This Objective-C class allows you to reorder cells in a UITableView. Each element in cells have to implement a property called "position".
You can use this to reorder simple elements or tables with subelements (i.e. tasks with subtasks)
This is an autoanswer to a StackOVerflow question (http://stackoverflow.com/questions/32521725/autoscroll-smoothly-uitableview-while-dragging-uitableviewcells-in-ios-app)
## Example of use ##
[[EMRReorderTableCells alloc] initWithTableView:_taskTableView
elements:[_tasks objectAtIndex:0]
elementsOffset:5
collapseSubElements:YES
collapseSubCellsAtIndexPathBlock:^(NSUInteger idx) {
// In case you have subelements
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:idx inSection:0];
[self expandCollapseSubtasksAtIndexPath:indexPath];
} removeSubElementsForElementBlock:^(id element) {
[self removeSubtasksForTask:(Task *)element];
} removeSubElementsForElementAtIndexPathBlock:^(NSIndexPath *indexPath) {
[self removeSubtasksAtIndexPath:indexPath];
} areBrothersElements:^BOOL(id source, id target) {
return [(Task *)source isBrotherOfTask:(Task *)target];
} isSubElementBlock:^BOOL(id element) {
return ![[(Task *)element subtask] isEqualToString:@"0"];
} isHidingSubElementsBlock:^BOOL(id element) {
return [[(Task *)element hidesubtasks] isEqualToNumber:@0];
} completionBlock:^(id element) {
// Update element
[_httpClient createUpdateRequestForObject:element withPath:@"task/" withRegeneration:NO];
[_httpClient update:nil];
}];
-
elements: NSArray with elements to reorder.
-
elementsOffset: Integer with an offset. Imagine a main menu where you have three main sections and a list of custom sections. If you want to allow only to reorder the custom sections, you have to specify an offset of 3. The first three cells will be locked.
-
collapseSubElements: Bool that specify if you want to collapse subelements or not
-
collapseSubCellsAtIndexPathBlock: A block that implement the action of collapsing subelements' cells
-
removeSubElementsForElementBlock: A block that implement the action of removing subelements from the element list for a given element.
-
removeSubElementsForElementAtIndexPathBlock: A block that implement the action of removing subelements from the element list for a given index path.
-
areBrothersElements: A block that return true if both elements are brothers (they are in the same level) or false if they are father and son or cousins.
-
isSubElementBlock: A block that return true if element is a subelement and false if is a single element without children.
-
isHidingSubElementsBlock: A block that return true if element if an element is hiding subelements and false if not.
-
completionBlock: A block that perform and action after finishing the reorder.
Example of blocks
-(void)expandCollapseSubtasksAtIndexPath:(NSIndexPath *)indexPath{
NSLog(@"Row: %ld - Section: %ld", (long)indexPath.row, (long)indexPath.section);
if (indexPath != nil)
{
Task *task = [[_tasks objectAtIndex:indexPath.section] objectAtIndex:indexPath.row];
TaskTitleCell *cell = (TaskTitleCell *)[_taskTableView cellForRowAtIndexPath:indexPath];
UILabel *subtasksNumberLabel = (UILabel *)[cell viewWithTag:107];
UIButton *subtasksButton = (UIButton *)[cell viewWithTag:108];
NSMutableArray *subtasksIndexPaths = [[NSMutableArray alloc] init];
NSDictionary *subtasksAndIndexesDictionary = [task getSubtasksIndexesInTaskCollection:[_tasks objectAtIndex:indexPath.section] ofList:task.list];
//NSDictionary *subtasksAndIndexesDictionary = [task getSubtasksIndexesInTaskCollection:[_tasks objectAtIndex:indexPath.section] ofList:task.list filteredBy:(int)_selectedFilter];
NSIndexSet *indexes = [subtasksAndIndexesDictionary objectForKey:@"indexes"];
NSArray *subtasks = [subtasksAndIndexesDictionary objectForKey:@"subtasks"];
[indexes enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {
NSIndexPath *subtaskIndexPath = [NSIndexPath indexPathForRow:idx inSection:indexPath.section];
