ios开发：如何加载大量图片相册示例

最新推荐文章于 2025-06-02 01:11:15 发布

转载最新推荐文章于 2025-06-02 01:11:15 发布 · 171 阅读

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原文链接：http://www.cnblogs.com/xiongqiangcs/archive/2013/06/13/3134486.html

文章标签：

#移动开发 #ui

本文介绍如何使用NSOperationQueue实现iOS应用中500张图片的后台批量下载，并通过NSInvocationOperation进行任务调度。同时，文章提供了详细的代码示例，包括图片加载、显示等关键步骤。

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1. Create a NSOperationQueue to handle background downloading.

NSOperationQueue *operationQueue = [[NSOperationQueue alloc]init];

2. Now create an NSInvocationOperation for each image that you want to download and add it to operationQueue.

int noOfImages = 500;
for(int i = 0; i  noOfImages; i++)
{
NSInvocationOperation *invocationOperation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(loadDataAsychn:) object:i];
[queue addOperation:invocationOperation];
[operation release];
}

In this code, we have created an operation calling loadDataAsynchn: method which is to be implemented and added to queue. After adding created operation to the queue, it will do the rest of the downloading work for your app. You can add more operations to the same queue to be performed later.

Now we will implement loadDataAsychn method.

3. Implement loadDataAsychn method for loading data from the given URL, creating an image and setting it to desired placeholder.

-(void)loadDataAsychn:(NSString*)imageNo
{
NSString *imgStr = [NSString stringWithFormat:@"http://192.168.0.163/Test/images/%@.jpg",imageNo];
NSData *imageData=[[NSData alloc] initWithContentsOfURL: [NSURL URLWithString:imgStr]];
UIImage *image=[[UIImage alloc]initWithData:imageData];
[imgDict setValue:image forKey:@"image"];
[imgDict setValue:imageNo forKey:@"imageNo"];
[self performSelectorOnMainThread:@selector(showImg:) withObject:imgDict waitUntilDone:NO];
}

The loadDataAsychn method is used to download the information from a given URL and creating an image with downloaded data. As we all know that none of the UI related methods can be performed on background thread. So, in loadDataAsychn method, we call showImage method on the main thread to display images.

4. We will now implement showImage which is responsible for updating UI.

(void)showImage:(NSMutableDictionary *)Dict
{
int i = [[Dict objectForKey:@"imageNo"] intValue];
UIImageView *imgView = [[UIImageView alloc] initWithFrame:CGRectMake(320*(i-1), 0, 320, 460)];
[imgView setImage:[Dict objectForKey:@"image"]];
[myScrollView addSubview:imgView];
}