一.项目需求
二.实现列表
本次列表展示参考博客为ios - 用UICollectionView实现瀑布流详解
具体分为Cell、Layout和Controller三个层面的实现,实现逻辑如下:
1.Cell
在Cell层,我们需要对其进行布局(用代码实现),类似于Android里面设置weight一样,只不过我通过手动设置比例来设置它们布局的相对大小。
- (instancetype) initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame: frame]) {
//设置imageView的布局
_imageView = [[UIImageView alloc] init];
[self.contentView addSubview:_imageView];
[_imageView mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(self.contentView).offset(0);
make.size.mas_equalTo(CGSizeMake(self.contentView.bounds.size.width, self.contentView.bounds.size.height * 0.85));
}];
//标记为需要重新布局
[_imageView setNeedsLayout];
//设置label的布局
_titleLabel = [[UILabel alloc] init];
[self.contentView addSubview:_titleLabel];
_titleLabel.textAlignment = NSTextAlignmentCenter;
_titleLabel.lineBreakMode = NSLineBreakByWordWrapping;
_titleLabel.font = [UIFont systemFontOfSize: 13];
[_titleLabel mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(self.imageView.mas_bottom).offset(self.contentView.bounds.size.height * 0.04);
make.bottom.equalTo(self.contentView.mas_bottom);
make.size.mas_equalTo(CGSizeMake(self.contentView.bounds.size.width, self.contentView.bounds.size.height * 0.11));
}];
}
return self;
}
有关setNeedsLayout的可以参考setNeedsLayout与layoutIfNeeded的区别
为了设置圆角,我们需要在layoutSublayersOfLayer中设置圆角,再用setNeedsLayout对UIImageView进行布局更新
- (void) layoutSublayersOfLayer:(CALayer *)layer
{
//设置圆角
UIBezierPath *maskPath;
maskPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds
byRoundingCorners:(UIRectCornerTopLeft | UIRectCornerTopRight)
cornerRadii:CGSizeMake(5.0f, 5.0f)];
CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
maskLayer.frame = self.bounds;
maskLayer.path = maskPath.CGPath;
self.layer.mask = maskLayer;
}
2.Layout
在Layout层,我们则需要对Cell的放置、高度等属性进行相应的设置,由于原demo是可以实现瀑布流的,其思路是:每次都将cell插入到瀑布流中最短的那一列,然后实时更新每一列的高度,直到cell放置结束。
但是我实现瀑布流之后发现效果惨不忍睹(因为给我的封面的高度和宽度参差不齐,不好看),因此套用了demo的模板对布局进行展示:
首先,通过Controller实现的委托,获得Cell对应的属性,将其放入属性数组当中:
//返回indexPath对应cell的布局属性
- (UICollectionViewLayoutAttributes *) layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
//创建布局属性
UICollectionViewLayoutAttributes *attrs = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath: indexPath];
//collectionView的宽度
CGFloat collectionViewWidth = self.collectionView.frame.size.width;
//设置布局属性的frame
CGFloat cellWidth = (collectionViewWidth - self.edgeInsets.left - self.edgeInsets.right - (self.columnCount - 1) * self.columnMargin) / self.columnCount;
CGFloat cellHeight = cellWidth * 0.8;
//找出最短那一列
NSInteger destColumn = 0;
CGFloat minColumnHeight = [self.columnHeights[0] doubleValue];
for (int i = 1; i < self.columnCount; i++) {
//取得第i列的高度
CGFloat columnHeight = [self.columnHeights[i] doubleValue];
if (minColumnHeight > columnHeight) {
minColumnHeight = columnHeight;
destColumn = I;
}
}
//设置cell的坐标
CGFloat cellX = self.edgeInsets.left + destColumn * (cellWidth + self.columnMargin);
CGFloat cellY = minColumnHeight;
if (cellY != self.edgeInsets.top)
cellY += self.rowMargin;
attrs.frame = CGRectMake(cellX, cellY, cellWidth, cellHeight);
//更新最短那一列的高度
self.columnHeights[destColumn] = @(CGRectGetMaxY(attrs.frame));
//记录内容的高度(即最长那一列的高度)
CGFloat maxColumnHeight = [self.columnHeights[destColumn] doubleValue];
