快速将图像从设备加载到tableView

Question

我在网上找不到有关从设备加载图像并通过tableview平滑滚动的任何信息。 关于这一点， 雷文上有一篇，但对我的情况并没有真正帮助我。

是否有人有任何建议或代码可帮助使tableview平滑滚动并从设备的临时目录加载图像？

Answer 1

我确实按照教程中所述进行了操作，但是对nsoperation子类进行了修改

这是获取方法

-(void) updateData
{


    [self.pendingOperations.downloadQueue addOperationWithBlock:^{
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *documentsDirectory = [paths objectAtIndex:0];
        NSArray *filePathes = [self recursiveRecordsForResourcesOfType:@[@"png", @"jpeg", @"jpg",@"pdf"] inDirectory:documentsDirectory];
        @synchronized (self) {
            self.documents = filePathes;
            NSLog(@"documents count %@", @([self.documents count]));
        }
        dispatch_async(dispatch_get_main_queue(), ^(void){
            //Run UI Updates
            [self.delegate modelDidUpdate:self];
        });

    }];


}

- (NSArray *)recursiveRecordsForResourcesOfType:(NSArray *)types inDirectory:(NSString *)directoryPath{

    NSMutableArray *filePaths = [[NSMutableArray alloc] init];

    NSMutableDictionary *typesDic = [NSMutableDictionary dictionary];
    for (NSString *type in types)
         [typesDic setObject:type forKey:type];

    // Enumerators are recursive
    NSDirectoryEnumerator *enumerator = [[NSFileManager defaultManager] enumeratorAtPath:directoryPath];

    NSString *filePath;

    while ((filePath = [enumerator nextObject]) != nil){

        // If we have the right type of file, add it to the list
        // Make sure to prepend the directory path
        if([typesDic objectForKey:[filePath pathExtension]]){
            //[filePaths addObject:[directoryPath stringByAppendingPathComponent:filePath]];
            CURFileRecord *record = [CURFileRecord new];
            record.filePath =[directoryPath stringByAppendingPathComponent:filePath];
            record.fileName = filePath;
            [filePaths addObject:record];
        }
    }


    return filePaths;
}

这是子类的.m

- (void)main {

    // 4
    @autoreleasepool {

        if (self.isCancelled)
            return;
        NSData *fileData = [[NSFileManager defaultManager] contentsAtPath:self.fileRecord.filePath];
       // self.fileRecord.fileData = fileData;
        if (self.isCancelled) {
            fileData = nil;
            return;
        }

        if (fileData) {
            UIImage *newImage;
            if ([[self.fileRecord.filePath pathExtension] isEqualToString:@"pdf"])
            {
                CGPDFDocumentRef doc = [CURDocumentViewerUtilities MyGetPDFDocumentRef:fileData];
                newImage = [CURDocumentViewerUtilities buildThumbnailImage:doc withSize:CGSizeMake(64, 96)];
            }
            else
            {
                newImage = [CURDocumentViewerUtilities makePreviewImageFromData:fileData];
            }
            self.fileRecord.previewImage = newImage;
        }
        else {
            self.fileRecord.failed = YES;
        }

        fileData = nil;

        if (self.isCancelled)
            return;

        // 5
        [(NSObject *)self.delegate performSelectorOnMainThread:@selector(imageDownloaderDidFinish:) withObject:self waitUntilDone:NO];

    }
}

使用update func，我已经获取了处理的路径，并且nsoperation子类加载了图像。 全高清可完美处理2000张图像-平稳且无任何延迟