![](/img/trans.png)
[英]“cellForRowAtIndexPath” for a tableview inside alertviewcontroller not called
[英]cellForRowAtIndexPath always nil when called from block inside tableView:cellForRowAtIndexPath:
我从cellView:cellForRowAtIndexPath调用时,cellForRowAtIndexPath总是返回nil的问题:
问题是我实际上是在tableView:cellForRowAtIndexPath:内的一个块内调用cellForRowAtIndexPath:我想这可能是问题所在。
我正在用临时加载(和缓存)远程图像填充单元。 当图像在完成处理程序块中返回满载时(在tableView:cellForRowAtIndexPath:内部),我需要再次获取该单元格,因为它可能已滚动出视图...所以我调用cellForRowAtIndexPath再次获取该单元格-cellForRowAtIndexPath仅返回一个单元格(如果可见)。 就我而言,除了nil之外,我什么也无法返回。 即使我滚动得非常慢(或快,或我尝试过的任何速度...),我得到的还是零。
我会尽快在这里获取一些代码,但是在那之前,为什么会出现这种情况的任何建议-我想块状的东西都是一个提示。
这是代码: https : //dl.dropboxusercontent.com/u/147970342/stackoverflow/appsappsappsappsapps.zip
-tableView:cellForRowAtIndexPath:实现:
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSNumber* numberAppleid = self.appids[indexPath.row];
UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:@"Mycell" forIndexPath:indexPath];
cell.textLabel.text = [NSString stringWithFormat:@"Appleid: %@", numberAppleid];
NSString* appleidasstring = [NSString stringWithFormat:@"%@", numberAppleid];
cell.imageView.hidden = YES; // Hide any previous until image loads
[self getAppIconForAppleid:appleidasstring handlerImage:^(UIImage *image) {
if (image == nil) {
return;
}
DLog(@"cellForRowAtIndexPath tableView: %@, indexPath: %@", tableView, indexPath);
UITableViewCell* localcell = [tableView cellForRowAtIndexPath:indexPath];
if (localcell != nil) {
localcell.imageView.image = image;
localcell.imageView.hidden = NO;
}
else {
DLog(@"Nah indexpath is not visible for: %@ because localcell is nil.", appleidasstring);
}
}];
return cell;
}
固定版本:
#define KEYAPPLEID @"keyappleid"
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSNumber* numberAppleid = self.appids[indexPath.row];
UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:@"Mycell" forIndexPath:indexPath];
cell.textLabel.text = [NSString stringWithFormat:@"Appleid: %@", numberAppleid];
NSString* appleidasstring = [NSString stringWithFormat:@"%@", numberAppleid];
[cell setAssociativeObject:appleidasstring forKey:KEYAPPLEID];
cell.imageView.hidden = YES; // Hide any previous until image loads
[self getAppIconForAppleid:appleidasstring handlerImage:^(UIImage *image) {
if (image == nil) {
return;
}
NSString* currentappleidofcell = [cell associativeObjectForKey:KEYAPPLEID];
if ([currentappleidofcell isEqualToString:appleidasstring]) {
cell.imageView.image = image;
cell.imageView.hidden = NO;
}
else {
DLog(@"Returning appleid: %@ is not matching current appleid: %@", appleidasstring, currentappleidofcell);
}
}];
return cell;
}
并且此类别是必需的: https : //stackoverflow.com/a/10319083/129202
如果该块位于tableView:cellForRowAtIndexPath:
回调内,则可以直接在该块中引用该单元格。 块将自动保持单元周围,直到块消失。 但是,请注意保留周期。 如果该块归单元所有,则必须对单元使用弱引用。
因此,您的实现应如下所示:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSNumber* numberAppleid = self.appids[indexPath.row];
// Create your own UITableViewCell subclass that has an "appleidasstring" property
MyTableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:@"Mycell" forIndexPath:indexPath];
cell.textLabel.text = [NSString stringWithFormat:@"Appleid: %@", numberAppleid];
NSString* appleidasstring = [NSString stringWithFormat:@"%@", numberAppleid];
cell.imageView.hidden = YES; // Hide any previous until image loads
// Set the appleidasstring on the cell to be checked later
cell. getAppIconForAppleid:appleidasstring = appleidasstring;
// Modify the handler callback to also callback with the appleidasstring
[self
getAppIconForAppleid:appleidasstring
handlerImage:^(UIImage *image, NSString *imageAppleIdaString)
{
if (image == nil) {
return;
}
// Ensure the cell hasn't been repurposed for a
// different imageAppleIdaString
if ([cell.appleidasstring isEqualToString:imageAppleIdaString]) {
cell.imageView.image = image;
cell.imageView.hidden = NO;
}
}
];
return cell;
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.