IOS开发之瀑布流照片墙实现

想必大家已经对互联网传统的照片布局方式司空见惯了，这种行列分明的布局虽然对用户来说简洁明了，但是长久的使用难免会产生审美疲劳。现在网上流行一种叫做“瀑布流”的照片布局样式，这种行与列参差不齐的状态着实给用户眼前一亮的感觉，这种不规则的方式也吸引着我，现在我们就来一起实现它吧 ：）
首先我们来看一下这种样式布局是如何体现的，请看示意图：

别看这种界面的布局好像毫无规律，其实它的排列还是很有规则的。我们拿手机屏幕举个例子，我们把屏幕等宽的划分为几个区域，由于手机屏幕比较小，我们就按照网上
最普遍的把屏幕分为等宽的三列，然后将图片加载在每一列中，在加入到列之前，要先判断哪一列的高度最低，然后把图片加到列高度最低的那列中。听起来是不是有些拗口，说简单点就是“哪列高度低就加哪”，这样听我一说是不是觉得原理其实很简单嘛！
下面我们就来用程序去实现他吧！首先看一张效果图。

新建一个Xcode工程，名字随便取吧（或者叫Album都可以）,然后新建三个类，分别是：MainViewController用于控制主界面， MyScrollView继承自UIScrollView用于控制界面滚动，以及图片的管理类ImageLoader。
我们先来看一下ImageLoader类，它是一个图片的处理类，负责对取到的图片进行等比例压缩，以至于加载到UImageView中时不会失真，代码如下：

#import "ImageLoader.h"@interface ImageLoader ()@end@implementation ImageLoader@synthesize imagesArray = _imagesArray;+ (ImageLoader *)shareInstance{    static ImageLoader *loader = nil;    static dispatch_once_t onceToken;    dispatch_once(&onceToken, ^{        loader = [[ImageLoader alloc] init];    });    return loader;}- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil{    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];    if (self) {        // Custom initialization    }    return self;}- (void)viewDidLoad{    [super viewDidLoad];// Do any additional setup after loading the view.}/*加载图片*/- (void)loadImage:(NSMutableArray *)array{    self.imagesArray = array;}/* 压缩图片，根据图片的大小按比例压缩 width:每列试图的宽度 返回一个UIImageView */- (UIImageView *)compressImage:(float)width imageName:(NSString *)name{    UIImageView *imgView = [[UIImageView alloc] init];    imgView.image = [UIImage imageNamed:name];        float orgi_width = [imgView image].size.width;    float orgi_height = [imgView image].size.height;        //按照每列的宽度，以及图片的宽高来按比例压缩    float new_width = width - 5;    float new_height = (width * orgi_height)/orgi_width;        //重置imageView的尺寸    [imgView setFrame:CGRectMake(0, 0, new_width, new_height)];        return imgView;}- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}- (void)dealloc{    [self.imagesArray release];    [super dealloc];}@end

这里将ImageLoader类设置成了单例，以便于在MainViewContrioller和MyScrollView中获取。
下面是MyScrollView的代码片段：

