长按即可移动cell的UITableView

期望效果

1.长按即可触发移动cell，操作逻辑简单；
2.移动cell时越靠近屏幕边缘，速度越快；
3.被移动cell的样式可以自定义；

github地址

JXMovableCellTableView,如果你喜欢，不妨给颗星吧^_~

调研

如果只是实现移动UITableViewCell，系统自带的API即可搞定。
调用下面的方法[tableView setEditing:YES animated:YES];即可进入编辑模式。然后实现下面的方法即可开启移动cell。

//默认编辑模式下，每个cell左边有个红色的删除按钮，设置为None即可去掉
- (UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return UITableViewCellEditingStyleNone;
}
//是否允许indexPath的cell移动
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath
{
    //更新数据源
}

用系统的方法有几个缺点：
1.需要用一个开关去控制编辑状态，不方便；
2.移动cell的时候cell右边有个指示图标，看着不爽；
3.被移动cell的样式不能自己定制。
综上所述，需要自己去写效果了。

实现原理

大概原理：为UITableView添加一个长按手势，然后给选中的cell截图；让截图随着手势移动，同时记录选中的indexPath，方便位置互换。

1.添加长按手势

- (void)jx_addGesture
{
    _gesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(jx_processGesture:)];
    _gesture.minimumPressDuration = _gestureMinimumPressDuration;
    [self addGestureRecognizer:_gesture];
}

2.处理手势开始，需要通过dataSource方法获取数据源

- (void)jx_gestureBegan:(UILongPressGestureRecognizer *)gesture
{
    CGPoint point = [gesture locationInView:gesture.view];
    NSIndexPath *selectedIndexPath = [self indexPathForRowAtPoint:point];
    if (!selectedIndexPath) {
        return;
    }
    if (self.delegate && [self.delegate respondsToSelector:@selector(tableView:willMoveCellAtIndexPath:)]) {
        [self.delegate tableView:self willMoveCellAtIndexPath:selectedIndexPath];
    }
    if (_canEdgeScroll) {
        //开启边缘滚动
        [self jx_startEdgeScroll];
    }
    //每次移动开始获取一次数据源
    if (self.dataSource && [self.dataSource respondsToSelector:@selector(dataSourceArrayInTableView:)]) {
        _tempDataSource = [self.dataSource dataSourceArrayInTableView:self].mutableCopy;
    }
    _selectedIndexPath = selectedIndexPath;
    UITableViewCell *cell = [self cellForRowAtIndexPath:selectedIndexPath];
    _tempView = [self jx_snapshotViewWithInputView:cell];
    if (_drawMovalbeCellBlock) {
        //将_tempView通过block让使用者自定义
        _drawMovalbeCellBlock(_tempView);
    }else {
        //配置默认样式
        _tempView.layer.shadowColor = [UIColor grayColor].CGColor;
        _tempView.layer.masksToBounds = NO;
        _tempView.layer.cornerRadius = 0;
        _tempView.layer.shadowOffset = CGSizeMake(-5, 0);
        _tempView.layer.shadowOpacity = 0.4;
        _tempView.layer.shadowRadius = 5;
    }
    _tempView.frame = cell.frame;
    [self addSubview:_tempView];
    //隐藏cell
    cell.hidden = YES;
    [UIView animateWithDuration:kJXMovableCellAnimationTime animations:^{
        _tempView.center = CGPointMake(_tempView.center.x, point.y);
    }];
}

3.处理手势变化，移动成功之后用delegate告诉使用者

- (void)jx_gestureChanged:(UILongPressGestureRecognizer *)gesture
{
    CGPoint point = [gesture locationInView:gesture.view];
    NSIndexPath *currentIndexPath = [self indexPathForRowAtPoint:point];
    if (currentIndexPath && ![_selectedIndexPath isEqual:currentIndexPath]) {
        //交换数据源和cell
        [self jx_updateDataSourceAndCellFromIndexPath:_selectedIndexPath toIndexPath:currentIndexPath];
        if (self.delegate && [self.delegate respondsToSelector:@selector(tableView:didMoveCellFromIndexPath:toIndexPath:)]) {
            [self.delegate tableView:self didMoveCellFromIndexPath:_selectedIndexPath toIndexPath:currentIndexPath];
        }
        _selectedIndexPath = currentIndexPath;
    }
    //让截图跟随手势
    _tempView.center = CGPointMake(_tempView.center.x, point.y);
}

交换数据源和cell

- (void)jx_updateDataSourceAndCellFromIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
    if ([self numberOfSections] == 1) {
        //只有一组
        [_tempDataSource exchangeObjectAtIndex:fromIndexPath.row withObjectAtIndex:toIndexPath.row];
        //交换cell
        [self moveRowAtIndexPath:fromIndexPath toIndexPath:toIndexPath];
    }else {
        //有多组
        id fromData = _tempDataSource[fromIndexPath.section][fromIndexPath.row];
        id toData = _tempDataSource[toIndexPath.section][toIndexPath.row];
        NSMutableArray *fromArray = [_tempDataSource[fromIndexPath.section] mutableCopy];
        NSMutableArray *toArray = [_tempDataSource[toIndexPath.section] mutableCopy];
        [fromArray replaceObjectAtIndex:fromIndexPath.row withObject:toData];
        [toArray replaceObjectAtIndex:toIndexPath.row withObject:fromData];
        [_tempDataSource replaceObjectAtIndex:fromIndexPath.section withObject:fromArray];
        [_tempDataSource replaceObjectAtIndex:toIndexPath.section withObject:toArray];
        //交换cell
        [self beginUpdates];
        [self moveRowAtIndexPath:fromIndexPath toIndexPath:toIndexPath];
        [self moveRowAtIndexPath:toIndexPath toIndexPath:fromIndexPath];
        [self endUpdates];
    }
}

