瀑布流

LWTWaterFlowView.h

//
//  LWTWaterFlowView.h
//  瀑布流
//
//  Created by apple on 14-7-29.
//  Copyright (c) 2014年 lwt. All rights reserved.
//

#import <UIKit/UIKit.h>

typedef enum {
    LWTWaterFlowViewMarginTypeTop, // 上
    LWTWaterFlowViewMarginTypeLeft, // 左
    LWTWaterFlowViewMarginTypeBotton, // 下
    LWTWaterFlowViewMarginTypeRight, // 右
    LWTWaterFlowViewMarginTypeRow, // 行
    LWTWaterFlowViewMarginTypeColumn, // 列
} LWTWaterFlowViewMarginType;

@class LWTWaterFlowView, LWTWaterFlowViewCell;
/**
 *  瀑布流数据源
 */
@protocol LWTWaterFlowViewDataSource <NSObject>

/**
 *  有多少个数据
 */
- (NSUInteger)numberOfCellInWaterFlowView:(LWTWaterFlowView *)waterFlowView;

/**  返回index位置对应的cell */
- (LWTWaterFlowViewCell *)waterFlowView:(LWTWaterFlowView *)waterFlowView cellAtIndex:(NSUInteger)index;
@optional
/**  一共有多少列 */
- (NSUInteger)numberOfColumnsInWaterFlowView:(LWTWaterFlowView *)waterFlowView;
@end

/**
 *  瀑布流代理
 */
@protocol LWTWaterFlowViewDelegate <UIScrollViewDelegate>
@optional
/**  第index位置cell对应的高度 */
- (CGFloat)waterFlowView:(LWTWaterFlowView *)waterFlowView heightForCellAtIndex:(NSUInteger)index;

/**  选中第index位置的cell */
- (void)waterFlowView:(LWTWaterFlowView *)waterFlowView didSelectForCellAtIndex:(NSUInteger)index;
/**
 *  间距
 */
- (CGFloat)waterFlowView:(LWTWaterFlowView *)waterFlowView marginForType:(LWTWaterFlowViewMarginType)type;
@end

@interface LWTWaterFlowView : UIScrollView
/**
 *  数据源
 */
@property (nonatomic, weak) id<LWTWaterFlowViewDataSource> dataSource;

/**
 *  代理
 */
@property (nonatomic, weak) id<LWTWaterFlowViewDelegate> delegate;

/**
 *  刷新数据（只要调用这个方法，会重新向数据源和代理发送请求，请求数据）
 */
- (void)reloadData;

/**
 *  cell的宽度
 */
- (CGFloat)cellWidth;

/**
 *  根据标识去缓存池查找可循环利用的cell
 */
- (id) dequeueReusableCellWithIdentifier:(NSString *)identifier;

@end

LWTWaterFlowView.m

//
//  LWTWaterFlowView.m
//  瀑布流
//
//  Created by apple on 14-7-29.
//  Copyright (c) 2014年 lwt. All rights reserved.
//

#import "LWTWaterFlowView.h"
#import "LWTWaterFlowViewCell.h"

#define KWaterflowViewDefaultCellH 70
#define KWaterflowViewDefaultMargin 8
#define KWaterflowViewDefaultNumberOfColumns 3

@interface LWTWaterFlowView ()
/**
 *  所有cell的frame数据
 */
@property (nonatomic, strong) NSMutableArray *cellFrames;
/**
 *  正在展示的cell
 */
@property (nonatomic, strong) NSMutableDictionary *displayCells;
/**
 *  缓存池（用Set，存放离开屏幕的cell）
 */
@property (nonatomic, strong) NSMutableSet *reusableCells;
@end

@implementation LWTWaterFlowView
#pragma mark - 初始化
- (NSMutableArray *)cellFrames
{
    if (nil == _cellFrames) {
        _cellFrames = [NSMutableArray array];
    }
    return _cellFrames;
}

- (NSMutableDictionary *)displayCells
{
    if (nil == _displayCells) {
        _displayCells = [NSMutableDictionary dictionary];
    }
    return _displayCells;
}

- (NSMutableSet *)reusableCells
{
    if (nil == _reusableCells) {
        _reusableCells = [NSMutableSet set];
    }
    return _reusableCells;
}