[subtasksIndexPaths addObject:subtaskIndexPath];
}];
NSNumber *hidden;
//Expand
if (!subtasksButton.selected){
hidden = @0;
//[task setHidesubtasks:@0];
subtasksNumberLabel.textColor = [UIColor colorWithRed:72.0/255.0 green:175.0/255.0 blue:237.0/255.0 alpha:1.0];
[[_tasks objectAtIndex:indexPath.section] insertObjects:subtasks atIndexes:indexes];
[_taskTableView insertRowsAtIndexPaths:subtasksIndexPaths withRowAnimation:UITableViewRowAnimationTop];
//Collapse
}else{
hidden = @1;
//[task setHidesubtasks:@1];
subtasksNumberLabel.textColor = [UIColor whiteColor];
NSArray *subtasks = [task getSubtasks];
if (subtasks){
[[_tasks objectAtIndex:indexPath.section] removeObjectsInArray:subtasks];
[_taskTableView deleteRowsAtIndexPaths:subtasksIndexPaths withRowAnimation:UITableViewRowAnimationBottom];
}
}
subtasksButton.selected = !subtasksButton.selected;
//task.hidesubtasksValue = !subtasksButton.selected;
task.hidesubtasks = hidden;
[[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreAndWait];
}
}
-(void)removeSubtasksForTask:(Task *)task{
NSNumber *hidden = @1;
NSArray *subtasks = [task getSubtasks];
[_tasks removeObjectsInArray:subtasks];
task.hidesubtasks = hidden;
[[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreAndWait];
}
-(void)removeSubtasksAtIndexPath:(NSIndexPath *)indexPath{
Task *task = [_tasks objectAtIndex:indexPath.row];
TaskTitleCell *cell = (TaskTitleCell *)[_taskTableView cellForRowAtIndexPath:indexPath];
UILabel *subtasksNumberLabel = (UILabel *)[cell viewWithTag:107];
UIButton *subtasksButton = (UIButton *)[cell viewWithTag:108];
NSMutableArray *subtasksIndexPaths = [[NSMutableArray alloc] init];
NSNumber *hidden = @1;
subtasksNumberLabel.textColor = [UIColor whiteColor];
NSArray *subtasks = [task getSubtasks];
[_tasks removeObjectsInArray:subtasks];
for (int i=1;i<=subtasks.count; i++){
NSIndexPath *subtaskIndexPath = [NSIndexPath indexPathForRow:indexPath.row+i inSection:0];
[subtasksIndexPaths addObject:subtaskIndexPath];
}
[_taskTableView deleteRowsAtIndexPaths:subtasksIndexPaths withRowAnimation:UITableViewRowAnimationBottom];
subtasksButton.selected = !subtasksButton.selected;
task.hidesubtasks = hidden;
[[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreAndWait];
}
I have use some inspiration from https://github.com/hpique/HPReorderTableView
A. Manage gestureRecognition
longPressGestureRecognized:
- (IBAction)longPressGestureRecognized:(id)sender {
_reorderGestureRecognizer = (UILongPressGestureRecognizer *)sender;
CGPoint location = [_reorderGestureRecognizer locationInView:_tableView];
NSIndexPath *indexPath = [self getCellIndexPathWithPoint:location];
UIGestureRecognizerState state = _reorderGestureRecognizer.state;
switch (state) {
case UIGestureRecognizerStateBegan: {
NSIndexPath *indexPath = [_tableView indexPathForRowAtPoint:location];
if (indexPath == nil)
{
[self gestureRecognizerCancel:_reorderGestureRecognizer];
break;
}
// For scrolling while dragging
_scrollDisplayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(scrollTableWithCell:)];
[_scrollDisplayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
// Check for the right indexes (between margins of offset
if (indexPath.row >=_elementsOffset && indexPath.row < [_elements count]+_elementsOffset){
if (indexPath) {
sourceIndexPath = indexPath;
id sourceElement = [_elements objectAtIndex:sourceIndexPath.row-_elementsOffset];
snapshot = [self createSnapshotForCellAtIndexPath:indexPath withPosition:location];
}
} else {
sourceIndexPath = nil;
snapshot = nil;
}
break;
}
case UIGestureRecognizerStateChanged: {
[self calculateScroll:_reorderGestureRecognizer];
if (sourceIndexPath != nil && indexPath.row >=_elementsOffset && indexPath.row < [_elements count]+_elementsOffset){
[self updateSnapshotWithPosition:location];
// Is destination valid and is it different from source?
