How to Start UITableView on the Last Cell?

Question

In Apple\'s Messages app, when you click a correspondent\'s name and switch to the table view of the conversation (with balloons for each message), the table appears scrolle

Answer 1

#import "ViewController.h"


@interface ViewController ()
@end

@implementation ViewController
CGFloat labelWidth = 260.0f;
CGFloat labelRequiredHeight = 180.0f;
@synthesize tblView;
@synthesize txtField;
@synthesize chatData;

- (void)viewDidLoad
{
    [super viewDidLoad];
    tblView.delegate = self;

    [self.tblView setSeparatorStyle:UITableViewCellSeparatorStyleNone];
    chatData  = [[NSMutableArray alloc] init];
    [self registerForKeyboardNotifications];

}

-(IBAction) textFieldDoneEditing : (id) sender
{
    NSLog(@"the text content%@",txtField.text);
    [sender resignFirstResponder];
    [txtField resignFirstResponder];
}

- (IBAction)sendButton:(id)sender
{
    if (txtField.text.length>0) {
        // updating the table immediately
        NSArray *data = [NSArray arrayWithObject:@"text"];
        NSArray *objects = [NSArray arrayWithObject:txtField.text];
        NSDictionary *dictionary = [NSDictionary dictionaryWithObjects:objects forKeys:data];
        [chatData addObject:dictionary];

        NSMutableArray *insertIndexPaths = [[NSMutableArray alloc] init];
        NSIndexPath *newPath = [NSIndexPath indexPathForRow:0 inSection:0];
        [insertIndexPaths addObject:newPath];
        [tblView beginUpdates];
        [tblView insertRowsAtIndexPaths:insertIndexPaths withRowAnimation:UITableViewRowAnimationTop];
        [tblView endUpdates];
        [tblView reloadData];

        txtField.text = @"";
        [self.view endEditing:YES];
    }
}

-(IBAction) backgroundTap:(id) sender
{
    [self.txtField resignFirstResponder];
}

-(BOOL)SendbtnShouldReturn:(UITextField *)textfield
{
    [textfield resignFirstResponder];
    return YES;
}

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    NSLog(@"the text content%@",txtField.text);
    [textField resignFirstResponder];
    if (txtField.text.length>0)
    {
        // updating the table immediately
        NSArray *keys = [NSArray arrayWithObject:@"text"];
        NSArray *objects = [NSArray arrayWithObject:txtField.text];
        NSDictionary *dictionary = [NSDictionary dictionaryWithObjects:objects forKeys:keys];
        [chatData addObject:dictionary];

        NSMutableArray *insertIndexPaths = [[NSMutableArray alloc] init];
        NSIndexPath *newPath = [NSIndexPath indexPathForRow:0 inSection:0];
        [insertIndexPaths addObject:newPath];
        [tblView beginUpdates];
        [tblView insertRowsAtIndexPaths:insertIndexPaths withRowAnimation:UITableViewRowAnimationTop];
        [tblView endUpdates];
        [tblView reloadData];
        txtField.text = @"";
    }
    return NO;
}


// Keyboard Functionality

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

-(void) freeKeyboardNotifications
{
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
}

-(void) keyboardWasShown:(NSNotification*)aNotification
{
    NSLog(@"Keyboard was shown");
    NSDictionary* info = [aNotification userInfo];
    // Get animation info from userInfo
    NSTimeInterval animationDuration;
    UIViewAnimationCurve animationCurve;
    CGRect keyboardFrame;
    [[info objectForKey:UIKeyboardAnimationCurveUserInfoKey] getValue:&animationCurve];
    [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] getValue:&animationDuration];
    [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] getValue:&keyboardFrame];
    // Move
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:animationDuration];
    [UIView setAnimationCurve:animationCurve];
    NSLog(@"frame..%f..%f..%f..%f",self.view.frame.origin.x, self.view.frame.origin.y, self.view.frame.size.width, self.view.frame.size.height);
    NSLog(@"keyboard..%f..%f..%f..%f",keyboardFrame.origin.x, keyboardFrame.origin.y, keyboardFrame.size.width, keyboardFrame.size.height);
    [self.view setFrame:CGRectMake(self.view.frame.origin.x, self.view.frame.origin.y- keyboardFrame.size.height, self.view.frame.size.width, self.view.frame.size.height)];
    [tblView setFrame:CGRectMake(self.view.frame.origin.x, self.view.frame.origin.y+ keyboardFrame.size.height, self.view.frame.size.width, self.view.frame.size.height-keyboardFrame.size.height)];
    [tblView scrollsToTop];
    [UIView commitAnimations];

