UICollectionView拖拽移动（类似于九宫格拖拽，学习于HXPhotoPicker）

collectionVIew 的拖拽，主要是利用手势，进行操作，就是 UILongPressGestureRecognizer，实现UICollectionVIewCell的手势，且借助于，

[locationOfTouch:0 inView:longPgr.view]

得到长按手势的CGPoint点，同时借助于

[self indexPathForItemAtPoint： ] 获取到某一点在cell上，是在那个indexPath

根据手势的不同状态去做相应的操作

-(void)longPrgEvent:(UILongPressGestureRecognizer*)longPger{
    if (longPger.state == UIGestureRecognizerStateBegan) {
        self.isDeleteItem = NO;
        [self gestureRecognizerBegan:longPger];
    }else if (longPger.state == UIGestureRecognizerStateChanged){
        if (self.originalIndexPath.section != 0) {
            return;
        }
        [self gestureRecognizerChange:longPger];
        [self moveCell];
    }else if (longPger.state == UIGestureRecognizerStateCancelled || longPger.state == UIGestureRecognizerStateEnded){
        
        [self handelItemInSpace];
        if (!self.isDeleteItem) {
            [self gestureRecognizerCancelOrEnd:longPger];
        }
    }
}

#当手势刚开始拖动的时候
- (void)gestureRecognizerBegan:(UILongPressGestureRecognizer *)longPgr{
    self.originalIndexPath = [self indexPathForItemAtPoint:[longPgr locationOfTouch:0 inView:longPgr.view]];
    SFCollectionViewCell * cell = (SFCollectionViewCell*)[self cellForItemAtIndexPath:self.originalIndexPath];
    UIView * tempMoveCell = [cell snapshotViewAfterScreenUpdates:NO];  //获取一个截屏试图，用于试图的移动，
    self.dragCell = cell;
    cell.hidden = YES;
    self.tempMoveCell = tempMoveCell;
    self.tempMoveCell.frame = cell.frame;
    [UIView animateWithDuration:0.25 animations:^{
        self.tempMoveCell.alpha = 0.8;
        self.tempMoveCell.transform = CGAffineTransformMakeScale(1.15, 1.15);
    }];
    [self addSubview:self.tempMoveCell];
    self.lastPoint = [longPgr locationOfTouch:0 inView:self];
    
}

#prarm 当拖拽手势处于变化状态时候，让刚开始获取到的cell截图，做一些移动动画
利用到矩阵变换

  //    CGAffineTransformMakeTranslation(x,y) 矩阵变换，位移
  //    CGAffineTransformMakeRotation(M_PI); 矩阵变换，旋转
  //    CGAffineTransformMakeScale(2, 2);    矩阵变换，缩放
  //    CGPointApplyAffineTransform(CGPoint point, CGAffineTransform t)  某点通过矩阵变换之后的点

- (void)gestureRecognizerChange:(UILongPressGestureRecognizer *)longPgr{
    CGFloat tranX = [longPgr locationOfTouch:0 inView:longPgr.view].x - self.lastPoint.x;
    CGFloat tranY = [longPgr locationOfTouch:0 inView:longPgr.view].y - self.lastPoint.y;
//    NSLog(@"start %@",NSStringFromCGPoint(self.tempMoveCell.center));
    self.tempMoveCell.center = CGPointApplyAffineTransform(self.tempMoveCell.center, CGAffineTransformMakeTranslation(tranX, tranY));
//    NSLog(@"end %@",NSStringFromCGPoint(self.tempMoveCell.center));
    self.lastPoint = [longPgr locationOfTouch:0 inView:longPgr.view];
//    NSLog(@"tranX:%f-tranY:%f--%@",tranX,tranY,NSStringFromCGPoint(self.lastPoint));

//    CGAffineTransformMakeTranslation(x,y) --相对平移 将view(泛指)移动到相对于“屏幕的左上角”
  
}

当然当手势处于移动状态下，cell整体需要根据移动的截图的位置，判断出，可能移动到的cell位置，然后做出动画

核心知识点     [self moveItemAtIndexPath:self.originalIndexPath toIndexPath:self.moveIndexPath];

- (void)moveCell{
    for (SFCollectionViewCell * cell in self.visibleCells) {
        if ([self indexPathForCell:cell] == self.originalIndexPath) {
            continue;
        }
        //计算中心距离
        CGFloat spaceingX = fabs(self.tempMoveCell.center.x - cell.center.x);
        CGFloat spaceingY = fabs(self.tempMoveCell.center.y - cell.center.y);
        if (spaceingX <= self.tempMoveCell.bounds.size.width/2.0f && spaceingY <= self.tempMoveCell.bounds.size.height/2.0f) {
            self.moveIndexPath = [self indexPathForCell:cell];
            if (self.moveIndexPath.section != 0) {
                return;
            }
            //更新数据源
            [self updateDataSource];
            //移动
            [self moveItemAtIndexPath:self.originalIndexPath toIndexPath:self.moveIndexPath];
            
            self.originalIndexPath = self.moveIndexPath;
        }
    }
}

那么剩下就是更新数据源，将拖拽更换位置更换对应的数据，跳换位置，根据移动位置，中拿到的。originalIndexPath：最初位置  moveIndexPath ： 移动到的位置，就行数据更新

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Demo地址 

https://github.com/wangsongfeng/CLYTabbarController-test.git