#import "MyScrollView.h"#define COORDINATE_X_LEFT 5#define COORDINATE_X_MIDDLE MY_WIDTH/3 + 5#define COORDINATE_X_RIGHT MY_WIDTH/3 * 2 + 5#define PAGESIZE 21@interface MyScrollView ()@end@implementation MyScrollView@synthesize mainScroll = _mainScroll;@synthesize isOnce = _isOnce;@synthesize imagesName = _imagesName;@synthesize loadedImageDic = _loadedImageDic;@synthesize leftColumHeight = _leftColumHeight;@synthesize midColumHeight = _midColumHeight;@synthesize rightColumHeight = _rightColumHeight;@synthesize loadedImageArray = _loadedImageArray;@synthesize imgTag = _imgTag;@synthesize imgTagDic = _imgTagDic;@synthesize imageLoad = _imageLoad;@synthesize page = _page;+ (MyScrollView *)shareInstance{    static MyScrollView *instance;    static dispatch_once_t onceToken;    dispatch_once(&onceToken, ^{        instance = [[self alloc] initWithFrame:CGRectMake(0, 0, MY_WIDTH, MY_HEIGHT)];        });        return instance;}/* 初始化scrollView的委托以及背景颜色，不显示它的水平，垂直显示条 */- (id)initWithFrame:(CGRect)frame{    self = [super initWithFrame:frame];    if(self){        self.delegate = self;        self.backgroundColor = [UIColor blackColor];        self.pagingEnabled = NO;        self.showsHorizontalScrollIndicator = NO;        self.showsVerticalScrollIndicator = NO;                self.isOnce = YES;        self.loadedImageDic = [[NSMutableDictionary alloc] init];        self.loadedImageArray = [[NSMutableArray alloc] init];        self.imgTagDic = [[NSMutableDictionary alloc] init];                //初始化列的高度        self.leftColumHeight = 3.0f;        self.midColumHeight = 3.0f;        self.rightColumHeight = 3.0f;        self.imgTag = 10086;        self.page = 1;                [self initWithPhotoBox];    }        return self;}/* 将scrollView界面分为大小相等的3个部分，每个部分为一个UIView, 并设置每一个UIView的tag */- (void)initWithPhotoBox{    UIView *leftView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, MY_WIDTH/3, self.frame.size.height)];    UIView *middleView = [[UIView alloc] initWithFrame:CGRectMake(leftView.frame.origin.x + MY_WIDTH/3, 0, MY_WIDTH/3,                                                                  self.frame.size.height)];    UIView *rightView = [[UIView alloc] initWithFrame:CGRectMake(middleView.frame.origin.x + MY_WIDTH/3, 0, MY_WIDTH/3,                                                                 self.frame.size.height)];    //设置三个部分的tag    leftView.tag = 100;    middleView.tag = 101;    rightView.tag = 102;        //设置背景颜色    [leftView setBackgroundColor:[UIColor clearColor]];    [middleView setBackgroundColor:[UIColor clearColor]];    [rightView setBackgroundColor:[UIColor clearColor]];        [self addSubview:leftView];    [self addSubview:middleView];    [self addSubview:rightView];        //第一次加载图片    self.imageLoad = [ImageLoader shareInstance];    for(int i = 0; i < PAGESIZE; i++){        NSString *imageName = [self.imageLoad.imagesArray objectAtIndex:i];        UIImageView *imgView = [self.imageLoad compressImage:MY_WIDTH/3 imageName:imageName];        [self addImage:imgView name:imageName];        [self checkImageIsVisible];    }    //第一页    self.page = 1;        [self adjustContentSize:NO];}/*调整scrollview*/- (void)adjustContentSize:(BOOL)isEnd{    UIView *leftView = [self viewWithTag:100];    UIView *middleView = [self viewWithTag:101];    UIView *rightView = [self viewWithTag:102];        if(_leftColumHeight >= _midColumHeight && _leftColumHeight >= _rightColumHeight){        self.contentSize = leftView.frame.size;    }else{        if(_midColumHeight >= _rightColumHeight){            self.contentSize = middleView.frame.size;        }else{            self.contentSize = rightView.frame.size;        }    }}/* 得到最短列的高度 */- (float)getTheShortColum{    if(_leftColumHeight <= _midColumHeight && _leftColumHeight <= _rightColumHeight){        return _leftColumHeight;    }else{        if(_midColumHeight <= _rightColumHeight){            return _midColumHeight;        }else{            return _rightColumHeight;        }    }}/* 添加一张图片 规则：根据每一列的高度来决定，优先加载列高度最短的那列 重新设置图片的x,y坐标 imageView:图片视图 imageName:图片名 */- (void)addImage:(UIImageView *)imageView name:(NSString *)imageName{    //图片是否加载    if([self.loadedImageDic objectForKey:imageName]){        return;    }        //若图片还未加载则保存    [self.loadedImageDic setObject:imageView forKey:imageName];    [self.loadedImageArray addObject:imageView];        [self imageTagWithAction:imageView name:imageName];        float width = imageView.frame.size.width;    