如果一个文本字段已添加到单元格中，如何不创建新的文本字段 [英] How NOT to create a new textfield if one textfield has been added to the cell

问题描述

我正在使用以下代码在 UITableView 单元格中创建文本字段:

I'm using the following code to create the textfield in a UITableView Cell:

static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

if (cell == nil)
{
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier];
    cell.showsReorderControl = YES;
}

if (indexPath.row == 1)
{
    UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(15,10,260,40)];
    textField.placeholder = @"Activity 1:  Type Name";
    textField.delegate = self;
    textField.clearButtonMode = YES;
    [textField setReturnKeyType:UIReturnKeyDone];
    [cell addSubview:textField];
}

return cell;

我正在以完全相同的方式创建 3 个 textField.唯一的区别是 placeHolder 文本.

I'm creating 3 textFields the exact same way. The only difference is the placeHolder text.

当键盘弹出时，视图向上滚动并且 textField 1 离开屏幕.返回后，我认为正在重新创建 textField.

When the keyboard pops up, the view scrolls up and the textField 1 goes off the screen. Upon return, I think the textField is being recreated.

以下是一些屏幕截图:

第一次出现单元格(看起来很棒):

First time appearance of the cell (looks great):

滚出屏幕后返回(注意第一个文本框):

Returns after being scrolled off the screen (notice the first textfield):

在第一个单元格中，当我开始输入时，第二个创建的 textField 的占位符消失了，但第一个 textField 的占位符仍然存在:

In cell one, when I start typing, the 2nd created textField's placeHolder disappears, but the first textField's Placeholder remains:

两个问题:

1. 如何避免在单元格中重新创建 textField?或者消除这个问题?
2. 重新创建时，为什么单元格 3 中的 textField 和 placeHolder 为Activity 3: Type Name"出现在单元格 1 的 textField 上?

推荐答案

我假设这段代码在 cellForRow tableview dataSource 协议方法中.问题是此方法被多次调用(有时在您意想不到的情况下)，导致创建一个新的文本字段并将其添加到同一个单元格中.为了解决这个问题你只需要在创建单元格时添加一个文本字段，然后在每次调用方法时配置单元格.我建议创建一个表格单元子类，但您可以将代码更改为此进行学习:

I am assuming this code is in the cellForRow tableview dataSource protocol method. The problem is that this method is called multiple times (sometimes when you wouldn't expect), causing a new text field to be created and added to the same cell. In order to resolve this issue you need to add a text field only when the cell is created, and then configure the cells each time the method is called. I would recommend creating a table cell subclass, but you can change your code to this for learning purposes:

#define kTextFieldTag 1

UITextField* textField = [cell viewWithTag:kTextFieldTag];
if (cell == nil)
{
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier];
    cell.showsReorderControl = YES;

    /* only called when cell is created */
    textField = [[UITextField alloc] initWithFrame:CGRectMake(15,10,260,40)];
    textField.delegate = self;
    textField.clearButtonMode = YES;
    textField.tag = kTextFieldTag; /* I would recommend a cell subclass with a textfield member over the tag method in real code*/
    [textField setReturnKeyType:UIReturnKeyDone];
    [cell addSubview:textField];
}

/* called whenever cell content needs to be updated */
if (indexPath.row == 1)
{
   textField.placeholder = @"Activity 1:  Type Name";
}
...
/* or replace if checks with with: */
textField.placeholder = [NSString stringWithFormat:@"Activity %i: Type Name", (int)indexPath.row]; /* Handles all fields :) */
...

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