Change UITableViewCell Height on Orientation Chang

问题:

I have a UITableView with cells containing variable-height UILabels. I am able to calculate the minimum height the label needs to be using sizeWithFont:constrainedToSize:lineBreakMode:, which works fine when the table view is first loaded. When I rotate the table view the cells become wider (meaning there are fewer lines required to display the content). Is there any way I can have the height of the cells redetermined by the UITableView during the orientation change animation or immediately before or after? Thank you.

回答1:

Your UITableViewController can implement the tableView:heightForRowAtIndexPath: method to specify the row height for a particular row, and it can look at the current orientation ([[UIDevice currentDevice] orientation]) to decide what height to return.

To make sure tableView:heightForRowAtIndexPath: gets called again when the orientation changes, you'll probably need to detect the orientation change as described in this question, and call [tableView reloadData].

回答2:

To improve slightly on the answer above from @David and to answer the last comment about how to animate it smoothly during a rotation, use this method:

- (void) willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
    [super willAnimateRotationToInterfaceOrientation:toInterfaceOrientation duration:duration];
    [self.tableView beginUpdates];
    [self.tableView endUpdates];
}

and of course the height delegate method:

- (CGFloat) tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    if (UIInterfaceOrientationIsLandscape([UIApplication sharedApplication].statusBarOrientation)) {
        return 171.0f;
    } else {
        return 128.0f;
    }
}