float height = imageView.frame.size.height;    //判断哪一列的高度最低    if(_leftColumHeight <= _midColumHeight && _leftColumHeight <= _rightColumHeight){        UIView *leftView = [self viewWithTag:100];        [leftView addSubview:imageView];        //重新设置坐标        [imageView setFrame:CGRectMake(2, _leftColumHeight, width, height)];        _leftColumHeight = _leftColumHeight + height + 3;        [leftView setFrame:CGRectMake(0, 0, MY_WIDTH/3, _leftColumHeight)];    }else{        if(_midColumHeight <= _rightColumHeight){            UIView *middleView = [self viewWithTag:101];            [middleView addSubview:imageView];            [imageView setFrame:CGRectMake(2, _midColumHeight, width, height)];            _midColumHeight = _midColumHeight + height + 3;            [middleView setFrame:CGRectMake(MY_WIDTH/3, 0, MY_WIDTH/3, _midColumHeight)];        }else{            UIView *rightView = [self viewWithTag:102];            [rightView addSubview:imageView];            [imageView setFrame:CGRectMake(2, _rightColumHeight, width, height)];            _rightColumHeight = _rightColumHeight + height + 3;            [rightView setFrame:CGRectMake(2 * MY_WIDTH/3, 0, MY_WIDTH/3, _rightColumHeight)];        }    }}/* 将图片tag保存，以及为UIImageView添加事件响应 */- (void)imageTagWithAction:(UIImageView *)imageView name:(NSString *)imageName{    //将要显示图片的tag保存    imageView.tag = self.imgTag;    [self.imgTagDic setObject:imageName forKey:[NSString stringWithFormat:@"%d", imageView.tag]];    self.imgTag++;        //图片添加事件响应    UITapGestureRecognizer *tapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(imageClickWithTag:)];    tapRecognizer.delegate = self;    imageView.userInteractionEnabled = YES;    [imageView addGestureRecognizer:tapRecognizer];    [tapRecognizer release];}/*     //若三列中最短列距离底部高度超过30像素，则请求加载新的图片 */- (void)scrollViewDidScroll:(UIScrollView *)scrollView{    //可视检查    [self checkImageIsVisible];    if((self.contentOffset.y + self.frame.size.height) - [self getTheShortColum] > 30){        [self pullRefreshImages];    }}/* 上拉时加载新的图片 */- (void)pullRefreshImages{    int index = self.page *PAGESIZE;    int imgNum = [self.imageLoad.imagesArray count];        if(index >= imgNum){        //图片加载完毕        [self adjustContentSize:YES];        [MyToast showWithText:@"没有更多图片"];    }else{        if((imgNum - self.page*PAGESIZE) > PAGESIZE){            for (int i = index; i < PAGESIZE; i++) {                NSString *imageName = [self.imageLoad.imagesArray objectAtIndex:i];                UIImageView *imgView = [self.imageLoad compressImage:MY_WIDTH/3 imageName:imageName];                [self addImage:imgView name:imageName];                [self checkImageIsVisible];            }        }else{            for (int i = index; i < imgNum; i++) {                NSString *imageName = [self.imageLoad.imagesArray objectAtIndex:i];                UIImageView *imgView = [self.imageLoad compressImage:MY_WIDTH/3 imageName:imageName];                [self addImage:imgView name:imageName];                [self checkImageIsVisible];            }        }        self.page++;    }        [self adjustContentSize:NO];}/* 检查图片是否可见，如果不在可见视线内，则把图片替换为nil */- (void)checkImageIsVisible{    for (int i = 0; i < [self.loadedImageArray count]; i++) {        UIImageView *imgView = [self.loadedImageArray objectAtIndex:i];                if((self.contentOffset.y - imgView.frame.origin.y) > imgView.frame.size.height ||           imgView.frame.origin.y > (self.frame.size.height + self.contentOffset.y)){            //不显示图片            imgView.image = nil;        }else{            //重新根据tag值显示图片            NSString *imageName = [self.imgTagDic objectForKey:[NSString stringWithFormat:@"%d", imgView.tag]];            if((NSNull *)imageName == [NSNull null]){                return;            }            UIImageView *view = [self.imageLoad compressImage:MY_WIDTH/3 imageName:imageName];            imgView.image = view.image;        }    }}//点击图片事件响应- (void)imageClickWithTag:(UITapGestureRecognizer *)sender{    UIImageView *view = (UIImageView *)sender.view;    NSString *imageName = [self.imgTagDic objectForKey:[NSString stringWithFormat:@"%d", view.tag]];    NSLog(@"%@", imageName);        PhotoViewController *photoView = [[PhotoViewController alloc] init];    photoView.imageName = imageName;    [self addSubview:photoView.view];}- (void)dealloc{    [self.imagesName release];    [self.imgTagDic release];    [self.loadedImageArray release];    [super dealloc];}@end

在这个类中，我将三列等宽的UIView加入到ScrollView中，每次加入一张图片的时候都会去判断一下哪一列的高度最低。为了避免手机被图片的占用内存过高导致程序
崩溃的问题，我还作了一个照片可见性的逻辑判断，具体函数名为checkImageIsVisible，当照片不可见时，将imageView中的image设为nil，一旦照片出现了就根据照片的tag
获取到照片名重新设置image。
最后，当照片加载出来以后当然不能少了点击查看相册的功能啊！于是新建一个UIViewController类取名为：PhotoViewController，代码如下：

#import "PhotoViewController.h"@interface PhotoViewController ()@end@implementation PhotoViewController@synthesize headView = _headView;@synthesize mainView = _mainView;- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil{    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];    if (self) {        // Custom initialization    }    return self;}- (void)viewDidLoad{    [super viewDidLoad];// Do any additional setup after loading the view.    [self.view setFrame:CGRectMake(0, 0, MY_WIDTH, MY_HEIGHT)];    [self.view setBackgroundColor:[UIColor blackColor]];        self.headView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, MY_WIDTH, 50)];    UIButton *cancelBtn = [[UIButton alloc] initWithFrame:CGRectMake(0, 20, 40, 30)];    [cancelBtn setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];    [cancelBtn setTitle:@"取消" forState:UIControlStateNormal];    [self.headView addSubview:cancelBtn];    [cancelBtn addTarget:self action:@selector(closePhotoView) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:self.headView];        self.mainView = [[UIView alloc] initWithFrame:CGRectMake(0, 80, MY_WIDTH, MY_HEIGHT)];    [self.view addSubview:self.mainView];}- (void)viewWillAppear:(BOOL)animated{    UIImageView *imageV = [self compressImage:MY_WIDTH imageName:_imageName];    [self.mainView addSubview:imageV];}- (UIImageView *)compressImage:(float)width imageName:(NSString *)name{    UIImageView *imgView = [[UIImageView alloc] init];    imgView.image = [UIImage imageNamed:name];        float orgi_width = [imgView image].size.width;    float orgi_height = [imgView image].size.height;        //按照每列的宽度，以及图片的宽高来按比例压缩    float new_width = width - 5;    float new_height = (width * orgi_height)/orgi_width;        //重置imageView的尺寸    [imgView setFrame:CGRectMake(0, 0, new_width, new_height)];        return imgView;}- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}//关闭- (void)closePhotoView{        [self.view removeFromSuperview];}- (void)dealloc{    [self.headView release];    [self.mainView release];    [super dealloc];}@end

这个类主要是用于显示大图片所用，用户点击小图片后，程序根据图片的tag来获取点击图片的名字，然后将名字传递给该类，完成对相应图片的显示，当然这里也要做对图片的压缩处理，使它显示的时候不失真。（由于本人有点懒，这个类的界面美观什么的就懒得调了，多多包涵）示意图如下：

以上就是这个例子的大部分代码了，如果要下载完整工程的话，请到我的上传中下载。

现在看一下整个效果;