iOS UICollectionView的实现

ios的UICollectionView并不能在iOS6之前的版本中使用，为了兼容之前的版本需要自定义UICollectionView。写完之后发现人家已经有开源了，下过来看了看发现我是用UIScrollerView的委托真是多此一举，完全可以用layout来实现嘛。我在判断重用的时候用了一大堆if没有别人写的简洁明了。

首先是定义委托，需要用户传入collection总item的总数与每一行中item的个数。其余的与UITableView的委托基本一致。
isNeedRefreshOrMore方法用来判断用户使用需要下拉刷新上拉更多的功能，返回YES就使用。
doCollectionRefresh即为响应下拉刷新事件。更多同样。。

#pragma mark -
#pragma mark 委托
@protocol CustomCollectionDataSource<NSObject>
@required
//item的总个数
-(NSInteger)numberOfItemsInCollection;
//每一行的个数
-(NSInteger)numberOfItemsInRow;
@end

@protocol CustomCollectionDelegate<NSObject>
@required
-(CustomCollectionItem *)itemInCollectionAtPoint:(CGPoint)point collectionView:(CustomCollectionView *)collection;
@optional
-(void)itemDidSelectedAtPoint:(CGPoint)point;
-(BOOL)isNeedRefreshOrMore;
-(void)doCollectionRefresh;
-(void)doCollectionMore;

-(UIView *)collectionViewForHeader;
@end

在同文件中定义了页面状态的枚举，用来区分Collcetion的状态。同时定义了一些public方法

#import <UIKit/UIKit.h>

typedef enum {
CS_Init,
CS_More,
CS_Refresh
}CollectionState;

@class CustomCollectionItem;
@protocol CustomCollectionDataSource;
@protocol CustomCollectionDelegate;

@interface CustomCollectionView : UIScrollView<UIScrollViewDelegate>
@property (weak, nonatomic) id<CustomCollectionDataSource> dataSource;
@property (weak, nonatomic) id<CustomCollectionDelegate> customDelegate;

-(CustomCollectionItem *)dequeueReusableItemWithIdentifier:(NSString *)identifier;
-(void)addItemsIntoDic;
-(void)itemClickedAtPoint:(CGPoint)point;
-(void)reloadData;
-(CustomCollectionItem *)getItemAtPoint:(CGPoint)point;

@property (strong,nonatomic) UIView *headerView;
@end

#import "CustomCollectionView.h"
#import "CustomCollectionItem.h"
#import "BaseRMView.h"
@interface CustomCollectionView()
//重用池--原谅这个名字
@property (strong, nonatomic) NSMutableDictionary *contentItemDictionary;
//能够显示的item数量（以行计）
@property(assign,nonatomic) NSInteger showCount;
@property (assign,nonatomic) NSInteger offRowIndex;
//分割线--没有用到 默认成了10px
@property (assign,nonatomic) CGFloat itemSpliteWidth;
//总行数
@property (assign,nonatomic) NSInteger rows;
//item个数
@property (assign, nonatomic) NSInteger numberOfItemsInCollection;
//每行item个数
@property (assign,nonatomic) NSInteger numberOfItemsInRow;
//每一行的高度
@property (assign, nonatomic) CGFloat heightOfRow;
//
@property (assign, nonatomic) CGRect viewFrame;
//是否第一次加载
@property (assign,nonatomic) BOOL isFirstLoad;
//上一次scrollview的offsetY，用来判断是向上滑动还是向下滑动
@property (assign,nonatomic) CGFloat lastOffsetY;
//当前最后一行的index，从0开始
@property (assign,nonatomic) NSInteger lastRowIndex;
//当前最上一行的index，从0开始
@property (assign,nonatomic) NSInteger topRowIndex;
//没用
@property (assign,nonatomic) NSInteger numberOfMore;
//是否需要显示刷新更多页面标志
@property (assign,nonatomic) BOOL isNeedShowMoreTag;
//刷新view
@property (strong,nonatomic) BaseRMView *refreshView;
//更多view
@property (strong,nonatomic) BaseRMView *moreView;

@property (assign,nonatomic) CGFloat baseOffsetY;
@property (assign,nonatomic) CGFloat baseCanMove;
//reload之前的行数，上拉更多的时候如果用户滑动的距离超过行高会出错，用beforeRowCount来比较rows来判断新增的item需要添加的坐标
@property (assign,nonatomic) NSInteger beforeRowCount;

//@property (assign,nonatomic) NSInteger firstShowCount;
@end

#pragma mark -
#pragma mark 页面初始化
-(id)init{
CGRect frame=[UIScreen mainScreen].applicationFrame;
self=[self initWithFrame:frame];
if(self){