if (indexPath && ![indexPath isEqual:sourceIndexPath]) {
if (indexPath.row - sourceIndexPath.row <= 1){
id sourceElement = [_elements objectAtIndex:sourceIndexPath.row-_elementsOffset];
id targetElement = [_elements objectAtIndex:indexPath.row-_elementsOffset];
sourceIndexPath = [self exchangeElement:sourceElement byElement:targetElement];
}
}
}
break;
}
case UIGestureRecognizerStateEnded:
{
// For scrolling while dragging
[_scrollDisplayLink invalidate];
_scrollDisplayLink = nil;
_scrollRate = 0;
// Check if it is the last element
if (sourceIndexPath != nil){
id element;
if (indexPath.row <=_elementsOffset){
element = [_elements firstObject];
} else if (indexPath.row > [_elements count]-1+_elementsOffset){
element = [_elements lastObject];
} else {
element = [_elements objectAtIndex:indexPath.row-_elementsOffset];
}
}
}
default: {
// Clean up.
[self deleteSnapshotForRowAtIndexPath:sourceIndexPath];
[appDelegate startTimer];
break;
}
}
}
gestureRecognizerCancel:
It is use to cancel gesture recognition to finish the reorder action.
-(void) gestureRecognizerCancel:(UIGestureRecognizer *) gestureRecognizer
{ // See: http://stackoverflow.com/a/4167471/143378
gestureRecognizer.enabled = NO;
gestureRecognizer.enabled = YES;
}
scrollTableWithCell:
The method it is called to make scrolling movement when you are in the limits of the table (up and down)
- (void)scrollTableWithCell:(NSTimer *)timer
{
UILongPressGestureRecognizer *gesture = _reorderGestureRecognizer;
const CGPoint location = [gesture locationInView:_tableView];
CGPoint currentOffset = _tableView.contentOffset;
CGPoint newOffset = CGPointMake(currentOffset.x, currentOffset.y + _scrollRate * 10);
if (newOffset.y < -_tableView.contentInset.top)
{
newOffset.y = -_tableView.contentInset.top;
}
else if (_tableView.contentSize.height + _tableView.contentInset.bottom < _tableView.frame.size.height)
{
newOffset = currentOffset;
}
else if (newOffset.y > (_tableView.contentSize.height + _tableView.contentInset.bottom) - _tableView.frame.size.height)
{
newOffset.y = (_tableView.contentSize.height + _tableView.contentInset.bottom) - _tableView.frame.size.height;
}
[_tableView setContentOffset:newOffset];
if (location.y >= 0 && location.y <= _tableView.contentSize.height + 50)
{
[self updateSnapshotWithPosition:location];
NSIndexPath *indexPath = [self getCellIndexPathWithPoint:location];
// CHeck if element is between offset limits.
if (![indexPath isEqual:sourceIndexPath] &&
indexPath.row >= _elementsOffset &&
indexPath.row - _elementsOffset < [_elements count] &&
sourceIndexPath.row >= _elementsOffset &&
sourceIndexPath.row - _elementsOffset < [_elements count])
{
id sourceElement = [_elements objectAtIndex:sourceIndexPath.row-_elementsOffset];
id targetElement = [_elements objectAtIndex:indexPath.row-_elementsOffset];
[self exchangeElement:sourceElement byElement:targetElement];
sourceIndexPath = indexPath;
}
}
}
B. Snapshot management
createSnapshotForCellAtIndexPath:withPosition
Method that creates a snapshot (a image copy) of the cell you are moving
-(UIView *)createSnapshotForCellAtIndexPath:(NSIndexPath *)indexPath withPosition:(CGPoint)location{
UITableViewCell *cell = [_tableView cellForRowAtIndexPath:indexPath];
// Take a snapshot of the selected row using helper method.
snapshot = [self customSnapshoFromView:cell];
// Add the snapshot as subview, centered at cell's center...