4.处理手势结束或取消，结束之后通过dataSource代理返回交换后的数据源。

- (void)jx_gestureEndedOrCancelled:(UILongPressGestureRecognizer *)gesture
{
    if (_canEdgeScroll) {
        [self jx_stopEdgeScroll];
    }
    //返回交换后的数据源
    if (self.dataSource && [self.dataSource respondsToSelector:@selector(tableView:newDataSourceArrayAfterMove:)]) {
        [self.dataSource tableView:self newDataSourceArrayAfterMove:_tempDataSource.copy];
    }
    if (self.delegate && [self.delegate respondsToSelector:@selector(tableView:endMoveCellAtIndexPath:)]) {
        [self.delegate tableView:self endMoveCellAtIndexPath:_selectedIndexPath];
    }
    UITableViewCell *cell = [self cellForRowAtIndexPath:_selectedIndexPath];
    [UIView animateWithDuration:kJXMovableCellAnimationTime animations:^{
        _tempView.frame = cell.frame;
    } completion:^(BOOL finished) {
        cell.hidden = NO;
        [_tempView removeFromSuperview];
        _tempView = nil;
    }];
}

5.开启边缘滚动
用CADisplayLink实现，1/60秒刷新一次，和屏幕刷新频率一样。

- (void)jx_startEdgeScroll
{
    _edgeScrollTimer = [CADisplayLink displayLinkWithTarget:self selector:@selector(jx_processEdgeScroll)];
    [_edgeScrollTimer addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
}

6.处理边缘滚动

- (void)jx_processEdgeScroll
{
    [self jx_gestureChanged:_gesture];
    CGFloat minOffsetY = self.contentOffset.y + _edgeScrollRange;
    CGFloat maxOffsetY = self.contentOffset.y + self.bounds.size.height - _edgeScrollRange;
    CGPoint touchPoint = _tempView.center;
    //处理上下达到极限之后不再滚动tableView，其中处理了滚动到最边缘的时候，当前处于edgeScrollRange内，但是tableView还未显示完，需要显示完tableView才停止滚动
    if (touchPoint.y < _edgeScrollRange) {
        if (self.contentOffset.y <= 0) {
            return;
        }else {
            if (self.contentOffset.y - 1 < 0) {
                return;
            }
            [self setContentOffset:CGPointMake(self.contentOffset.x, self.contentOffset.y - 1) animated:NO];
            _tempView.center = CGPointMake(_tempView.center.x, _tempView.center.y - 1);
        }
    }
    if (touchPoint.y > self.contentSize.height - _edgeScrollRange) {
        if (self.contentOffset.y >= self.contentSize.height - self.bounds.size.height) {
            return;
        }else {
            if (self.contentOffset.y + 1 > self.contentSize.height - self.bounds.size.height) {
                return;
            }
            [self setContentOffset:CGPointMake(self.contentOffset.x, self.contentOffset.y + 1) animated:NO];
            _tempView.center = CGPointMake(_tempView.center.x, _tempView.center.y + 1);
        }
    }
    //处理滚动
    CGFloat maxMoveDistance = 20;
    if (touchPoint.y < minOffsetY) {
        //cell在往上移动, moveDistance越大移动越快
        CGFloat moveDistance = (minOffsetY - touchPoint.y)/_edgeScrollRange*maxMoveDistance;
        [self setContentOffset:CGPointMake(self.contentOffset.x, self.contentOffset.y - moveDistance) animated:NO];
        _tempView.center = CGPointMake(_tempView.center.x, _tempView.center.y - moveDistance);
    }else if (touchPoint.y > maxOffsetY) {
        //cell在往下移动, moveDistance越大移动越快
        CGFloat moveDistance = (touchPoint.y - maxOffsetY)/_edgeScrollRange*maxMoveDistance;
        [self setContentOffset:CGPointMake(self.contentOffset.x, self.contentOffset.y + moveDistance) animated:NO];
        _tempView.center = CGPointMake(_tempView.center.x, _tempView.center.y + moveDistance);
    }
}

使用

直接继承JXMovableCellTableView就可以使用了，然后通过公开属性进行自定义：

/**
 *  长按手势最小触发时间，默认1.0，最小0.2
 */
@property (nonatomic, assign) CGFloat gestureMinimumPressDuration;

/**
 *  自定义可移动cell的截图样式
 */
@property (nonatomic, copy) void(^drawMovalbeCellBlock)(UIView *movableCell);

/**
 *  是否允许拖动到屏幕边缘后，开启边缘滚动，默认YES
 */
@property (nonatomic, assign) BOOL canEdgeScroll;

/**
 *  边缘滚动触发范围，默认150，越靠近边缘速度越快
 */
@property (nonatomic, assign) CGFloat edgeScrollRange;

总结

通过截图大法实现以假乱真，自由移动截图产生的"cell"；交换的时候，首先要交换数据源，再交换cell；处理边缘滚动的时候，需要小心各种边界条件。
既然UITableViewCell可以自由移动了，那么UICollectionViewCell同理也可以实现。下篇文章就讲可移动UICollectionViewCell的实现。