SDWebimage 在内存方面存在很大的内存问题，静态的图片也会出现拉伸问题，动态的gif图内存峰值更加的高，内存释放不会及时，
- SDWebImage 对gif的处理主要是在UIImage+GIF这个文件里面，利用ImageIO函数创建二进制数据，如下：
#import "UIImage+GIF.h"
#import <ImageIO/ImageIO.h>
@implementation UIImage (GIF)
+ (UIImage *)sd_animatedGIFWithData:(NSData *)data {
if (!data) {
return nil;
}
//
CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
// 取得gif的帧数
size_t count = CGImageSourceGetCount(source);
UIImage *animatedImage;
// 判断图片数量如果是1 返回静态图片
if (count <= 1) {
animatedImage = [[UIImage alloc] initWithData:data];
}
else {
// 消耗性能的根源 ，在放入数组中播放的时候，核心动画会在两帧之间自动生成股间动画，十分消耗内存，
NSMutableArray *images = [NSMutableArray array];
NSTimeInterval duration = 0.0f;
for (size_t i = 0; i < count; i++) {
CGImageRef image = CGImageSourceCreateImageAtIndex(source, i, NULL);
// 累加时常
duration += [self sd_frameDurationAtIndex:i source:source];
//添加数组
[images addObject:[UIImage imageWithCGImage:image scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp]];
//释放image对象
CGImageRelease(image);
}
if (!duration) {
duration = (1.0f / 10.0f) * count;
}
// 设置动图数组 ，生成动图
animatedImage = [UIImage animatedImageWithImages:images duration:duration];
}
CFRelease(source);
return animatedImage;
}
由于SDWebImage通过动图数组来实现动态，造成内存不能及时释放
解决方法
1 开启时钟 ，每次只加载一张图片，之前的立即释放 2 使用YYWebimage代替SDWebimage -静态图片加载 产生拉伸，如下图黄色表示拉伸，
#import "ViewController.h"
#import "YYWebImage.h"
static NSString *KDGroundLxrCellID = @"KDGroundLxrCellID";
@interface ViewController ()<UITableViewDelegate,UITableViewDataSource>
@property(strong, nonatomic) UITableView * mainTable;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
[self CreatMainTable];
}
/**
* 创建maintable
*/
#pragma mark-
#pragma mark- 创建tableview
-(void)CreatMainTable
{
self.mainTable = [[UITableView alloc] initWithFrame:[UIScreen mainScreen].bounds style:UITableViewStyleGrouped];
self.mainTable.delegate = self ;
self.mainTable.dataSource = self ;
self.mainTable.separatorStyle = UITableViewCellSeparatorStyleNone ;
[self.mainTable registerClass:[UITableViewCell class] forCellReuseIdentifier:KDGroundLxrCellID];
//[self.mainTable registerClass:<#(nullable Class)#> forCellReuseIdentifier:<#(nonnull NSString *)#>]
[self.view addSubview:self.mainTable];
}
/**
* mainTable 代理方法实现
*/
-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return 100;
}
-(UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell =[tableView dequeueReusableCellWithIdentifier:KDGroundLxrCellID];
NSString * str =@"https://d13yacurqjgara.cloudfront.net/users/288987/screenshots/1913272/depressed-slurp-cycle.gif";
NSURL *url =[NSURL URLWithString:str];
UIImage *image =[UIImage imageNamed:@"icon-120.png"];
// [cell.imageView yy_setImageWithURL:url placeholder:image];
[cell.imageView sd_setImageWithURL:url placeholderImage:image];
return cell;
}
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
return 107.0;
}
-(CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section
{
return 10.0;
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end ```
不懂红绿色代表的意思参考:http://www.jianshu.com/p/92d949a6d4e7
* 动态gif效果 注意此时占用内存是110MB ，cpu占用率是0
* 切换YYWebimage对比，内存消耗50MB而cpu占用40%
import "YYWebImageCell.h"
import "YYWebImage.h"
@implementation YYWebImageCell
-(instancetype)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
if (self) {
// @property (nonatomic, readonly, strong, nullable) UIImageView *imageView NS_AVAILABLE_IOS(3_0); // default is nil. image view will be created if necessary.
[self setValue:[[YYAnimatedImageView alloc] init] forKey:@"imageView"];
}
return self;
}```
#import "ViewController.h"
#import "YYWebImage.h"
#import "YYWebImageCell.h"
static NSString *KDGroundLxrCellID = @"KDGroundLxrCellID";
@interface ViewController ()<UITableViewDelegate,UITableViewDataSource>
@property(strong, nonatomic) UITableView * mainTable;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
[self CreatMainTable];
}
/**
* 创建maintable
*/
#pragma mark-
#pragma mark- 创建tableview
-(void)CreatMainTable
{
self.mainTable = [[UITableView alloc] initWithFrame:[UIScreen mainScreen].bounds style:UITableViewStyleGrouped];
self.mainTable.delegate = self ;
self.mainTable.dataSource = self ;
self.mainTable.separatorStyle = UITableViewCellSeparatorStyleNone ;
[self.mainTable registerClass:[YYWebImageCell class] forCellReuseIdentifier:KDGroundLxrCellID];
//[self.mainTable registerClass:<#(nullable Class)#> forCellReuseIdentifier:<#(nonnull NSString *)#>]
[self.view addSubview:self.mainTable];
}
/**
* mainTable 代理方法实现
*/
-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return 100;
}
-(UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
YYWebImageCell *cell =[tableView dequeueReusableCellWithIdentifier:KDGroundLxrCellID];
NSString * str =@"https://d13yacurqjgara.cloudfront.net/users/288987/screenshots/1913272/depressed-slurp-cycle";
NSURL *url =[NSURL URLWithString:str];
UIImage *image =[UIImage imageNamed:@"icon-120.png"];
[cell.imageView yy_setImageWithURL:url placeholder:image];
return cell;
}
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
return 107.0;
}
-(CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section
{
return 10.0;
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end```
相比较YYWebimage对内存方面的处理好好过于SDWebImage是牺牲内存来换取流畅度，而对于流畅度SDWebImage缺要好于YYWebimage，各有所长吧