用NSOperation写下载队列
说明
1. 支持缓存机制
2. 图片都是在主线程中加载
3. 文件名用了md5加密
*这东西被人写烂了,但大伙如果对NSOperation不熟悉的话,可以看看本人的实现.
源码
https://github.com/YouXianMing/NSOperationExample
//
// ImageDownloadOperation.h
// NSOperationDownloadImage
//
// Created by YouXianMing on 15/9/7.
// Copyright (c) 2015年 YouXianMing. All rights reserved.
//
#import <Foundation/Foundation.h>
@class ImageDownloadOperation;
@protocol ImageDownloadOperationDelegate <NSObject>
@required
- (void)imageDownloadOperation:(ImageDownloadOperation *)operation data:(NSData *)data;
@end
@interface ImageDownloadOperation : NSOperation {
BOOL _executing;
BOOL _finished;
}
/**
* 代理
*/
@property (nonatomic, weak) id <ImageDownloadOperationDelegate> delegate;
/**
* 图片地址
*/
@property (nonatomic, strong) NSString *imageUrlString;
/**
* 便利构造器
*
* @param urlString 图片地址
* @param delegate 代理
*
* @return 实例对象
*/
+ (instancetype)operationWithImageUrlString:(NSString *)urlString
delegate:(id <ImageDownloadOperationDelegate>)delegate;
@end//
// ImageDownloadOperation.m
// NSOperationDownloadImage
//
// Created by YouXianMing on 15/9/7.
// Copyright (c) 2015年 YouXianMing. All rights reserved.
//
#import "ImageDownloadOperation.h"
#import <CommonCrypto/CommonDigest.h>
@interface ImageDownloadOperation ()
@property (nonatomic, strong) NSURLConnection *connection;
@property (nonatomic, strong) NSString *md5String;
@property (nonatomic, strong) NSString *filePathString;
@end
@implementation ImageDownloadOperation
- (void)main {
// 验证图片地址是否为空
if (_imageUrlString.length <= 0) {
[self delegateEventWithData:nil];
[self completeOperation];
return;
}
// 生成文件路径
self.md5String = [self MD5HashWithString:_imageUrlString];
self.filePathString = [self pathWithFileName:self.md5String];
// 文件如果存在则直接读取
BOOL exist = [[NSFileManager defaultManager] fileExistsAtPath:self.filePathString isDirectory:nil];
if (exist) {
[self delegateEventWithData:[NSData dataWithContentsOfFile:self.filePathString]];
[self completeOperation];
return;
}
NSURL *url = [NSURL URLWithString:_imageUrlString];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
self.connection = [NSURLConnection connectionWithRequest:request delegate:self];
// 让线程不结束
do {
@autoreleasepool {
[[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:0.1]];
if (self.isCancelled) {
[self completeOperation];
}
}
} while (self.isExecuting && self.isFinished == NO);
}
#pragma mark - 网络代理
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[self writeData:data toPath:self.filePathString];
[self delegateEventWithData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[self completeOperation];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
[self delegateEventWithData:nil];
[self completeOperation];
}
#pragma mark -
+ (instancetype)operationWithImageUrlString:(NSString *)urlString
delegate:(id <ImageDownloadOperationDelegate>)delegate {
ImageDownloadOperation *operation = [[ImageDownloadOperation alloc] init];
operation.delegate = delegate;
operation.imageUrlString = urlString;
return operation;
}
#pragma mark -
- (void)completeOperation {
[self willChangeValueForKey:@"isFinished"];
[self willChangeValueForKey:@"isExecuting"];
_executing = NO;
_finished = YES;
[self didChangeValueForKey:@"isExecuting"];
[self didChangeValueForKey:@"isFinished"];
}
- (void)start {
if ([self isCancelled]) {
[self willChangeValueForKey:@"isFinished"];
_finished = YES;
[self didChangeValueForKey:@"isFinished"];
return;
}
[self willChangeValueForKey:@"isExecuting"];
[NSThread detachNewThreadSelector:@selector(main) toTarget:self withObject:nil];
_executing = YES;
[self didChangeValueForKey:@"isExecuting"];
}
- (BOOL)isExecuting {
return _executing;
}
- (BOOL)isFinished {
return _finished;
}
- (BOOL)isConcurrent {
return YES;
}
#pragma mark -
- (NSString *)MD5HashWithString:(NSString *)string {
CC_MD5_CTX md5;
CC_MD5_Init(&md5);
CC_MD5_Update(&md5, [string UTF8String], (CC_LONG) [string length]);
unsigned char digest[CC_MD5_DIGEST_LENGTH];
CC_MD5_Final(digest, &md5);
NSString *s = [NSString stringWithFormat: @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
digest[0], digest[1],
digest[2], digest[3],
digest[4], digest[5],
digest[6], digest[7],
digest[8], digest[9],
digest[10], digest[11],
digest[12], digest[13],
digest[14], digest[15]];
return s;
}
- (NSString *)pathWithFileName:(NSString *)name {
NSString *path = [NSString stringWithFormat:@"/Documents/%@", name];
return [NSHomeDirectory() stringByAppendingPathComponent:path];
}
- (void)delegateEventWithData:(NSData *)data {
if (_delegate && [_delegate respondsToSelector:@selector(imageDownloadOperation:data:)]) {
dispatch_async(dispatch_get_main_queue(), ^{
[_delegate imageDownloadOperation:self data:data];
});
}
}
- (void)writeData:(NSData *)data toPath:(NSString *)path {
dispatch_async(dispatch_get_global_queue(0, 0), ^{
[data writeToFile:path atomically:YES];
});
}
@end细节
