可拖拽重排的CollectionView
http://www.jianshu.com/p/8f0153ce17f9
拖拽重排的CollectionView
https://github.com/henrytkirk/HTKDragAndDropCollectionViewLayout
http://www.cnblogs.com/YouXianMing/p/4156559.html
draggedIndexPath // 要拖动的cell的索引
finalIndexPath // 最终要插入的索引
在prepareLayout中，构建 itemArray 和 itemDictionary；itemArray是按顺序保存cell对应的LayoutAttributes；itemDictionary保存是，IndexPath(key)：LayoutAttributes(value);
但是UICollectionViewLayout的，代理方法不怎么熟悉；
好像自己的逻辑还没有理清楚；
HTKDragAndDropCollectionViewController；
//
// HTKDragAndDropCollectionViewLayout.m
// HTKDragAndDropCollectionView
//
// Created by Henry T Kirk on 11/9/14.
// Copyright (c) 2014 Henry T. Kirk (http://www.henrytkirk.info)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#import "HTKDragAndDropCollectionViewLayout.h"
#import "HTKDragAndDropCollectionViewLayoutConstants.h"
@interface HTKDragAndDropCollectionViewLayout ()
/**
* Our item array that holds the "sorted" items in the collectionView.
* this array is re-ordered while user is dragging a cell. Our layout
* uses this to then show the items in that sorted order.
*/
@property (nonatomic, strong) NSMutableArray *itemArray;
/**
* Our dictionary of layout attributes where the indexPath is the key. Used
* to retrieve the layout attributes for a particular indexPath since
* it may be different than the order in itemArray.
*/
@property (nonatomic, strong) NSMutableDictionary *itemDictionary;
/**
* Returns number of items that will fit per row based on fixed
* itemSize.
*/
@property (readonly, nonatomic) NSInteger numberOfItemsPerRow;
/**
* Resets the frames based on new position in the itemArray. Will
* loop over all items in the new sorted order and lay them out.
*/
- (void)resetLayoutFrames;
/**
* Applys the dragging attributes to the attributes passed. Will
* apply dragging state if the attributes are being dragged. If not, will
* apply default state.
*/
- (void)applyDragAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes;
/**
* Inserts the dragged item into the indexPath passed. Will reorder
* the items.
*/
- (void)insertDraggedItemAtIndexPath:(NSIndexPath *)intersectPath;
/**
* Helper to determine what indexPath of the item is below the point
* passed. Used to identify what item is below the item being dragged.
*/
- (NSIndexPath *)indexPathBelowDraggedItemAtPoint:(CGPoint)point;
/**
* Creates and inserts layout attributes for indexPath provided. Used
* for insertions into the collectionView.
*/
- (void)insertItemAtIndexPath:(NSIndexPath *)indexPath;
@end
@implementation HTKDragAndDropCollectionViewLayout
- (instancetype)init {
self = [super init];
if (self) {
_itemArray = [NSMutableArray array];
_itemDictionary = [NSMutableDictionary dictionary];
}
return self;
}
- (void)invalidateLayoutWithContext:(UICollectionViewLayoutInvalidationContext *)context {
[super invalidateLayoutWithContext:context];
// reset so we re-calc entire layout again
if (context.invalidateEverything) {
[self.itemArray removeAllObjects];
}
}
- (void)prepareLayout {
[super prepareLayout];
// Make sure we have item size set.
if (CGSizeEqualToSize(self.itemSize, CGSizeZero)) {
return;
}
// If we already have our model, don't build it.
