControlEventValueChanged];
            cell.userInteractionEnabled = YES;
            cell.selectionStyle = UITableViewCellSelectionStyleNone;
        }
    }

    if  (indexPath.section == 1) {
        if (indexPath.row == 0) {
            cell.textLabel.text = @"Department Based";
            if (departmentBased) {
                cell.accessoryType = UITableViewCellAccessoryCheckmark;
            }
            else {
                cell.accessoryType = UITableViewCellAccessoryNone;
            }
            cell.userInteractionEnabled = YES;
        }
        if (indexPath.row == 1) {
            cell.textLabel.text = @"Location Based (GPS)";
            if (locationBased) {
                cell.accessoryType = UITableViewCellAccessoryCheckmark;
            }
            else {
                cell.accessoryType = UITableViewCellAccessoryNone;
            }            cell.userInteractionEnabled = YES;
        }
    }

    if (departmentBased) {
        if (indexPath.section == 2) {
            if (indexPath.row == 0) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 1) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 2) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 3) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 4) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 5) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 6) {
                cell.textLabel.text = @"xxxxxx";
            }
        }
        if (indexPath.section == 3) {
            if (indexPath.row == 0) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 1) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 2) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 3) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 4) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 5) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 6) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 7) {
                cell.textLabel.text = @"xxxxxx";
            }
            if (indexPath.row == 8) {
                cell.textLabel.text = @"xxxxxx";
            }
        }
    }
    return cell;
}

Answer 1

您正在体验 iOS 中单元可重用性的影响。您对所有单元格使用相同的单元格标识符，因此当您滚动时，旧单元格将变得可用并从 tableView 中出列。

尝试在之后立即将 cell.accessoryView 设置为 nil:

if (cell == nil) {
    cell = [[PrettyTableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier];
    cell.tableViewBackgroundColor = tableView.backgroundColor;
}

cell.accessoryView = nil;

或者，为第一个 indexPath 选择一个不同的单元格标识符，确保在出队时考虑到这一点。

BOOL firstCell = indexPath.row == 0 && indexPath.section == 0;
NSString *CellIdentifier = firstCell ? @"CellWithSwitch" : @"Cell";

PrettyTableViewCell *cell = 
       [tableViewdequeueReusableCellWithIdentifier: CellIdentifier];

if (cell == nil) {
    cell = [[PrettyTableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier];
    cell.tableViewBackgroundColor = tableView.backgroundColor;
}