当滚动单元格队列时，如何维护和保存自定义单元格文本字段输入数据

Question

遗憾的是，我知道问题是什么，但我是绿色的，不知道最好的方法去处理它。我已经阅读了苹果的文档和所有相关的问题，但无法找到或充分解释这些信息。

如下所示。我有一个表视图，有19个单元格。2在第0部分，17在第1部分。一切正常，除了当我滚动时，我知道这是因为tableview在重用单元格，所以当我尝试保存时，看到下面的代码这些单元格根本不存在因此，当我尝试保存时，我的视图中的任何东西都是nil字符串参数所以我的实体最终是NaN。

维护和保存所有单元格的文本字段信息的适当方法是什么?提前感谢任何帮助!

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

{

    UITableViewCell *newCell;
if (indexPath.section == 0 && indexPath.row == 0) {
    NSString *cellIdentifier = @"RNDateCell";
    RNCommentCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
    if (cell == nil) {
        NSArray *nib = [[NSBundle mainBundle]loadNibNamed:@"RNCommentCell" owner:self options:nil];
        cell = [nib objectAtIndex:0];
        cell.commentLabel.text = NSLocalizedString(@"Date:", @"Date:");
        cell.commentField.text = [NSString stringWithFormat:@"%@", self.metrics.timeStamp.description];
        newCell = cell;
    }
}
if (indexPath.section == 0 && indexPath.row == 1) {
    NSString *cellIdentifier = @"RNCommentCell";
    RNCommentCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
    if (cell == nil) {
        NSArray *nib = [[NSBundle mainBundle]loadNibNamed:@"RNCommentCell" owner:self options:nil];
        cell = [nib objectAtIndex:0];
        cell.commentLabel.text = NSLocalizedString(@"Comment:", @"Comment:");
        cell.commentField.text = self.metrics.comment;
        newCell = cell;
    }
}
if (indexPath.section == 1) {
    static NSString *numericCellIdentifier = @"RNNumericCell";
    RNNumericCell *cell = (RNNumericCell *)[tableView dequeueReusableCellWithIdentifier:numericCellIdentifier];
    if (cell == nil) {
        NSArray *nib = [[NSBundle mainBundle]loadNibNamed:@"RNNumericCell" owner:self options:nil];
        cell = [nib objectAtIndex:0];
        switch (indexPath.row) {
            case 0:
                cell.numericCellLabel.text = NSLocalizedString(@"Weight:", @"Weight:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.weight];
                newCell = cell;
                break;
            case 1:
                cell.numericCellLabel.text = NSLocalizedString(@"Height:", @"Height:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.height];
                newCell = cell;
                break;
            case 2:
                cell.numericCellLabel.text = NSLocalizedString(@"Neck:", @"Neck:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.neck];
                newCell = cell;
                break;
            case 3:
                cell.numericCellLabel.text = NSLocalizedString(@"Chest:", @"Chest:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.chest];
                newCell = cell;
                break;
            case 4:
                cell.numericCellLabel.text = NSLocalizedString(@"Waist:", @"Waist:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.waist];
                newCell = cell;
                break;
            case 5:
                cell.numericCellLabel.text = NSLocalizedString(@"Hips:", @"Hips:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.hips];
                newCell = cell;
                break;
            case 6:
                cell.numericCellLabel.text = NSLocalizedString(@"Biceps:", @"Biceps:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.biceps];
                newCell = cell;
                break;
            case 7:
                cell.numericCellLabel.text = NSLocalizedString(@"Forearms:", @"Forearms:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.forearms];
                newCell = cell;
                break;
            case 8:
                cell.numericCellLabel.text = NSLocalizedString(@"Wrists:", @"Wrists:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.wrists];
                newCell = cell;
                break;
            case 9:
                cell.numericCellLabel.text = NSLocalizedString(@"Quads Thighs:", @"Quads Thighs:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.quadsThighs];
                newCell = cell;
                break;
            case 10:
                cell.numericCellLabel.text = NSLocalizedString(@"Calves:", @"Calves:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.calves];
                newCell = cell;
                break;
            case 11:
                cell.numericCellLabel.text = NSLocalizedString(@"Ankles:", @"Ankles:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.ankles];
                newCell = cell;
                break;
            case 12:
                cell.numericCellLabel.text = NSLocalizedString(@"Feet:", @"Feet:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.feet];
                newCell = cell;
                break;
            case 13:
                cell.numericCellLabel.text = NSLocalizedString(@"BMI:", @"BMI:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.bmi];
                newCell = cell;
                break;
            case 14:
                cell.numericCellLabel.text = NSLocalizedString(@"BMR:", @"BMR:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.bmr];
                newCell = cell;
                break;
            case 15:
                cell.numericCellLabel.text = NSLocalizedString(@"Waist/Height R:", @"Waist/Height R:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.waistToHeightRatio];
                newCell = cell;
                break;
            case 16:
                cell.numericCellLabel.text = NSLocalizedString(@"Waist/Hips R:", @"Waist/Hips R:");
                cell.numericField.text = [NSString stringWithFormat:@"%@", self.metrics.waistToHipRatio];
                newCell = cell;
                break;
            default:
                break;
        }
    }
}
return newCell;

