UICollectionView使用reloadData()方法之后，Cell 里面的控件报错找不到

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell{

        NSLog("\(indexPath.row)")

        let collectionCell = collectionView.dequeueReusableCellWithReuseIdentifier("collectionCellLocation", forIndexPath: indexPath) as UICollectionViewCell

        

        let cityLocationButton = collectionCell.viewWithTag(1) as! UIButton

        let autoLocationButton = collectionCell.viewWithTag(2) as! UIButton

        if indexPath.row > 0 {

            NSLog("1111111")

            autoLocationButton.hidden = true

            cityLocationButton.setTitle(searchCityList[indexPath.row-1], forState: UIControlState.Normal)

        }else{

            cityLocationButton.hidden = true

        }

        

        //添加手动定位点击事件

        cityLocationButton.tag = indexPath.row

        let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: "clickForCityName:")

        cityLocationButton.addGestureRecognizer(tapGestureRecognizer)

        //添加自动定位点击事件

        autoLocationButton.tag = indexPath.row

        autoLocationButton.addTarget(self, action: "clickAutoLocation:", forControlEvents: UIControlEvents.TouchUpInside)

        

        return collectionCell

    }

刚进来的时候可以正常显示控件，但是reloadData()之后，就报错：

let cityLocationButton = collectionCell.viewWithTag(1) as! UIButton

这一行显示错误信息是：fatal error: unexpectedly found nil while unwrapping an Optional value

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