修复数据源改变后，刷新崩溃的bug

Author: 肖睿

XRWaterfallLayout/XRWaterfallLayout.m

@@ -59,14 +59,15 @@ - (void)setColumnSpacing:(NSInteger)columnSpacing rowSpacing:(NSInteger)rowSepac
 #pragma mark- 布局相关方法
 //布局前的准备工作
 - (void)prepareLayout {
+    [super prepareLayout];
     //初始化字典，有几列就有几个键值对，key为列，value为列的最大y值，初始值为上内边距
     for (int i = 0; i < self.columnCount; i++) {
         self.maxYDic[@(i)] = @(self.sectionInset.top);
     }
 
     //根据collectionView获取总共有多少个item
     NSInteger itemCount = [self.collectionView numberOfItemsInSection:0];
-    
+    [self.attributesArray removeAllObjects];
     //为每一个item创建一个attributes并存入数组
     for (int i = 0; i < itemCount; i++) {
         UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:i inSection:0]];

XRWaterfallLayoutDemo/XRWaterfallLayoutDemo/ViewController.m

@@ -32,19 +32,15 @@ - (NSMutableArray *)images {
 
 - (void)viewDidLoad {
     [super viewDidLoad];
+    
     //创建瀑布流布局
-    //方式一
-//    XRWaterfallLayout *waterfall = [[XRWaterfallLayout alloc] init];
-//    waterfall.columnCount = 3;
-    //方式二
-//    XRWaterfallLayout *waterfall = [[XRWaterfallLayout alloc] initWithColumnCount:3];
-    //方式三
     XRWaterfallLayout *waterfall = [XRWaterfallLayout waterFallLayoutWithColumnCount:3];
 
     //设置各属性的值
 //    waterfall.rowSpacing = 10;
 //    waterfall.columnSpacing = 10;
 //    waterfall.sectionInset = UIEdgeInsetsMake(10, 10, 10, 10);
+    
     //或者一次性设置
     [waterfall setColumnSpacing:10 rowSpacing:10 sectionInset:UIEdgeInsetsMake(10, 10, 10, 10)];
 
@@ -62,10 +58,21 @@ - (void)viewDidLoad {
 
     //创建collectionView
     self.collectionView = [[UICollectionView alloc] initWithFrame:self.view.bounds collectionViewLayout:waterfall];
+    self.collectionView.frame = CGRectMake(0, 50, self.view.frame.size.width, self.view.frame.size.height - 50);
     self.collectionView.backgroundColor = [UIColor whiteColor];
     [self.collectionView registerNib:[UINib nibWithNibName:@"XRCollectionViewCell" bundle:nil] forCellWithReuseIdentifier:@"cell"];
     self.collectionView.dataSource = self;
     [self.view addSubview:self.collectionView];
+    
+    UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(100, 20, 100, 30)];
+    [btn addTarget:self action:@selector(click) forControlEvents:UIControlEventTouchUpInside];
+    btn.backgroundColor = [UIColor blueColor];
+    [self.view addSubview:btn];
+}
+
+- (void)click {
+    [self.images removeAllObjects];
+    [self.collectionView reloadData];
 }
 
 

XRWaterfallLayoutDemo/XRWaterfallLayoutDemo/XRCollectionViewCell.xib

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="9531" systemVersion="15C50" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES">
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="9532" systemVersion="15D21" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES">
     <dependencies>
         <deployment identifier="iOS"/>
-        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="9529"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="9530"/>
     </dependencies>
     <objects>
         <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File's Owner"/>

XRWaterfallLayoutDemo/XRWaterfallLayoutDemo/XRWaterfallLayout/XRWaterfallLayout.m

@@ -59,14 +59,15 @@ - (void)setColumnSpacing:(NSInteger)columnSpacing rowSpacing:(NSInteger)rowSepac
 #pragma mark- 布局相关方法
 //布局前的准备工作
 - (void)prepareLayout {
+    [super prepareLayout];
     //初始化字典，有几列就有几个键值对，key为列，value为列的最大y值，初始值为上内边距
     for (int i = 0; i < self.columnCount; i++) {
         self.maxYDic[@(i)] = @(self.sectionInset.top);
     }
 
     //根据collectionView获取总共有多少个item
     NSInteger itemCount = [self.collectionView numberOfItemsInSection:0];
-    
+    [self.attributesArray removeAllObjects];
     //为每一个item创建一个attributes并存入数组
     for (int i = 0; i < itemCount; i++) {
         UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:i inSection:0]];