Incorrect row height returned when iOS device rotated

2018-06-20 18:29:57

I'm having an issues with displaying UITableViewCells with the correct height in a UITableView once the device is rotated. When the table view is initially loaded the rows all have the correct size as you can see on the image below:

正确的行高

However, when I rotate the device to landscape mode I get shorter rows than I would like and consequently, parts of the view's background are visible, see here: 行太短，查看背景可见的表视图的底部

When turning the phone back to portrait mode again, the row sizes are larger then when the view was loaded for the first time and as a result, the bottom cell seems smaller, and the text does not look centred in the cell, see here:

细胞在第一次加载时略高一点

This is the method and variables I'm using for row height calculation:

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UIDeviceOrientation orientation = [UIDevice currentDevice].orientation;
    CGFloat screenHeight = [UIScreen mainScreen].bounds.size.height;
    CGFloat screenWidth = [UIScreen mainScreen].bounds.size.width;
    CGFloat statusBarHeight = [UIApplication sharedApplication].statusBarFrame.size.height;
    CGFloat statusBarWidth = [UIApplication sharedApplication].statusBarFrame.size.width;
    CGFloat navigationBarHeight = self.navigationController.navigationBar.frame.size.height;
    CGFloat rowHeight;

    NSUInteger numberOfRows = self.orderedCategories.count;

    if (orientation == UIDeviceOrientationPortrait) {
        rowHeight = ((screenHeight - navigationBarHeight - statusBarHeight) / numberOfRows);
        NSLog(@"portrait: %f", rowHeight);
    } else {
        rowHeight = ((screenWidth - navigationBarHeight - statusBarWidth) / numberOfRows);
        NSLog(@"landscape: %f", rowHeight);
    }

    return rowHeight;
}

I don't have a definite answer, but here are a few things to consider:

1) why are you calling [self.tableview setNeedsDisplay] inside tableView:heightForRowAtIndexPath? If you need to reset the display here, there's probably something wrong with your overall logic.

2) what about moving the calculation code out to the didRotateFromInterfaceOrientation: method? Then call reloadData when you're done. Store the height in an instance variable, and just return that in tableView:heightForRowAtIndexPath:.

2) does this code get run after the rotation. Try logging out the different constants and double check the math by hand. That may give you a better idea of what's going on. There may be a timing issue--for example, you may be getting the status bar height before the rotation occurs, instead of after it occurs.

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