Iphone 重用UITableViewCell'；s

我有一个UITableView，当用户滚动时，它会重复使用单元格。所有内容都显示并滚动良好，但当用户单击实际行时，高亮显示的单元格将显示另一个单元格中的某些文本。我不太清楚为什么

#define IMAGE_TAG 1111
#define LOGIN_TAG 2222
#define FULL_NAME_TAG 3333

// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *CellIdentifier = @"Cell";

    STUser *mySTUser = [[[STUser alloc]init]autorelease];
    mySTUser = [items objectAtIndex:indexPath.row];

    AsyncImageView* asyncImage = nil;
    UILabel* loginLabel = nil;
    UILabel* fullNameLabel = nil;

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    }
    else {
        asyncImage = (AsyncImageView *) [cell.contentView viewWithTag:IMAGE_TAG];
        loginLabel = (UILabel *) [cell.contentView viewWithTag:LOGIN_TAG];
        fullNameLabel = (UILabel *) [cell.contentView viewWithTag:FULL_NAME_TAG];
    }

    // Configure the cell...

    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

    CGRect frame = CGRectMake(0, 0, 44, 44);
    asyncImage = [[[AsyncImageView alloc]initWithFrame:frame] autorelease];
    asyncImage.tag = IMAGE_TAG;
    NSURL* url = [NSURL URLWithString:mySTUser.avatar_url_large];
    [asyncImage loadImageFromURL:url];
    [cell.contentView addSubview:asyncImage];

    loginLabel.tag = LOGIN_TAG;
    CGRect loginLabelFrame = CGRectMake(60, 0, 200, 10);
    loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];
    loginLabel.text = [NSString stringWithFormat:@"%@",mySTUser.login];
    [cell.contentView addSubview:loginLabel];

    fullNameLabel.tag = FULL_NAME_TAG;
    CGRect fullNameLabelFrame = CGRectMake(60, 20, 200, 10);
    fullNameLabel = [[[UILabel alloc] initWithFrame:fullNameLabelFrame] autorelease];
    fullNameLabel.text = [NSString stringWithFormat:@"%@ %@",mySTUser.first_name, mySTUser.last_name]; //[NSString stringWithFormat:@"%@",mySTUser.login];
    [cell.contentView addSubview:fullNameLabel];    


    return cell;
}

---

如果单元格不是nil，则首先从单元格中指定image和labels变量，然后重新初始化它们。对吗？

如果单元格不是nil，则首先从单元格中指定图像和标签变量，然后重新初始化它们。对吗？

此行分配一个对象，然后丢弃它。不要分配您将不使用的项目

STUser *mySTUser = [[[STUser alloc]init]autorelease];
mySTUser = [items objectAtIndex:indexPath.row];

相反，只需声明一个变量并使用它

STUser *mySTUser;
mySTUser = [items objectAtIndex:indexPath.row];

此行创建一个新对象并将其指定给单元，但每次使用单元时都会发生

asyncImage = [[[AsyncImageView alloc]initWithFrame:frame] autorelease];
[cell.contentView addSubview:asyncImage];

相反，将所有addSubview行置于创建单元格的if条件下

if (cell == nil) {
    CGRect frame = CGRectMake(0, 0, 44, 44);
    CGRect loginLabelFrame = CGRectMake(60, 0, 200, 10);
    CGRect fullNameLabelFrame = CGRectMake(60, 20, 200, 10);
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    asyncImage = [[[AsyncImageView alloc]initWithFrame:frame] autorelease];
    [cell.contentView addSubview:asyncImage];
    loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];
    [cell.contentView addSubview:loginLabel];
    fullNameLabel = [[[UILabel alloc] initWithFrame:fullNameLabelFrame] autorelease];
    [cell.contentView addSubview:fullNameLabel];    
    asyncImage.tag = IMAGE_TAG;
    loginLabel.tag = LOGIN_TAG;
    fullNameLabel.tag = FULL_NAME_TAG;
} else ...

if块之外应该发生的唯一事情是分配给每个单元格更改的属性，如

[asyncImage loadImageFromURL:url]并将文本指定给标签

此行将一个属性分配给可能为零的对象，然后分配该对象

loginLabel.tag = LOGIN_TAG;
loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];

loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];
loginLabel.tag = LOGIN_TAG;

而是在创建对象后指定属性

loginLabel.tag = LOGIN_TAG;
loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];

loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];
loginLabel.tag = LOGIN_TAG;

这一行使用了一个格式化的字符串，其中一个简单的赋值就可以了

loginLabel.text = [NSString stringWithFormat:@"%@",mySTUser.login];

相反，假设mySTUser.login，只需直接分配它

loginLabel.text = mySTUser.login;

此行分配一个对象，然后丢弃它。不要分配您将不使用的项目

STUser *mySTUser = [[[STUser alloc]init]autorelease];
mySTUser = [items objectAtIndex:indexPath.row];

相反，只需声明一个变量并使用它

STUser *mySTUser;
mySTUser = [items objectAtIndex:indexPath.row];

此行创建一个新对象并将其指定给单元，但每次使用单元时都会发生

asyncImage = [[[AsyncImageView alloc]initWithFrame:frame] autorelease];
[cell.contentView addSubview:asyncImage];

相反，将所有addSubview行置于创建单元格的if条件下

if (cell == nil) {
    CGRect frame = CGRectMake(0, 0, 44, 44);
    CGRect loginLabelFrame = CGRectMake(60, 0, 200, 10);
    CGRect fullNameLabelFrame = CGRectMake(60, 20, 200, 10);
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    asyncImage = [[[AsyncImageView alloc]initWithFrame:frame] autorelease];
    [cell.contentView addSubview:asyncImage];
    loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];
    [cell.contentView addSubview:loginLabel];
    fullNameLabel = [[[UILabel alloc] initWithFrame:fullNameLabelFrame] autorelease];
    [cell.contentView addSubview:fullNameLabel];    
    asyncImage.tag = IMAGE_TAG;
    loginLabel.tag = LOGIN_TAG;
    fullNameLabel.tag = FULL_NAME_TAG;
} else ...

if块之外应该发生的唯一事情是分配给每个单元格更改的属性，如
[asyncImage loadImageFromURL:url]并将文本指定给标签

此行将一个属性分配给可能为零的对象，然后分配该对象

loginLabel.tag = LOGIN_TAG;
loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];

loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];
loginLabel.tag = LOGIN_TAG;

而是在创建对象后指定属性

loginLabel.tag = LOGIN_TAG;
loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];

loginLabel = [[[UILabel alloc] initWithFrame:loginLabelFrame] autorelease];
loginLabel.tag = LOGIN_TAG;

这一行使用了一个格式化的字符串，其中一个简单的赋值就可以了

loginLabel.text = [NSString stringWithFormat:@"%@",mySTUser.login];

相反，假设mySTUser.login，只需直接分配它

loginLabel.text = mySTUser.login;