iOS-TableView拖动Cell更换次序

效果：

长按某个Cell，Cell会有一个明显的弹起放大效果。这时候，你可以通过拖动cell和其他Cell更换顺序。

 

实现的原理：

1，浮层

长按后，UITableViewCell上会出现一个浮层，同时UITableViewCell隐藏。并且浮层可拖动。（对UITableViewCell生成一个快照）

 1 #pragma mark - Helper methods

 2 

 3 /** @brief Returns a customized snapshot of a given view. */

 4 - (UIView *)customSnapshoFromView:(UIView *)inputView {

 5     UIView* snapshot = nil;

 6     

 7     if ([[[UIDevice currentDevice] systemVersion] doubleValue] < 7.0) {

 8         //ios7.0 以下通过截图形式保存快照

 9         snapshot = [self customSnapShortFromViewEx:inputView];

10     }else{

11         //ios7.0 系统的快照方法

12         snapshot = [inputView snapshotViewAfterScreenUpdates:YES];

13     }

14     

15     snapshot.layer.masksToBounds = NO;

16     snapshot.layer.cornerRadius = 0.0;

17     snapshot.layer.shadowOffset = CGSizeMake(-5.0, 0.0);

18     snapshot.layer.shadowRadius = 5.0;

19     snapshot.layer.shadowOpacity = 0.4;

20     

21     return snapshot;

22 }

23 

24 - (UIView *)customSnapShortFromViewEx:(UIView *)inputView

25 {

26     CGSize inSize = inputView.bounds.size;

27     // 下面方法，第一个参数表示区域大小。第二个参数表示是否是非透明的。如果需要显示半透明效果，需要传NO，否则传YES。第三个参数就是屏幕密度了

28     UIGraphicsBeginImageContextWithOptions(inSize, NO, [UIScreen mainScreen].scale);

29     [inputView.layer renderInContext:UIGraphicsGetCurrentContext()];

30     UIImage *image= UIGraphicsGetImageFromCurrentImageContext();

31     UIGraphicsEndImageContext();

32     UIImageView* snapshot = [[UIImageView alloc] initWithImage:image];

33     

34     return snapshot;

35 }

2，更换某对UITableViewCell的位置

// ... update data source.

[_items exchangeObjectAtIndex:indexPath.row withObjectAtIndex:sourceIndexPath.row];              

// ... move the rows.

[_tableView moveRowAtIndexPath:sourceIndexPath toIndexPath:indexPath];

datasource里面的data的位置替换，同时将tableView的Cell位置替换。

 1 - (void)longPressGestureRecognized:(id)sender {

 2     

 3     UILongPressGestureRecognizer *longPress = (UILongPressGestureRecognizer *)sender;

 4     UIGestureRecognizerState state = longPress.state;

 5     

 6     CGPoint location = [longPress locationInView:_tableView];

 7     NSIndexPath *indexPath = [_tableView indexPathForRowAtPoint:location];

 8     

 9     static UIView       *snapshot = nil;        ///< A snapshot of the row user is moving.

10     static NSIndexPath  *sourceIndexPath = nil; ///< Initial index path, where gesture begins.

11     

12     switch (state) {

13         case UIGestureRecognizerStateBegan: {

14             if (indexPath) {

15                 sourceIndexPath = indexPath;

16                 

17                 UITableViewCell *cell = [_tableView cellForRowAtIndexPath:indexPath];

18                 

19                 // Take a snapshot of the selected row using helper method.

20                 snapshot = [self customSnapshoFromView:cell];

21                 

22                 // Add the snapshot as subview, centered at cell's center...

23                 __block CGPoint center = cell.center;

24                 snapshot.center = center;

25                 snapshot.alpha = 0.0;

26                 [_tableView addSubview:snapshot];

27                 [UIView animateWithDuration:0.25 animations:^{

28                     

29                     // Offset for gesture location.

30                     center.y = location.y;

31                     snapshot.center = center;

32                     snapshot.transform = CGAffineTransformMakeScale(1.05, 1.05);

33                     snapshot.alpha = 0.98;

34                     

35                     cell.alpha = 0.0f;

36                 } completion:^(BOOL finished) {

37                     cell.hidden = YES;

38                 }];

39             }

40             break;

41         }

42             

43         case UIGestureRecognizerStateChanged: {

44             CGPoint center = snapshot.center;

45             center.y = location.y;

46             snapshot.center = center;

47             

48             // Is destination valid and is it different from source?

49             if (indexPath && ![indexPath isEqual:sourceIndexPath]) {

50                 

51                 // ... update data source.

52                 [_items exchangeObjectAtIndex:indexPath.row withObjectAtIndex:sourceIndexPath.row];

53                 

54                 // ... move the rows.

55                 [_tableView moveRowAtIndexPath:sourceIndexPath toIndexPath:indexPath];

56                 

57                 // ... and update source so it is in sync with UI changes.

58                 sourceIndexPath = indexPath;

59             }

60             break;

61         }

62             

63         default: {

64             // Clean up.

65             UITableViewCell *cell = [_tableView cellForRowAtIndexPath:sourceIndexPath];

66             [UIView animateWithDuration:0.25 animations:^{

67                 

68                 snapshot.center = cell.center;

69                 snapshot.transform = CGAffineTransformIdentity;

70                 snapshot.alpha = 0.0;

71                 

72                 cell.alpha = 1.0f;

73             } completion:^(BOOL finished) {

74                 cell.hidden = NO;

75                 [snapshot removeFromSuperview];

76                 snapshot = nil;

77                 

78             }];

79             sourceIndexPath = nil;

80             break;

81         }

82     }

83 }

3,  ......似乎没有其他了吧？

你看，是不是很简单呢！只需要上面几行代码，你就可以实现一个稍微有点好看的UITableViewCell变换位置的效果了。

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