从底部快速启动tableView (反向tableView)

Question

是否有可能倒序一个tableView？我找了很多解决办法，但都没有用。

效果就像whatsapp聊天一样。

正常的tableView是：

----------
label 1
----------
label 2
----------
label 3
----------
empty
----------
empty
----------

scroll direction
   |
   |
   v

预期结果：

----------
empty
----------
empty
----------
empty
----------
empty
----------
label 3
----------
label 2
----------
label 1
----------

 scroll direction
      ^
      |
      |

谢谢你的帮助

Answer 1

只要滚动到末尾，每次插入单元格时都执行同样的操作。

tableView.scrollToRowAtIndexPath(bottomIndexPath, atScrollPosition: .Bottom,
          animated: true)

Answer 2

为了补充上面的答案，我包含了使用Parse加载、加载更多和刷新的方法。或者，您可以使用任何其他的提取方法来替换Parse。

第一次加载

    var query = PFQuery(className: "Comments")
    query.orderByDescending("createdAt")
    // limit the number of objects
    query.limit = objectsPerPage
    query.findObjectsInBackgroundWithBlock { (comments: [AnyObject]?, error: NSError?) -> Void in
        // clean array if loading for the first time
        self.objects.removeAll()
        for eachComment in comments!
            if self.objects.count < self.objectsPerPage
            {
                self.objects.append(eachComment as! PFObject)
            }
        }

        // reverse the array
        self.objects = self.objects.reverse()

        self.tableView.reloadData()
        self.tableView.scrollToRowAtIndexPath(NSIndexPath(forRow: self.objects.count - 1, inSection: 0), atScrollPosition: UITableViewScrollPosition.Bottom, animated: false)

加载更多的

    // for the query
    //skip already loaded objects
    query.skip = self.objects.count; 
    // limit the number of objects
    query.limit = objectsPerPage
    // find the number of objects already loaded
    let numberOfAlreadyLoadedObjects = self.objects.count

    // add your  query.findObjects here

    // correct the order to update the array in the right order
    self.objects = self.objects.reverse()

    // add new posts
    for eachComment in comments!
            if (self.objects.count < self.objectsPerPage + numberOfAlreadyLoadedObjects)
            {
                self.objects.append(eachComment as! PFObject)
            }
    }

    // reverse again
    self.tableView.reloadData()

    let lastIndex = NSIndexPath(forRow: self.objectsPerPage - 2 , inSection: 0)
    self.tableView.scrollToRowAtIndexPath(lastIndex, atScrollPosition: UITableViewScrollPosition.Top, animated: false)

刷新

    // skip already loaded objects
    let numberOfAlreadyLoadedObjects = self.objects.count
    query.skip = numberOfAlreadyLoadedObjects

    // add your  query.findObjects here

    // correct the order
    self.objects = self.objects.reverse()

    // count the number of new objects found
    let newObjectsFound = comments?.count
    // append just the new ones
    for eachComment in comments!
    {
            if self.objects.count < numberOfAlreadyLoadedObjects + newObjectsFound!
            {
                self.objects.append(eachComment as! PFObject)
            }
     }
     // reverse
     self.objects = self.objects.reverse()

     self.tableView.reloadData()
     let lastIndex = NSIndexPath(forRow: self.objects.count - 1, inSection: 0)
     self.tableView.scrollToRowAtIndexPath(lastIndex, atScrollPosition: UITableViewScrollPosition.Bottom, animated: true)

Answer 3

解决方案是只找到反向数组并加载它，如下所示：

变量messagesArray =字符串

self.messagesArray = self.messageArray.reversed()

聊天应用程序

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