我想優化我的應用程序中的加載，事實上，我有很多加載在我的應用程序中的圖像，並且我花了很多時間等待視圖控制器打開，特別是包含大量圖像的第一個初始視圖。在後臺加載圖像以優化ios中的加載
我看了看apple sample
，但我不能再工作，整個應用程序，我想只是告訴我具體是什麼，應該怎麼做什麼？我實現？
在tableview，其中單元實現cellforrowatindexpath:
NSURL *imageURL = ......;
NSData *imageData = [NSData dataWithContentsOfURL:imageURL];
UIImage *imageLoad;
imageLoad = [[UIImage alloc] initWithData:imageData];
imageView.image = imageLoad;
我能做些什麼？
謝謝你的幫助！
是的，你可以添加佔位形象吧。
它不會減慢滾動速度，並會隨着時間的推移相應加載圖像。
而且進口這個文件的UIImageView + WebCache.m和MapKit框架
Here is the link下載的文件。
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
UIImageview* iV = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 50, 50)];
[iV setImageWithURL:[NSURL URLWithString:url] placeholderImage:[UIImage imageNamed:@"image_placeholder.gif"]];
[cell.contentView addSubview:iV];
[iV release];
}
只是清潔，建造和運行。
在此控制請看： https://github.com/nicklockwood/AsyncImageView
這是非常容易實現的（僅1個文件），將滿足您的需求就好了。
採用這種控制： 而不是聲明的：
NSURL *imageURL = ......;
NSData *imageData = [NSData dataWithContentsOfURL:imageURL];
UIImage *imageLoad;
imageLoad = [[UIImage alloc] initWithData:imageData];
imageView.image = imageLoad;
用途：
NSURL *imageURL = ......;
imageView.imageURL = imageURL;
我會嘗試並給予ua反饋 – CarinaM
啓用的應用，同時正在從服務器和禁用塊的圖像，同時加載圖像嘗試使用UIImageView + AFNetworking庫以異步方式從服務器加載圖像AFNetworking
NSString *imageUrl = [[dict objectForKey:@"photo"] objectForKey:@"url"];
UIImageView *myImage = [[UIImageView alloc] init];
[myImage setImageWithURL:[NSURL URLWithString:imageUrl] placeholderImage:[UIImage imageNamed:@"PlaceHolder.png"]];
只需添加這個庫和包括的UIImageView + AFNetworking這樣你就可以使用新的UIImageView類別imageWithUrl
試試這個代碼：
dispatch_queue_t q = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(q, ^{
/* Fetch the image from the server... */
NSData *data = [NSData dataWithContentsOfURL:url];
UIImage *img = [[UIImage alloc] initWithData:data];
dispatch_async(dispatch_get_main_queue(), ^{
/* This is the main thread again, where we set the tableView's image to
be what we just fetched. */
cell.imgview.image = img;
});
});
你可以嘗試這樣的事情......！ 。
dispatch_queue_t checkInQueueForPostImage = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(checkInQueueForPostImage, ^{
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:postAndCheckInDetails.postImageURL]]];
dispatch_sync(dispatch_get_main_queue(), ^{
if (image!=nil) {
[uploadImage setImage:image];
}
[cell setNeedsLayout];
});
});
我會嘗試並給你一個反饋 – CarinaM
您可以使用異步imageview。
- (void) loadImageFromURL:(NSURL*)url placeholderImage:(UIImage*)placeholder cachingKey:(NSString*)key {
self.imageURL = url;
self.image = placeholder;
NSData *cachedData = [FTWCache objectForKey:key];
if (cachedData) {
self.imageURL = nil;
self.image = [UIImage imageWithData:cachedData];
return;
}
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(queue, ^{
NSData *data = [NSData dataWithContentsOfURL:url];
UIImage *imageFromData = [UIImage imageWithData:data];
[FTWCache setObject:data forKey:key];
if (imageFromData) {
if ([self.imageURL.absoluteString isEqualToString:url.absoluteString]) {
dispatch_sync(dispatch_get_main_queue(), ^{
self.image = imageFromData;
});
} else {
// NSLog(@"urls are not the same, bailing out!");
}
}
self.imageURL = nil;
});
}
看看this link。你會對使用異步imageview有一個想法。
我會盡力給你一個反饋 – CarinaM
你可以查看本教程NSOperationQueue和GCD這個完全相同。你也可以嘗試使用：
// Block variable to be assigned in block.