}
return self;
}

- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
_viewFrame=frame;
self.delegate=self;
_isFirstLoad=YES;
_contentItemDictionary=[[NSMutableDictionary alloc] init];
_isNeedShowMoreTag=NO;
}
return self;
}

#pragma mark -
#pragma mark 数据初始化
-(void)loadData{
if ([_dataSource respondsToSelector:@selector(numberOfItemsInCollection)]) {
_numberOfItemsInCollection=[_dataSource numberOfItemsInCollection];
}else{
_numberOfItemsInCollection=0;
}
if([_dataSource respondsToSelector:@selector(numberOfItemsInRow)]){
_numberOfItemsInRow=[_dataSource numberOfItemsInRow];
_heightOfRow=((300.0-(_numberOfItemsInRow-1)*10)/_numberOfItemsInRow);
_itemSpliteWidth=10;
}else{
_numberOfItemsInRow=3;//默认为3
_heightOfRow=88;
_itemSpliteWidth=18;
}
if ([_dataSource respondsToSelector:@selector(numberofMore)]) {
_numberOfMore=[_dataSource numberofMore];
}
if ([_customDelegate respondsToSelector:@selector(isNeedRefreshOrMore)]) {
_isNeedShowMoreTag=[_customDelegate isNeedRefreshOrMore];
}
if ([_customDelegate respondsToSelector:@selector(collectionViewForHeader)]) {
_headerView=[_customDelegate collectionViewForHeader];
if (![self.subviews containsObject:_headerView]) {
[self addSubview:_headerView];
}
}
//计算行数
_rows=ceil((float)_numberOfItemsInCollection/_numberOfItemsInRow);
CGFloat contentHeight=(_rows*_heightOfRow + (_rows+1)*10+_headerView.frame.size.height);
CGFloat scrollContentHeight=contentHeight>_viewFrame.size.height?contentHeight:_viewFrame.size.height;
//计算一页能显示多少行
_showCount=  (NSInteger)ceil((self.frame.size.height/(_heightOfRow+10)));
[self setContentSize:CGSizeMake(320, scrollContentHeight)];
//判断是否有新增行，如果有当前最上义行index+1
if (_rows!=_beforeRowCount&&_beforeRowCount!=0) {
_topRowIndex++;
}
　　//从当前最上一行开始增加showcount行的item
for (int i=_topRowIndex; i<_topRowIndex+_showCount; i++) {
[self creatItem:i];
}
if (_isNeedShowMoreTag==YES) {
if (![self.subviews containsObject:_refreshView]) {
_refreshView=[[BaseRMView alloc] initWithState:Refresh];
[_refreshView setFrame:CGRectMake(0, -50, 320, 50)];
[_refreshView setBackgroundColor:[UIColor grayColor]];
[self addSubview:_refreshView];
}

if (![self.subviews containsObject:_moreView]) {
_moreView=[[BaseRMView alloc] initWithState:More];
[_moreView setFrame:CGRectMake(0, self.contentSize.height, 320, 50)];
[_moreView setBackgroundColor:[UIColor grayColor]];
[self addSubview:_moreView];
}else{
[_moreView setFrame:CGRectMake(0, self.contentSize.height, 320, 50)];
}
}
}

-(void)layoutSubviews{
//第一次加载时初始化数据，之后不需要重新计算
if (_isFirstLoad) {
[self loadData];
//offsetY基数 只在第一次移动时候，10为默认的分割线高度
_baseOffsetY=(10*(_showCount+1)+_heightOfRow*_showCount)-self.frame.size.height;
//移动基数
_baseCanMove=10+_heightOfRow;
_isFirstLoad=NO;
_lastRowIndex=_showCount-1;
_topRowIndex=0;
}
}

//重新加载数据，记录加载前的行数
-(void)reloadData{
_beforeRowCount=_rows;
[self loadData];
}

#pragma mark -
#pragma mark Item相关
-(void)creatItem:(NSInteger)rowIndex{
if ([_customDelegate respondsToSelector:@selector(itemInCollectionAtPoint:collectionView:)]) {
for (int j=0; j<_numberOfItemsInRow; j++) {
//判断当前个数是否超过了总个数（单数情况下）
if (!(((rowIndex)*_numberOfItemsInRow+j+1)>_numberOfItemsInCollection)) {
//根据委托创建item
CustomCollectionItem *item=[_customDelegate itemInCollectionAtPoint:CGPointMake(rowIndex, j) collectionView:self];
//设置item的大小
[item setFrame:CGRectMake(10+_heightOfRow*j+_itemSpliteWidth*j, 10+_heightOfRow*rowIndex+10*rowIndex+_headerView.frame.size.height, _heightOfRow, _heightOfRow)];
//设置item的point坐标
item.point=CGPointMake(rowIndex, j);
//在view中加入item
[self addSubview:item];
}
}
}
}

