//
// ViewController.m
// test-alert
//
// Created by 姜维克 on 2017/4/20.
// Copyright © 2017年 O2O_iOS_jiangweike. All rights reserved.
//

import "ViewController.h"

@interface WKCollectionView : UICollectionView

@end

@interface WKCollectionView ()
//@property (nonatomic, strong) UICollectionView *collection;
@end
@implementation WKCollectionView
@end

@interface WKCollectionViewCell : UICollectionViewCell

@end

@interface WKCollectionViewCell ()
@property (nonatomic, strong) UILabel *testLabel;
@end

@implementation WKCollectionViewCell

//必须重写initWithFrame 方法 否则deque方法 第一次得到的cell 的testLabel是nil

• (instancetype)initWithFrame:(CGRect)frame
  {
  self = [super initWithFrame:frame];
  if (self) {
  UILabel *label = [[UILabel alloc] initWithFrame:self.contentView.bounds];
  label.text = @"ceshi";
  label.textColor = [UIColor blackColor];
  [self.contentView addSubview:label];

    self.testLabel = label;
    self.contentView.backgroundColor = [UIColor darkGrayColor];
  

  }
  return self;
  }

@end

@interface ViewController ()<UICollectionViewDelegate,UICollectionViewDataSource>
@property (nonatomic, strong) UICollectionView *collection;
@property (nonatomic, strong) NSIndexPath *indexPath;
@property (nonatomic, strong) WKCollectionViewCell *oldCell;
@end

@implementation ViewController

• (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.
  [self test];
  [self initCollectionView];
  }

• (void)test
  {
  UIAlertView *alert = [[UIAlertView alloc] init];

  UILabel *l = [[UILabel alloc] init];
  l.text = @"下午";
  l.frame = CGRectMake(20, 20, 100, 40);
  [self.view addSubview:l];
  [l setTextColor:[UIColor redColor]];

}

• (void)didReceiveMemoryWarning {
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
  }

static NSString * const reuseIdentifier = @"Cell";

• (void)initCollectionView
  {

  UICollectionViewFlowLayout *flow = [[UICollectionViewFlowLayout alloc] init];
  flow.itemSize = CGSizeMake(100, 40);
  flow.scrollDirection = UICollectionViewScrollDirectionVertical;

  WKCollectionView *collection = [[WKCollectionView alloc] initWithFrame:self.view.bounds collectionViewLayout:flow];
  [collection registerClass:[WKCollectionViewCell class] forCellWithReuseIdentifier:reuseIdentifier];
  collection.dataSource = self;
  collection.delegate = self;
  collection.backgroundColor = [UIColor whiteColor];
  [self.view addSubview:collection];
  self.collection = collection;
  }

pragma mark - UICollectionViewDataSource

• (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
  return 1;
  }

• (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
  return 4000;
  }

• (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{

  WKCollectionViewCell *cell = (WKCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];
  //如果重写cell的init方法;dequeueReusableCellWithReuseIdentifier方法 得到的cell 一定不为nil 但是cell的testLabel一定是nil;不会走cell的init方法,而是initWithFrame方法
  if([indexPath isEqual:self.indexPath]){
  cell.testLabel.textColor = [UIColor yellowColor];
  }else{
  cell.testLabel.textColor = [UIColor blackColor];
  }
  //if(!cell) 判断没有效果,因为前面collectionView注册了[WKCollectionViewCell class]
  if(!cell){
  cell = [[WKCollectionViewCell alloc] init];
  }

  return cell;
  }

• (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
  if (self.indexPath) {
  WKCollectionViewCell *oldCell = (WKCollectionViewCell *)[collectionView cellForItemAtIndexPath:self.indexPath];
  oldCell.testLabel.textColor = [UIColor blackColor];
  // NSLog(@"indexpath :%@",[collectionView indexPathForCell:self.oldCell]);
  }
  //oldCell 记不住 因为每次复用之后 cell的地址就会改变

  WKCollectionViewCell *cell = (WKCollectionViewCell *)[collectionView cellForItemAtIndexPath:indexPath];
  cell.testLabel.textColor = [UIColor yellowColor];
  // self.oldCell = cell;
  // NSLog(@"点击oldCell:%@",self.oldCell);
  self.indexPath = indexPath;
  }
  @end