向headerview添加子视图：添加到错误的部分

Question

I have a tableview with 2 sections

-(NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
  switch (section) { 
    case 0: return @"s1"; 
    case 1: return @"s2"; 
  } 
}

I wanted to add a label to section 0.

-(void) tableView:(UITableView *)tableView willDisplayHeaderView(nonnull UIView *)view forSection:(NSInteger)section {
  if (section == 0) {
    for (UIView *subView in view.subviews) {
      if (subView.tag == 99) {
         [subView removeFromSuperview];
         break;
      }
    }

    UITableViewHeaderFooterView *headerView = (UITableViewHeaderFooterView *)view;
    UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake([[UIScreen mainScreen] bounds].size.width - 150 - headerView.textLabel.frame.origin.x, headerView.textLabel.frame.origin.y, 150, hederView.textLabel.frame.size.height)];

    label.text = @"test";
    label.tag = 99;
    [headerView addSubview:label];
  }
}

It works ok for initial display.

Then I use presentViewController to pop up a camera Image Picker, but whenever I dismiss the image picker, and return back to the current view, the "test" label will be in both seciton 0 and section 1.

Meaning that there will be 2 "test" in both two sections.

If I use

if (section == 1) {
  for (UIView *subView in view.subviews) {
    if (subView.tag == 99) {
      [subView removeFromSuperview];
      break;
    }
  }
}

This will remove the extra "test" from section 1.

Is there any possible reasons for that? I tried to debug and cannot see anything useful on why this happens, because after the if (section == 0) block finished running, it will go into assembly mode, if I continue running from the break, section 1 will show up "test", and I don't know where it comes from.

I am not asking for solution (I had one, just to remove the tag 99 label from section 1), I am asking for reason and any place that I did wrong.

Any suggestions will be appreciated. Thank you very much.

Answer 1

The first time you instantiate the UITableViewController class, the TableView is reloaded with two different views for both your sections. When you return to the same UITableViewController a new instance is not instantiated. But probably you have a reloadData() call in viewWillAppear or viewDidAppear . Now the TableView is reloaded with the previous views reused for your Headers . The view1 for section 1 in previous instantiation becomes the view for section 0 now.(at this point you add the UILabel as subView for this view1) The view0 of previous instantiation becomes the view for section 1 now.(it already has label as subView from previous instantiation). Thus when you return to this same TableViewController and since it is not instantiated again, both the views for header has label as subView

You can avoid the reloadData() call from view will appear and it looks fine or follow the best practice of overriding the method

func tableView(tableView: UITableView, viewForHeaderInSection section: Int) ->     UIView?

Answer 2

You can add header in following way..

add two function

func tableView(tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {

            return 40.0
    }



func tableView(tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
    let vw_header : UIView = UIView()
    vw_header.frame = CGRectMake(10, 0, ScreenSize.SCREEN_WIDTH, 40)
    vw_header.backgroundColor = Validation.getColorByRGB(227, G: 227, B: 227)
    vw_header.layer.borderWidth = 1
    vw_header.layer.borderColor = UIColor.darkGrayColor().CGColor


    let txtHeaderText : UILabel = UILabel()
    txtHeaderText.frame = CGRectMake(5, 0, ScreenSize.SCREEN_WIDTH, 40)
    txtHeaderText.textColor = appTextPurpleColor
    txtHeaderText.textAlignment = NSTextAlignment.Left
    txtHeaderText.text = “Simple Header”

    vw_header.addSubview(txtHeaderText)

    return vw_header
}

Now u can customize the header section view according ur requirement