__block CGPoint center = cell.center;
snapshot.center = center;
snapshot.alpha = 0.0;
[_tableView addSubview:snapshot];
[UIView animateWithDuration:0.25 animations:^{
// Offset for gesture location.
center.y = location.y;
snapshot.center = center;
snapshot.transform = CGAffineTransformMakeScale(1.05, 1.05);
snapshot.alpha = 0.98;
cell.alpha = 0.0;
} completion:^(BOOL finished) {
cell.hidden = YES;
}];
return snapshot;
}
customSnapshoFromView:
Returns a customized snapshot of a given view. */
- (UIView *)customSnapshoFromView:(UIView *)inputView {
// Make an image from the input view.
UIGraphicsBeginImageContextWithOptions(inputView.bounds.size, NO, 0);
[inputView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// Create an image view.
snapshot = [[UIImageView alloc] initWithImage:image];
snapshot.layer.masksToBounds = NO;
snapshot.layer.cornerRadius = 0.0;
snapshot.layer.shadowOffset = CGSizeMake(-5.0, 0.0);
snapshot.layer.shadowRadius = 5.0;
snapshot.layer.shadowOpacity = 0.4;
return snapshot;
}
updateSnapshotWithPosition:
Given a CGPoint, it changes the snapshot position to show the cell you are moving in the right place of the _tableView
-(void)updateSnapshotWithPosition:(CGPoint)location{
CGPoint center = snapshot.center;
center.y = location.y;
snapshot.center = center;
}
deleteSnapshotForRowAtIndexPath:
When dragging finishes, you need to delete the snapshot from the _tableView
-(void)deleteSnapshotForRowAtIndexPath:(NSIndexPath *)sourceIndexPath{
UITableViewCell *cell = [_tableView cellForRowAtIndexPath:sourceIndexPath];
cell.hidden = NO;
cell.alpha = 0.0;
[UIView animateWithDuration:0.25 animations:^{
snapshot.center = cell.center;
snapshot.transform = CGAffineTransformIdentity;
snapshot.alpha = 0.0;
cell.alpha = 1.0;
} completion:^(BOOL finished) {
[snapshot removeFromSuperview];
}];
}
calculateScroll
-(void)calculateScroll:(UIGestureRecognizer *)gestureRecognizer{
const CGPoint location = [gestureRecognizer locationInView:_tableView];
CGRect rect = _tableView.bounds;
// adjust rect for content inset as we will use it below for calculating scroll zones
rect.size.height -= _tableView.contentInset.top;
//[self updateCurrentLocation:gestureRecognizer];
// tell us if we should scroll and which direction
CGFloat scrollZoneHeight = rect.size.height / 6;
CGFloat bottomScrollBeginning = _tableView.contentOffset.y + _tableView.contentInset.top + rect.size.height - scrollZoneHeight;
CGFloat topScrollBeginning = _tableView.contentOffset.y + _tableView.contentInset.top + scrollZoneHeight;
// we're in the bottom zone
if (location.y >= bottomScrollBeginning)
{
_scrollRate = (location.y - bottomScrollBeginning) / scrollZoneHeight;
}
// we're in the top zone
else if (location.y <= topScrollBeginning)
{
_scrollRate = (location.y - topScrollBeginning) / scrollZoneHeight;
}
else
{
_scrollRate = 0;
}
}
C. How to use it
In your init method, assign a gesture recognizer to the table view. Assign as action the method longPressGestureRecognized: as follows:
_reorderGestureRecognizer = [[UILongPressGestureRecognizer alloc]
initWithTarget:self action:@selector(longPressGestureRecognized:)];
[_tableView addGestureRecognizer:_reorderGestureRecognizer];
Declare the variables you will need to use the above code explained
@implementation YourClassName{
CADisplayLink *_scrollDisplayLink;
CGFloat _scrollRate;
UIView *snapshot; // A snapshot of the row user is moving.
NSIndexPath *sourceIndexPath; // Initial index path, where gesture begins.
}
Copyright (c) 2017. Enrique Ismael Mendoza Robaina
EMRReorderTableCElls is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.
Playtch is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.