if (self.contentHeight < maxColumnHeight)
self.contentHeight = maxColumnHeight;
return attrs;
}
获得属性数组之后,在prepareLayout中,对所有的属性(高宽、位置、页边距)对应的数组进行初始化
//初始化
- (void) prepareLayout
{
[super prepareLayout];
self.contentHeight = 0;
//清除之前计算的所有高度
[self.columnHeights removeAllObjects];
// 设置每一列默认的高度
for (NSInteger i = 0; i < HobenDefaultColumnCount ; i ++) {
[self.columnHeights addObject:@(HobenDefaultEdgeInsets.top)];
}
// 清除之前所有的布局属性
[self.attrsArr removeAllObjects];
// 开始创建每一个cell对应的布局属性
NSInteger count = [self.collectionView numberOfItemsInSection:0];
for (int i = 0; i < count; i++) {
// 创建位置
NSIndexPath * indexPath = [NSIndexPath indexPathForItem:i inSection:0];
// 获取indexPath位置上cell对应的布局属性
UICollectionViewLayoutAttributes * attrs = [self layoutAttributesForItemAtIndexPath:indexPath];
[self.attrsArr addObject:attrs];
}
}
设置Cell的大小:
//cell的大小
- (NSArray<UICollectionViewLayoutAttributes *> *) layoutAttributesForElementsInRect:(CGRect)rect
{
return self.attrsArr;
}
注意cell和cell之间是有间距的,需要通过计算,获得Layout大小:
//内容的大小
- (CGSize) collectionViewContentSize
{
return CGSizeMake(0, self.contentHeight + self.edgeInsets.bottom);
}
3.Controller
Controller是对每一个Cell的内容属性(封面图片等)进行设置,并且获得每一个Cell的布局属性,实现委托,传递给Layout:
首先,一定要记得,有个ID需要注册:
static NSString * const HobenCoverId = @"HobenCoverId";
/**
* 创建布局和collectionView
*/
- (void)setupLayoutAndCollectionView
{
// 创建布局
HobenWaterFallLayout * waterFallLayout = [[HobenWaterFallLayout alloc] init];
waterFallLayout.delegate = self;
// 创建collectionView
UICollectionView * collectionView = [[UICollectionView alloc] initWithFrame: self.view.bounds
collectionViewLayout: waterFallLayout];
collectionView.backgroundColor = [UIColor whiteColor];
//设置DataSource和Delegate
collectionView.dataSource = self;
collectionView.delegate = self;
[self.view addSubview:collectionView];
// 注册
[collectionView registerClass: [HobenCoverCell class]
forCellWithReuseIdentifier: HobenCoverId];
self.collectionView = collectionView;
}
解析json:
- (void) refreshCover
{
_isEnd = NO;
[self.collectionView.mj_footer resetNoMoreData];
NSURL *url = [NSURL URLWithString: @"http://*******"];
NSString *jsonString;
jsonString = [NSString stringWithContentsOfURL: url
encoding: NSUTF8StringEncoding
error: nil];
NSData* jsonData;
jsonData = [jsonString dataUsingEncoding: NSUTF8StringEncoding];
//获得解析的json
_dict = [NSJSONSerialization JSONObjectWithData: jsonData
options: NSJSONReadingMutableContainers
error: nil];
//获得需要的json数组
_totalCovers = _dict[@"data"][@"info_list"];
}
在本次项目中,我实现了加载,因此需要对获得的数据进行分页,在这里,我设置每页有10个数据:
/**
* 初始化
*/
- (void)initialize
{
[self refreshCover];
//设置每页大小和当前页数
_sectionNum = 10;
_currentPageNum = 0;
self.title = @"视频列表";
self.view.backgroundColor = [UIColor whiteColor];
}
刷新控件相应的逻辑如下:
/**
* 刷新控件
*/
- (void)setupRefresh
{
self.collectionView.mj_header = [MJRefreshNormalHeader headerWithRefreshingTarget:self refreshingAction:@selector(loadNewCovers)];
self.collectionView.mj_header.backgroundColor = [UIColor whiteColor];
[self.collectionView.mj_header beginRefreshing];
self.collectionView.mj_footer = [MJRefreshAutoNormalFooter footerWithRefreshingTarget:self refreshingAction:@selector(loadMoreShops)];