}

    - (void)saveData

{

NSDateFormatter *dateFormat;
RNCommentCell *dateCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]];
self.metrics.timeStamp = [dateFormat dateFromString:dateCell.commentField.text];
RNCommentCell *commentCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:1 inSection:0]];
self.metrics.comment = commentCell.commentField.text;

RNNumericCell *weightCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:1]];
self.metrics.weight = [NSDecimalNumber decimalNumberWithString:weightCell.numericField.text];
RNNumericCell *heightCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:1 inSection:1]];
self.metrics.height = [NSDecimalNumber decimalNumberWithString:heightCell.numericField.text];
RNNumericCell *neckCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:2 inSection:1]];
self.metrics.neck = [NSDecimalNumber decimalNumberWithString:neckCell.numericField.text];
RNNumericCell *chestCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:3 inSection:1]];
self.metrics.chest = [NSDecimalNumber decimalNumberWithString:chestCell.numericField.text];
RNNumericCell *waistCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:4 inSection:1]];
self.metrics.waist = [NSDecimalNumber decimalNumberWithString:waistCell.numericField.text];
RNNumericCell *hipsCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:5 inSection:1]];
self.metrics.hips = [NSDecimalNumber decimalNumberWithString:hipsCell.numericField.text];
RNNumericCell *bicepsCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:6 inSection:1]];
self.metrics.biceps = [NSDecimalNumber decimalNumberWithString:bicepsCell.numericField.text];
RNNumericCell *forearmCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:7 inSection:1]];
self.metrics.forearms = [NSDecimalNumber decimalNumberWithString:forearmCell.numericField.text];
RNNumericCell *wristsCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:8 inSection:1]];
self.metrics.wrists = [NSDecimalNumber decimalNumberWithString:wristsCell.numericField.text];
RNNumericCell *quadsCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:9 inSection:1]];
self.metrics.quadsThighs = [NSDecimalNumber decimalNumberWithString:quadsCell.numericField.text];
RNNumericCell *calvesCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:10 inSection:1]];
self.metrics.calves = [NSDecimalNumber decimalNumberWithString:calvesCell.numericField.text];
RNNumericCell *anklesCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:11 inSection:1]];
self.metrics.ankles = [NSDecimalNumber decimalNumberWithString:anklesCell.numericField.text];
RNNumericCell *feetCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:12 inSection:1]];
self.metrics.feet = [NSDecimalNumber decimalNumberWithString:feetCell.numericField.text];
RNNumericCell *bmiCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:13 inSection:1]];
self.metrics.bmi = [NSDecimalNumber decimalNumberWithString:bmiCell.numericField.text];
RNNumericCell *bmrCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:14 inSection:1]];
self.metrics.bmr = [NSDecimalNumber decimalNumberWithString:bmrCell.numericField.text];
RNNumericCell *waistToHeightCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:15 inSection:1]];
self.metrics.waistToHeightRatio = [NSDecimalNumber decimalNumberWithString:waistToHeightCell.numericField.text];
RNNumericCell *waistToHipCell = (id)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:16 inSection:1]];
self.metrics.waistToHipRatio = [NSDecimalNumber decimalNumberWithString:waistToHipCell.numericField.text];
NSError *error;
if (![self.managedObjectContext save:&error]) {
    NSLog(@"Error saving context: %@", error);
}

}

Answer 1

请记住，UITextField是视图，不应该存储数据，而应该简单地显示/检索数据。您的模型(self.metrics)应该是存储信息的地方，并且应该在您从用户收到信息后立即存储，以便文本字段是否消失或被重用无关紧要。

为了做到这一点，你使用以下方法，当有人停止编辑文本字段时调用(确保你设置了所有文本字段的委托到你的控制器):

-(void) textFieldDidEndEditing:(UITextField *)textField
{
    // Figure out which textField this is and save the data to the appropriate place in your model
}

现在，稍微棘手的部分是确定您在此方法中使用的文本字段。

您可以在cellForRowAtIndexPath中设置标签，然后在这里查找标签编号以确定它是哪个，或者您可以通过索引路径来完成，因为这是您已经在做的:

CGRect position = [self convertRect:textField.frame toView:self.tableView];
NSArray *indexPaths = [self.tableView indexPathsForRowsInRect:position];
NSIndexPath *indexPath = [indexPaths objectAtIndex:0];

Answer 2

更新您的self.metrics.'whatever'数据，每当它发生变化，只保存您的save指标，而不是试图从单元格中抓取它。换句话说，不要将单元格用作数据存储位置。