//根据重用标志（reuseidentifier）从重用池中获取item
-(CustomCollectionItem *)dequeueReusableItemWithIdentifier:(NSString *)identifier{
NSArray *cellArray=[self.contentItemDictionary objectForKey:identifier];
if (cellArray.count==0) {
return nil;
}else{
id firstObject=[cellArray objectAtIndex:0];
if([firstObject isKindOfClass:[CustomCollectionItem class]]){
//获取item后从重用池中删除item;
CustomCollectionItem *item=firstObject;
[[self.contentItemDictionary objectForKey:identifier] removeObject:firstObject];
[item reset];
return item;
}else{
return nil;
}
}
}

//根据point坐标从当前item数组中获取item
-(CustomCollectionItem *)getItemAtPoint:(CGPoint)point{
CustomCollectionItem *result=nil;
for (id item in self.subviews) {
if ([item isKindOfClass:[CustomCollectionItem class]]) {
if (((CustomCollectionItem *)item).point.x==point.x
&& ((CustomCollectionItem *)item).point.y==point.y) {
result=item;
}
}
}
return result;
}

-(void)addItemToPool:(CustomCollectionItem *)item{
if([[self.contentItemDictionary allKeys] containsObject:item.reuseIdentifier]){
[[self.contentItemDictionary objectForKey:item.reuseIdentifier] addObject:item];
}else{
NSMutableArray *cellArray=[NSMutableArray arrayWithObject:item];
[self.contentItemDictionary setObject:cellArray forKey:item.reuseIdentifier];
}
}

#pragma mark -
#pragma mark 页面滚动
//topRowIndex   ---> 当前最上一行的index(从0开始);
//lastRowIndex  ---> 当前最后一行的index
//removeIndex   ---> 当前被移除的最后一行的行数(从1开始)
//addIndex      ---> 在showcount基础上增加的行数
-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
@try {
//手指向上移动移动基数后将显示下一页面
//手指向下移动移动基数将移除最下一行
BOOL isMoveUp=TRUE;//是否向下滑
if (scrollView.contentOffset.y-_lastOffsetY>0) {
isMoveUp=FALSE;
}else{
isMoveUp=TRUE;
}
_lastOffsetY=scrollView.contentOffset.y;

//刷新更多
if (scrollView.contentOffset.y==0) {
if ([self.subviews containsObject:_refreshView]) {
[_refreshView changeState:Refresh];
}
}else if(scrollView.contentOffset.y==scrollView.contentSize.height-scrollView.frame.size.height){
if ([self.subviews containsObject:_moreView]) {
[_moreView changeState:More];
}
}else if (scrollView.contentOffset.y>(scrollView.contentSize.height-scrollView.frame.size.height) ||
scrollView.contentOffset.y<0) {
if (scrollView.contentOffset.y>=(scrollView.contentSize.height-scrollView.frame.size.height+50)) {
if ([self.subviews containsObject:_moreView]&&_moreView.viewState==More) {
[_moreView changeState:ToMore];
}
}else if (scrollView.contentOffset.y<-50){
if ([self.subviews containsObject:_refreshView]&&_refreshView.viewState==Refresh) {
[_refreshView changeState:ToRefresh];
}
}
}else{
//判断重用
if (scrollView.contentOffset.y>_headerView.frame.size.height) {
CGFloat realMove=scrollView.contentOffset.y-_headerView.frame.size.height;
//增加的row坐标 初始为0 移动一个移动基数后加/减1
NSInteger addIndex=ceil((realMove-_baseOffsetY)/_baseCanMove);
//删除的row坐标 初始为0 移动一个移动基数后加/减1
NSInteger removeIndex=(realMove/_baseCanMove);

//手指向上移动
if (!isMoveUp) {
//如果最后一行编号==增加的row坐标+1&&增加的row坐标<总行数-1
if (_lastRowIndex==addIndex+_showCount-2&&addIndex<_rows-1) {
//最后一行坐标++
_lastRowIndex++;
//如果最后一行坐标！=总行数；如果相等则为最后一行不需要增加
if (_lastRowIndex!=_rows) {
[self creatItem:_lastRowIndex];
}
}
//如果删除的row坐标！=0&&删除的row坐标！=最上一行坐标&&最上一行坐标<总行数-显示行数
if (removeIndex!=0&&removeIndex!=_topRowIndex&&_topRowIndex<_rows-_showCount) {
for (int i=0; i<_numberOfItemsInRow; i++) {
CustomCollectionItem *item=[self getItemAtPoint:CGPointMake(removeIndex-1, i)];
if (item!=nil) {
[self addItemToPool:item];
[item removeFromSuperview];
}
}
_topRowIndex++;
}
}else{//remove-->add add-->remove
if (removeIndex==_topRowIndex-1) {
[self creatItem:removeIndex];
_topRowIndex--;
}
if (addIndex!=0&&addIndex!=_lastRowIndex-_showCount+1) {
if (_lastRowIndex==_rows) {
_lastRowIndex--;
}else{
for (int i=0; i<_numberOfItemsInRow; i++) {
CustomCollectionItem *item=[self getItemAtPoint:CGPointMake(_lastRowIndex, i)];
if (item!=nil) {
[self addItemToPool:item];
[item removeFromSuperview];
}
}
_lastRowIndex--;
}
}
}
}
}
}
@catch (NSException *exception) {
NSLog(@"customCollectionView exception %@",exception.reason);
}
}

