我已经在这个任务上挣扎了相当长的时间。我的目标是开发一个可以在垂直和水平方向上连续滚动的scrollview或collectionview。
以下是我认为应该看起来像的图片。透明的方框是从内存中重新加载的视图/单元格。只要一个视图/单元格移出屏幕，它就应该被重用于即将到来的新单元格..就像UITableViewController一样工作。
我知道UICollectionView只能做到水平或垂直无限滚动，而不能同时做到两者。但是，我不知道如何使用UIScrollView实现此目标。
我尝试了此问题答案附带的代码，我可以通过它重新创建视图（例如% 20），但那并不是我需要的..而且，它也不是连续的。
我知道这是可能的，因为HBO Go应用程序就是这样做的..我想要完全相同的功能。
我的问题：我如何实现我的目标？有没有指南/教程可以向我展示如何做？我找不到任何东西。
通过在距离中心一定距离后重新对UIScrollView进行居中操作，您可以获得无限滚动的效果。首先，您需要使contentSize足够大，以便可以滚动一点，因此我返回我的分区中项数的4倍和分区数的4倍，并在cellForItemAtIndexPath方法中使用mod运算符来获取正确的数组索引。然后，您必须在UICollectionView子类中重写layoutSubviews以进行重新居中（这在WWDC 2011视频“高级滚动视图技术”中有演示）。这是具有集合视图（在IB中设置）作为子视图的控制器类:
#import "ViewController.h"
#import "MultpleLineLayout.h"
#import "DataCell.h"
@interface ViewController ()
@property (weak,nonatomic) IBOutlet UICollectionView *collectionView;
@property (strong,nonatomic) NSArray *theData;
@end
@implementation ViewController
- (void)viewDidLoad {
self.theData = @[@[@"1",@"2",@"3",@"4",@"5"], @[@"6",@"7",@"8",@"9",@"10"],@[@"11",@"12",@"13",@"14",@"15"],@[@"16",@"17",@"18",@"19",@"20"]];
MultpleLineLayout *layout = [[MultpleLineLayout alloc] init];
self.collectionView.collectionViewLayout = layout;
self.collectionView.showsHorizontalScrollIndicator = NO;
self.collectionView.showsVerticalScrollIndicator = NO;
layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
self.view.backgroundColor = [UIColor blackColor];
[self.collectionView registerClass:[DataCell class] forCellWithReuseIdentifier:@"DataCell"];
[self.collectionView reloadData];
}
- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section {
return 20;
}
- (NSInteger)numberOfSectionsInCollectionView: (UICollectionView *)collectionView {
return 16;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
DataCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"DataCell" forIndexPath:indexPath];
cell.label.text = self.theData[indexPath.section %4][indexPath.row %5];
return cell;
}
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
// UICollectionViewCell *item = [collectionView cellForItemAtIndexPath:indexPath];
NSLog(@"%@",indexPath);
}
这是UICollectionViewFlowLayout子类：
#define space 5
#import "MultpleLineLayout.h"
@implementation MultpleLineLayout { // a subclass of UICollectionViewFlowLayout
NSInteger itemWidth;
NSInteger itemHeight;
}
-(id)init {
if (self = [super init]) {
itemWidth = 60;
itemHeight = 60;
}
return self;
}
-(CGSize)collectionViewContentSize {
NSInteger xSize = [self.collectionView numberOfItemsInSection:0] * (itemWidth + space); // "space" is for spacing between cells.
NSInteger ySize = [self.collectionView numberOfSections] * (itemHeight + space);
return CGSizeMake(xSize, ySize);
}
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)path {
UICollectionViewLayoutAttributes* attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:path];
attributes.size = CGSizeMake(itemWidth,itemHeight);
int xValue = itemWidth/2 + path.row * (itemWidth + space);
int yValue = itemHeight + path.section * (itemHeight + space);
attributes.center = CGPointMake(xValue, yValue);
return attributes;
}
-(NSArray*)layoutAttributesForElementsInRect:(CGRect)rect {
NSInteger minRow = (rect.origin.x > 0)? rect.origin.x/(itemWidth + space) : 0; // need to check because bounce gives negative values for x.
