UICollectionView仅显示一个单元格 - 在滚动视图时会更改

Question

I have a UICollectionView which is supposed to show items from an array. I have checked the array - and it is populated with the right number and type of objects.

The UICollectionView however shows only one UICollectionView cell - and it changes when I pull the cell down to the previous object. I've not seen this behaviour before. Below is my code:

(It's the SourceTankCollectionView that is causing the problem (and I assume the destination collection view cell will too)

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    if (collectionView==self.movementsIndexCollectionView)
    {

        TransfersListCollectionViewCell* tempCell = [collectionView dequeueReusableCellWithReuseIdentifier: @"Transfer List Cell" forIndexPath:indexPath];
        if (!tempCell)
        {
            tempCell = [[TransfersListCollectionViewCell alloc] init];
        }

        Movement* thisMovement = [self.arrayOfAllMovements objectAtIndex:indexPath.item];

        tempCell.sourceTankLabel.text = thisMovement.sourceTank.tankNumber;
        tempCell.destinationTankLabel.text = thisMovement.destinationTank.tankNumber;
        tempCell.layer.borderWidth = 1.5;
        tempCell.layer.borderColor = [[UIColor darkGrayColor] CGColor];
        tempCell.layer.cornerRadius = 4;
        return tempCell;
    }

    else if (collectionView==self.sourceTanksCollectionView)
    {
        SourceTankCollectionViewCell* tempCell = [collectionView dequeueReusableCellWithReuseIdentifier: @"Source Tank Collection Cell" forIndexPath:indexPath];
        if (!tempCell)
        {
            tempCell = [[SourceTankCollectionViewCell alloc] init];
        }
        int index = indexPath.row;

        if (!tempCell)
        {
            tempCell = [[SourceTankCollectionViewCell alloc] init];
        }

        Tank* thisSourceTank = [self.arrayOfSourceTanks objectAtIndex:indexPath.row];
        Product* thisSourceTankProduct = thisSourceTank.tankProduct;

        tempCell.tankNumberLabel.text = thisSourceTank.tankNumber;
        tempCell.tankProductLabel.text = thisSourceTankProduct.name;
        tempCell.tankVolumeLabel.text = thisSourceTank.tankTotalVolume;
        tempCell.tankVolumeGauge.percentFilled = [thisSourceTank.tankTotalVolume doubleValue]/[thisSourceTank.tankMaxVolume doubleValue];
        //tempCell.tankVolumeToTransferLabel.text = [thisMovement.volume stringValue];
        //tempCell.tankVolumeTransferredLabel.text = @"35000";
        tempCell.transferStatusLabel.text = @"In progress";

        tempCell.backgroundColor = [UIColor darkGrayColor];
        tempCell.layer.borderWidth = 1.5;
        tempCell.layer.borderColor = [[UIColor whiteColor] CGColor];
        tempCell.layer.cornerRadius = 8;

        tempCell.frame = CGRectMake(self.sourceTanksCollectionView.frame.size.width * 0.05, self.sourceTanksCollectionView.frame.size.width * 0.05, self.sourceTanksCollectionView.frame.size.width * 0.9, 103);
        return tempCell;
    }
    else //if (collectionView==self.destinationTanksCollectionView)
    {
        DestinationTankCollectionViewCell* tempCell = [collectionView dequeueReusableCellWithReuseIdentifier: @"Destination Tank Collection Cell" forIndexPath:indexPath];
        if (!tempCell)
        {
            tempCell = [[DestinationTankCollectionViewCell alloc] init];
        }
        Tank* thisDestinationTank = [self.arrayOfDestinationTanks objectAtIndex:indexPath.item];
        Product* thisDestinationTankProduct = thisDestinationTank.tankProduct;

        tempCell.tankNumberLabel.text = thisDestinationTank.tankNumber;
        tempCell.tankProductLabel.text = thisDestinationTankProduct.name;
        tempCell.tankVolumeLabel.text = thisDestinationTank.tankTotalVolume;
        tempCell.tankVolumeGauge.percentFilled = [thisDestinationTank.tankTotalVolume doubleValue]/[thisDestinationTank.tankMaxVolume doubleValue];

        tempCell.backgroundColor = [UIColor darkGrayColor];
        tempCell.layer.borderWidth = 1.5;
        tempCell.layer.borderColor = [[UIColor whiteColor] CGColor];
        tempCell.layer.cornerRadius = 8;

        tempCell.frame = CGRectMake(self.destinationTanksCollectionView.frame.size.width * 0.05, self.destinationTanksCollectionView.frame.size.width * 0.05, self.destinationTanksCollectionView.frame.size.width * 0.9, 103);
        return tempCell;
    }
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    if (collectionView == self.movementsIndexCollectionView)
    {
        return self.arrayOfAllMovements.count;
    }
    else if (collectionView == self.sourceTanksCollectionView)
    {
        return self.arrayOfSourceTanks.count;
    }
    else //(collectionView == self.destinationTanksCollectionView)
    {
        return self.arrayOfDestinationTanks.count;
    }
}

Many thanks for any help! I assume it is an easy fix!

Answer 1

You are not supposed to set the frame of the UICollectionViewCell. You only can set the width and height. and that should be done in:

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{

    return CGSizeMake(collectionView.frame.size.width/2.0, collectionView.frame.size.height/2.0);
}

As I can observe all your cells for this collection view have the same frame rectangle. maybe that what is causing the problem. all the cells are on top of each other.

tempCell.frame = CGRectMake(self.sourceTanksCollectionView.frame.size.width * 0.05, self.sourceTanksCollectionView.frame.size.width * 0.05, self.sourceTanksCollectionView.frame.size.width * 0.9, 103);

Answer 2

@hasan83's answer in Swift 3:

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    return CGSize(width: collectionView.frame.size.width / 2.0, height: collectionView.frame.size.height / 2.0)
}