我有一个显示图片和文字的UITableView。它是一个社交应用程序，所以我必须从数据库中检索所有数据，我正在使用Parse。继承人的代码。我知道它很长，但如果你可以掠过它那将是伟大的。我有三个不同的自定义单元格（笔尖）将根据内容加载。一个cell - 只是一个字符串帖子，groupPost - 也是一个字符串帖子，一个imageCell - 用于图片帖子。我很困惑如何制作更流畅的滚动，如facebooks或instagrams。我应该如何加载图像，并检索数据？我查看了帖子并看到了缓存它的建议，但不确定如何做到这一点。谢谢你的帮助
postCell *cell = (postCell *)[tableView dequeueReusableCellWithIdentifier:@"postCell"];
groupPostCell *groupPost = (groupPostCell *) [self.tableView dequeueReusableCellWithIdentifier:@"groupPostCell"];
pictureCell *imageCell = (pictureCell *) [self.tableView dequeueReusableCellWithIdentifier:@"imageCell"];
PFObject *object = [self.friendPosts objectAtIndex:indexPath.row];
if ([object objectForKey:@"Image"] != nil) {
if (imageCell == nil) {
imageCell = [[pictureCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"imageCell"];
}
PFFile *file = [object objectForKey:@"Image"];
NSData *data = [file getData];
imageCell.imagePost.image = [UIImage imageWithData:data];
imageCell.caption.text = [object objectForKey:@"stringPost"];
PFFile *profileFile = [object objectForKey:@"profileImage"];
NSData *profileData = [profileFile getData];
imageCell.profileImage.image = [UIImage imageWithData:profileData];
[imageCell.name setTitle:[object objectForKey:@"User_Name"] forState:UIControlStateNormal];
[imageCell.eventButton setTitle:[object objectForKey:@"Event"] forState:UIControlStateNormal];
imageCell.name.hidden = false;
imageCell.eventButton.hidden = false;
imageCell.name.tag = indexPath.row;
imageCell.profileImageButton.tag = indexPath.row;
imageCell.eventButton.tag = indexPath.row;
[imageCell.name addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];
[imageCell.profileImageButton addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];
[imageCell.eventButton addTarget:self action:@selector(eventPage:) forControlEvents:UIControlEventTouchUpInside];
NSArray *likesArray = [object objectForKey:@"likes"];
NSString *likeString = [NSString stringWithFormat:@"%lu Likes", (unsigned long)likesArray.count];
if ([likesArray containsObject:[PFUser currentUser].objectId]) {
imageCell.rateButton.hidden = true;
}
else{
imageCell.rateButton.hidden = false;
}
NSArray *commentArray = [object objectForKey:@"Comments"];
NSString *commentString = [NSString stringWithFormat:@"%lu Comments", (unsigned long)commentArray.count];
[imageCell.likesButton setTitle:likeString forState:UIControlStateNormal];
[imageCell.commentsButton setTitle:commentString forState:UIControlStateNormal];
imageCell.rateButton.tag = indexPath.row;
imageCell.likesButton.tag = indexPath.row;
imageCell.commentsButton.tag = indexPath.row;
imageCell.flagButton.tag = indexPath.row;
[imageCell.rateButton addTarget:self action:@selector(like:) forControlEvents:UIControlEventTouchUpInside];
[imageCell.likesButton addTarget:self action:@selector(likesPage:) forControlEvents:UIControlEventTouchUpInside];
[imageCell.commentsButton addTarget:self action:@selector(imageComment:) forControlEvents:UIControlEventTouchUpInside];
[imageCell.flagButton addTarget:self action:@selector(flagPost:) forControlEvents:UIControlEventTouchUpInside];
[imageCell.timeButton setTitle:[self getDaysBetween:object.createdAt] forState:UIControlStateNormal];
return imageCell;
}
if ([object objectForKey:@"Group"] == nil) {
if (cell == nil) {
cell = [[postCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"postCell"];
}
cell.personStringPost.text = [object objectForKey:@"stringPost"];
if ([object objectForKey:@"Event"] == nil) {
[cell.noEventNameButton setTitle:[object objectForKey:@"User_Name"] forState:UIControlStateNormal];
cell.noEventNameButton.tag = indexPath.row;
[cell.noEventNameButton addTarget:self action:@selector(buttonPressed:) forControlEvents: UIControlEventTouchUpInside];
cell.nameLabel.hidden = true;
cell.eventLabel.hidden = true;
cell.noEventNameButton.hidden = false;
}
else{
[cell.nameLabel setTitle:[object objectForKey:@"User_Name"] forState:UIControlStateNormal];
cell.nameLabel.tag = indexPath.row;
[cell.nameLabel addTarget:self action:@selector(buttonPressed:) forControlEvents: UIControlEventTouchUpInside];
cell.noEventNameButton.hidden = true;
cell.nameLabel.hidden = false;
cell.eventLabel.hidden = false;
[cell.eventLabel setTitle:[object objectForKey:@"Event"] forState:UIControlStateNormal];
[cell.eventLabel addTarget:self action:@selector(eventPage:) forControlEvents:UIControlEventTouchUpInside];
