Odd UITableView Behavior - iphone

Question

Please take a look at the image.
I have a UITableView with custom cells and 2 sections. Once the UITableView populates enough cells that they all can't be shown on the screen, the last cell in the last section appears at the very top of the screen. The cell shouldn't even be visible in the UITableView since it's the last cell, and it is appearing completely outside the UITableView, at the top of the screen. I'm at a loss for even knowing where to begin to look in my code for this issue. I've only created a couple of UITableViews so I'm definitely not an expert on all the potential causes for this bug. The Table is set up through IB and the initialization code is in viewWillAppear, although there isn't much set up code. I am currently reading up on UITableView's scrollView, along with contentInset to see if there might be an explanation for this behavior. Has anyone encountered such a bug? I feel like it's unique enough that it may not be necessary to comb through all my code to determine. Regardless, I will post the relevant code below. Thank you for your help!
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *uniqueIdentifierForPlayerCell = #"customPlayerCell";
//Initialize PlayerTableViewCell and set it's properties
PlayerTableViewCell *playerCell = nil;
playerCell = (PlayerTableViewCell *)[tableView dequeueReusableCellWithIdentifier:uniqueIdentifierForPlayerCell];
if (playerCell == nil) {
NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:#"PlayerTableViewCell" owner:nil options:nil];
for(id currentObject in topLevelObjects) {
if([currentObject isKindOfClass:[PlayerTableViewCell class]]) {
playerCell = (PlayerTableViewCell *)currentObject;
break;
}
}
}
playerCell.textLabel.opaque = NO;
playerCell.textLabel.textColor = self.textColor;
playerCell.textLabel.font = [UIFont systemFontOfSize:18.0];
playerCell.textLabel.backgroundColor = [UIColor clearColor];
playerCell.selectionStyle = UITableViewCellSelectionStyleNone;
playerCell.accessoryButton.hidden = YES;
playerCell.reorderButton.hidden = YES;
NSString *uniqueIdentifierForAlleyCell = #"customAlleyCell";
//Initialize AlleyTableViewcell and set it's properties
AlleyTableViewCell *alleyCell = nil;
alleyCell = (AlleyTableViewCell *)[tableView dequeueReusableCellWithIdentifier:uniqueIdentifierForAlleyCell];
if (alleyCell == nil) {
NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:#"AlleyTableViewCell" owner:nil options:nil];
for(id currentObject in topLevelObjects) {
if([currentObject isKindOfClass:[AlleyTableViewCell class]]) {
alleyCell = (AlleyTableViewCell *)currentObject;
break;
}
}
}
alleyCell.textLabel.opaque = NO;
alleyCell.textLabel.textColor = self.textColor;
alleyCell.textLabel.font = [UIFont systemFontOfSize:18.0];
alleyCell.textLabel.backgroundColor = [UIColor clearColor];
alleyCell.selectionStyle = UITableViewCellSelectionStyleNone;
alleyCell.accessoryButton.hidden = YES;
alleyCell.deleteButton.hidden = YES;
//Alternate background colors for each section where section 0 is Alley section and section 1 is Player section. Stores the RGB values of the specific background color to the specific cell for future use
if(indexPath.section == 0 && (indexPath.row %2 == 0)) {
alleyCell.contentView.backgroundColor = self.backgroundColor;
alleyCell.isRed = 95.0/255.0;
alleyCell.isGreen = 94.0/255.0;
alleyCell.isBlue = 94.0/255.0;
self.alleyField.backgroundColor = self.backgroundColor;
}
else if(indexPath.section == 0 && (indexPath.row %2 == 1)){
alleyCell.contentView.backgroundColor = self.alternateColor;
alleyCell.isRed = 92.0/255.0;
alleyCell.isGreen = 92.0/255.0;
alleyCell.isBlue = 92.0/255.0;
self.alleyField.backgroundColor = self.alternateColor;
}
else if(indexPath.section == 1 && (indexPath.row %2 == 0)) {
playerCell.contentView.backgroundColor = self.backgroundColor;
playerCell.isRed = 95.0/255.0;
playerCell.isGreen = 94.0/255.0;
playerCell.isBlue = 94.0/255.0;
self.playerField.backgroundColor = self.backgroundColor;
}
else if(indexPath.section == 1 && (indexPath.row %2 == 1)) {
playerCell.contentView.backgroundColor = self.alternateColor;
playerCell.isRed = 92.0/255.0;
playerCell.isGreen = 92.0/255.0;
playerCell.isBlue = 92.0/255.0;
self.playerField.backgroundColor = self.alternateColor;
}
//If Alley array is empty, add alley TextField and return cell
