IOS瀑布流通过UICollectionView控件实现

#define screenHeight [[UIScreen mainScreen]bounds].size.height //屏幕高度
#define screenWidth [[UIScreen mainScreen]bounds].size.width   //屏幕宽度
#define colletionCell 3  //设置具体几列
@interface HomeViewController (){
UICollectionView *collectionView;
NSMutableArray  *hArr; //记录每个cell的高度
}

@end

@implementation HomeViewController
- (void)viewDidLoad {
[super viewDidLoad];
hArr = [[NSMutableArray alloc] init];
UICollectionViewFlowLayout *flowLayout=[[UICollectionViewFlowLayout alloc]init];
[flowLayout setScrollDirection:UICollectionViewScrollDirectionVertical]; //设置横向还是竖向
collectionView=[[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, screenWidth ,screenHeight) collectionViewLayout:flowLayout];
collectionView.dataSource=self;
collectionView.delegate=self;
[collectionView setBackgroundColor:[UIColor clearColor]];
[collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"UICollectionViewCell"];
[self.view addSubview:collectionView];
}
#pragma mark -- UICollectionViewDataSource

//定义展示的UICollectionViewCell的个数
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return 20;
}

//定义展示的Section的个数
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}

//每个UICollectionView展示的内容
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
static NSString * CellIdentifier = @"UICollectionViewCell";
UICollectionViewCell * cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];

cell.backgroundColor = [UIColor colorWithRed:((10 * indexPath.row) / 255.0) green:((20 * indexPath.row)/255.0) blue:((30 * indexPath.row)/255.0) alpha:1.0f];
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 20, 20)];
label.textColor = [UIColor redColor];
label.text = [NSString stringWithFormat:@"%d",indexPath.row];
//移除cell
for (id subView in cell.contentView.subviews) {
[subView removeFromSuperview];
}
NSInteger remainder=indexPath.row%colletionCell;
NSInteger currentRow=indexPath.row/colletionCell;
CGFloat   currentHeight=[hArr[indexPath.row] floatValue];

CGFloat positonX=(screenWidth/colletionCell-8)*remainder+5*(remainder+1);
CGFloat positionY=(currentRow+1)*5;
for (NSInteger i=0; i<currentRow; i++) {
NSInteger position=remainder+i*colletionCell;
positionY+=[hArr[position] floatValue];
}
cell.frame = CGRectMake(positonX, positionY,screenWidth/colletionCell-8,currentHeight) ;//重新定义cell位置、宽高

[cell.contentView addSubview:label];
return cell;
}

#pragma mark --UICollectionViewDelegateFlowLayout

//定义每个Item 的大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
CGFloat height=100+(arc4random()%120);
[hArr addObject:[NSString stringWithFormat:@"%f",height]];
return  CGSizeMake(screenWidth/colletionCell-8, height);  //设置cell宽高
}

//定义每个UICollectionView 的 margin
-(UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
return UIEdgeInsetsMake(0,0, 0, 0);
}

#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 greenColor];
}

//返回这个UICollectionView是否可以被选择
-(BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
return YES;
}

@end