}
[cell.timeLabel setTitle:[self getDaysBetween:object.createdAt] forState:UIControlStateNormal];
PFFile *imageFile = [object objectForKey:@"profileImage"];
NSData *data = [imageFile getData];
cell.profileImage.image = [UIImage imageWithData:data];
NSArray *likesArray = [object objectForKey:@"likes"];
NSString *likeString = [NSString stringWithFormat:@"%lu Likes", (unsigned long)likesArray.count];
if ([likesArray containsObject:[PFUser currentUser].objectId]) {
cell.likeButton.hidden = true;
}
else{
cell.likeButton.hidden = false;
}
NSArray *commentArray = [object objectForKey:@"Comments"];
NSString *commentString = [NSString stringWithFormat:@"%lu Comments", (unsigned long)commentArray.count];
[cell.likePage setTitle:likeString forState:UIControlStateNormal];
[cell.commentButton setTitle:commentString forState:UIControlStateNormal];
cell.eventLabel.tag = indexPath.row;
cell.profileImageButton.tag = indexPath.row;
cell.likeButton.tag = indexPath.row;
cell.commentButton.tag = indexPath.row;
cell.likePage.tag = indexPath.row;
cell.flagButton.tag = indexPath.row;
[cell.flagButton addTarget:self action:@selector(flagPost:) forControlEvents:UIControlEventTouchUpInside];
[cell.profileImageButton addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];
[cell.likePage addTarget:self action:@selector(likesPage:) forControlEvents:UIControlEventTouchUpInside];
[cell.likeButton addTarget:self action:@selector(like:) forControlEvents:UIControlEventTouchUpInside];
[cell.commentButton addTarget:self action:@selector(commentsPage:) forControlEvents:UIControlEventTouchUpInside];
return cell;
}
if ([object objectForKey:@"Group"] != nil) {
if (groupPost == nil) {
groupPost = [[groupPostCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"groupPostCell"];
}
[groupPost.groupNameButton setTitle:[object objectForKey:@"Group"] forState:UIControlStateNormal];
groupPost.groupNameButton.tag = indexPath.row;
[groupPost.groupNameButton addTarget:self action:@selector(groupPage:) forControlEvents:UIControlEventTouchUpInside];
[groupPost.groupNameButton setTitleColor:[self checkType:[object objectForKey:@"Type"]] forState:UIControlStateNormal];
NSArray *likesArray = [object objectForKey:@"likes"];
NSString *likeString = [NSString stringWithFormat:@"%lu Likes", (unsigned long)likesArray.count];
if ([likesArray containsObject:[PFUser currentUser].objectId]) {
groupPost.likeButton.hidden = true;
}
else{
groupPost.likeButton.hidden = false;
}
NSArray *commentArray = [object objectForKey:@"Comments"];
NSString *commentString = [NSString stringWithFormat:@"%lu Comments", (unsigned long)commentArray.count];
[groupPost.likePage setTitle:likeString forState:UIControlStateNormal];
[groupPost.commentsButton setTitle:commentString forState:UIControlStateNormal];
groupPost.likePage.tag = indexPath.row;
groupPost.likeButton.tag = indexPath.row;
groupPost.commentsButton.tag = indexPath.row;
[groupPost.likeButton addTarget:self action:@selector(like:) forControlEvents:UIControlEventTouchUpInside];
[groupPost.likePage addTarget:self action:@selector(likesPage:) forControlEvents:UIControlEventTouchUpInside];
[groupPost.commentsButton addTarget:self action:@selector(commentsPage:) forControlEvents:UIControlEventTouchUpInside];
if ([object objectForKey:@"Event"] == nil) {
groupPost.eventButton.hidden = true;
}
else{
groupPost.eventButton.hidden = false;
[groupPost.eventButton setTitle:[object objectForKey:@"Event"] forState:UIControlStateNormal];
groupPost.eventButton.tag = indexPath.row;
[groupPost.eventButton addTarget:self action:@selector(eventPage:) forControlEvents:UIControlEventTouchUpInside];
}
groupPost.flagButton.tag = indexPath.row;
[groupPost.flagButton addTarget:self action:@selector(flagPost:) forControlEvents:UIControlEventTouchUpInside];
[groupPost.timeButton setTitle:[self getDaysBetween:object.createdAt] forState:UIControlStateNormal];
groupPost.postLabel.text = [object objectForKey:@"stringPost"];
return groupPost;
}
答案 0 :(得分：0)
每当您处理服务器上的数据时，请尽量避免不惜一切代价同步加载数据。该行
NSData *data = [imageFile getData];[imageFile getData];
将使得在完成下载数据之前，其他任何东西都无法在主线程上执行。这是你应该怎么做的：
[imageFile getDataInBackgroundWithBlock:^(NSData *imageData, NSError *error) {
if (!error) {
cell.profileImage.image = [UIImage imageWithData:imageData];
}
}];
这将使得所有其他代码在主线程上执行，然后当数据完成下载时，它将加载到图像中。我建议在“cell.profileImage”中放置占位符或加载视图，然后当从Parse加载图像时，它将覆盖该占位符。