（原）UICollectionView的基本使用

UICollectionView基本使用

学习iOS一段时间了，早听说了UICollectionView的强大一直没有机会使用，今天自己研究了一下。

UICollectonView类似UITableView 用法基本相似， UICollectionView 更灵活，更强大
UICollectonView 将其子视图的位置，大小和外观的控制权委托给一个单独的布局对象。通过提供一个自定义布局对象，你几乎可以实现任何你能想象到得布局。

下面是UICollectionView 常用的代理方法。

//定义展示的UICollectionViewCell的个数
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return ;
}
//定义展示的Section的个数
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return ;
}

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString * CellIdentifier = @"CollectionCell";

    CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
    cell.imageView.image = [UIImage imageNamed:@"1680_1050_3983.jpg"];
//    [cell sizeToFit];
    return cell;
}

#pragma mark --UICollectionViewDelegateFlowLayout
//定义每个UICollectionView 的大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return CGSizeMake(, );
}
//定义每个UICollectionView 的 margin
-(UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    return UIEdgeInsetsMake(, , , );
}

#pragma mark --UICollectionViewDelegate
//UICollectionView被选中时调用的方法
-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell * cell = (UICollectionViewCell *)[collectionView cellForItemAtIndexPath:indexPath];
    cell.backgroundColor = [UIColor whiteColor];
}
//返回这个UICollectionView是否可以被选择
-(BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}

下面给出一个实例

首先自定义一个UICollectionViewCell

#import <UIKit/UIKit.h>

@interface CollectionViewCell : UICollectionViewCell

@property (nonatomic, strong)   UIImageView *imageView;
@property (nonatomic, strong)   UILabel *titleLabel;

@end

#import "CollectionViewCell.h"

@interface CollectionViewCell()

@end

@implementation CollectionViewCell

- (instancetype)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        self.backgroundColor = [UIColor purpleColor];
        [self createView];
    }
    return self;
}

- (UIImageView *)imageView {
    if (_imageView == nil) {
        CGRect frame = CGRectMake(, , , );
        _imageView = [[UIImageView alloc] initWithFrame:frame];
    }
    return _imageView;
}

- (UILabel *)titleLabel {
    if (_titleLabel == nil) {
        CGRect frame = CGRectMake(, , , );
        _titleLabel = [[UILabel alloc] initWithFrame:frame];
        _titleLabel.textAlignment = NSTextAlignmentCenter;
    }
    return _titleLabel;
}

- (void)createView {
    [self.contentView addSubview:self.imageView];
    [self.contentView addSubview:self.titleLabel];
}

@end

在控制器里设置代理

UICollectionView 初始化是一定要指定布局对象

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@end

//
//  ViewController.m
//  CollectionViewController
//
//  Created by chao on 15/8/3.
//  Copyright (c) 2015年 chao. All rights reserved.
//

#import "ViewController.h"
#import "CollectionViewCell.h"

@interface ViewController ()<UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout>

@property (nonatomic, strong) UICollectionView *collectionView;

@end

@implementation ViewController

- (UICollectionView *)collectionView {
    if (_collectionView == nil) {
        CGRect frame = CGRectMake(, , [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height);
        UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
        _collectionView = [[UICollectionView alloc] initWithFrame:frame collectionViewLayout:flowLayout];
        _collectionView.dataSource = self;
        _collectionView.delegate = self;
    }
    return _collectionView;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.collectionView registerClass:[CollectionViewCell class] forCellWithReuseIdentifier:@"CollectionCell"];
    [self.view addSubview:self.collectionView];
    // Do any additional setup after loading the view, typically from a nib.
}

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

//定义展示的UICollectionViewCell的个数
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return ;
}
//定义展示的Section的个数
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return ;
}
//每个UICollectionView展示的内容
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString * CellIdentifier = @"CollectionCell";

    CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
    cell.imageView.image = [UIImage imageNamed:@"1680_1050_3983.jpg"];
    cell.titleLabel.text = [NSString stringWithFormat:@"%ld", indexPath.row];
//    [cell sizeToFit];
    return cell;
}

#pragma mark --UICollectionViewDelegateFlowLayout
//定义每个UICollectionView 的大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return CGSizeMake(, );
}
//定义每个UICollectionView 的 margin
-(UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    return UIEdgeInsetsMake(, , , );
}
#pragma mark --UICollectionViewDelegate
//UICollectionView被选中时调用的方法
-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell * cell = (UICollectionViewCell *)[collectionView cellForItemAtIndexPath:indexPath];
    cell.backgroundColor = [UIColor whiteColor];
}
//返回这个UICollectionView是否可以被选择
-(BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}

@end

//
//  AppDelegate.h
//  CollectionViewController
//
//  Created by chao on 15/8/3.
//  Copyright (c) 2015年 chao. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@end

#import "AppDelegate.h"
#import "ViewController.h"

@interface AppDelegate ()

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
    ViewController *vc = [[ViewController alloc] init];
    self.window.rootViewController = vc;
    [self.window makeKeyAndVisible];
    return YES;
}

@end