}

-(void) keyboardWillHide:(NSNotification*)aNotification
{
    NSLog(@"Keyboard will hide");
    NSDictionary* info = [aNotification userInfo];
    // Get animation info from userInfo
    NSTimeInterval animationDuration;
    UIViewAnimationCurve animationCurve;
    CGRect keyboardFrame;
    [[info objectForKey:UIKeyboardAnimationCurveUserInfoKey] getValue:&animationCurve];
    [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] getValue:&animationDuration];
    [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] getValue:&keyboardFrame];
    // Move
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:animationDuration];
    [UIView setAnimationCurve:animationCurve];
    [self.view setFrame:CGRectMake(self.view.frame.origin.x, self.view.frame.origin.y + keyboardFrame.size.height, self.view.frame.size.width, self.view.frame.size.height)];
    [tblView setFrame:CGRectMake(self.view.frame.origin.x, self.view.frame.origin.y, self.view.frame.size.width, self.view.frame.size.height)];
    [UIView commitAnimations];
    UIEdgeInsets contentInsets = UIEdgeInsetsZero;
    self.tblView.contentInset = contentInsets;
    self.tblView.scrollIndicatorInsets = contentInsets;
    self.tblView.scrollEnabled=chatData;


}

#pragma mark UITableViewDataSource protocol methods
- (void)scrollTableToBottom
{
    int rowNumber = [self.tblView numberOfRowsInSection:1];
    if (rowNumber > 0) [self.tblView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:rowNumber-1 inSection:0] atScrollPosition:UITableViewScrollPositionBottom animated:YES];
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [chatData count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellIdentifier=@"chatCell";
    chatCell *cell = (chatCell *)[tableView dequeueReusableCellWithIdentifier: @"chatCellIdentifier"];
    if(!cell)
        cell =[[chatCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
//    NSUInteger row = [chatData count]-[indexPath row]-1;
    NSUInteger row=[indexPath row];
    NSUInteger count = [chatData count];
    if (row <chatData.count)
    {
        NSString *chatText = [[chatData objectAtIndex:row] objectForKey:@"text"];
        cell.txtMsg.text = chatText;
    }
    return cell;
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSString *cellText = [[chatData objectAtIndex:chatData.count-indexPath.row-1] objectForKey:@"text"];
    UIFont *cellFont = [UIFont fontWithName:@"Helvetica" size:20.0];
    CGSize constraintSize = CGSizeMake(225.0f, MAXFLOAT);
    CGSize labelSize = [cellText sizeWithFont:cellFont constrainedToSize:constraintSize lineBreakMode:UILineBreakModeWordWrap];
        return labelSize.height + 40;
}


//-(void)scrollToBottomTableView
//{
//    if (self.tblView.contentOffset.y > self.tblView.frame.size.height)
//    {
//        [self.tblView scrollToRowAtIndexPath:[self. indexPathForLastMessage]
//                              atScrollPosition:UITableViewScrollPositionBottom animated:YES];
//    }
//}


-(void)viewWillAppear:(BOOL)animated
{

//        [tblView reloadData];
//   
//    int lastRowNumber = [tblView numberOfRowsInSection:0] - 1;
//    NSIndexPath* ip = [NSIndexPath indexPathForRow:lastRowNumber inSection:0];
//    [tblView scrollToRowAtIndexPath:ip atScrollPosition:UITableViewScrollPositionTop animated:NO];
}
-(void)viewDidAppear:(BOOL)animated
{
//[tblView reloadData];

}
- (void)reloadTableViewDataSource
{
    [tblView reloadData];

}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
@end

Answer 2

I'm using autolayout and none of the answers worked for me. Here is my solution that finally worked:

@property (nonatomic, assign) BOOL shouldScrollToLastRow;


- (void)viewDidLoad
{
    [super viewDidLoad];

    _shouldScrollToLastRow = YES;
}


- (void)viewDidLayoutSubviews
{
    [super viewDidLayoutSubviews];

    // Scroll table view to the last row
    if (_shouldScrollToLastRow)
    {
        _shouldScrollToLastRow = NO;
        [self.tableView setContentOffset:CGPointMake(0, CGFLOAT_MAX)];
    }
}