Question

我正在查询我的解析数据库以从特定表中下载图像。一切正常，除非我认为是一个小故障。

仅在我稍微滚动UITableView时才会显示图像。

是的我正在异步下载图像。

干杯

更新

PFQuery *imageQuery = [PFQuery queryWithClassName:@"WallImageObject"];
    //[imageQuery orderByAscending:@"createdAt"];
    [imageQuery whereKey:@"geoPoint" nearGeoPoint:currentLocationInGeoPoint withinKilometers:3.0];
    NSLog(@"PFGeoPoint current location: %f and %f", currentLocationInGeoPoint.latitude, currentLocationInGeoPoint.longitude);
    [imageQuery findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error){
        if (error)
        {
            NSLog(@"Error retreiving images: %@", error.localizedDescription);
        }else
        {
            for (PFObject *wallImageObject in objects) {
                WallImage *wallImage = [[WallImage alloc] init];
                wallImage.fbID = wallImageObject[@"UserId"];
                wallImage.username = wallImageObject[@"userName"];
                wallImage.createdAt = wallImageObject.createdAt;

                [[NSOperationQueue pffileOperationQueue]addOperationWithBlock:^{
                    wallImage.image = [UIImage imageWithData:[(PFFile *)wallImageObject[@"image"] getData]];
                    [[NSNotificationCenter defaultCenter]postNotificationName:N_ImageDownloaded object:nil];
                }];

                wallImage.imageID = wallImageObject.objectId;
                wallImage.geoPoint = wallImageObject[@"geoPoint"];
                NSLog(@"Image latitude: %f and londitude %f", wallImage.geoPoint.latitude, wallImage.geoPoint.longitude);
                [[DataStore instance].wallImages addObject:wallImage];
            }
            NSLog(@"%lu images in this location", (unsigned long)[[DataStore instance].wallImages count]);
            if ([delegate respondsToSelector:@selector(communicationDidGetWallImages:)]) {
                [delegate communicationDidGetWallImages:YES];
            }
        }

在这里我展示图片

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Post";
    FeedPhotoCell *feedPhotoCell = (FeedPhotoCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    WallImage *wallImage = [DataStore instance].wallImages[indexPath.row];

    [feedPhotoCell.photoPost setImage:wallImage.image];

    NSString *facebbokUserID = wallImage.fbID;
    NSString *urlString = [NSString stringWithFormat:@"https://graph.facebook.com/%@/picture?type=large",facebbokUserID];
    NSURL *facebookProfilePicURL = [NSURL URLWithString:urlString];

    [feedPhotoCell.profilePhoto setImageWithURL:facebookProfilePicURL];
    feedPhotoCell.profilePhoto.layer.cornerRadius = 10.0;
    feedPhotoCell.profilePhoto.layer.borderColor = [UIColor orangeColor].CGColor;
    feedPhotoCell.profilePhoto.layer.borderWidth = 1.0;
    feedPhotoCell.profilePhoto.clipsToBounds = YES;

    NSLog(@"image cell height: %f", feedPhotoCell.photoPost.image.size.height);

    return feedPhotoCell;
}

Answer 1

如果图像占用大量内存，则会将其删除以释放内存。

然后，当您的表视图尝试绘制它们时，它必须再次下载它们，这需要时间。

解决方案是将图像下载到手机上的磁盘，然后从磁盘上的文件中加载图像。

在向下滚动之前，图像不会显示在TableViewCells中

1 个答案: