how to determine exact spacing between UICollectionView cells - ios

Question

I am newbie in IOS dev . I was given job to make calendar app. I am using UICollectionViewCell to display days 1-30. for daynames like "S M T W TH F S" I used supplementary view(headerCell) and adding 7 UILabels with SPACING same as distance between two cells. I see Daynames are not aligned vertically to Day Numbers. I have extended UICollectionViewDelegateFlowLayout to set minimumInteritemSpacingForSectionAtIndex to 2 and I managed the cell sizes to display only 7 days(1 week) per row.
I also calculated distance between 2 cells using their centres , taking that distance as reference and adding it as distance between labels in HeaderCell, but still they are not getting aligned.
I am looking to exactly calculate distance between cells in UICollectionView. the spacing we set is just minimum and it differs sometimes depending on iPhone screen size.
Here is the Pic:
missing alignment with day cells
Here is my code:
extension FirstViewController: UICollectionViewDelegateFlowLayout {
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
var cwidth:CGFloat = 0.0
cwidth = (collectionView.frame.size.width/7 - PADDING - SPACING)
let cheight = collectionView.frame.size.height/7
cellWidth = cwidth
cellHeight = cheight
print("Cell width is \(cellWidth) and view width is \(collectionView.frame.size.width)")
return CGSize(width: cwidth, height: cheight )
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAtIndex section: Int) -> UIEdgeInsets {
return UIEdgeInsets(top:1.0,left:1.0,bottom:1.0,right:1.0)
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAtIndex section: Int) -> CGFloat {
return 1.0
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAtIndex section: Int) -> CGFloat {
return SPACING
}
}
class FirstViewController:
UIViewController,UICollectionViewDataSource,UICollectionViewDelegate
{
func collectionView(collectionView: UICollectionView,
viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath:
NSIndexPath) -> UICollectionReusableView
{
let cell = collectionView.dequeueReusableSupplementaryViewOfKind(kind, withReuseIdentifier: "headerCell", forIndexPath: indexPath)
var prevWidth:CGFloat = 5.0
var frame1 :CGRect? = nil
for (index,i) in daynames.enumerate() {
if (index == 0){
frame1 = CGRect(x: 1.0, y: -2.0, width: cellWidth , height: cellHeight)
}
else{
frame1 = CGRect(x: CGFloat(prevWidth) , y: -2.0,width:cellWidth , height: cellHeight)
}
if (index < 6){
prevWidth = frame1!.origin.x + cellWidth + distances[index] - SPACING
}
let label = UILabel(frame:frame1!)
label.text = i
label.textAlignment = NSTextAlignment.Center
label.textColor = UIColor.whiteColor()
label.font = UIFont(name:"Helvetica",size:16)
label.backgroundColor = UIColor.blackColor()
// label.center.x = cell_centres[index]
cell.addSubview(label)
}
return cell
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("Cell", forIndexPath: indexPath)
let label = cell.contentView.viewWithTag(1) as! UILabel
//testing purpose
label.text = String(days[indexPath.row])
if indexPath.row == 0{
cell_centres.removeAll()
}
cell.backgroundColor = UIColor.greenColor()
if indexPath.row < 7{
cell_centres.append(cell.center.x)
print("appending \(cell.center.x)")
}
//code for calc distances between cells
if(prevX == 0){
prevX = cell.center.x
}
else if(indexPath.row < 7){
distance = floor((cell.center.x - prevX) - cellWidth)
print("distance \(distance) ")
distances.append(distance)
prevX = cell.center.x
}
return cell
}
}