Why does UICollectionView refresh data after scrolling? - ios

UICollectionView refreshes data after scrolling and changes the position of the cells. How can I stop it? I don't want to call cellForItemAtIndexPath on every scrolling?
I don't have too much data.
- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath {
CCell *cell = [cv dequeueReusableCellWithReuseIdentifier:#"cell" forIndexPath:indexPath];
cell.logo.image=[UIImage imageNamed:[NSString stringWithFormat:#"%#.jpg",news[indexPath.row]]];
return cell;
}

Related

Scrolling of CollectionView in CustomKeyboard JERKs

Facing an issue with the scrolling of CollectionView. When user drags the scroll and leaves it the collectionView scroll jerks just before stopping. The jerk/flicker is very less but I am not able to understand why it is not as smooth as collection view usually is.
I am just using these methods to load CollectionView:
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return 500;
}
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
EmojiCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:EmojiCellIdentifier forIndexPath:indexPath];
return cell;
}
Below is the link of the code: CODE

UICollectionView does not stay selected after scrolling

When I select a cell, it turns blue, which is good. Then when I scroll up and the cell out of view, it turns back to original color. Not sure how to fix this.
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
cell.backgroundColor=[UIColor lightGrayColor];
[collectionView selectItemAtIndexPath:indexPath animated:NO scrollPosition:UICollectionViewScrollPositionNone];
self.collectionView.allowsMultipleSelection=YES;
return cell;
}
-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
UICollectionViewCell *datasetCell =[collectionView cellForItemAtIndexPath:indexPath];
datasetCell.backgroundColor = [UIColor blueColor];
}
-(void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath {
UICollectionViewCell *datasetCell =[collectionView cellForItemAtIndexPath:indexPath];
}
In your first method, you are practically telling the collection view to select any cell that it asks for. Instead, you should check whether the cell you return has the same path as the selected one, and only then give it color:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
if ([indexPath isEqual:self.selectedIndexPath]) // you need to create selectedIndexPath as a property
{
cell.backgroundColor=[UIColor blueColor];
}
else
{
cell.backgroundColor=[UIColor lightGrayColor];
}
return cell;
}
And then:
-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
self.selectedIndexPath = indexPath;
}
When cell are reused, the selection state is lost. So you need to save the indexPath of the selection in didSelectItemAtIndexPath. And when you dequeue the cell you need to check and restore the state

Display different cells based on data type in UICollectionView

I have three different types of cells with different content size (containing image, label and button) in UICollectionview. I am getting data from web services. I want to show correct cell based on these types.
Firstly you register nibs of layouts for your cells:
[collectionView registerNib:myCellTypeImageNib forCellWithReuseIdentifier:#"MyModelTypeImageCellIdentifier"];
[collectionView registerNib:myCellTypeLabelNib forCellWithReuseIdentifier:#"MyModelTypeLabelCellIdentifier"];
[collectionView registerNib:myCellTypeButtonNib forCellWithReuseIdentifier:#"MyModelTypeButtonCellIdentifier"];
Then return them appropriately:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
MyModel *modelObject = self.dataArray[indexPath.item];
UICollectionViewCell *cell = nil;
switch (modelObject.type) {
case MyModelTypeImage:
cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"MyModelTypeImageCellIdentifier" forIndexPath:indexPath];
//adjust cell
break;
case MyModelTypeLabel:
cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"MyModelTypeLabelCellIdentifier" forIndexPath:indexPath];
//adjust cell
break;
case MyModelTypeButton:
cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"MyModelTypeButtonCellIdentifier" forIndexPath:indexPath];
//adjust cell
break;
}
return cell;
}
You can use
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
Note: indexpath
For example. Add all the images in to an array.
self.myArray = [[NSArray alloc] initWithObjects:#"first.jpg",
#"second.jpg",
#"third.jpg",
#"last.jpg",nil]
Then in cellForRow... do the following:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
// configure cell
...
cell.myImageView = [self.myArray objectAtIndex:indexPath.row;
}

UICollectionViewCell Only Updates After Scrolling

I've got an issue with my UICollectionView where my cells are always initiated blank/in a default state with no data.
The data only appears in the cells after scrolling them in and out of view.
Code:
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIdentifier = #"EquipmentCell";
APInventoryCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];
if (!cell) cell = [[APInventoryCollectionViewCell alloc] init];
//set cell data...
cell.label.text = [arrayOfStrings objectAtIndex:indexPath.row];
return cell;
}
Your problem is that you probably set the arrayOfStrings somewhere in the viewDidLoad method of your view controller, the problem with that is that the collectionview datasource calls are done before that.
What you should do in your viewDidLoad method just call [collectionview reloadData]; an you will be fine

Adding UICollectionView to UIView

All,
I am adding a UICollectionView to a UIView but it's failing to load cells because it seems that this:
[self.buttonsCollectionView registerNib:[UINib nibWithNibName:#"AccountMenuCollectionViewCell" bundle:nil] forCellWithReuseIdentifier:#"AccountMenuCell"];
Is getting loaded after it hits the delegates for the UICollectionView. Normally this would be placed in viewDidLoad but is not available in a UIView.
- (AccountMenuCollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
AccountMenuCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"AccountMenuCell" forIndexPath:indexPath];
[cell.accountMenuButton setTitle:#"Deposit" forState:UIControlStateNormal];
return cell;
}
Any guidance?
EDIT:
So I am using a view from the storyboard initially and then adding a subview which is Account Menu. Within this view I have a Collection View.
Try to use with the default method and instantiate your Cell inside of the cellForItem...
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
AccountMenuCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"AccountMenuCell" forIndexPath:indexPath];
[cell.accountMenuButton setTitle:#"Deposit" forState:UIControlStateNormal];
return cell;
}
and .. verify with Breakpoints if your code is running..

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