拖放工作 - 自动滚动不

Question

我的 table 有一个拖放功能（下面的代码），效果很好。除了，我无法将单元格拖到屏幕上/视图中未显示的位置。

换句话说，我还没有想出如何让它自动滚动。

是否有人能够查看我的代码并知道在何处添加代码以在用户将单元格拖向视图的顶部或底部时启用自动滚动？

func animateCellDrag (gestureRecognizer: UIGestureRecognizer, tableView: UITableView, whichList: String) {

    let longPress = gestureRecognizer as! UILongPressGestureRecognizer
    let state = longPress.state
    var locationInView = longPress.locationInView(tableView)
    var indexPath = tableView.indexPathForRowAtPoint(locationInView)
    var count = 0

    struct My {
        static var cellSnapshot : UIView? = nil
    }
    struct Path {
        static var initialIndexPath : NSIndexPath? = nil
    }

    if indexPath != nil {
        //Steps to take a cell snapshot. Function to be called in switch statement
        func snapshotOfCell(inputView: UIView) -> UIView {
            UIGraphicsBeginImageContextWithOptions(inputView.bounds.size, false, 0.0)
            inputView.layer.renderInContext(UIGraphicsGetCurrentContext()!)
            let image = UIGraphicsGetImageFromCurrentImageContext() as UIImage
            UIGraphicsEndImageContext()
            let cellSnapshot : UIView = UIImageView(image: image)
            cellSnapshot.layer.masksToBounds = false
            cellSnapshot.layer.cornerRadius = 0.0
            cellSnapshot.layer.shadowOffset = CGSizeMake(-5.0, 0.0)
            cellSnapshot.layer.shadowRadius = 5.0
            cellSnapshot.layer.shadowOpacity = 0.4
            return cellSnapshot
        }

        switch state {
        case UIGestureRecognizerState.Began:
            //Calls above function to take snapshot of held cell, animate pop out
            //Run when a long-press gesture begins on a cell
            if indexPath != nil {
                Path.initialIndexPath = indexPath
                let cell = tableView.cellForRowAtIndexPath(indexPath!) as UITableViewCell!
                My.cellSnapshot  = snapshotOfCell(cell)
                var center = cell.center

                My.cellSnapshot!.center = center
                My.cellSnapshot!.alpha = 0.0

                tableView.addSubview(My.cellSnapshot!)

                UIView.animateWithDuration(0.25, animations: { () -> Void in
                    center.y = locationInView.y

                    My.cellSnapshot!.center = center
                    My.cellSnapshot!.transform = CGAffineTransformMakeScale(1.05, 1.05)
                    My.cellSnapshot!.alpha = 0.98

                    cell.alpha = 0.0

                    }, completion: { (finished) -> Void in

                        if finished {
                            cell.hidden = true
                        }
                })
            }
        case UIGestureRecognizerState.Changed:

            if My.cellSnapshot != nil || indexPath != nil {
                //Runs when the user "lets go" of the cell
                //Sets CG Y-Coordinate of snapshot cell to center of current location in table (snaps into place)
                var center = My.cellSnapshot!.center
                center.y = locationInView.y
                My.cellSnapshot!.center = center

                let appDel: AppDelegate = (UIApplication.sharedApplication().delegate as! AppDelegate)
                let context: NSManagedObjectContext = appDel.managedObjectContext!
                let fetchRequest = NSFetchRequest(entityName: whichList)
                let sortDescriptor = NSSortDescriptor(key: "displayOrder", ascending: true )
                fetchRequest.sortDescriptors = [ sortDescriptor ]

                //If the indexPath is not 0 AND is not the same as it began (didn't move): Update array and table row order
                if ((indexPath != nil) && (indexPath != Path.initialIndexPath) && (indexPath?.row < taskList_Cntxt.count)) {

                    switch whichList {
                        case "TodayTask", "TomTask", "TBDTask", "FinTask":
                            swap(&taskList_Cntxt[indexPath!.row], &taskList_Cntxt[Path.initialIndexPath!.row])
                            tableView.moveRowAtIndexPath(Path.initialIndexPath!, toIndexPath: indexPath!)
                            toolBox.updateDisplayOrder()
                        default:
                            swap(&curLifeList_Context[indexPath!.row], &curLifeList_Context[Path.initialIndexPath!.row])
                            tableView.moveRowAtIndexPath(Path.initialIndexPath!, toIndexPath: indexPath!)
                            toolBox.llvc_updateDisplayOrder()
                    }

                    do {
                        try context.save()
                    } catch _ { print("Drag and drop error. State: Changed")}

                    Path.initialIndexPath = indexPath
                }
            }
        default:
            if My.cellSnapshot != nil || indexPath != nil {
                //Runs continuously while a long press is recognized / Animates cell movement
                let cell = tableView.cellForRowAtIndexPath(Path.initialIndexPath!) as UITableViewCell!

                cell.hidden = false
                cell.alpha = 0.0
                UIView.animateWithDuration(0.25, animations: { () -> Void in
                    My.cellSnapshot!.center = cell.center
                    My.cellSnapshot!.transform = CGAffineTransformIdentity
                    My.cellSnapshot!.alpha = 0.0
                    cell.alpha = 1.0
                    }, completion: { (finished) -> Void in
                        if finished {
                            //Completion block removes snapshot of cell, cleans everything up
                            Path.initialIndexPath = nil
                            My.cellSnapshot!.removeFromSuperview()
                            My.cellSnapshot = nil
                        }
                })//End of competion block & end of animation
            }//End of 'if nil'
        }//End of switch
    }//End of longPress if-nil
}//End of longPressGestureRecognized

Answer 1

我能够使用以下代码解决它：

if locationOnScreen.y < 200 && indexPath!.row > 1 {
    let indexPath = NSIndexPath(forRow: indexPath!.row-1, inSection: 0)
    tableView.scrollToRowAtIndexPath(indexPath, atScrollPosition: UITableViewScrollPosition.Top, animated: false)
} else if locationOnScreen.y > 550 && indexPath!.row < listCount {
    let indexPath = NSIndexPath(forRow: indexPath!.row+1, inSection: 0)
    tableView.scrollToRowAtIndexPath(indexPath, atScrollPosition: UITableViewScrollPosition.Bottom, animated: false)
}

其中：

var locationOnScreen = longPress.locationInView(tableView.superview)
listCount = listArrayOrContext.count

插入开关盒：

case UIGestureRecognizerState.Changed:

我将 animate 设置为 false，否则我的滚动会非常不稳定、混乱。如果有人知道如何获得缓慢、渐进的滚动，请post。

拖放工作 - 自动滚动不

Drag & Drop Works - Autoscroll Doesn't

drag-and-drop

uitableview

autoscroll

ios

swift