iOS程序开发之使用PlaceholderImageView实现优雅的图片加载效果

//// PlaceholderImageView.h// SDWebImageViewPlaceHorder//// Created by YouXianMing on 16/9/14.// Copyright © 2016年 YouXianMing. All rights reserved.//#import <UIKit/UIKit.h>@interface PlaceholderImageView : UIView/*** Picture's url string.*/@property (nonatomic, strong) NSString *urlString;/*** The placeholder's image.*/@property (nonatomic, strong) UIImage *placeholderImage;/*** Default is UIViewContentModeScaleAspectFill.*/@property (nonatomic) UIViewContentMode placeholderImageContentMode;/*** Default is UIViewContentModeScaleAspectFill.*/@property (nonatomic) UIViewContentMode contentImageContentMode;@end

//// ImageCell.h// SDWebImageViewPlaceHorder//// Created by YouXianMing on 16/9/14.// Copyright © 2016年 YouXianMing. All rights reserved.//#import <UIKit/UIKit.h>#import "PlaceholderImageView.h"@interface ImageCell : UITableViewCell@property (nonatomic, strong) PlaceholderImageView *placeholderImageView;@end//// ImageCell.m// SDWebImageViewPlaceHorder//// Created by YouXianMing on 16/9/14.// Copyright © 2016年 YouXianMing. All rights reserved.//

@implementation ImageCell- (instancetype)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier {if (self = [super initWithStyle:style reuseIdentifier:reuseIdentifier]) {self.selectionStyle = UITableViewCellSelectionStyleNone;self.placeholderImageView = [[PlaceholderImageView alloc] initWithFrame:CGRectMake(0, 0, 150.f, 150.f)];self.placeholderImageView.placeholderImage = [UIImage imageNamed:@"1"];[self addSubview:self.placeholderImageView];}return self;}@end

//// ViewController.m// SDWebImageViewPlaceHorder//// Created by YouXianMing on 16/9/14.// Copyright © 2016年 YouXianMing. All rights reserved.//#import "ViewController.h"#import "UIImageView+WebCache.h"#import "PlaceholderImageView.h"#import "ImageCell.h"@interface ViewController () <UITableViewDelegate, UITableViewDataSource>@property (nonatomic, strong) UITableView *tableView;@property (nonatomic, strong) NSArray *pictures;@end@implementation ViewController- (void)viewDidLoad {[super viewDidLoad];self.pictures = @[@"https://pic.cnblogs.com/avatar/607542/20151017230728.png",@"https://pic.cnblogs.com/face/607741/20140226202001.png",@"https://pic.cnblogs.com/face/815231/20150923160245.png",@"https://pic.cnblogs.com/face/993558/20160729092113.png",@"https://pic.cnblogs.com/face/894202/20160217151952.png",@"https://pic.cnblogs.com/face/968459/20160709111712.png",@"https://pic.cnblogs.com/face/145865/20160210174306.png",@"https://pic.cnblogs.com/face/796658/20151026090914.png",@"https://pic.cnblogs.com/face/933887/20160629214007.png",@"https://pic.cnblogs.com/face/125303/20130313094252.png",@"https://pic.cnblogs.com/face/976232/20160730173456.png",@"https://pic.cnblogs.com/face/969708/20160602120239.png",@"https://pic.cnblogs.com/face/954541/20160705113740.png",@"https://pic.cnblogs.com/face/799942/20150818204115.png"];PlaceholderImageView *pImageView = [[PlaceholderImageView alloc] initWithFrame:CGRectMake(0, 0, 150.f, 150.f)];[self.view addSubview:pImageView];pImageView.urlString = @"https://pic.cnblogs.com/avatar/607542/20151017230728.png";self.tableView = [[UITableView alloc] initWithFrame:self.view.bounds];self.tableView.delegate = self;self.tableView.dataSource = self;self.tableView.rowHeight = 150.f;[self.view addSubview:self.tableView];[self.tableView registerClass:[ImageCell class] forCellReuseIdentifier:@"ImageCell"];}- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {return _pictures.count;}- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {ImageCell *cell = [tableView dequeueReusableCellWithIdentifier:@"ImageCell"];cell.placeholderImageView.urlString = _pictures[indexPath.row];return cell;}@end