if (self.itemArray.count > 0) {
return;
}
// Start to build our array and dictionary of items
self.draggedIndexPath = nil;
self.finalIndexPath = nil;
self.draggedCellFrame = CGRectZero;
[self.itemArray removeAllObjects];
[self.itemDictionary removeAllObjects];
// setup values
CGFloat collectionViewWidth = CGRectGetWidth(self.collectionView.bounds) - self.sectionInset.right;
CGFloat xValue = self.sectionInset.left;
CGFloat yValue = self.sectionInset.top;
NSInteger sectionCount = [self.collectionView numberOfSections];
// Now build our items array/dictionary
// 构建 itemArray 和 itemDictionary；
for (NSInteger section = 0; section < sectionCount; section ++) {
NSInteger itemCount = [self.collectionView numberOfItemsInSection:section];
for (NSInteger item = 0; item < itemCount; item ++) {
// Check our xvalue
if ((xValue + self.itemSize.width) > collectionViewWidth) // 换行了
{
// reset our x, increment our y.
xValue = self.sectionInset.left;
yValue += self.itemSize.height + self.lineSpacing;
}
// Create IndexPath
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:item inSection:section];
UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForItemAtIndexPath:indexPath];
// Create frame
attributes.frame = CGRectMake(xValue, yValue, self.itemSize.width, self.itemSize.height);
// add to our dict
self.itemDictionary[indexPath] = attributes;
[self.itemArray addObject:attributes];
// Increment our x value
xValue += self.itemSize.width + self.minimumInteritemSpacing;
}
}
}
- (CGSize)collectionViewContentSize {
CGFloat collectionViewWidth = CGRectGetWidth(self.collectionView.bounds);
// Determine number of sections
// 决定sections的数量
NSInteger totalItems = 0;
for (NSInteger i = 0; i < [self.collectionView numberOfSections]; i++) {
totalItems += [self.collectionView numberOfItemsInSection:i];
}
// When the totalItems % 2 == 1, do this.
if (totalItems % 2 == 1) {
totalItems = totalItems + 1;
}
// Determine how many rows we will have
// row的数量； 总共的item cell / 每行itemcell的数量；
NSInteger rows = ceil((CGFloat)totalItems / self.numberOfItemsPerRow);
// Determine height of collectionView
// collectionView 的高度
CGFloat height = (rows * (self.itemSize.height + self.lineSpacing)) + self.sectionInset.top + self.sectionInset.bottom;
return CGSizeMake(collectionViewWidth, height);
}
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
NSMutableArray *elementArray = [NSMutableArray array];
// Loop over our items and find elements that
// intersect the rect passed.
[[self.itemArray copy] enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
UICollectionViewLayoutAttributes *attribute = (UICollectionViewLayoutAttributes *)obj;
if (CGRectIntersectsRect(attribute.frame, rect)) {
[self applyDragAttributes:attribute];
[elementArray addObject:attribute];
}
}];
return elementArray;
}
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath {
UICollectionViewLayoutAttributes *layoutAttributes = self.itemDictionary[indexPath];
if (!layoutAttributes) {
layoutAttributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
}
[self applyDragAttributes:layoutAttributes];
return layoutAttributes;
}
- (UICollectionViewLayoutAttributes *)initialLayoutAttributesForAppearingItemAtIndexPath:(NSIndexPath *)itemIndexPath {
UICollectionViewLayoutAttributes *attributes = [self.itemDictionary[itemIndexPath] copy];
return attributes;
}
- (UICollectionViewLayoutAttributes *)finalLayoutAttributesForDisappearingItemAtIndexPath:(NSIndexPath *)itemIndexPath {
UICollectionViewLayoutAttributes *attributes = [self.itemDictionary[itemIndexPath] copy];
return attributes;
}
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {
if (!CGSizeEqualToSize(self.collectionView.bounds.size, newBounds.size)) {
// reset so we re-calc entire layout again
[self.itemArray removeAllObjects];
return YES;
}
return NO;
}
- (void)prepareForCollectionViewUpdates:(NSArray *)updateItems {
[updateItems enumerateObjectsUsingBlock:^(UICollectionViewUpdateItem *updateItem, NSUInteger idx, BOOL *stop) {
switch (updateItem.updateAction) {
case UICollectionUpdateActionInsert: {
