uicollectionview以及uiwindowlevel

好久没用UICollectionView，此处Mark一下。还有就是解决在window上面添加一个新的view，statusbar不显示的问题。

//
//  ProductModalView.m
//  guolongcustom
//
//  Created by JY on 2018/1/16.
//  Copyright © 2018年 jianyong.wang. All rights reserved.
//

#import "ProductModalView.h"
#import "ResourceCollectionViewCell.h"
static ProductModalView * productModal = nil;
#define COLLECTION_WIDTH (315.0 * kScreenWidth / 375 )
@interface ProductModalView()<UICollectionViewDelegate,UICollectionViewDataSource,UICollectionViewDelegateFlowLayout>
@property (nonatomic, strong) UIWindow * myWindow;
@end
@implementation ProductModalView
+(ProductModalView *)shareInstance
{
    static dispatch_once_t productPredicate;
    dispatch_once(&productPredicate, ^{
        productModal = [[self alloc]init];
    });
    return productModal;
}
-(instancetype)init
{
    if(self = [super init]){
        [self setSubView];
    }
    return self;
}
-(void)setSubView
{
    WS(ws);
    self.frame = [UIScreen mainScreen].bounds;
    
    UIView * view = [[UIView alloc]init];
    view.userInteractionEnabled = true;
    view.backgroundColor = [UIColor blackColor];
    view.alpha = 0.5;
    [self addSubview:view];
    UITapGestureRecognizer * tap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(tapClcik)];
    [view addGestureRecognizer:tap];
    [view mas_makeConstraints:^(MASConstraintMaker *make) {
        make.edges.equalTo(ws);
    }];
    //创建UICollectionViewFlowLayout
    UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
    //设置滚动方向
    [layout setScrollDirection:UICollectionViewScrollDirectionVertical];
    //设置header大小
//    layout.headerReferenceSize = CGSizeMake(COLLECTION_WIDTH, 20);
    //创建CollectionView
    UICollectionView * collectionview = [[UICollectionView alloc]initWithFrame:CGRectZero collectionViewLayout:layout];
    collectionview.backgroundColor = [UIColor whiteColor];
    [self addSubview:collectionview];
    //注册Header类
    [collectionview registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"UICollectionElementKindSectionHeader"];
    //注册自定义的CollectionViewCell
    [collectionview registerNib:[UINib nibWithNibName:NSStringFromClass([ResourceCollectionViewCell class]) bundle:nil] forCellWithReuseIdentifier:@"ResourceCollectionViewCell"];
    //添加代理
    collectionview.delegate = self;
    collectionview.dataSource = self;
    [collectionview mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.bottom.right.equalTo(ws);
        make.width.mas_equalTo(COLLECTION_WIDTH);
    }];
    //创建window，如果用 [UIApplication sharedApplication].keyWindow; window.windowLevel = UIWindowLevelNormal;状态栏会在最上方，window.windowLevel = UIWindowLevelAlert或者statusBar;状态栏默认会隐藏，不显示;，因此此处需要自己创建window进行视图的加载
    UIWindow * window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
    window.backgroundColor = [UIColor clearColor];
    window.windowLevel = UIWindowLevelAlert;
    window.hidden = true;
    [window addSubview:self];
    self.myWindow = window;
}
#pragma mark - delegate
//collectionviewcell代理，注意与上面注册的nib文件的标识符一致
- (nonnull __kindof UICollectionViewCell *)collectionView:(nonnull UICollectionView *)collectionView cellForItemAtIndexPath:(nonnull NSIndexPath *)indexPath {
    ResourceCollectionViewCell *cell = (ResourceCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"ResourceCollectionViewCell" forIndexPath:indexPath];
    return cell;
}
//每个section的上下左右边距，如果只有一个section那么久代表整个collectionview的上下左右边距
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    return UIEdgeInsetsMake(0, 20, 0, 18);
}
//每一个cell的上下间距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
{
    return 10;
}
//每一个cell的左右间距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    return 10;
}
//返回多少个section
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 6;
}
//每个section中包含的cell个数
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return arc4random_uniform(10);
}
//每个cell的大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return CGSizeMake((COLLECTION_WIDTH - 20 - 38)/3.0, 35);
}
//每个section的header
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
        UICollectionReusableView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"UICollectionElementKindSectionHeader" forIndexPath:indexPath];
        headerView.backgroundColor =[UIColor whiteColor];
        //注意此处需要移出上次添加的label
        for (UIView * view in headerView.subviews) {
            [view removeFromSuperview];
        }
        UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(20, 0, COLLECTION_WIDTH-38, headerView.bounds.size.height)];
        label.text = @"这是collectionView的头部";
        label.font = [UIFont systemFontOfSize:15.];
        [headerView addSubview:label];
        return headerView;
    }
    return nil;
}
//每个section对应的header的大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout
referenceSizeForHeaderInSection:(NSInteger)section {
    
    if (section == 0) {
        return CGSizeMake(COLLECTION_WIDTH, 72);
    }
    else {
        return CGSizeMake(COLLECTION_WIDTH,64);
    }
}
//显示与隐藏，注意此处是将此view添加到自己创建的window上面，因此只需要设置window的hidden属性即可
+(void)showProductModalView:(BOOL)show
{
    [[ProductModalView shareInstance].myWindow setHidden:!show];
//    [UIView animateWithDuration:.3 animations:^{
//            UIWindow *window = [UIApplication sharedApplication].keyWindow;
//            window.windowLevel = UIWindowLevelNormal;
//            [window addSubview:[ProductModalView shareInstance]];
//            [[ProductModalView shareInstance].myWindow setHidden:!show];
//    }];
}
-(void)tapClcik
{
    [[ProductModalView shareInstance].myWindow setHidden:true];
}
/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code
}
*/

@end

详见代码。