如何动态更改UITableView中单元格的高度？

Question

I have:

A UITableView in my UIViewcontroller

var searchResults: UITableView = UITableView();

A custom UITableViewCell class:

class CellSearchResult: UITableViewCell { ... }

I register my cell for the tableview:

searchResults.registerClass(CellSearchResult.self, forCellReuseIdentifier: "Cell");

I have my tableView method to fill my table:

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    var cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as! CellSearchResult
    cell.frame.height = 100;   <<<< ERROR

    ...
}

I would like to change the height of my cell like:

cell.frame.height = 100;   <<<< ERROR

How to do this ?

Answer 1

You need to override heightForRowAtIndexPath function. Example:

override func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
        return 100
    }

EDIT:

If you are not subclassing UITableViewController , you can't access tableView functions unless you conform UITableViewDelegate , UITableViewDataSource protocols. You can do this by

class myViewController: UIViewController, UITableViewDataSource, UITableViewDelegate { ....

.

  tableview.delegate = self
  tableview.datasource = self

Answer 2

If the heights of all cells are the same the most efficient way is to set the rowHeight property of the UITableView itself.

tableView.rowHeight = 100.0

There are performance implications to using tableView:heightForRowAtIndexPath: instead of rowHeight. Every time a table view is displayed, it calls tableView:heightForRowAtIndexPath: on the delegate for each of its rows, which can result in a significant performance problem with table views having a large number of rows (approximately 1000 or more).

If the cells have variable heights you will need to implement the UITableViewDelegate method tableView:heightForRowAtIndexPath:

func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {

    var height = // do something to calculate height

    return height
}

If you need to do expensive calculations in tableView:heightForRowAtIndexPath: it is also advisable to implement another UITableViewDelegate method, tableView:estimatedHeightForRowAtIndexPath: (available since iOS 7). Any code you put in this method needs to be efficient.

func tableView(tableView: UITableView, estimatedHeightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
    return 100.0
}

Providing an estimate the height of rows can improve the user experience when loading the table view. If the table contains variable height rows, it might be expensive to calculate all their heights and so lead to a longer load time. Using estimation allows you to defer some of the cost of geometry calculation from load time to scrolling time.

Answer 3

You have to implement the following to increase a particular row height at run time without calling the reloadData()

Example to increase height of row 10:

 rowHightUpdateReqd = true
 tableView.beginUpdates()
 tableView.reloadRowsAtIndexPaths([NSIndexPath(forRow: 10, inSection: 0)], withRowAnimation: UITableViewRowAnimation.Fade)
 tableView.endUpdates()

 override func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {

   var rowHight: CGFloat = 50

   if rowHightUpdateReqd == true{
      rowHight = 100
      rowHightUpdateReqd = false
   }
   return rowHight
}

Answer 4

override func tableView(tableView: UITableView!, heightForRowAtIndexPath indexPath: NSIndexPath!) -> CGFloat {
 return 100.0;   
}