self.collectionView.mj_footer.backgroundColor = [UIColor whiteColor];
self.collectionView.mj_footer.hidden = YES;
}
下拉刷新,将会加载新的数据,其实现逻辑如下:
/**
* 加载新的视频
*/
- (void) loadNewCovers
{
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[self refreshCover];
//刷新,当前页数置0
[_covers removeAllObjects];
_currentPageNum = 0;
int endValue = 0;
//如果到底了
if ((_currentPageNum + 1)* _sectionNum >= [_totalCovers count]) {
endValue = (int)[_totalCovers count] - _currentPageNum * _sectionNum;
}
else {
endValue = _sectionNum;
}
NSArray * cover = [_totalCovers subarrayWithRange: NSMakeRange(_currentPageNum * _sectionNum, endValue)];
[_covers addObjectsFromArray:cover];
// 刷新表格
[self.collectionView reloadData];
[self.collectionView.mj_header endRefreshing];
});
}
上拉加载则需要判断是否到底,如果到底了,则需要显示no more data:
//加载更多视频
- (void) loadMoreCovers
{
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
if (_isEnd)
return;
//刷新
_currentPageNum++;
int endValue = 0;
//如果到底了
if ((_currentPageNum + 1)* _sectionNum >= [_totalCovers count]) {
endValue = (int)[_totalCovers count] - _currentPageNum * _sectionNum;
_isEnd = YES;
}
else {
endValue = _sectionNum;
}
NSArray * cover = [_totalCovers subarrayWithRange: NSMakeRange(_currentPageNum * _sectionNum, endValue)];
[_covers addObjectsFromArray:cover];
// 刷新表格
[self.collectionView reloadData];
[self.collectionView.mj_footer endRefreshing];
if (_isEnd)
[self.collectionView.mj_footer endRefreshingWithNoMoreData];
});
}
对每一个cell与数据一一对应,并设置进cell里面:
- (UICollectionViewCell *) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
HobenCoverCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier: HobenCoverId
forIndexPath: indexPath];
NSDictionary *cover = [[NSDictionary alloc] init];
cover = self.covers[indexPath.item];
/** 图片 */
NSString *img = cover[@"cover"];
/** 视频标题 */
NSString *title = cover[@"title"];
/** 视频字段 */
NSString *flv = cover[@"flv"];
/** 视频时长 */
NSString *duration = cover[@"duration"];
/** 列表到底 */
NSString *end = cover[@"end"];
/** 宽高 */
NSNumber *height = cover[@"height"];
NSNumber *width = cover[@"width"];
HobenCover *cellCover = [[HobenCover alloc] init];
//设置内容
[cellCover setImg: img];
[cellCover setTitle: title];
[cellCover setFlv: flv];
[cellCover setDuration: duration];
[cellCover setEnd: end];
[cellCover setW: [width floatValue]];
[cellCover setH: [height floatValue]];
cell.cover = cellCover;
return cell;
}
设置点击跳转事件:
- (void) collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
HobenCoverCell *cell = (HobenCoverCell *)[collectionView cellForItemAtIndexPath: indexPath];
HobenCover *cover = cell.cover;
HobenVideoController *videoController = [[HobenVideoController alloc] init];
[videoController setCover: cover];
//点击跳转
[self.navigationController pushViewController: videoController
animated: YES];
}
其他的就不用说了,和之前学习的TableView差不多,需要设置section数量和section里面的item的数量:
- (NSInteger) numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
self.collectionView.mj_footer.hidden = self.covers.count == 0;
return self.covers.count;
}
最后实现委托,传递给Layout:
- (CGFloat) waterFallLayout:(HobenWaterFallLayout *)waterFallLayout heightForItemAtIndexPath:(NSUInteger)indexPath itemWidth:(CGFloat)itemWidth
{
NSDictionary *cover = _covers[indexPath];