if(indexPath.section == 0) {
if([self.allAlleys count] == 0) {
[alleyCell addSubview:self.alleyField];
self.alleyField.text = nil;
return alleyCell;
}
//Else set the alley name to the nameLabel text and return cell
else {
if(indexPath.row < [self.allAlleys count]) {
alleyCell.textLabel.text = [self.allAlleys objectAtIndex:indexPath.row];
if([alleyCell.textLabel.text isEqualToString: self.selectedAlley]) {
alleyCell.accessoryButton.hidden = NO;
}
else {
alleyCell.accessoryButton.hidden = YES;
}
return alleyCell;
}
//Add alley TextField to the last cell of the UITableView and return cell
else {
[alleyCell addSubview:self.alleyField];
self.alleyField.text = nil;
return alleyCell;
}
}
}
//If Player array is empty, add Player TextField and return cell
else if(indexPath.section == 1) {
if([self.bowlrNames count] == 0) {
[playerCell addSubview:self.playerField];
self.playerField.text = nil;
return playerCell;
}
//Else set the Player name to the nameLabel text and return cell
else {
if(indexPath.row < [self.bowlrNames count]) {
playerCell.textLabel.text = [self.bowlrNames objectAtIndex:indexPath.row];
for(int i = 0; i < [self.selectedBowlrs count]; i++) {
if([playerCell.textLabel.text isEqualToString: [self.selectedBowlrs objectAtIndex:i]]) {
playerCell.accessoryButton.hidden = NO;
playerCell.reorderButton.hidden = NO;
}
}
return playerCell;
}
//Add Player textField to the last cell of the UITableView and return cell
else {
[playerCell addSubview:self.playerField];
self.playerField.text = nil;
return playerCell;
}
}
}
}
//Actions for selecting a row in the UITable
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
//If it is in the Alley section
if(indexPath.section == 0) {
//If the selected cell is the same as the last selected cell
if(self.lastIndexPathForAlleyCells && indexPath.row == self.lastIndexPathForAlleyCells.row) {
[tableView beginUpdates];
self.lastIndexPathForAlleyCells = nil;
AlleyTableViewCell *previousCell = (AlleyTableViewCell *)[tableView cellForRowAtIndexPath:indexPath];
//[tableView deselectRowAtIndexPath:[tableView indexPathForSelectedRow] animated:YES];
previousCell.selected = NO;
self.selectedAlley = nil;
previousCell.accessoryButton.hidden = YES;
[tableView endUpdates];
return;
}
//Else the selected cell is not the last selected cell
AlleyTableViewCell *previousCell = (AlleyTableViewCell *)[tableView cellForRowAtIndexPath:self.lastIndexPathForAlleyCells];
previousCell.selected = NO;
previousCell.accessoryButton.hidden = YES;
AlleyTableViewCell *cell = (AlleyTableViewCell *)[tableView cellForRowAtIndexPath:indexPath];
cell.selected = YES;
cell.accessoryButton.hidden = NO;
self.selectedAlley = cell.textLabel.text;
self.lastIndexPathForAlleyCells = indexPath;
[self.tableView reloadData];
}
else if(indexPath.section == 1) {
PlayerTableViewCell *cell = (PlayerTableViewCell *)[tableView cellForRowAtIndexPath:indexPath];
//If player is not already selected
if([self playerIsSelected:cell.textLabel.text] == NO) {
//Set selected to YES and reveal buttons
cell.selected = YES;
cell.accessoryButton.hidden = NO;
cell.reorderButton.hidden = NO;
//If 8 Players are currently selected, UIAlertView informs user they have reached the limit
if([self.selectedBowlrs count] == 8) {
NSString *message = #"You can only select up to 8 players";
UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:#"Max Players Selected" message:message delegate:self cancelButtonTitle:[self okButtonTitle] otherButtonTitles:nil, nil];
alertView.tag = TAG_FULLGAME;
[alertView show];
}
else {
//Insert name into selectedBowlrs array
[self.selectedBowlrs insertObject:cell.textLabel.text atIndex:0];
//Reorder bowlrNames array
NSString *bowlrName = [self.bowlrNames objectAtIndex:indexPath.row];
[self.bowlrNames removeObjectAtIndex:indexPath.row];
[self.bowlrNames insertObject:bowlrName atIndex:0];
//Move selected row to top of section
[self moveIndexPathToTop:indexPath];
}
}
//Else the player is already selected
else {
//Set selected to NO and hide buttons
cell.selected = NO;
cell.accessoryButton.hidden = YES;
cell.reorderButton.hidden = YES;
[self.selectedBowlrs removeObject:cell.textLabel.text];
[self.bowlrNames removeObject:cell.textLabel.text];
[self.bowlrNames insertObject:cell.textLabel.text atIndex:[self.selectedBowlrs count]];
[self moveIndexPathToMiddle:indexPath];
