Parse.com 保存图像示例。只检索一张图像

Posted 2023-03-08

【中文标题】Parse.com 保存图像示例。只检索一张图像

【英文标题】：Parse.com Saving images sample. retrieve only one image

【发布时间】：2014-09-25 13:07:52

【问题描述】：

我从 parse.com 设置了示例，您可以在其中从相机上传图像，然后在网格视图中显示所有图像。

我想要的是只显示最近拍摄的图像而不是总网格视图。

示例位于此处：Parse example

正在下载图像并将其放置在某种网格视图中。

使用NSMutableArray *allImages;获取所有图片。

输出的图像带有按钮类和指向新视图的链接。

然后新视图只包含来自网格视图（您单击的那个）的图像。

我不想下载所有图像并将它们放在网格视图中 - 只是为了显示最新图像。

他们用于将图像从小缩略图获取到完整图像视图的代码是这样的：

// When picture is touched, open a viewcontroller with the image
    PFObject *theObject = (PFObject *)[allImages objectAtIndex:[sender tag]];
    PFFile *theImage = [theObject objectForKey:@"imageFile"];

    NSData *imageData;
    imageData = [theImage getData];
    UIImage *selectedPhoto = [UIImage imageWithData:imageData];
    PhotoDetailViewController *pdvc = [[PhotoDetailViewController alloc] init];

    pdvc.selectedImage = selectedPhoto;
    [self presentViewController:pdvc animated:YES completion:nil];

获取allImages的代码如下：

// Contains a list of all the BUTTONS
    allImages = [images mutableCopy];

    // This method sets up the downloaded images and places them nicely in a grid
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_async(queue, ^
        NSMutableArray *imageDataArray = [NSMutableArray array];

        // Iterate over all images and get the data from the PFFile
        for (int i = 0; i < images.count; i++) 
            PFObject *eachObject = [images objectAtIndex:i];
            PFFile *theImage = [eachObject objectForKey:@"imageFile"];
            NSData *imageData = [theImage getData];
            UIImage *image = [UIImage imageWithData:imageData];
            [imageDataArray addObject:image];
        

        // Dispatch to main thread to update the UI
        dispatch_async(dispatch_get_main_queue(), ^
            // Remove old grid
            for (UIView *view in [photoScrollView subviews]) 
                if ([view isKindOfClass:[UIButton class]]) 
                    [view removeFromSuperview];
                
            

            // Create the buttons necessary for each image in the grid
            for (int i = 0; i < [imageDataArray count]; i++) 
                PFObject *eachObject = [images objectAtIndex:i];
                UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
                UIImage *image = [imageDataArray objectAtIndex:i];
                [button setImage:image forState:UIControlStateNormal];
                button.showsTouchWhenHighlighted = YES;
                [button addTarget:self action:@selector(buttonTouched:) forControlEvents:UIControlEventTouchUpInside];
                button.tag = i;
                button.frame = CGRectMake(THUMBNAIL_WIDTH * (i % THUMBNAIL_COLS) + PADDING * (i % THUMBNAIL_COLS) + PADDING,
                                          THUMBNAIL_HEIGHT * (i / THUMBNAIL_COLS) + PADDING * (i / THUMBNAIL_COLS) + PADDING + PADDING_TOP,
                                          THUMBNAIL_WIDTH,
                                          THUMBNAIL_HEIGHT);
                button.imageView.contentMode = UIViewContentModeScaleAspectFill;
                [button setTitle:[eachObject objectId] forState:UIControlStateReserved];
                [photoScrollView addSubview:button];
            

            // Size the grid accordingly
            int rows = images.count / THUMBNAIL_COLS;
            if (((float)images.count / THUMBNAIL_COLS) - rows != 0) 
                rows++;
            
            int height = THUMBNAIL_HEIGHT * rows + PADDING * rows + PADDING + PADDING_TOP;

            photoScrollView.contentSize = CGSizeMake(self.view.frame.size.width, height);
            photoScrollView.clipsToBounds = YES;
        );
    );

我不是 ios 编码方面的专家，我只是在寻找一种简单的解决方案来显示最近发布的图像。

【问题讨论】：

您是要获取所有图像并呈现最近的图像，还是仅获取最近的图像并呈现它？

对我来说这并不重要。无论是最省电的手机还是最简单的方式。我只需要显示在 UIImageView 中拍摄的最近图像。 Ty 回复

【参考方案1】：

查看发布的示例代码，修改它以仅处理一个图像（主要是删除很多同步对象 id 的恶心）将是一项艰巨的任务。如果您只想以最快的方式开始使用，您可以这样做：

// ...
// where you do the query for UserPhoto
[query orderByAscending:@"createdAt"];

// use the getFirst form of the query
[query getFirstObjectInBackgroundWithBlock:^(PFObject *object, NSError *error) 
    if (!error) 
        // build the objects array that the demo code expects, but out of just one object
        NSArray *objects = @[ object ];
        // the remainder of the code as it is

很多 UI 代码也可以变得更简单。但关键是跳过所有网格/按钮构建代码并执行以下操作：

 // ...
 // inside the method called setUpImages:
 // this loop will only run once since we have only one object in the array
 for (int i = 0; i < [imageDataArray count]; i++) 
     PFObject *eachObject = [images objectAtIndex:i];
     UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
     UIImage *image = [imageDataArray objectAtIndex:i];

     // you're essentially done here.  add a big image view
     // that replaces photoScrollView, then:
     self.myBigImageView.image = image;

希望对您有所帮助。

【讨论】：

泰。我以前不明白你的帖子。我会试试这个并回复你。