iOS如何有效地将UIView添加到tableview单元格

Question

我有一个表格，其中每个单元格都有一个由 XMLParser feed 提供的 UIView。如果我保持原样，每次刷新 View 时， View 都会相互构建，因为它们没有被释放/删除，这是完全有道理的。我将如何编写代码来避免这个问题，而不必每次刷新时都重建 View 。我被它的逻辑和实际语法所困扰。谢谢。

代码:

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

  static NSString *CellIdentifier = @"Cell";
  JointCAD *currentCall = [[xmlParser calls] objectAtIndex:indexPath.row];
  self.tableView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"texture.png"]];

  UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
  if (cell == nil)
  {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];

    UIView *selectionView = [[UIView alloc] initWithFrame:CGRectMake(10, 7, 200, 65)];
    [selectionView setBackgroundColor: [UIColor clearColor]];
    cell.selectedBackgroundView = selectionView;
  }

  // Display content in each cell

  cellSeparator = [[UIView alloc] initWithFrame:CGRectMake(10, 7, 300, 65)];
  [cellSeparator setAutoresizingMask:UIViewAutoresizingFlexibleLeftMargin |
   UIViewAutoresizingFlexibleRightMargin |
   UIViewAutoresizingFlexibleWidth];
  [cellSeparator setContentMode:UIViewContentModeTopLeft];
  [cellSeparator setBackgroundColor: [UIColor colorWithRed:240.0/255.0 green:240.0/255.0 blue:240.0/255.0 alpha:1.0]];
  cellSeparator.layer.borderWidth = 1.0;
  cellSeparator.layer.borderColor = [UIColor blackColor].CGColor;
  [cell addSubview:cellSeparator];

  callTypeLabel = [[UILabel alloc]initWithFrame:CGRectMake(5, 2, 190, 21)];
  callTypeLabel.text =  [currentCall currentCallType];
  callTypeLabel.backgroundColor = [UIColor clearColor];
  callTypeLabel.font = [UIFont boldSystemFontOfSize:12.0];
  [cellSeparator addSubview:callTypeLabel];

  locationLabel = [[UILabel alloc]initWithFrame:CGRectMake(5, 17 , 190, 15)];
  locationLabel.text = [currentCall location];
  locationLabel.backgroundColor = [UIColor clearColor];
  locationLabel.font = [UIFont systemFontOfSize:10.0];
  [cellSeparator addSubview:locationLabel];

  unitsLabel = [[UILabel alloc]initWithFrame:CGRectMake(4, 43, 190, 21)];
  unitsLabel.text = [currentCall units];
  unitsLabel.backgroundColor = [UIColor clearColor];
  unitsLabel.font = [UIFont italicSystemFontOfSize:10.0];
  [cellSeparator addSubview:unitsLabel];

  stationLabel = [[UILabel alloc]initWithFrame:CGRectMake(195 , 25, 75, 20)];
  NSString *station = [@"Station: " stringByAppendingString:currentCall.station];
  stationLabel.text = station;
  stationLabel.backgroundColor = [UIColor clearColor];
  stationLabel.font = [UIFont boldSystemFontOfSize:11.0];
  [cellSeparator addSubview:stationLabel];

  if ([currentCall.county isEqualToString:@"W"]) {
    UIImage  *countyImage = [UIImage imageNamed:@"blue.png"];
    CGRect countyImageFrame = CGRectMake(275, 10, 18, 18);
    UIImageView *countyImageLabel = [[UIImageView alloc] initWithFrame:countyImageFrame];
    countyImageLabel.image = countyImage;
    [cellSeparator addSubview:countyImageLabel];
  } else {
    UIImage  *countyImage = [UIImage imageNamed:@"green.png"];
    CGRect countyImageFrame = CGRectMake(275, 10, 18, 18);
    UIImageView *countyImageLabel = [[UIImageView alloc] initWithFrame:countyImageFrame];
    countyImageLabel.image = countyImage;
    [cellSeparator addSubview:countyImageLabel];
  }

  if ([currentCall.callType isEqualToString:@"F"]) {
    UIImage  *callTypeImage = [UIImage imageNamed:@"red.png"];
    CGRect callTypeImageFrame = CGRectMake(275, 37, 18, 18);
    UIImageView *callTypeImageLabel = [[UIImageView alloc] initWithFrame:callTypeImageFrame];
    callTypeImageLabel.image = callTypeImage;
    [cellSeparator addSubview:callTypeImageLabel];
  } else {
    UIImage  *callTypeImage = [UIImage imageNamed:@"yellow.png"];
    CGRect callTypeImageFrame = CGRectMake(275, 37, 18, 18);
    UIImageView *callTypeImageLabel = [[UIImageView alloc] initWithFrame:callTypeImageFrame];
    callTypeImageLabel.image = callTypeImage;
    [cellSeparator addSubview:callTypeImageLabel];
  }

  return cell;
}

Answer 1

如果我正确理解你的问题，我认为你想要的解决方案是子类化 UITableViewCell，设置你的 subview (UIImageViews 等)并使其属性你的子类。然后你就可以

if (!cell.imageView) {
    cell.imageView = [[UIImageView alloc] initWithFrame:myFrame];
}

然后只需设置图像即可。这样，您就可以确保不会将 ImageView 堆叠在一起，并且当单元格出队时，将设置正确的图像。

编辑:

创建一个名为 MyTableViewCell 的类(或者任何你想要的名称，但要确保它是 UITableViewCell 的子类)添加@property(强，非原子)UIImageView *imageView;

然后在 cellForRowAtIndexPath 中使用 MyTableViewCell 而不是 UITableViewCell，您可以访问自定义 TableView 单元格的图像属性，检查它是否存在，如果不存在则创建它(这就是上面代码的作用)，然后设置图像。我会给你密码，但我在打电话。 Google 子类化 UITableviewCell。您应该找到大量示例。