__block NSData *imageData;
dispatch_queue_t backgroundQueue = dispatch_queue_create("com.razeware.imagegrabber.bgqueue", NULL);
// Dispatch a background thread for download
dispatch_async(backgroundQueue, ^(void) {
imageData = [NSData dataWithContentsOfURL:imageURL];
UIImage *imageLoad;
imageLoad = [[UIImage alloc] initWithData:imageData];
// Update UI on main thread
dispatch_async(dispatch_get_main_queue(), ^(void) {
imageView.image = imageLoad;
});
});
我會盡力給你一個反饋 – CarinaM
這是一個略有修改的方法拉穆Pasupoletis答案。我添加了 __block 修飾符，使var img在主線程中調用的塊內可見。這裏是我在
中使用的完整方法定義-(UITableViewCell*)cellforRowAtIndexPath:(UIIndexPath*)indexPath;
用於緩慢提取縮略圖。我還爲單元格UIImageViews添加了佔位符。
//lazy loading of thumbnails for images in cell via bg thread
-(void)loadImageForCell:(CustomEditTableViewCell*)theCell withFilepath: (NSString*)filepath{
dispatch_queue_t q = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(q, ^{
UIImage (__block *img) = [UIImage imageWithContentsOfFile:filepath];
UIImage *thumbnail = [[GlobalFunctions sharedGlobalFunctions] imageOfSize:CGSizeMake(40, 40) fromImage:img];
dispatch_async(dispatch_get_main_queue(), ^{
theCell.imageView.image = thumbnail;
});
});
}
使用IDAsyncImageView.h
//////////////////////////////////////
IDAsyncImageView.h
/////////////////////////////////////
@interface IDAsyncImageView : NSObject
@property (nonatomic, strong) NSCache *cache;
+ (instancetype)instance;
- (void)loadImageView:(UIImageView*)imageView withURLString:(NSString *)urlString;
@end
//////////////////////////////////////
IDAsyncImageView.m
/////////////////////////////////////
#import "IDAsyncImageView.h"
@implementation IDAsyncImageView
+ (instancetype)instance
{
static IDAsyncImageView *_instance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
_instance = [[self alloc] init];
});
return _instance;
}
- (instancetype)init
{
self = [super init];
if (self) {
self.cache = [[NSCache alloc] init];
}
return self;
}
- (void)loadImageView:(UIImageView*)imageView withURLString:(NSString *)urlString
{
UIActivityIndicatorView* activityView;
activityView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
activityView.hidesWhenStopped = YES;
activityView.center = CGPointMake(imageView.bounds.size.width/2.0f, imageView.bounds.size.height/2.0f);
activityView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleBottomMargin;
[imageView addSubview:activityView];
[activityView startAnimating];
UIImage* imageLoad = [self.cache objectForKey:urlString];
if (nil != imageLoad) {
imageView.image = imageLoad;
[activityView removeFromSuperview];
}
else {
// Block variable to be assigned in block.
__block NSData *imageData;
// Dispatch a background thread for download
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:urlString]];
UIImage* imageLoad = [[UIImage alloc] initWithData:imageData];
// Update UI on main thread
dispatch_async(dispatch_get_main_queue(), ^(void) {
[self.cache setObject:imageLoad forKey:urlString];
imageView.image = imageLoad;
[activityView removeFromSuperview];
});
});
}
}
//////////////////////////////////////
ViewController.m
//////////////////////////////////////
- (void)viewDidLoad {
[super viewDidLoad];
[[IDAsyncImageView instance] loadImageView:myImageView withURLString:aUrl];
}
的NSData *的imageData = [NSData的dataWithContentsOfURL：IMAGEURL];將需要很長的..異步加載的圖像 –
你可以把它寫爲代碼？請告訴我如何？ – CarinaM