- (void)willMoveToSuperview:(UIView *)newSuperview
{
    [self reloadData];
}

#pragma mark - 公共接口

- (void)reloadData
{
    // 清空之前的所有数据
    // 移除正在正在显示cell
    [self.displayCells.allValues makeObjectsPerformSelector:@selector(removeFromSuperview)];
    [self.displayCells removeAllObjects];
    [self.cellFrames removeAllObjects];
    [self.reusableCells removeAllObjects];
    
    // cell的总数
    int numbersOfCell = [self.dataSource numberOfCellInWaterFlowView:self];
    
    // 总列数
    int numberOfColumns = [self numberOfColumns];
    // 间距
    CGFloat topMargin = [self marginForType:LWTWaterFlowViewMarginTypeTop];
    CGFloat leftMargin = [self marginForType:LWTWaterFlowViewMarginTypeLeft];
    CGFloat bottomMargin = [self marginForType:LWTWaterFlowViewMarginTypeBotton];
    CGFloat rowMargin = [self marginForType:LWTWaterFlowViewMarginTypeRow];
    CGFloat columnMargin = [self marginForType:LWTWaterFlowViewMarginTypeColumn];
    
    // cell的宽度
    CGFloat cellWidth = [self cellWidth];
    
    // 用一个C语言数组存放所有列的最大Y值
    CGFloat maxYOfColumns[numberOfColumns];
    for (int i = 0; i<numberOfColumns; i++) {
        maxYOfColumns[i] = 0.0;
    }
    
    // 计算所有cell的frame
    for (int i = 0; i < numbersOfCell ; i++) {
        // cell的高度
        CGFloat cellHeight = [self heightAtIndex:i];
        
        // cell处在第几列(最短的一列)
        NSUInteger cellColumn = 0;
        // cell所处那列的最大的Y值(最短那一列的最大的Y值)
        NSUInteger maxYOfCellColumn = maxYOfColumns[cellColumn];
        // 求出最短的一列
        for (int j = 1 ; j < numberOfColumns; j++) {
            if (maxYOfColumns[j] < maxYOfCellColumn) {
                cellColumn = j;
                maxYOfCellColumn = maxYOfColumns[j];
            }
        }
        
        CGFloat cellX = leftMargin + (cellWidth + columnMargin) * cellColumn;
        
        CGFloat cellY = 0;
        if (maxYOfCellColumn == 0.0) {  // 首行
            cellY = topMargin;
        } else {
            cellY = maxYOfCellColumn + rowMargin;
        }
        
        CGRect cellFrame = CGRectMake(cellX, cellY, cellWidth, cellHeight);
        [self.cellFrames addObject:[NSValue valueWithCGRect:cellFrame]];
        
        maxYOfColumns[cellColumn] = CGRectGetMaxY(cellFrame);
    }
    
    // 设置contentSize
    CGFloat contentH = maxYOfColumns[0];
    for (int j = 1 ; j < numberOfColumns; j++) {
        if (maxYOfColumns[j] > contentH) {
            contentH = maxYOfColumns[j];
        }
    }
    self.contentSize = CGSizeMake(0, contentH + bottomMargin);
    
    
}

/**
 *  当UIScrollView滚动的时候也会调用这个方法
 */
- (void)layoutSubviews
{
    [super layoutSubviews];
    
    int numberOfCell = self.cellFrames.count;
    
    // 向数据源索要对应位置的cell
    for (int i = 0; i<numberOfCell; i++) {
        // 取出i位置的frame
        CGRect cellFrame = [self.cellFrames[i] CGRectValue];
        
        // 优先从字典中取出i位置的cell
        LWTWaterFlowViewCell *cell = self.displayCells[@(i)];
        
        // 判断i位置对应的frame在不在屏幕上（能否看见）
        if ([self isInScreen:cellFrame]) {
            if (cell == nil) {  // 在屏幕上
                cell = [self.dataSource waterFlowView:self cellAtIndex:i];
                cell.frame = cellFrame;
                [self addSubview:cell];
                
                // 存放到字典中
                [self.displayCells setObject:cell forKey:@(i)];
            }
        } else {   // 不在屏幕上
            if (cell) {
                // 存放进缓存池
                [self.reusableCells addObject:cell];
                
                // 从scrollView和字典中移除
                [self.displayCells removeObjectForKey:@(i)];
                [cell removeFromSuperview];
            }
        }
    }
}