NSNumber *height = cover[@"height"];
NSNumber *width = cover[@"width"];
return itemWidth / [width floatValue] * [height floatValue];
}
- (CGFloat) rowMarginInWaterFallLayout:(HobenWaterFallLayout *)waterFallLayout
{
return 10;
}
- (NSUInteger) columnCountInWaterFallLayout:(HobenWaterFallLayout *)waterFallLayout
{
return 2;
}
- (UIEdgeInsets) edgeInsetdInWaterFallLayout:(HobenWaterFallLayout *)waterFallLayout
{
return UIEdgeInsetsMake(10, 10, 10, 10);
}
三.实现视频播放
这次的视频播放器使用的是基于AVPlayer封装的ZFPlayer,不得不说这个作者真的很强大:
具体参考他的GitHub和博客文档,配置的话GitHub有说得很完整了。
当控制器的view将要布局子控件时,就会调用viewWillLayoutSubviews,因此我们首先对视频的布局进行配置:
- (void) viewWillLayoutSubviews
{
[super viewWillLayoutSubviews];
CGFloat w = CGRectGetWidth(self.view.frame);
CGFloat h = w * 9 / 16;
//视频布局
CGFloat x = 0;
CGFloat y = (CGRectGetHeight(self.view.frame) - h) / 2;
self.containerView.frame = CGRectMake(x, y, w, h);
w = 44;
h = w;
//按钮居中
x = (CGRectGetWidth(self.containerView.frame) - w) / 2;
y = (CGRectGetHeight(self.containerView.frame) - h) / 2;
self.playBtn.frame = CGRectMake(x, y, w, h);
}
对于布局加载的各个函数的调用顺序,可以看这篇文章
而在控制器的view布局子控件完成时,将调用viewDidLayoutSubviews,在下面进行播放器的初始化:
- (void) initialize
{
//将flv转换成mp4
NSMutableString *flv = [[NSMutableString alloc] initWithString: self.cover.flv];
if (flv == nil)
return;
NSRange range = [flv rangeOfString: @".flv"];
[flv replaceCharactersInRange: range withString: @".mp4"];
_flvReadOnly = [[NSString alloc] initWithString: flv];
//设置相应布局
self.view.backgroundColor = [UIColor whiteColor];
[self.view addSubview:self.containerView];
[self.containerView addSubview:self.playBtn];
ZFAVPlayerManager *playerManager = [[ZFAVPlayerManager alloc] init];
/// 播放器相关
self.player = [ZFPlayerController playerWithPlayerManager: playerManager
containerView: self.containerView];
self.player.controlView = self.controlView;
//全屏之后,顶部栏隐藏
@weakify(self)
self.player.orientationWillChange = ^(ZFPlayerController * _Nonnull player, BOOL isFullScreen) {
@strongify(self)
[self setNeedsStatusBarAppearanceUpdate];
};
//结束播放之后停止
self.player.playerDidToEnd = ^(id _Nonnull asset) {
@strongify(self)
if (self.player.isFullScreen) {
[self.player enterFullScreen:NO animated:YES];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(self.player.orientationObserver.duration * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[self.player stop];
});
} else {
[self.player stop];
}
};
}
在播放键点击之后进行播放:
- (void) playClick:(UIButton *)sender
{
self.player.assetURL = [NSURL URLWithString: _flvReadOnly];
[self.player playTheIndex: 0];
[self.controlView showTitle: self.cover.title
coverURLString: self.cover.img
fullScreenMode: ZFFullScreenModeLandscape];
}
在加载视频之前显示封面图,注意要先将封面图进行比例压缩:
- (UIImage*)imageCompressWithSimple:(UIImage*)image scaledToSize:(CGSize)size
{
UIGraphicsBeginImageContext(size);
[image drawInRect:CGRectMake(0,0,size.width,size.height)];
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
获得压缩完毕的封面图后,我们可以用BackgroundColor的方法,让视频未加载前显示封面图:
- (UIView *) containerView
{
if (!_containerView) {
_containerView = [UIView new];
NSURL *imageURL = [NSURL URLWithString: self.cover.img];
NSData *data = [NSData dataWithContentsOfURL: imageURL];
UIImage *image = [[UIImage alloc] initWithData: data];
