拖放作品 - 自动滚动不

Posted 2023-05-08

【中文标题】拖放作品 - 自动滚动不

【英文标题】：Drag & Drop Works - Autoscroll Doesn't

【发布时间】：2016-05-09 20:59:11

【问题描述】：

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

换句话说，我还没有弄清楚如何让它自动滚动。

当用户将单元格拖向视图的顶部或底部时，是否有人能够查看我的代码并知道在哪里添加启用自动滚动的代码？

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

【参考方案1】：

我能够使用此代码解决它：

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)

地点：

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

插入开关盒：

case UIGestureRecognizerState.Changed:

我将 animate 设置为 false，否则我的滚动会变得非常生涩、混乱。如果有人知道如何获得缓慢、渐进的滚动，请发布。