UIImageView图片加载的几种方式

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#>]