for(int i = 0; i < [self.selectedBowlrs count]; i++) {
NSLog(#"%#", [self.selectedBowlrs objectAtIndex:i]);
}
}
}
[self performSelector:#selector(reloadData) withObject:nil afterDelay:.25];
}
//Returns the number of rows for each section
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
switch (section) {
//For Alley section
case 0:
//If the array is empty, return 1 row for the Alley Textfield
if([self.allAlleys count] == 0)
return 1;
//Else return the number of elements in the array + 1 for the Alley Textfield
else
return [self.allAlleys count] + 1;
break;
//For Player section
case 1:{
//If the array is empty, return 1 row for the Player Textfield
if([self.bowlrNames count] == 0)
return 1;
//Else return the number of elements in the array + 1 for the Player Textfield
else
return [self.bowlrNames count] + 1;
break;
}
default:
break;
}
return 0;
}
//Set up appearance for section headers
-(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
UIView *headerView = [[UIView alloc] initWithFrame:CGRectMake(0,0, self.tableView.bounds.size.width, 25.0)];
UILabel *headerLabel = [[UILabel alloc] initWithFrame:CGRectZero];
CGFloat isRed = 84.0/255.0;
CGFloat isGreen = 84.0/255.0;
CGFloat isBlue = 84.0/255.0;
self.headerColor = [[UIColor alloc]initWithRed:isRed green:isGreen blue:isBlue alpha:0.5];
headerLabel.backgroundColor = self.headerColor;
headerLabel.opaque = NO;
headerLabel.textColor = self.textColor;
headerLabel.highlightedTextColor = [UIColor whiteColor];
headerLabel.font = [UIFont systemFontOfSize:18.0];
headerLabel.frame = CGRectMake(0.0, 0.0, self.tableView.bounds.size.width, 25.0);
if (section == 0) {
[headerView setBackgroundColor:self.backgroundColor];
headerLabel.text = #"Alley";
[headerView addSubview:headerLabel];
}
else {
[headerView setBackgroundColor:self.backgroundColor];
headerLabel.text = #"Bowlr";
[headerView addSubview:headerLabel];
}
return headerView;
}
-(BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
return YES;
}
//Used to delete row of UITable
-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
self.indexPathForEditing = indexPath;
if(editingStyle == UITableViewCellEditingStyleDelete) {
//For Alley section
if(indexPath.section == 0) {
//Set up UIAlertView
NSString *message = #"Are you sure?";
UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:#"Delete Alley?" message:message delegate:self cancelButtonTitle:[self cancelButtonTitle] otherButtonTitles:[self deleteButtonTitle], nil];
alertView.tag = TAG_Alley;
[alertView show];
}
//For Player section
else if(indexPath.section == 1) {
//Set up UIAlertView
NSString *message = #"All information for this Bowlr will be deleted";
UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:#"Delete Bowlr?" message:message delegate:self cancelButtonTitle:[self cancelButtonTitle] otherButtonTitles:[self deleteButtonTitle], nil];
alertView.tag = TAG_Player;
[alertView show];
}
}
[self performSelector:#selector(reloadData) withObject:nil afterDelay:.25];
}

Answer 1

Okay, I think there's two basic things you need to remember here.
(1) You must never add something to the cell as a subview. Add it only to the cell's contentView. This code is wrong: [alleyCell addSubview:self.alleyField];
(2) These cells are being reused. You may have 100 rows but only 10 cells, being constantly reused as the user scrolls. Therefore you must completely set up every cell from an empty state, and if it isn't in the empty state to start with, you need to get it into the empty state. If you add a textfield to a cell in one pass thru cellForRowAtIndexPath, you must remember to remove the textfield in every other pass thru cellForRowAtIndexPath, or the textfield can show up in other rows because another row might reuse that same cell.
(See also the discussion towards the end of this section of my book: http://www.apeth.com/iOSBook/ch21.html#_the_three_big_questions It discusses a simple consequence of forgetting that the cells are reused.)
Also, I need hardly add that frame matters. You are adding a subview, but I have no idea what its frame is. With the right (meaning wrong) frame value, that subview could appear outside the cell. Also, are you using cells of different heights? If so, remember that because the cell is being reused, its height can change. Thus, autoresizing behavior can cause the frame to change.