这里需要创建一个imageCacheObject对象。存放一些缓存数据
一个imageViewController视图。展示下载的图片
一个imagesTableViewController表格。展示可下载的图片
****************************imageCacheObject.h*********************************************
#import <Foundation/Foundation.h>
@interface ImageCacheObject : NSObject
//用于存放所有图片信息
@property (nonatomic,strong) NSMutableDictionary * imageCacheDic;
//单例 方法保证整个进程仅有一份
+(id)shareImageCache;
@end
******************************imageCacheObject.m*******************************************
#import "ImageCacheObject.h"
@implementation ImageCacheObject
+ (id)shareImageCache{
static ImageCacheObject * obj = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
obj = [ImageCacheObject new];
});
return obj;
}
- (instancetype)init{
if (self =[super init]) {
self.imageCacheDic = [NSMutableDictionary new];
}
return self;
}
@end
******************************imageViewController.m*******************************************
在.h文件中申明一个 nsstring * imagePath注意和.m文件中的imagesPath分开
#import "ImageViewController.h"
#import "ImageCacheObject.h"
@interface ImageViewController ()
@property (weak, nonatomic) IBOutlet UIScrollView *scrollerView;
@property (weak, nonatomic) IBOutlet UIActivityIndicatorView *activityView;
@property (nonatomic,strong) UIImageView *imageView;
//获取图片存放的地址
@property (nonatomic,strong) NSString * imagesPath;
@end
@implementation ImageViewController
- (NSString *)imagesPath{
if (!_imagesPath) {
NSString * documentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject;
_imagesPath = [documentPath stringByAppendingPathComponent:@"images"];
NSLog(@"%@",_imagesPath);
//需要判断文件夹是否存在，如果不存在需要创建一个
NSFileManager * manager =[NSFileManager defaultManager];
if (![manager fileExistsAtPath:self.imagesPath]) {
[manager createDirectoryAtPath:self.imagesPath withIntermediateDirectories:YES attributes:nil error:nil];
}
}
return _imagesPath;
}
- (void)viewDidLoad {
[super viewDidLoad];
//先通过路径从单例的字典中获取值，如果有值说明图片下载过，不需要重复下载
ImageCacheObject * cacheObj = [ImageCacheObject shareImageCache];
UIImage * img = [cacheObj.imageCacheDic objectForKey:self.imagePath];
if (img) {
UIImageView * imageView1 = [[UIImageView alloc]initWithImage:img];
[self.scrollerView addSubview:imageView1];
self.scrollerView.contentSize = img.size;
UIPinchGestureRecognizer * pgc = [[UIPinchGestureRecognizer alloc]initWithTarget:self action:@selector(scalechange:)];
[self.view addGestureRecognizer:pgc];
return;//让代码停住，不继续执行
}
//nsstring - url - data -uiimage
//**/**/photo_1.jpg -> ~/Documents/images/pthot_1.jpg
NSString * lastcomponent = self.imagePath.lastPathComponent;//获取网络地址的最后一段。
NSString * filePath = [self.imagesPath stringByAppendingPathComponent:lastcomponent];
NSFileManager * manager = [NSFileManager defaultManager];
if ([manager fileExistsAtPath:filePath]) {
UIImage *img = [UIImage imageWithContentsOfFile:filePath];
UIImageView * imageview = [[UIImageView alloc]initWithImage:img];
[self.scrollerView addSubview:imageview];
self.scrollerView.contentSize =img.size;
return;
}
dispatch_queue_t globalQueue = dispatch_get_global_queue(0, 0);
[self.activityView startAnimating];// 开始读取动画
//在状态栏上显示网络活动,同时要在下载完成后结束该方法。
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];;
dispatch_async(globalQueue, ^{
NSURL * imageURL = [NSURL URLWithString:self.imagePath];
NSData *data = [NSData dataWithContentsOfURL:imageURL];
UIImage * image = [UIImage imageWithData:data];
[data writeToFile:filePath atomically:YES];
dispatch_async(dispatch_get_main_queue(), ^{
[self.activityView stopAnimating]; //结束读取动画
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
UIImageView * imageView = [[UIImageView alloc]initWithImage:image];
self.imageView = imageView;
[self.scrollerView addSubview:imageView];
self.scrollerView.contentSize = image.size;
//图片加载完成就添加到单例的字典中保存起来，保存的时间是整个进程。
ImageCacheObject *obj = [ImageCacheObject shareImageCache];
[obj.imageCacheDic setObject:image forKey:self.imagePath];
});
});
UIPinchGestureRecognizer * pgc = [[UIPinchGestureRecognizer alloc]initWithTarget:self action:@selector(scalechange:)];
[self.view addGestureRecognizer:pgc];
}
-(void)scalechange:(UIPinchGestureRecognizer *)pgc{
CGFloat scale = pgc.scale;
self.imageView.transform = CGAffineTransformScale(self.imageView.transform, scale, scale);
CGFloat max = MAX((self.imageView.bounds.size.width/self.view.bounds.size.width), (self.imageView.bounds.size.height/self.view.bounds.size.height));
self.scrollerView.minimumZoomScale = 1/max;
pgc.scale =1;
}
@end
********************************imagesTableViewController.m*****************************************
#import "ImagesTableViewController.h"
#import "ImageViewController.h"
@interface ImagesTableViewController ()
@property (nonatomic,strong) NSArray * imageNames;
@end
@implementation ImagesTableViewController
//筹备用于展示的数据
- (NSArray *)imageNames{
if (!_imageNames) {
_imageNames =@[@"鲜花",@"彩椒",@"水母",@"日落",@"孩子",@"滑板少年"];
}
return _imageNames;
}
- (void)viewDidLoad {
[super viewDidLoad];
self.tableView.tableFooterView = [UIView new];
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return self.imageNames.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];
cell.textLabel.text = self.imageNames[indexPath.row];
return cell;
}
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
//下面方法让选中的行恢复到原来样子，取消选中状态
[tableView deselectRowAtIndexPath:indexPath animated:YES];
}
//通过点击Cell跳转，如果是storyboard连线模式，会自动触发
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
//用户点击Cell发生的跳转，所以sender就是Cell
//获取当前Cell所在的行
NSIndexPath * indexPath = [self.tableView indexPathForCell:sender];
NSString * imagePath = [NSString stringWithFormat:@"http://images.apple.com/v/iphone-5s/gallery/a/images/download/photo_%ld.jpg",indexPath.row+1];
ImageViewController * imagevc = segue.destinationViewController;
imagevc.imagePath =imagePath;
}
@end
*************************************************************************