CGFloat w = CGRectGetWidth(self.view.frame);
CGFloat h = w * 9 / 16;
//设置封面图的大小
image = [self imageCompressWithSimple: image scaledToSize: CGSizeMake(w, h)];
UIColor *bgColor = [UIColor colorWithPatternImage: image];
[_containerView setBackgroundColor: bgColor];
}
return _containerView;
}
对播放按钮进行初始化:
- (UIButton *) playBtn
{
if (!_playBtn) {
_playBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[_playBtn setImage:[UIImage imageNamed:@"播放"] forState:UIControlStateNormal];
[_playBtn addTarget:self action:@selector(playClick:) forControlEvents:UIControlEventTouchUpInside];
}
return _playBtn;
}
大功告成,这个ZFPlayer支持手势滑动调节亮度、音量、进度、重力感应等功能,可以说是非常强大了。
还有一点就是,使用视频播放器的时候不要加断点!否则会出现一些很奇怪的错误,我是看了这篇博客才知道的,真的太坑了。
四.问题反馈与纠正
1.关于ViewDidLoad、viewDidLayoutSubviews、layoutSubviews的调用问题
参考文章:UI篇-VC的生命周期以及UIView的layoutSubviews和drawRect方法
首先看看单个viewController的生命周期:
- loadView:加载view 会多次调用并且会使viewWillLayoutSubviews、viewDidLayoutSubviews不再执行
- viewDidLoad:view加载完毕
- viewWillAppear:控制器的view将要显示
- viewWillLayoutSubviews:控制器的view将要布局子控件
-
viewDidLayoutSubviews:控制器的view布局子控件完成
这期间系统可能会多次调用viewWillLayoutSubviews 、 viewDidLayoutSubviews 俩个方法 - viewDidAppear:控制器的view完全显示
- viewWillDisappear:控制器的view即将消失的时候
- viewDidDisappear:控制器的view完全消失的时候
整个控制器生命周期: viewDidLoad -> viewWillAppear -> viewWillLayoutSubviews -> viewDidLayoutSubviews -> viewDidAppear -> viewWillDisappear -> viewDidDisappear
viewWillLayoutSubviews 在 viewWillAppear 之后 viewDidAppear 之前执行,这个方法会被调用多次,如果在此创建视图,可能会创建多个,而且这个方法中执行耗时操作依然会造成跳转卡顿的问题。
viewDidLoad是当程序第一次加载view时调用,以后都不会用到,而viewDidAppear是每当切换到view时就调用。
科普完以上知识之后,再看看我的代码:
1) viewDidLoad和viewDidLayoutSubviews
//不正确的方法
- (void)viewDidLoad
{
[super viewDidLoad];
}
- (void)viewDidLayoutSubviews
{
[super viewDidLayoutSubviews];
[self initialize];
}
可以看到,如果创建多个视图的话,就会不断加载,可以说会非常消耗了!
2) viewDidLayoutSubviews和viewWillLayoutSubviews
再来看看我的布局代码放哪了:
- (void) viewWillLayoutSubviews
{
[super viewWillLayoutSubviews];
CGFloat w = CGRectGetWidth(self.view.frame);
CGFloat h = w * 9 / 16;
//视频布局
CGFloat x = 0;
CGFloat y = (CGRectGetHeight(self.view.frame) - h) / 2;
self.containerView.frame = CGRectMake(x, y, w, h);
w = 44;
h = w;
//按钮居中
x = (CGRectGetWidth(self.containerView.frame) - w) / 2;
y = (CGRectGetHeight(self.containerView.frame) - h) / 2;
self.playBtn.frame = CGRectMake(x, y, w, h);
}
是的,放在了控制器的view将要布局子控件里面,还用到了view的frame!如果我view大小改变了的话,这个布局就会不准确了!
2.关于使用frame进行布局的问题
在Cell的initWithFrame
里面,我的布局是这样的:
[_imageView mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(self.contentView).offset(0);
make.size.mas_equalTo(CGSizeMake(self.contentView.bounds.size.width, self.contentView.bounds.size.height * 0.85));
}];
这样做的问题在于,我是直接获得了contentView
的大小(即写死了),当其布局大小发生改变的时候,用mas_equal
的方法可不会随之而改变。怎么办?改成这样:
[_imageView mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(self.contentView).offset(0);
make.width.equalTo(self.contentView);
make.height.equalTo(self.contentView).multipliedBy(0.85);
}];
但因为offset的问题(无法设置成weight形式),imageView和Label之间还是会有约束冲突,这时候我们可以定义一个空白的View来解决:
//添加空隙
UIView *space = [[UIView alloc] init];
[self.contentView addSubview: space];
[space mas_makeConstraints:^(MASConstraintMaker *make) {
make.width.equalTo(self.contentView);
