Question

我正在构建一篇阅读app的文章。我以JSON格式从服务器获取数据并加载到UITableView中 UIWebView。
一篇文章包含图片，视频和文字。我想做离线缓存的意思，如果没有互联网用户可以阅读以前加载的我已经使用了异步线程来处理图像。

这是我的代码：

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self checkInternetConnection];
    UILabel *titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(20,10,0,20)];
    titleLabel.textColor = [UIColor blackColor];
    titleLabel.backgroundColor = [UIColor clearColor];
    titleLabel.text = @"Story";
    [self.navigationItem setTitleView:titleLabel];

    UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
    spinner.center = CGPointMake(160, 240);
    spinner.hidesWhenStopped = YES;
    [self.view addSubview:spinner];
    [spinner startAnimating];
    BOOL myBool = [self isNetworkAvailable];
    if (myBool)
    {
        @try {

            self.tableView.separatorColor = [UIColor colorWithRed:190/255.0 green:190/255.0 blue:190/255.0 alpha:1.0];

            // for displaying the previous screen lable with back button in details view controller        UIBarButtonItem *backbutton1 = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStyleBordered target:nil action:nil];
            [[self navigationItem] setBackBarButtonItem:backbutton1];
            _Title1 = [[NSMutableArray alloc] init];
            _Author1 = [[NSMutableArray alloc] init];
            _Images1 = [[NSMutableArray alloc] init];
            _Details1 = [[NSMutableArray alloc] init];
            _link1 = [[NSMutableArray alloc] init];
            _Date1 = [[NSMutableArray alloc] init];
            pageNumber=1;
            NSData* data = [NSData dataWithContentsOfURL:ysURL];
            NSArray *ys_avatars = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
            if(ys_avatars){
                for (int j=0;j<ys_avatars.count;j++)
                {
                    [_Title1 addObject:ys_avatars[j][@"title"]];
                    [_Author1 addObject: ys_avatars[j][@"author"]];
                    [_Images1 addObject: ys_avatars[j][@"featured_img"]];
                    [_Details1 addObject:ys_avatars[j][@"content"]];
                    [_link1 addObject:ys_avatars[j][@"permalink"]];
                    NSString *newStr=[ys_avatars[j][@"date"] substringToIndex:[ys_avatars[j]        [@"date"] length]-3];
                    [_Date1 addObject:newStr];
                }
            }
            else
            {
                NSLog(@"asd");
            }
        }
        @catch (NSException *exception) {

        }
        dispatch_queue_t downloadQueue = dispatch_queue_create("downloader", NULL);
        dispatch_async(downloadQueue, ^{
            // do our long running process here
            [NSThread sleepForTimeInterval:3];
            // do any UI stuff on the main UI thread
            dispatch_async(dispatch_get_main_queue(), ^{
                [spinner stopAnimating];
            });
        });
    }
}

- (UITableViewCell *)tableView:(UITableView *)tableView
         cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *Cellidentifier1 = @"ysTableViewCell";
    ysTableViewCell *cell1 = [tableView      dequeueReusableCellWithIdentifier:Cellidentifier1 forIndexPath:indexPath];
    long row = [indexPath row];
    cell1.TitleLabel1.text = _Title1[row];
    cell1.AuthorLabel1.text = _Author1[row];
    NSString *yourStoryUrl = [_Images1[indexPath.row]  stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding];
    if(yourStoryUrl) {
        NSArray *subStringsUrl = [yourStoryUrl componentsSeparatedByString:@"/"];
        NSString *stripedName = [subStringsUrl lastObject];
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,  NSUserDomainMask, YES);
        NSString *documentsDirectory = [paths objectAtIndex:0];
        NSString* filePath =[documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@",stripedName]];
        NSLog(@"File Path retrieved %@", filePath);
        if(filePath) {
            UIImage *image = [UIImage imageWithContentsOfFile:filePath];
            if(image) {
                ysTableViewCell  *updateCell =(id)[tableView cellForRowAtIndexPath:indexPath];
                if(updateCell)
                    updateCell.ThumbImage1.image=image;
                cell1.ThumbImage1.image=image;
            } else {
                dispatch_queue_t taskQ = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
                dispatch_async(taskQ, ^{
                    NSURL *Imageurl = [NSURL URLWithString:yourStoryUrl];
                    NSData *data =  [NSData dataWithContentsOfURL:Imageurl];
                    UIImage *images1 = [[UIImage alloc] initWithData:data];
                    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
                    NSString *documentsDirectory = [paths objectAtIndex:0];
                    NSData *imageData = UIImagePNGRepresentation(images1);
                    //_imagePath =[documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",stripedName]];
                    if (![imageData writeToFile:filePath atomically:NO])
                    {
                        NSLog((@"Failed to cache image data to disk"));
                    }
                    else
                    {
                        NSLog((@"the cachedImagedPath is %@",filePath));
                    }
                    dispatch_sync(dispatch_get_main_queue(), ^{
                        ysTableViewCell  *updateCell =(id)[tableView cellForRowAtIndexPath:indexPath];
                        if(updateCell)
                            updateCell.ThumbImage1.image=images1;
                        cell1.ThumbImage1.image=images1;
                    });
                });
                return cell1;
            }

Answer 1

对于离线商店，您已制作一个sqlite文件，将从JSON获取的所有详细信息存储到数据库中。在数据库中仅存储图像和视频的文件路径。下载这些资产并将其存储在文档目录中。

感谢。

Answer 2

您可以使用密钥存档（NSKeyedArchiver/NSKeyedUnarchiver）

这是tutorial

如何在iOS中实现离线缓存文章阅读应用程序？

2 个答案: