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;