iphone - UITableViewCell中UILabel宽度的动态计算

Question

我正在构建一个基于 UITableViewCellStyle1 (或类似)的自定义应用程序内设置 View 。

我正在尝试动态计算单元格左侧标签(标题)的宽度，以确定右侧文本字段的宽度。

当我在模拟器中启动应用程序并加载 View 时，标题标签的宽度为零，直到我向下 ScrollView 并且单元格不可见，然后当我向上滚动时，大小会按预期调整。我相信这可能与细胞的再利用有关。

我需要单元格中的标题标签在 View 加载时具有正确的宽度，而不是在它们消失一次之后。

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

UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:reuseIdentifier];

if ( !cell )
{   
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:reuseIdentifier] autorelease];
    [cell setBackgroundColor:[UIColor baeDarkGrayColor]];


    UILabel* cellLabel = [cell textLabel];
    [cellLabel setTextColor:[UIColor whiteColor]];
    [cellLabel setBackgroundColor:[UIColor clearColor]];

    [cell setUserInteractionEnabled:YES];
    [cell setSelectionStyle:UITableViewCellSelectionStyleGray];
}

// Populate cell with corresponding data.
NSDictionary* tableSection = [_tableData objectAtIndex:indexPath.section];

// Set the label
UILabel* textLabel = [cell textLabel];
NSString* labelString = [[tableSection objectForKey:@"itemTitles"] objectAtIndex:indexPath.row];
[textLabel setText:labelString];

   //   CGSize constrainedSize;
  //    constrainedSize.width = MAXFLOAT;
 // constrainedSize.height = MAXFLOAT;

CGSize textLabelSize = [textLabel.text sizeWithFont:textLabel.font /*constrainedToSize:constrainedSize*/];

NSLog(@"text label width: %f", textLabelSize.width);    


// Set the accessory view
BAESettingsTableCellAccessoryType accessoryType = [[[tableSection objectForKey:@"itemAccessories"] objectAtIndex:indexPath.row] integerValue];
switch ( accessoryType )
{
    case BAESettingsTableCellAccessoryDisclosureIndicator:
    {
        UIImageView* disclosureView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"AccessoryDisclosure.png"]];
        [cell setAccessoryView:disclosureView];
        [disclosureView release];
        break;
    }
    case BAESettingsTableCellAccessoryOnOffSwitch:
    {
        UISwitch* onOffSwitch = [[UISwitch alloc] initWithFrame:CGRectZero];
        [onOffSwitch setOn:YES];
        [cell setAccessoryView:onOffSwitch];
        [onOffSwitch release];
        break;
    }
    case BAESettingsTableCellAccessoryNone:
        // default:
        // break;
    {

        CGRect cellFrame = [cell frame];

        float detailTextFieldWidth = cellFrame.size.width - ( textLabelSize.width + 50 );
        float detailTextFieldHeight = cellFrame.size.height - 1;

        NSLog(@"detail text field calculated frame width, height, %f, %f", detailTextFieldWidth, detailTextFieldHeight);


        CGRect frame = CGRectMake(cellFrame.origin.x, cellFrame.origin.y, detailTextFieldWidth, detailTextFieldHeight);


        UITextField* textField = [[UITextField alloc] initWithFrame:frame];
        NSString* detailLabelString = [[tableSection objectForKey:@"itemDetailStrings"] objectAtIndex:indexPath.row];
        textField.text = detailLabelString;
        textField.textColor = cell.detailTextLabel.textColor;
        textField.textAlignment = UITextAlignmentRight;
        textField.borderStyle = UITextBorderStyleRoundedRect;
        [cell setAccessoryView:textField];
        [textField release];
        break;
    }

}

return cell;
   }

Answer 1

显式设置字体可以解决您的问题。

CGSize textLabelSize = [textLabel.text sizeWithFont:[UIFont systemFontOfSize:17]];

血淋淋的详细信息:
当表格 View 首次加载时，由于字体大小为 0，此代码段返回零宽度。

[textLabel.text sizeWithFont:textLabel.font]

我通过显示单元格字体的磅值来解决这个问题。

NSLog(@"font size: %f", cell.textLabel.font.pointSize);

正如您所描述的，在单元格离开屏幕并返回之前，点大小为零。