现在很多项目都会用到类似拖动的效果，比如今日头条和网易新闻之类的资讯类产品，都有用该技术设置模块顺序的操作。
在 iOS9.0 之后，苹果提供相关的方法，非常方便。
设定三个私有属性
@property(nonatomic,strong) NSMutableArray *arr;
@property(nonatomic,weak) UICollectionView *colView;
@property(nonatomic,strong) UILongPressGestureRecognizer *longPress;
// 数据源
– (NSMutableArray *)arr{
if (!_arr) {
_arr = [NSMutableArray arrayWithObjects:@(1),@(2),@(3),@(4),@(5),@(6),@(7),@(8),@(9), nil];
}
return _arr;
}
先创建 UICollectionView
// 创建布局对象
UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc]init];
//view
UICollectionView *colView = [[UICollectionView alloc]initWithFrame:self.view.bounds collectionViewLayout:flowLayout];
// 背景色
colView.backgroundColor = [UIColor whiteColor];
colView.delegate = self;
colView.dataSource = self;
// 控制布局
colView.contentInset = UIEdgeInsetsMake(30, 20, 0, 20);
CGFloat screenW = [UIScreen mainScreen].bounds.size.width;
CGFloat space = 20;
NSInteger col = 3;
CGFloat itemSize = (screenW – (( col + 1) * space) – 6) / 3;
flowLayout.itemSize = CGSizeMake(itemSize, itemSize);
flowLayout.minimumInteritemSpacing = space;
flowLayout.minimumLineSpacing = space;
// 添加长按手势
_longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressMoving:)];
[colView addGestureRecognizer:_longPress];
// 属性连接
self.colView = colView;
// 注册 cell, 记得先创建一个自定义 cell
[colView registerNib:[UINib nibWithNibName:@”MyCollectionViewCell” bundle:nil] forCellWithReuseIdentifier:@”cell”];
[self.view addSubview:colView];
————————————– 数据源方法 ———————————————
– (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
return self.arr.count;
}
// The cell that is returned must be retrieved from a call to -dequeueReusableCellWithReuseIdentifier:forIndexPath:
– (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
MyCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@”cell” forIndexPath:indexPath];
cell.num.text = [NSString stringWithFormat:@”%@”,self.arr[indexPath.row]];
return cell;
}
2. 长按手势响应事件
– (void)longPressMoving:(UILongPressGestureRecognizer *)longPress{
// 筛选长按手势状态
switch (_longPress.state) {
// 开始
case UIGestureRecognizerStateBegan: {
{
// 手势作用的位置
NSIndexPath *selectIndexPath = [self.colView indexPathForItemAtPoint:[_longPress locationInView:self.colView]];
// 找到当前的 cell
MyCollectionViewCell *cell = (MyCollectionViewCell *)[self.colView cellForItemAtIndexPath:selectIndexPath];
// 拽起变大动画效果
[UIView animateWithDuration:0.3 animations:^{
[cell setTransform:CGAffineTransformMakeScale(1.2, 1.2)];
}];
// 开始移动
[_colView beginInteractiveMovementForItemAtIndexPath:selectIndexPath];
}
break;
}
case UIGestureRecognizerStateChanged: {
// 更新移动的位置
[self.colView updateInteractiveMovementTargetPosition:[longPress locationInView:_longPress.view]];
break;
}
case UIGestureRecognizerStateEnded: {
// 结束移动
[self.colView endInteractiveMovement];
break;
}
default: [self.colView cancelInteractiveMovement];
break;
}
}
3. 实现苹果官方的代理方法
– (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath *)indexPath{
return YES;
}
– (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath{
NSLog(@”%zd—%zd”,sourceIndexPath.row,destinationIndexPath.row);
NSIndexPath *selectIndexPath = [self.colView indexPathForItemAtPoint:[_longPress locationInView:self.colView]];
// 交换数据源的内容
[self.arr exchangeObjectAtIndex:sourceIndexPath.item withObjectAtIndex:destinationIndexPath.item];
// [self.colView reloadData];
NSLog(@”%@”,self.arr);
}
实现完以上的方法，可以快速构建一个可拖拽排序的 cell 界面。