Update UITableView height when tweet loaded

Question

I have a UITableViewCell which contains a TWTRTweetView with auto layout. I am loading a tweet like this:

- (void)loadTweetWithId:(NSString *)tweetId {

    if (mTweetId == nil || ![mTweetId isEqualToString:tweetId]) {
        mTweetId = tweetId;
        [[[TWTRAPIClient alloc] init] loadTweetWithID:tweetId completion:^(TWTRTweet *tweet, NSError *error) {
            if (tweet) {
                NSLog(@"Tweet loaded!");
                [mTweetView configureWithTweet:tweet];
                [mTweetView setShowActionButtons:YES];
                //[mTweetView setDelegate:self];
                [mTweetView setPresenterViewController:self.viewController];
                [mTweetView setNeedsLayout];
                [mTweetView layoutIfNeeded];
                [mTweetView layoutSubviews];
                hc.constant = mTweetView.frame.size.height;
                [self updateConstraints];
                [self layoutIfNeeded];
                [self layoutSubviews];
                [self.tableView setNeedsLayout];
                [self.tableView layoutIfNeeded];
                [self.tableView layoutSubviews];
            } else {
                NSLog(@"Tweet load error: %@", [error localizedDescription]);
            }
        }];
    }
}

When tweet loaded cell doesn't resize unless I scroll it out and scroll it to back. I have tried several approaches as you can see in code snippet. But non of these works. My table view uses full auto layout approach which doesn't implement cell height for row function. How can i fix this?

UPDATE:

Using:

[self.tableView beginUpdates];
[self.tableView endUpdates];

is not possible because when I do that all cells being redrawn and very big jumping happens and that is not acceptable. Also I have confirmed that tweet completion block runs in main thread.

UPDATE 2:

I have also tried to cache tweet view with tweet id and reload cell for related index path and give the same tweet view for tweet id. The cell height is corrected but it doesn't become visible until scroll out/in.

UPDATE 3:

I give constraints to tweet view in xib of the cell and height constraint is connected. So this is not a main thread issue. I have also mentioned that reloading particular cell at index doesn't work.

While working an other solution I have seen some sample TwitterKit codes that uses TWTRTweetTableViewCell but was preloading tweets to configure the cells. So I have done the same. This is a workaround of course.

Answer 1

Updated Answer:

You're doing a couple of things wrong that are likely to cause (or at least contribute to) the jumping:

• Never call layoutSubviews yourself. It's a method called by the system to resolve your constraints. It's automatically triggered when calling setNeedsLayout and layoutIfNeeded in a row.

• The same applies to updateConstraints. It is called by the system during a layout pass. You can manually trigger it by subsequently calling setNeedsUpdateContraints and updateConstraintsIfNeeded. Furthermore, it only has an effect if you actually implemented (overrode) that method in your custom view (or cell).

• When you call layoutIfNeeded on a view it layouts its subviews. Thus, when you change the constant of a constraint that constrains your mTweetView, it probably won't have any effect (unless the view hierarchy is invalidated during the triggered layout pass). You need to call layoutIfNeeded on mTweetView's superview which is the cell's content view (judging from the screenshot you added to your post):

  [contentView layoutIfNeeded];
  

Furthermore, there is one more thing you need to be aware of that can cause flickering as well:

• Cells in a table view are being recycled. Each time a cell is reused you load a new tweet. I guess it's from an asynchronous network request? If so, there is the possibility that the completion block from the first tweet you load for that cell instance returns after the completion block from the second tweet you load for that (recycled) cell when you scroll really fast or you internet connection is really slow. Make sure you cancel the request or invalidate it somehow when your cell is reused (prepareForReuse method).

Please make sure you've fixed all these issues and see if animation now works as expected. (My original answer below remains valid.)

---

Original Answer:

I'm pretty sure that

[self.tableView beginUpdates];
[self.tableView endUpdates];

is the only way to have a cell auto-resize itself while being displayed.

Reason:

For historic and performance reasons a UITableView always works with fixed-height cells (internally). Even when using self-sizing cells by setting an estimatedRowHeight etc. the table view will compute the height of a cell when it's dequeued, i.e. before it appears on screen. It will then add some internal constraints to the cell to give it a fixed width and a fixed height that just match the size computed by Auto Layout.

These internal constraints are only updated when needed, i.e. when a row is reloaded. Now when you add any constraints inside you cell you will "fight" against these internal constraints which have a required priority (aka 1000). In other words: There's no way to win!

The only way to update these internal (fixed) cell constraints is to tell the table view that it should. And as far as I know the only public (documented) API for that is

- (void)beginUpdates;
- (void)endUpdates;

---

So the only question that remains is:

Why is this approach not an option for you?

I think it's legitimate to redraw a cell after it's been resized. When you expand the cell to show a longer tweet than before the cell needs to be redrawn anyway!

You probably won't (and shouldn't) resize all visible cells all the time. (That would be quite confusing for the user...)