make.height.equalTo(self.contentView).multipliedBy(0.04);
}];
这样就可以按照0.85 : 0.04 : 0.11的比例来控制这个Cell布局了。
3.关于网络请求与阻塞主线程的问题
在请求数据的时候,我曾经是这样请求的:
- (void) refreshCover
{
_isEnd = NO;
[self.collectionView.mj_footer resetNoMoreData];
NSURL *url = [NSURL URLWithString: @"http://*******"];
NSString *jsonString;
jsonString = [NSString stringWithContentsOfURL: url
encoding: NSUTF8StringEncoding
error: nil];
NSData* jsonData;
jsonData = [jsonString dataUsingEncoding: NSUTF8StringEncoding];
//获得解析的json
_dict = [NSJSONSerialization JSONObjectWithData: jsonData
options: NSJSONReadingMutableContainers
error: nil];
//获得需要的json数组
_totalCovers = _dict[@"data"][@"info_list"];
}
这个有什么问题呢?问题在于,这个函数是写在了主线程里面,如果加载很久的话,就会造成阻塞UI的后果。幸运的是,AFNetWorking提供了异步请求方法,参考iOS9之后AFNetWorking的使用(详细),就可以将代码修改成这样:
NSString *URLString = @"http://*******";
//使用AFNetWorking请求
AFHTTPSessionManager *session = [AFHTTPSessionManager manager];
//这一行是解决bug的
session.responseSerializer.acceptableContentTypes=[NSSet setWithObjects:@"application/json", @"text/json", @"text/javascript",@"text/html", @"application/javascript", nil];
//get请求
[session GET: URLString
parameters: nil
progress: nil
success: ^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
NSLog(@"请求成功");
//获得字典
_dict = responseObject;
//获得需要的json数组
_totalCovers = _dict[@"data"][@"info_list"];
}
failure: ^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
NSLog(@"请求失败:%@", error);
}];
看到那行解决bug没有,那行好像是因为这个框架本身的问题导致报错"Request failed: unacceptable content-type: application/javascript"
,参考了解决方案。
同样地,在cell里面,设置加载中的图片时,我也直接暴力地请求了网络:
NSURL *url = [NSURL URLWithString: @"https://image.baidu.com/search/detail?ct=503316480&z=0&ipn=d&word=正在加载图片gif&hs=2&pn=9&spn=0&di=122397146850&pi=0&rn=1&tn=baiduimagedetail&is=0%2C0&ie=utf-8&oe=utf-8&cl=2&lm=-1&cs=4034065388%2C2568359934&os=124701788%2C3310077975&simid=0%2C0&adpicid=0&lpn=0&ln=30&fr=ala&fm=&sme=&cg=&bdtype=0&oriquery=正在加载图片gif&objurl=http%3A%2F%2Fimgsrc.baidu.com%2Fforum%2Fw%3D580%2Fsign%3D4fc40444dec451daf6f60ce386fd52a5%2Faef6d933c895d143f95a783970f082025aaf0749.jpg&fromurl=ippr_z2C%24qAzdH3FAzdH3Fptjkwv_z%26e3Bkwt17_z%26e3Bv54AzdH3FrAzdH3Fndb8c999ad%3Frt1%3Dc0al99dn8n0%26fjj_sz%3D8&gsm=0&islist=&querylist="];
NSData *data = [NSData dataWithContentsOfURL: url];
UIImage *image = [UIImage sd_animatedGIFWithData:data];
事实上,只需要将这个Gif下载下来,放入Assets文件里面,再这样加载就OK了:
UIImage *image = [UIImage imageNamed: @"loading"];
(解决失败,不知道怎么加载gif类型的Placeholder,算了。。)
4.使用官方的UICollectionViewFlowLayout
鉴于自定义Layout太复杂,在这里还是尝试一下使用官方的UICollectionViewFlowLayout
,好像真的免去了委托等繁杂的工作(不过还是需要计算,因为UICollectionViewFlowLayout
好像没有提供列数这个接口)
//collectionView的宽度
CGFloat collectionViewWidth = self.view.frame.size.width;
//内边距
UIEdgeInsets edgeInsets = UIEdgeInsetsMake(10, 10, 10, 10);
//列数
int columnCount = 2;
//列间距
CGFloat columnMargin = 10;
//设置布局属性的frame
CGFloat cellWidth = (collectionViewWidth - edgeInsets.left - edgeInsets.right - (columnCount - 1) * columnMargin) / columnCount;
CGFloat cellHeight = cellWidth * 0.8;
UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc]init];
//设置UICollectionViewFlowLayout的属性
layout.scrollDirection = UICollectionViewScrollDirectionVertical;
layout.sectionInset = edgeInsets;
