本篇文章主要介绍了ios如何通过按钮点击异步来加载图片，希望小编整理的相关知识和资料都对你们有所帮助。
比较原始的方法：
AsyncImageView.h:
#import
@interface AsyncImageView : UIView
{
NSURLConnection* connection;
NSMutableData* data;
}
- (void)loadImageFromURL:(NSURL*)url;
@end
AsyncImageView.m:
#import "AsyncImageView.h"
@implementation AsyncImageView
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if(self) {
// Initialization code
}
returnself;
}
- (void)loadImageFromURL:(NSURL*)url {
if(connection!=nil) { [connection release]; }
if(data!=nil) { [data release]; }
NSURLRequest* request = [NSURLRequest requestWithURL:url
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
connection = [[NSURLConnection alloc]
initWithRequest:request delegate:self];
}
- (void)connection:(NSURLConnection *)theConnection
didReceiveData:(NSData *)incrementalData {
if(data==nil) {
data =
[[NSMutableData alloc] initWithCapacity:2048];
}
[data appendData:incrementalData];
}
- (void)connectionDidFinishLoading:(NSURLConnection*)theConnection {
[connection release];
connection=nil;
if([[self subviews] count] > 0) {
[[[self subviews] objectAtIndex:0] removeFromSuperview];
}
UIImageView *imageView = [[[UIImageView alloc] initWithImage:[UIImage imageWithData:data]] autorelease];
imageView.contentMode = UIViewContentModeScaleAspectFit;
imageView.autoresizingMask = ( UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight );
[self addSubview:imageView];
imageView.frame = self.bounds;
[imageView setNeedsLayout];
[self setNeedsLayout];
[data release];
data=nil;
}
- (UIImage*) image {
UIImageView* iv = [[self subviews] objectAtIndex:0];
return[iv image];
}
- (void)dealloc {
[connection cancel];
[connection release];
[data release];
[super dealloc];
}
@end
方法二：
@interface UIButton (AsyncImage)
//size by point
- (void)setImageFromURL:(NSString *)urlString adjustToSize:(CGSize)size completion:(void (^)(void))completion logo:(UIImage *)logoImage;
@end
@implementation UIButton (AsyncImage)
- (void)setImageFromURL:(NSString *)urlString adjustToSize:(CGSize)size completion:(void (^)(void))completion logo:(UIImage *)logoImage
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
UIImage *image = nil;
NSURL *url = [NSURL URLWithString:urlString];
NSData *data = [NSData dataWithContentsOfURL:url];
image = [UIImage imageWithData:data];
if (image) {
if (!CGSizeEqualToSize(size, CGSizeZero)) {
image = [UIImage imageWithCGImage:image.CGImage scale:[self scaleImage:image adjustToSize:size] orientation:image.imageOrientation];
}
if (logoImage) {
image = [self addLogoImage:logoImage toImage:image];
}
dispatch_async(dispatch_get_main_queue(), ^{
[self setImage:image forState:UIControlStateNormal];
completion();
});
}
else {
NSLog(@"async load error.");
}
});
}
// 缩放图片以适应按钮大小
- (CGFloat)scaleImage:(UIImage *)image adjustToSize:(CGSize)size
{
CGFloat xScale = size.width / image.size.width;
CGFloat yScale = size.height / image.size.height;
return 1.0 / MIN(xScale, yScale);
}
- (UIImage *)addLogoImage:(UIImage *)logo toImage:(UIImage *)img
{
//get image width and height
CGFloat scale = [UIScreen mainScreen].scale;
int w = scale * img.size.width;
int h = scale * img.size.height;
int logoWidth = logo.scale * logo.size.width;
int logoHeight = logo.scale * logo.size.height;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
//create a graphic context with CGBitmapContextCreate
CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage);
CGContextDrawImage(context, CGRectMake(w - logoWidth, 0, logoWidth, logoHeight), [logo CGImage]);
CGImageRef imageMasked = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
return [UIImage imageWithCGImage:imageMasked scale:scale orientation:img.imageOrientation];
}
@end
方法三：
#import#import "StringUtils.h" @interface ImageManager : NSObject { NSMutableDictionary *_imageDict; NSMutableArray *_imageArr; } @property(nonatomic, strong) NSString *httpUrl; @property(nonatomic, strong) NSMutableDictionary *imageDict; @property(nonatomic, assign) dispatch_queue_t networkQueue; + (ImageManager *) sharedInstance; - (void)asyncImage:(NSString *)imageName imageView:(UIImageView *)imageView; //插队 - (void)asyncImageInsert:(NSString *)imageName imageView:(UIImageView *)imageView insert:(BOOL)insert; //不要在下载之前的数据 - (void)asyncImageCleanOld:(NSString *)imageName imageView:(UIImageView *)imageView cleanOld:(BOOL)cleanOld; @end
实现文件：
//
// ImageManager.m
// myb-ios
//
// Created by warrior gao on 13-6-5.
