UITableView in iOS 7 not scrolling to correct loca

问题:

I have a table view with static cells. One cell contains a UITextView and the heightForRowAtIndexPath: is calculated dynamically so that the cell is always tall enough to accomodate the text (that part took some work under iOS 7, actually, as it's no longer possible to simply ask the textView for its contentSize).

When I tap within the text view to start editing, the keyboard animates into place, the contentInsets on the tableView are automatically adjusted to account for this (ie, bottom inset of 216px for iPhone portrait orientation), the cursor / caret becomes visible, and then the table view scrolls to another location. It ends up looking like a bounce.

Here's a video of this in the simulator: https://www.dropbox.com/s/htdbb0t7985u6n4/textview-bounce.mov

Notice that for a second the caret is just above the keyboard. I've been logging the table view's contentOffset and I can see it scroll to a nice value and then suddenly "turn around" and scroll back.

Oddly, if I turn on slow animations in the simulator the problem disappears; the contentOffset reversal doesn't happen and things work as I expect (ie, iOS 6 behavior).

Here's the video with slow animations: https://www.dropbox.com/s/nhn7vspx86t4exb/textview-nobounce.mov

Implementation notes:

• The text view is pink and has AutoLayout constraints that keep it pinned to the cell at distance 0 (except left side, which is 10pts)
• I'm using boundingRectWithSize: to calculate the table view height, adjusting for lineFragmentPadding and any top/bottom insets. Seems to work.
• I have set the textView to not be scrollable, but didn't notice anything different when scrollEnabled == YES
• This is a table view controller and automaticallyAdjustsScrollViewInsets == YES

回答1:

Try to adjust UITableView frame when keyboard appears. Call [self attachKeyboardHelper] in viewWillAppear and [self detachKeyboardHelper] in viewWillDisappear.

- (void)attachKeyboardHelper{
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillAppear:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillHide:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];
}

- (void)detachKeyboardHelper{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)keyboardWillAppear:(NSNotification *)notification{
    NSDictionary* userInfo = [notification userInfo];

    NSTimeInterval animationDuration;
    UIViewAnimationCurve animationCurve;
    CGRect keyboardEndFrame;

    [[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] getValue:&animationCurve];
    [[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] getValue:&animationDuration];
    [[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardEndFrame];

    // Animate up or down
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:animationDuration];

    CGRect keyboardFrame = [self.view convertRect:keyboardEndFrame toView:nil];
    if(self.view==self.tableView){
        CGRect newTableFrame = CGRectMake(self.tableView.frame.origin.x, self.tableView.frame.origin.y, self.tableView.frame.size.width, self.view.bounds.size.height-keyboardFrame.size.height);
        self.tableView.frame = newTableFrame;
    }else{
        CGRect newTableFrame = CGRectMake(self.tableView.frame.origin.x, self.tableView.frame.origin.y, self.tableView.frame.size.width, self.view.bounds.size.height-self.tableView.frame.origin.y-keyboardFrame.size.height);
        self.tableView.frame = newTableFrame;
    }

    [UIView commitAnimations];
}

- (void)keyboardWillHide:(NSNotification *)notification{
    NSDictionary* userInfo = [notification userInfo];

    NSTimeInterval animationDuration;
    UIViewAnimationCurve animationCurve;
    CGRect keyboardEndFrame;

    [[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] getValue:&animationCurve];
    [[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] getValue:&animationDuration];
    [[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardEndFrame];


    CGRect newTableFrame = CGRectMake(self.tableView.frame.origin.x, self.tableView.frame.origin.y, self.tableView.frame.size.width, self.view.superview.bounds.size.height-self.tableView.frame.origin.y);
    self.tableView.frame = newTableFrame;
    if(newTableFrame.size.height>self.tableView.contentSize.height-self.tableView.contentOffset.y){
        float newOffset=MAX(self.tableView.contentSize.height-newTableFrame.size.height, 0);
        [self.tableView setContentOffset:CGPointMake(0, newOffset) animated:YES];
    }

}