/**
 *  cell的宽度
 */
- (CGFloat)cellWidth
{
    // 总列数
    int numberOfColumns = [self numberOfColumns];
    CGFloat leftMargin = [self marginForType:LWTWaterFlowViewMarginTypeLeft];
    CGFloat rightMargin = [self marginForType:LWTWaterFlowViewMarginTypeRight];
    CGFloat columnMargin = [self marginForType:LWTWaterFlowViewMarginTypeColumn];
    
    return (self.bounds.size.width - leftMargin - rightMargin - (numberOfColumns - 1) * columnMargin) / numberOfColumns;
}

- (id)dequeueReusableCellWithIdentifier:(NSString *)identifier
{
    __block LWTWaterFlowViewCell *reusableCell = nil;
    [self.reusableCells enumerateObjectsUsingBlock:^(LWTWaterFlowViewCell *cell, BOOL *stop) {
        if ([cell.identifier isEqualToString:identifier]) {
            reusableCell = cell;
            *stop = YES;
        }
    }];
    
    if (reusableCell) {  // 从缓存池中移除
        [self.reusableCells removeObject:reusableCell];
    }
    
    return reusableCell;
}
#pragma mark - 私有方法
- (BOOL)isInScreen:(CGRect)frame
{
    return (CGRectGetMaxY(frame) > self.contentOffset.y) && (CGRectGetMinY(frame) < (self.contentOffset.y + self.bounds.size.height));
}

/**
 *  获取总列数
 */
- (NSUInteger)numberOfColumns
{
    if ([self.dataSource respondsToSelector:@selector(numberOfColumnsInWaterFlowView:)]) {
        return [self.dataSource numberOfColumnsInWaterFlowView:self];
    } else {
        return KWaterflowViewDefaultNumberOfColumns;
    }
}

/**
 *  获取间距
 */
- (CGFloat)marginForType:(LWTWaterFlowViewMarginType)type
{
    if ([self.delegate respondsToSelector:@selector(waterFlowView:marginForType:)]) {
        return [self.delegate waterFlowView:self marginForType:type];
    } else {
        return KWaterflowViewDefaultMargin;
    }
}

/**
 *  index位置对应cell的高度
 */
- (CGFloat)heightAtIndex:(NSUInteger)index
{
    if ([self.delegate respondsToSelector:@selector(waterFlowView:heightForCellAtIndex:)]) {
        return [self.delegate waterFlowView:self heightForCellAtIndex:index];
    } else {
        return KWaterflowViewDefaultCellH;
    }
}


#pragma mark - 事件处理
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    if (![self.delegate respondsToSelector:@selector(waterFlowView:didSelectForCellAtIndex:)]) return;
    
    // 获得触摸点
    UITouch *touch = [touches anyObject];
    CGPoint point = [touch locationInView:self];
    
    __block NSNumber *selectedIndex = nil;
    [self.displayCells enumerateKeysAndObjectsUsingBlock:^(id key, LWTWaterFlowViewCell *cell, BOOL *stop) {
        if (CGRectContainsPoint(cell.frame, point)) {
            selectedIndex = key;
            *stop = YES;
        }
    }];
    
    if (selectedIndex) {
        NSUInteger number = selectedIndex.unsignedIntegerValue;
        [self.delegate waterFlowView:self didSelectForCellAtIndex:number];
    }
}

@end

LWTWaterFlowViewCell.h

//
//  LWTWaterFlowViewCell.h
//  瀑布流
//
//  Created by apple on 14-7-29.
//  Copyright (c) 2014年 lwt. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface LWTWaterFlowViewCell : UIView
@property (nonatomic, copy) NSString *identifier;

- (instancetype)initWithIdentifier:(NSString *)identifier;

@end

LWTWaterFlowViewCell.m

//
//  LWTWaterFlowViewCell.m
//  瀑布流
//
//  Created by apple on 14-7-29.
//  Copyright (c) 2014年 lwt. All rights reserved.
//

#import "LWTWaterFlowViewCell.h"

@implementation LWTWaterFlowViewCell

- (id)initWithIdentifier:(NSString *)identifier
{
    self = [super init];
    if (self) {
        self.identifier = identifier;
    }
    return self;
}
@end