uitableview - 如何为 iPad 创建类似于 Safari 工具栏自定义的拖放功能

Question

我有一个 UIViewController，上面有一个 UITable 和一个 UIView。我希望能够拾取 UIView 中显示的项目并将它们放到 UITableView 中的单元格上。我不得不恢复使用触摸事件而不是新的 UIGestureRecognisers 来拍摄被点击的 UIView 的快照以便将此快照拖到 UITableView 而不是触摸的 UIView。使用以下方法效果很好，

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch *t =[touches anyObject];

    UIGraphicsBeginImageContext(t.view.bounds.size);
    [t.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage * img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    self.draggedView = [[UIImageView alloc] initWithImage:img];

    CGPoint centre = [[touches anyObject] locationInView:self.view];
    [self.draggedView setCenter:centre];
    [self.draggedView setAlpha:0.5];
    [self.view addSubview:self.draggedView];   
}

但是，在 touchesEnded 事件中，当我尝试评估触摸在哪个 UIView 上结束时，当我放下它时，我总是得到一个 UIView 而不是 UITableView。任何想法都会非常受欢迎。

Answer 1

我想我已经使用最新的 GestureRecognisers 为这个问题提出了更好的解决方案。我在基本 TableView Controller 中使用以下 LongPress 手势识别器。

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer{
    if([gestureRecognizer isKindOfClass:[UILongPressGestureRecognizer class]]){
        [gestureRecognizer addTarget:self action:@selector(longGestureAction:)];
    }
    return YES;
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
    return YES;
}

-(void)longGestureAction:(UILongPressGestureRecognizer *)gesture{
    UITableViewCell *cell= (UITableViewCell *)[gesture view];

    switch ([gesture state]) {
        case UIGestureRecognizerStateBegan:{          
            NSIndexPath *ip = [self.tableView indexPathForCell:cell];
            [self.tableView setScrollEnabled:NO];
            if(ip!=nil){
                [self.draggableDelegate dragAndDropTableViewController:self  draggingGestureWillBegin:gesture forCell:cell];
                UIView *draggedView = [self.draggableDelegate dragAndDropTableViewControllerView:self ];
                //switch the view the gesture is associated with this will allow the dragged view to continue on where the cell leaves off from
                [draggedView addGestureRecognizer:[[cell gestureRecognizers]objectAtIndex:0]]; 
                [self.draggableDelegate dragAndDropTableViewController:self draggingGestureDidBegin:gesture forCell:cell];
            }
        }
            break;
        case UIGestureRecognizerStateChanged:{
            [self.draggableDelegate dragAndDropTableViewController:self draggingGestureDidMove:gesture];
        }
            break;
        case UIGestureRecognizerStateEnded:{
            UIView *draggedView = [self.draggableDelegate dragAndDropTableViewControllerView:self];
            if(draggedView==nil)
                return;

            //this does not seem like the best way to do this yet you really don't want to fire one after the other I don't think
            [self.draggableDelegate dragAndDropTableViewController:self draggingGestureDidEnd:gesture];
            [self.dropableDelegate dragAndDropTableViewController:self droppedGesture:gesture];           

            [self.tableView setScrollEnabled:YES];
            [self.tableView reloadData];
        }
            break;

//        case UIGestureRecognizerStateCancelled:
//        case UIGestureRecognizerStateFailed:
//        case UIGestureRecognizerStatePossible:
//            [self.dragAndDropDelegate dragAndDropTableViewController:self draggingGesture:gesture endedForItem:nil];
            break;
        default:
            break;
    }
}

在扩展此基类的 TableViews 中，我将以下内容添加到 cellForIndexPath TableViewDataSource 中的每个单元格，

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:cell action:nil];
longPress.delegate = self;
[cell addGestureRecognizer:longPress];

最后你需要做的就是像这样实现委托(delegate)方法，

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer{
    if([gestureRecognizer isKindOfClass:[UILongPressGestureRecognizer class]]){
        [gestureRecognizer addTarget:self action:@selector(longGestureAction:)];
    }
    return YES;
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
    return YES;
}

-(void)longGestureAction:(UILongPressGestureRecognizer *)gesture{
    UITableViewCell *cell= (UITableViewCell *)[gesture view];

    switch ([gesture state]) {
        case UIGestureRecognizerStateBegan:{          
            NSIndexPath *ip = [self.tableView indexPathForCell:cell];
            [self.tableView setScrollEnabled:NO];
            if(ip!=nil){
                [self.draggableDelegate dragAndDropTableViewController:self  draggingGestureWillBegin:gesture forCell:cell];
                UIView *draggedView = [self.draggableDelegate dragAndDropTableViewControllerView:self ];
                //switch the view the gesture is associated with this will allow the dragged view to continue on where the cell leaves off from
                [draggedView addGestureRecognizer:[[cell gestureRecognizers]objectAtIndex:0]]; 
                [self.draggableDelegate dragAndDropTableViewController:self draggingGestureDidBegin:gesture forCell:cell];
            }
        }
            break;
        case UIGestureRecognizerStateChanged:{
            [self.draggableDelegate dragAndDropTableViewController:self draggingGestureDidMove:gesture];
        }
            break;
        case UIGestureRecognizerStateEnded:{
            UIView *draggedView = [self.draggableDelegate dragAndDropTableViewControllerView:self];
            if(draggedView==nil)
                return;

            //this does not seem like the best way to do this yet you really don't want to fire one after the other I don't think
            [self.draggableDelegate dragAndDropTableViewController:self draggingGestureDidEnd:gesture];
            [self.dropableDelegate dragAndDropTableViewController:self droppedGesture:gesture];           

            [self.tableView setScrollEnabled:YES];
            [self.tableView reloadData];
        }
            break;

//        case UIGestureRecognizerStateCancelled:
//        case UIGestureRecognizerStateFailed:
//        case UIGestureRecognizerStatePossible:
//            [self.dragAndDropDelegate dragAndDropTableViewController:self draggingGesture:gesture endedForItem:nil];
            break;
        default:
            break;
    }
}

您可以找到此 here 的来源.我花了很长时间才做到这一点，所以我真的希望这可以节省其他人的时间。