// Copyright (c) 2013年 51myb. All rights reserved.
//
#import "ImageManager.h"
@interface ImageManager()
@end
@implementation ImageManager
//缓存图片的最大数量
static int counter = 0;
@synthesize imageDict = _imageDict;
//Singleton
+ (ImageManager *)sharedInstance
{
static id instance;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
instance = self.new;
});
return instance;
}
- (id)init
{
if((self = [super init]))
{
self.networkQueue = dispatch_queue_create("com.warrior.network.image", nil);
_imageDict = [[NSMutableDictionary alloc] init];
_imageArr = [[NSMutableArray alloc] init];
}
return self;
}
- (NSString *) fileFullPath:(NSString *)fileName
{
NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *fileFullPath = [NSString stringWithFormat:@"%@/%@",cachePath,fileName];
return fileFullPath;
}
//不要在下载之前的数据
- (void)asyncImageCleanOld:(NSString *)imageName imageView:(UIImageView *)imageView cleanOld:(BOOL)cleanOld
{
if(cleanOld)
{
[_imageArr removeAllObjects];
}
[self asyncImage:imageName imageView:imageView];
}
//插队，优先
- (void)asyncImageInsert:(NSString *)imageName imageView:(UIImageView *)imageView insert:(BOOL)insert
{
if([StringUtils isEmpty:imageName]){
return;
}
NSData *data = [NSData dataWithContentsOfFile:[self fileFullPath:[imageName stringByReplacingOccurrencesOfString:@"/" withString:@"-"]]];
if(data == nil){
[_imageDict setValue:imageView forKey:imageName];
if(insert)
{
[_imageArr insertObject:imageName atIndex:0];
}
else
{
[_imageArr addObject:imageName];
}
[self cacheImage];
} else {
[imageView setImage:[UIImage imageWithData:data]];
}
}
//正常，附加到后面
- (void)asyncImage:(NSString *)imageName imageView:(UIImageView *)imageView
{
[self asyncImageInsert:imageName imageView:imageView insert:NO];
}
//异步缓存图片到本地，最多有两个线程
-(void)cacheImage
{
for (; counter 0; counter++)
{
NSString *imageName = nil;
@synchronized(self){
imageName = [[_imageArr objectAtIndex:0] copy];
[_imageArr removeObjectAtIndex:0];
}
if(imageName == nil) continue;
dispatch_async(self.networkQueue, ^{
NSLog(@"Starting: %@", imageName);
UIImage *avatarImage = nil;
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"%@%@",self.httpUrl, imageName]];
NSData *responseData = [NSData dataWithContentsOfURL:url];
if(responseData.length > 0)
{
[responseData writeToFile:[self fileFullPath:[imageName stringByReplacingOccurrencesOfString:@"/" withString:@"-"]] atomically:NO];
avatarImage = [UIImage imageWithData:responseData];
NSLog(@"Finishing: %@", imageName);
if (avatarImage) {
dispatch_async(dispatch_get_main_queue(), ^{
UIImageView *imageView = [_imageDict objectForKey:imageName];
if(imageView != nil && avatarImage != nil){
[imageView setImage:avatarImage];
}
[_imageDict removeObjectForKey:imageName];
[imageName release];
});
}
}
counter--;
[self cacheImage];
});
}
}
@end以上所述就是ios如何通过按钮点击异步来加载图片的介绍，希望大家能够喜欢，更多内容请继续关注中国E盟技术频道网站！
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