// insert new item
[self insertItemAtIndexPath:updateItem.indexPathAfterUpdate];
break;
}
case UICollectionUpdateActionDelete:
case UICollectionUpdateActionMove:
case UICollectionUpdateActionNone:
case UICollectionUpdateActionReload:
default:
break;
}
}];
}
#pragma mark - Getters
/**
* collectionView每行，itemcell的数量
*
*/
- (NSInteger)numberOfItemsPerRow {
// Determine how many items we can fit per row
CGFloat collectionViewWidth = CGRectGetWidth(self.collectionView.bounds) - self.sectionInset.right - self.sectionInset.left;
NSInteger numberOfItems = collectionViewWidth / (self.itemSize.width + _minimumInteritemSpacing);
return numberOfItems;
}
/**
* collectionView，返回minimumInteritemSpacing；
*
*/
- (CGFloat)minimumInteritemSpacing {
// return minimum item spacing
CGFloat collectionViewWidth = CGRectGetWidth(self.collectionView.bounds) - self.sectionInset.right - self.sectionInset.left;
CGFloat actualItemSpacing = MAX(_minimumInteritemSpacing, collectionViewWidth - (self.numberOfItemsPerRow * self.itemSize.width));
return actualItemSpacing / self.numberOfItemsPerRow;
}
#pragma mark - Drag and Drop methods
- (void)resetDragging {
// Set our dragged cell back to it's "home" frame
UICollectionViewLayoutAttributes *attributes = self.itemDictionary[self.draggedIndexPath];
attributes.frame = self.draggedCellFrame;
self.finalIndexPath = nil;
self.draggedIndexPath = nil;
self.draggedCellFrame = CGRectZero;
// Put the cell back animated.
[UIView animateWithDuration:0.2 animations:^{
[self invalidateLayout];
}];
}
/**
* 重新布局
*
*/
- (void)resetLayoutFrames {
// Get width of collectionView and adjust by section insets
CGFloat collectionViewWidth = CGRectGetWidth(self.collectionView.bounds) - self.sectionInset.right;
CGFloat xValue = self.sectionInset.left;
CGFloat yValue = self.sectionInset.top;
for (NSInteger i = 0; i < self.itemArray.count; i++) {
// Get attributes to work with
UICollectionViewLayoutAttributes *attributes = self.itemArray[i];
// Check our xvalue
// 相当于item cell换行了；
if ((xValue + self.itemSize.width) > collectionViewWidth) {
// reset our x, increment our y.
xValue = self.sectionInset.left;
yValue += self.itemSize.height + self.lineSpacing;
}
// Set new frame
attributes.frame = CGRectMake(xValue, yValue, self.itemSize.width, self.itemSize.height);
// Increment our x value
xValue += self.itemSize.width + self.minimumInteritemSpacing;
}
}
/**
* 设置被拖动cell的属性；
*
*/
- (void)applyDragAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes {
if ([layoutAttributes.indexPath isEqual:self.draggedIndexPath]) {
// Set dragged attributes
layoutAttributes.center = self.draggedCellCenter;
layoutAttributes.zIndex = 1024;
layoutAttributes.alpha = HTKDraggableCellInitialDragAlphaValue;
} else {
// Default attributes
layoutAttributes.zIndex = 0;
layoutAttributes.alpha = 1.0;
}
}
- (void)setDraggedCellCenter:(CGPoint)draggedCellCenter {
_draggedCellCenter = draggedCellCenter;
[self invalidateLayout];
}
// draggedIndexPath, 设置新的finalIndexPath; 要拖动cell的frame设置为新的frame;
- (void)insertDraggedItemAtIndexPath:(NSIndexPath *)intersectPath {
// Get attributes to work with
UICollectionViewLayoutAttributes *draggedAttributes = self.itemDictionary[self.draggedIndexPath];
UICollectionViewLayoutAttributes *intersectAttributes = self.itemDictionary[intersectPath];
// get index of items
NSUInteger draggedIndex = [self.itemArray indexOfObject:draggedAttributes];
NSUInteger intersectIndex = [self.itemArray indexOfObject:intersectAttributes];
// Move item in our array
// 将draggedIndex从itemArray移除，再插入到intersectIndex(拖动最后要插入的位置)
[self.itemArray removeObjectAtIndex:draggedIndex];
[self.itemArray insertObject:draggedAttributes atIndex:intersectIndex];
// Set our new final indexPath
// 设置新的finalIndexPath; 要拖动cell的frame设置为新的frame;
self.finalIndexPath = intersectPath;
self.draggedCellFrame = intersectAttributes.frame;
// relayout frames for items
[self resetLayoutFrames];
// Animate change
[UIView animateWithDuration:0.10 animations:^{
[self invalidateLayout];
}];
}
- (void)exchangeItemsIfNeeded {
// Exchange objects if we're touching.