#pragma mark-
#pragma mark item点击
-(void)itemClickedAtPoint:(CGPoint)point{
if ([_customDelegate respondsToSelector:@selector(itemDidSelectedAtPoint:)]) {
[_customDelegate itemDidSelectedAtPoint:point];
}
}

#pragma mark-
#pragma mark 刷新更多

-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
if (scrollView.contentOffset.y<-50) {
if (_isNeedShowMoreTag==YES&&[self.subviews containsObject:_refreshView]) {
if ([_customDelegate respondsToSelector:@selector(doCollectionRefresh)]) {
[_customDelegate doCollectionRefresh];
}
[_refreshView changeState:EndRefresh];
}
}else if (scrollView.contentOffset.y>scrollView.contentSize.height-scrollView.frame.size.height+50){
if (_isNeedShowMoreTag==YES&&[self.subviews containsObject:_moreView]) {
if ([_customDelegate respondsToSelector:@selector(doCollectionMore)]) {
[_customDelegate doCollectionMore];
}
[_moreView changeState:EndMore];
}
}
}

#import <UIKit/UIKit.h>
#import <objc/runtime.h>
#import <Foundation/Foundation.h>
@interface CustomCollectionItem : UIView<UIGestureRecognizerDelegate,NSCoding>
@property (strong,nonatomic) UIImageView *backgroundImage;
@property (strong,nonatomic) NSString *reuseIdentifier;
@property (assign,nonatomic) CGPoint point;
-(id)initWithReuseIdentifier:(NSString *)identifier;
-(void)itemTaped;
-(void)reset;
@end

#import "CustomCollectionItem.h"
#import "CustomCollectionView.h"

@interface CustomCollectionItem()
@property(strong,nonatomic) UIView *contentView;
@end

@implementation CustomCollectionItem

-(id)initWithReuseIdentifier:(NSString *)identifier{
self=[super init];
if (self) {
_reuseIdentifier=identifier;
[self setUserInteractionEnabled:YES];
_backgroundImage= [[UIImageView alloc] init];
}
return self;
}

-(void)setFrame:(CGRect)frame {
[super setFrame:frame];
[_backgroundImage setFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
_backgroundImage.tag=10099;
}

-(void)layoutSubviews {
[super layoutSubviews];
if([self viewWithTag:10099]== nil)   {
[self addSubview:_backgroundImage];
[self sendSubviewToBack:_backgroundImage];
}
UITapGestureRecognizer *tapGR=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(itemTaped)];
[self addGestureRecognizer:tapGR];
}

-(void)itemTaped{
[(CustomCollectionView *)[self superview] itemClickedAtPoint:self.point];
}

-(void)setBackgroundImage:(UIImageView *)backgroundImage {
_backgroundImage=backgroundImage;
}

#pragma override
-(void)reset{

}

- (void)encodeWithCoder:(NSCoder*)coder
{
Class clazz = [self class];
u_int count;

objc_property_t* properties = class_copyPropertyList(clazz, &count);
NSMutableArray* propertyArray = [NSMutableArray arrayWithCapacity:count];
for (int i = 0; i < count ; i++)
{
const char* propertyName = property_getName(properties[i]);
[propertyArray addObject:[NSString  stringWithCString:propertyName encoding:NSUTF8StringEncoding]];
}
free(properties);

for (NSString *name in propertyArray)
{
id value = [self valueForKey:name];
[coder encodeObject:value forKey:name];
}
}

- (id)initWithCoder:(NSCoder*)decoder
{
if (self = [super init])
{
if (decoder == nil)
{
return self;
}

Class clazz = [self class];
u_int count;

objc_property_t* properties = class_copyPropertyList(clazz, &count);
NSMutableArray* propertyArray = [NSMutableArray arrayWithCapacity:count];
for (int i = 0; i < count ; i++)
{
const char* propertyName = property_getName(properties[i]);
[propertyArray addObject:[NSString  stringWithCString:propertyName encoding:NSUTF8StringEncoding]];
}
free(properties);

for (NSString *name in propertyArray)
{
id value = [decoder decodeObjectForKey:name];
[self setValue:value forKey:name];
}
}
return self;
}
@end