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| #define APPImageFile(url) [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)lastObject] stringByAppendingPathComponent:[url lastPathComponent]]
#import "ILAppsViewController.h"
#import "App.h"
@interface ILAppsViewController ()
//存放数据
@property(nonatomic,strong) NSMutableArray *apps;
//存放所有下载操作的队列
@property(nonatomic,strong) NSOperationQueue *queue;
//存放所有的下载操作(url是key,operation是value)
@property(nonatomic,strong) NSMutableDictionary *operations;
//存放所有下载完的图片
@property(nonatomic,strong) NSMutableDictionary *images;
@end
@implementation ILAppsViewController
#pragma mark-懒加载代码
-(NSMutableArray *)apps
{
if (!_apps) {
NSMutableArray *appArray=[NSMutableArray array];
//加载plist
NSString *file=[[NSBundle mainBundle]pathForResource:@"apps" ofType:@"plist"];
NSArray *dicctArray=[NSArray arrayWithContentsOfFile:file];
//2-字典转模型
for(NSDictionary *dict in dicctArray){
App *app=[App appWithDict:dict];
[appArray addObject:app];
}
//3.赋值
self.apps=appArray;
}
return _apps;
}
-(NSOperationQueue *)queue
{
if (!_queue) {
self.queue=[[NSOperationQueue alloc]init];
}
return _queue;
}
-(NSMutableDictionary *)operations
{
if (!_operations) {
self.operations=[[NSMutableDictionary alloc]init];
}
return _operations;
}
- (NSMutableDictionary *)images
{
if (!_images) {
self.images=[[NSMutableDictionary alloc]init];
}
return _images;
}
- (void)viewDidLoad {
[super viewDidLoad];
}
-(void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
//移除下载操作
[self.queue cancelAllOperations];
[self.images removeAllObjects];
[self.operations removeAllObjects];
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
#warning Incomplete implementation, return the number of sections
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
#warning Incomplete implementation, return the number of rows
return self.apps.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *ID=@"app";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];
if (!cell) {
cell=[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:ID];
}
//取出模型
App *app=self.apps[indexPath.row];
cell.textLabel.text=app.name;
cell.detailTextLabel.text=app.download;
//方法四-先从images缓存中取出url对应的UIImage对象
UIImage *image=self.images[app.icon];
if (image) { //说明图片已经下载成功
cell.imageView.image=image;
//NSLog(@"----从缓存中取得图片---%d",indexPath.row);
}else{ //说明图片并未下载成功过(并未缓存过)
//NSString *caches=[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)lastObject];
//NSString *filename=[app.icon lastPathComponent];
NSString *file=APPImageFile(app.icon);
//先从沙盒中取出文件
NSData *data=[NSData dataWithContentsOfFile:file];
if (data) {//沙盒中存在这个文件
cell.imageView.image=[UIImage imageWithData:data];
}else{ //沙盒中不存在这个文件
//NSLog(@"----缓存中没有图片---%d",indexPath.row);
//显示占位图片
cell.imageView.image=[UIImage imageNamed:@"placeholder"];
//下载图片
[self download:app.icon indexPath:indexPath];
}
}
return cell;
}
-(void)download:(NSString *)imageUrl indexPath:(NSIndexPath *)indexPath{
//取出当前图片url对应的下载操作(operation对象)
NSBlockOperation *operation=self.operations[imageUrl];
if (operation) return;
__weak typeof(self) appsVc=self;
operation=[NSBlockOperation blockOperationWithBlock:^{
[NSThread sleepForTimeInterval:0]; //演示图片错乱等问题延时
NSURL *url=[NSURL URLWithString:imageUrl];
NSData *data=[NSData dataWithContentsOfURL:url];
UIImage *image=[UIImage imageWithData:data];
//NSLog(@"正在下载图片----%@",url);
[[NSOperationQueue mainQueue]addOperationWithBlock:^{
//cell.imageView.image=image;//直接设置图片会导致图片错乱
//存放图片到字典中
if(image){
//self.images[imageUrl]=image;
appsVc.images[imageUrl]=image;//循环引用换成weak
//将图片存入沙盒中：UIImage->Data——>File
NSData *data=UIImagePNGRepresentation(image);
//获取Caches路径
//NSString *caches=[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)lastObject];
//NSLog(@"%@",caches);
//拼接文件路径
//NSString *filename=[imageUrl lastPathComponent];
//NSString *file=[caches stringByAppendingPathComponent:filename];
//NSLog(@"%@----%@",filename,file);
//放入文件到沙盒中
[data writeToFile:APPImageFile(imageUrl) atomically:YES];
}
//从字典中移除下载操作
[self.operations removeObjectForKey:imageUrl];
//刷新表格
//[self.tableView reloadData];
[self.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationNone];//刷新一行
}];
}];
//添加操作到队列
[self.queue addOperation:operation];
//添加到字典中(为了解决重复下载)
self.operations[imageUrl]=operation;
}
//当用户开始拖拽表格时调用开始拖拽
//1-会阻塞主线程，影响用户体验
//2-重复下载，浪费流量，浪费时间，影响用户体验
//保证：1张图片只下载1次
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
//暂停下载
[self.queue setSuspended:YES];
}
//当用户停止拖表格拽时
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
//恢复下载
[self.queue setSuspended:NO];
}
@end
|