NSInteger maxRow = rect.size.width/(itemWidth + space) + minRow;
NSMutableArray* attributes = [NSMutableArray array];
for(NSInteger i=0 ; i < self.collectionView.numberOfSections; i++) {
for (NSInteger j=minRow ; j < maxRow; j++) {
NSIndexPath* indexPath = [NSIndexPath indexPathForItem:j inSection:i];
[attributes addObject:[self layoutAttributesForItemAtIndexPath:indexPath]];
}
}
return attributes;
}
最后，这是UICollectionView的子类：
-(void)layoutSubviews {
[super layoutSubviews];
CGPoint currentOffset = self.contentOffset;
CGFloat contentWidth = self.contentSize.width;
CGFloat contentHeight = self.contentSize.height;
CGFloat centerOffsetX = (contentWidth - self.bounds.size.width)/ 2.0;
CGFloat centerOffsetY = (contentHeight - self.bounds.size.height)/ 2.0;
CGFloat distanceFromCenterX = fabsf(currentOffset.x - centerOffsetX);
CGFloat distanceFromCenterY = fabsf(currentOffset.y - centerOffsetY);
if (distanceFromCenterX > contentWidth/4.0) { // this number of 4.0 is arbitrary
self.contentOffset = CGPointMake(centerOffsetX, currentOffset.y);
}
if (distanceFromCenterY > contentHeight/4.0) {
self.contentOffset = CGPointMake(currentOffset.x, centerOffsetY);
}
}
layoutSubviews会导致我的视图重复显示相同的内容。有时在滚动一点之后我也会接收到异常[UICollectionViewData validateLayoutInRect:]。你们中间有人有更多的建议吗，该如何让它正常工作？ - Alex CioUICollectionView？我在你的代码中没有看到它。你正在使用普通的UICollectionVIew类。DataCell是一个nib文件还是在代码中创建的？我认为是后者。collectionView是放在nib文件中并通过outlet连接的吗？当你通过Interface Builder添加一个collection view时，他需要一个重用标识符，并且在Interface Builder和代码中注册DataCell，这会导致黑屏。 - testing@更新了Swift 3，并更改了maxRow的计算方式，否则最后一列将被截断并可能导致错误。
import UIKit
class NodeMap : UICollectionViewController {
var rows = 10
var cols = 10
override func viewDidLoad(){
self.collectionView!.collectionViewLayout = NodeLayout(itemWidth: 400.0, itemHeight: 300.0, space: 5.0)
}
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return rows
}
override func numberOfSections(in collectionView: UICollectionView) -> Int {
return cols
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
return collectionView.dequeueReusableCell(withReuseIdentifier: "node", for: indexPath)
}
}
class NodeLayout : UICollectionViewFlowLayout {
var itemWidth : CGFloat
var itemHeight : CGFloat
var space : CGFloat
var columns: Int{
return self.collectionView!.numberOfItems(inSection: 0)
}
var rows: Int{
return self.collectionView!.numberOfSections
}
init(itemWidth: CGFloat, itemHeight: CGFloat, space: CGFloat) {
self.itemWidth = itemWidth
self.itemHeight = itemHeight
self.space = space
super.init()
}
required init(coder aDecoder: NSCoder) {
self.itemWidth = 50
self.itemHeight = 50
self.space = 3
super.init()
}
override var collectionViewContentSize: CGSize{
let w : CGFloat = CGFloat(columns) * (itemWidth + space)
let h : CGFloat = CGFloat(rows) * (itemHeight + space)
return CGSize(width: w, height: h)
}
override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
let x : CGFloat = CGFloat(indexPath.row) * (itemWidth + space)
let y : CGFloat = CGFloat(indexPath.section) + CGFloat(indexPath.section) * (itemHeight + space)
attributes.frame = CGRect(x: x, y: y, width: itemWidth, height: itemHeight)
return attributes
}
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
let minRow : Int = (rect.origin.x > 0) ? Int(floor(rect.origin.x/(itemWidth + space))) : 0
let maxRow : Int = min(columns - 1, Int(ceil(rect.size.width / (itemWidth + space)) + CGFloat(minRow)))
var attributes : Array<UICollectionViewLayoutAttributes> = [UICollectionViewLayoutAttributes]()
for i in 0 ..< rows {
for j in minRow ... maxRow {
attributes.append(self.layoutAttributesForItem(at: IndexPath(item: j, section: i))!)
}
}
return attributes
}
}
let y: CGFloat = CGFloat(indexPath.section) * (itemHeight + space)。他将索引添加了两次。 - K. Janjuhaclass NodeMap : UICollectionViewController {
@IBOutlet var activateNodeButton : UIBarButtonItem?
var rows = 10
var cols = 10
override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return rows
}
override func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
return cols
}
override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
return collectionView.dequeueReusableCellWithReuseIdentifier("node", forIndexPath: indexPath)
}
override func viewDidLoad() {
self.collectionView!.collectionViewLayout = NodeLayout(itemWidth: 100.0, itemHeight: 100.0, space: 5.0)
}
}
class NodeLayout : UICollectionViewFlowLayout {
var itemWidth : CGFloat
var itemHeight : CGFloat
var space : CGFloat
init(itemWidth: CGFloat, itemHeight: CGFloat, space: CGFloat) {
self.itemWidth = itemWidth
self.itemHeight = itemHeight
self.space = space
super.init()
}
required init(coder aDecoder: NSCoder) {
self.itemWidth = 50
self.itemHeight = 50
self.space = 3
super.init()
}
override func collectionViewContentSize() -> CGSize {
let w : CGFloat = CGFloat(self.collectionView!.numberOfItemsInSection(0)) * (itemWidth + space)
let h : CGFloat = CGFloat(self.collectionView!.numberOfSections()) * (itemHeight + space)
return CGSizeMake(w, h)
}
override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes! {
let attributes = UICollectionViewLayoutAttributes(forCellWithIndexPath: indexPath)
let x : CGFloat = CGFloat(indexPath.row) * (itemWidth + space)
let y : CGFloat = CGFloat(indexPath.section) + CGFloat(indexPath.section) * (itemHeight + space)
attributes.frame = CGRectMake(x, y, itemWidth, itemHeight)
return attributes
}
override func layoutAttributesForElementsInRect(rect: CGRect) -> [AnyObject]? {
let minRow : Int = (rect.origin.x > 0) ? Int(floor(rect.origin.x/(itemWidth + space))) : 0
let maxRow : Int = Int(floor(rect.size.width/(itemWidth + space)) + CGFloat(minRow))
var attributes : Array<UICollectionViewLayoutAttributes> = [UICollectionViewLayoutAttributes]()
for i in 0...self.collectionView!.numberOfSections()-1 {
for j in minRow...maxRow {
attributes.append(self.layoutAttributesForItemAtIndexPath(NSIndexPath(forItem: j, inSection: i)))
}
}
return attributes
}
}
需要采取以下几个步骤：