layout.itemSize = CGSizeMake(cellWidth, cellHeight);
// 创建collectionView
UICollectionView * collectionView = [[UICollectionView alloc] initWithFrame: self.view.bounds
collectionViewLayout: layout];
5.分页加载与超时功能的完善
项目给出的HTTP的地址里面有page=和size=,这其实是用于分页加载的(之前一直理解错了= =)
所以我们要用占位符来得出加载出来的地址。(这里略)
同时,使用了AFNetworking
进行了异步加载,则需要处理好MJRefresh控件
和AFNetworking
逻辑,MJRefresh控件
的加载完成必须是在AFNetworking
请求完成并且读取完毕之后才能隐藏:
//get请求
[session GET: URLString
parameters: nil
progress: nil
success: ^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
NSLog(@"请求成功");
//获得字典
_dict = responseObject;
//获得需要的json数组
_totalCovers = _dict[@"data"][@"info_list"];
//获得该数据请求是否结束
if ([_dict[@"data"][@"end"] intValue] == 1)
_isEnd = YES;
else
_isEnd = NO;
if ([load isEqualToString: @"loadNewCovers"]) {
//加载成功,更新列表
[_covers addObjectsFromArray: _totalCovers];
[self.collectionView reloadData];
[self.collectionView.mj_header endRefreshing];
}
if ([load isEqualToString: @"loadMoreCovers"]) {
if (_isEnd) {
//加载到底,结束加载
[self.collectionView.mj_footer endRefreshingWithNoMoreData];
return;
}
else {
//加载成功,更新列表
[_covers addObjectsFromArray: _totalCovers];
[self.collectionView reloadData];
[self.collectionView.mj_footer endRefreshing];
}
}
}
设置请求的超时时间:
[session.requestSerializer willChangeValueForKey: @"timeoutInterval"];
session.requestSerializer.timeoutInterval = 10.0f;
[session.requestSerializer didChangeValueForKey: @"timeoutInterval"];
在网络请求失败的同时,也需要抛出警告视图。
failure: ^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
//加载失败,抛出异常
NSLog(@"请求失败:%@", error);
UIAlertController *alert = [UIAlertController alertControllerWithTitle: @"加载超时"
message: @"请检查你的网络"
preferredStyle: UIAlertControllerStyleAlert];
UIAlertAction *action = [UIAlertAction actionWithTitle: @"了解"
style: UIAlertActionStyleDefault
handler: nil];
[alert addAction: action];
[self presentViewController: alert
animated: YES
completion: nil];
[self.collectionView.mj_header endRefreshing];
[self.collectionView.mj_footer endRefreshing];
}];
}
为防止下拉加载的时候多次误触控件,需要设置一个延时:
//加载更多视频
- (void) loadMoreCovers
{
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
//刷新
_currentPageNum++;
//开始加载
[self refreshCover: @"loadMoreCovers"];
});
}
自此,分页加载即可完成了!
6.模拟差网络环境下的刷新
在这里下载网络环境模拟器Network Link Conditioner
:
一开始我的footer
在差网络环境下不断上拉就会不断刷新currentPageNum
,导致UI操作和刷新操作不同步,在这里需要添加一个逻辑:即在进行UI上拉操作后,footer
应该在UICollectionView
加载完成之后,才能继续上拉,由此,我加上了这样一个操作:dispatch_async(dispatch_get_main_queue())
if ([load isEqualToString: @"loadNewCovers"]) {
//加载成功,更新列表
[_covers addObjectsFromArray: _totalCovers];
[self.collectionView reloadData];
dispatch_async(dispatch_get_main_queue(), ^{
[self.collectionView.mj_header endRefreshing];
});
}
if ([load isEqualToString: @"loadMoreCovers"]) {
if (_isEnd) {
//加载到底,结束加载
[self.collectionView.mj_footer endRefreshingWithNoMoreData];
return;
}
else {
//加载成功,更新列表
[_covers addObjectsFromArray: _totalCovers];
[self.collectionView reloadData];
dispatch_async(dispatch_get_main_queue(), ^{
[self.collectionView.mj_footer endRefreshing];
});
}
}
加上以后,即可实现我想要的逻辑。同时记得下拉刷新后resetNoMoreData
:
if ([load isEqualToString: @"loadNewCovers"]) {
[_covers removeAllObjects];
[self.collectionView.mj_footer resetNoMoreData];
}