// 相交cell的索引
NSIndexPath *intersectPath = [self indexPathBelowDraggedItemAtPoint:self.draggedCellCenter];
UICollectionViewLayoutAttributes *attributes = self.itemDictionary[intersectPath];
// Create a "hit area" that's 20 pt over the center of the intersected cell center
CGRect centerBox = CGRectMake(attributes.center.x - HTKDragAndDropCenterTriggerOffset, attributes.center.y - HTKDragAndDropCenterTriggerOffset, HTKDragAndDropCenterTriggerOffset * 2, HTKDragAndDropCenterTriggerOffset * 2);
// Determine if we need to move items around
if (intersectPath != nil && ![intersectPath isEqual:self.draggedIndexPath] && CGRectContainsPoint(centerBox, self.draggedCellCenter)) {
[self insertDraggedItemAtIndexPath:intersectPath];
}
}
- (BOOL)isDraggingCell {
return self.draggedIndexPath != nil;
}
#pragma mark - Helper Methods
/**
* 返回拖动cell，下面要相交cell的索引IndexPath
*
*/
- (NSIndexPath *)indexPathBelowDraggedItemAtPoint:(CGPoint)point {
__block NSIndexPath *indexPathBelow = nil;
__weak HTKDragAndDropCollectionViewLayout *weakSelf = self;
[self.collectionView.indexPathsForVisibleItems enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSIndexPath *indexPath = (NSIndexPath *)obj;
// Skip our dragged cell
if ([self.draggedIndexPath isEqual:indexPath]) {
return;
}
UICollectionViewLayoutAttributes *attribute = weakSelf.itemDictionary[indexPath];
// Create a "hit area" that's 20 pt over the center of the testing cell
// 创建 类似相交区域，中心点20范围内；
CGRect centerBox = CGRectMake(attribute.center.x - HTKDragAndDropCenterTriggerOffset, attribute.center.y - HTKDragAndDropCenterTriggerOffset, HTKDragAndDropCenterTriggerOffset * 2, HTKDragAndDropCenterTriggerOffset * 2);
if (CGRectContainsPoint(centerBox, weakSelf.draggedCellCenter)) {
indexPathBelow = indexPath;
*stop = YES;
}
}];
return indexPathBelow;
}
/**
* 插入新的item cell；
*
*/
- (void)insertItemAtIndexPath:(NSIndexPath *)indexPath {
// get attributes of item before this inserted one
UICollectionViewLayoutAttributes *prevAttributes = self.itemArray[indexPath.row - 1];
// Check our values
CGFloat xValue = CGRectGetMaxX(prevAttributes.frame) + self.minimumInteritemSpacing;
CGFloat yValue = CGRectGetMinY(prevAttributes.frame);
CGFloat collectionViewWidth = CGRectGetWidth(self.collectionView.bounds) - self.sectionInset.right;
if ((xValue + self.itemSize.width) > collectionViewWidth) {
// reset our x, increment our y.
xValue = self.sectionInset.left;
yValue += self.itemSize.height + self.lineSpacing;
}
// create attributes
UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForItemAtIndexPath:indexPath];
// Create frame
attributes.frame = CGRectMake(xValue, yValue, self.itemSize.width, self.itemSize.height);
// add to our dict
self.itemDictionary[indexPath] = attributes;
[self.itemArray addObject:attributes];
}
@end