UIImageView图片加载很常用...所以我们需要每个人都熟练掌握网络图片加载的方式和用法.....其实我说这些都是废话，但是** 大碗 **入场之前一般都有一段开场，小编在此装一下逼不过分....希望大家理解，，
废话不多说,,,,大家往下看
1、NSURLSessionDataTask
- (IBAction)dataTask:(UIButton *)sender {
//1 准备url
NSURL *url =[NSURL URLWithString:IMG_URL];
//2 准备Session
NSURLSession *session = [NSURLSession sharedSession];
//3 准备会话
NSURLSessionDataTask *task = [session dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
UIImage *image = [UIImage imageWithData:data];
//在主线程刷新
dispatch_async(dispatch_get_main_queue(), ^{
self.aImageView.image = image;
});
}];
[task resume];//执行
}
2、NSURLSessionDownloadTask
- (IBAction)downLoad:(UIButton *)sender {
//准备URL
NSURL *url = [NSURL URLWithString:IMG_URL];
//准备Session
NSURLSession *session =[NSURLSession sharedSession];
//创建会话
NSURLSessionDownloadTask *downLoadTask =[session downloadTaskWithURL:url completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
//打印临时文件
NSLog(@"临时文件：%@",location);
//根据下载存放到的本地路径的文件来创建data对象
NSData *tempData = [NSData dataWithContentsOfURL:location];
UIImage *image =[UIImage imageWithData:tempData];
//刷新UI
dispatch_async(dispatch_get_main_queue(), ^{
self.aImageView.image = image;
});
}];
//启动任务
[downLoadTask resume];
//打印临时文件夹
NSString *temp = NSTemporaryDirectory();
NSLog(@"%@",temp);
}
小伙伴们看了以上内容此时你是什么心情呢？ 不要激动~~~~~~精彩的还在后面呢！下面见哥赠送一份 由于本人从小学开始就死了语文老师，，，如有错误 还请谅解 咱们继续。
3、封装Delegate 方法对UIImageView图片加载
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@protocol ImageDownLoadDelegate <NSObject>
//图片加载完成之后代理对象执行此方法 将解析好的图片传出去
//@param image 下载完的图片对象
-(void)imageDownLoadFanishLoadingImage:(nonnull UIImage *)image;
@end
@interface ImageDownLoad : NSObject
//这是一个封装下载图片的方法 urlString 网址字符串 delegate 将图片传送出去的对象
+(void)downLoadImageWithURLString:(nonnull NSString *)urlString delegate:(nonnull id<ImageDownLoadDelegate>)delegate;
@end
.m中实现+(void)downLoadImageWithURLString:(nonnull NSString *)urlString delegate:(nonnull id<ImageDownLoadDelegate>)delegate;方法
#import "ImageDownLoad.h"
@implementation ImageDownLoad
+(void)downLoadImageWithURLString:(nonnull NSString *)urlString delegate:(nonnull id<ImageDownLoadDelegate>)delegate{
//准备URL
NSURL *url =[NSURL URLWithString:urlString];
//准备Session对象
NSURLSession *session =[NSURLSession sharedSession];
//创建下载对象
NSURLSessionDownloadTask *downLoadTask = [session downloadTaskWithURL:url completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
//获取图片对象
UIImage *image =[UIImage imageWithData:[NSData dataWithContentsOfURL:location]];
if (delegate != nil && [delegate respondsToSelector:@selector(imageDownLoadFanishLoadingImage:)]) {
//让代理在主线程内执行图片的方法 确保UI正常显示
dispatch_async(dispatch_get_main_queue(), ^{
[delegate imageDownLoadFanishLoadingImage:image];
});
}
}];
//执行任务
[downLoadTask resume];
}
ViewController.m中进行调用
- (IBAction)delegate:(UIButton *)sender {
NSLog(@"delegate");
[ImageDownLoad downLoadImageWithURLString:IMG_URL delegate:self]; //类调用
}
实现协议里面的方法-----
-(void)imageDownLoadFanishLoadingImage:(UIImage *)image{
self.aImageView.image = image;
}
见哥是一个肤浅的人,,,, 嘿嘿 ....所以写出来的东西都是都很容易接受,,,,这还是局废话 咱们继续
3、封装Block 方法对UIImageView图片加载
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
//这是一个能够传递image对象的Block image是解析完成的image对象 用于回调
typedef void(^ImageDownLoadBlock)(UIImage *__nonnull image);
@interface ImageDownLoad : NSObject
//这是一个封装的解析图片的方法 使用Block经值传出去 能够传递image对象的回调函数urlString网址字符串
+(void)downLoadImageWithURLString:(nonnull NSString *)urlString andBlock:(ImageDownLoadBlock __nonnull)block;
@end
.m实现部分
+(void)downLoadImageWithURLString:(nonnull NSString *)urlString andBlock:(ImageDownLoadBlock __nonnull)block{
NSString *hesderString = [urlString substringToIndex:4];
if ([hesderString isEqualToString:@"http"]) {
NSURLSession *session =[NSURLSession sharedSession];
NSURLSessionDownloadTask *task = [session downloadTaskWithURL:[NSURL URLWithString:urlString] completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
UIImage *image =[UIImage imageWithData:[NSData dataWithContentsOfURL:location]];
dispatch_async(dispatch_get_main_queue(), ^{
//使用Block将值传递出去
block(image);
});
}];
[task resume];
}else{
//抛出异常
@throw [NSException exceptionWithName:@"ImageDownLoad Error" reason:@"Your urlString mayBe an Illegal string" userInfo:nil];
}
}
ViewVontroller.m调用
- (IBAction)block:(UIButton *)sender {
NSLog(@"block");
[ImageDownLoad downLoadImageWithURLString:IMG_URL andBlock:^(UIImage * _Nonnull image) {
self.aImageView.image = image;
}];
}
下面介绍完最后一种方法之后，睡觉 ，昨天失眠 做梦梦见自己结婚 激动之下醒了 然后就没有结果了。。。。。
5、SDWebImage 第三方
导入头文件import "UIImageView+WebCache.h" 一行代码搞定 一下是其中几种方法 供参考
[cell.imageView sd_setImageWithURL:<#(NSURL *)#> placeholderImage:<#(UIImage *)#>]
[cell.imageView sd_setImageWithURL:<#(NSURL *)#> placeholderImage:<#(UIImage *)#> completed:<#^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL)completedBlock#>]
[cell.imageView sd_setImageWithURL:<#(NSURL *)#> placeholderImage:<#(UIImage *)#> options:<#(SDWebImageOptions)#>]
[cell.imageView sd_setImageWithURL:<#(NSURL *)#> placeholderImage:<#(UIImage *)#> options:<#(SDWebImageOptions)#> completed:<#^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL)completedBlock#>]
[cell.imageView sd_setImageWithURL:<#(NSURL *)#> placeholderImage:<#(UIImage *)#> options:<#(SDWebImageOptions)#> progress:<#^(NSInteger receivedSize, NSInteger expectedSize)progressBlock#> completed:<#^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL)completedBlock#>]
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