I am developing an application that shows all the courses that take place in a class room depending on the time and date. In the prototype I was thinking to implement a UITableView, with two sections, one for previous clases(top) and one for next classes. I want to add the previous button as the header of the section with following classes and when I press it I want to programatically add a new section and populate it with the previous courses. I am not sure how to implement this, what methods I should override, etc.
I found something quite similar but I couldn't find any details of how he actually implemented it.
Thank you.
You will need to read up on UITableViews and the delegate methods. The sections are controlled in:
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
You can put conditional logic here to control how many sections you need. Button pressed calls [tableView reloadData]; and will update the sections with it. How you control the data going into the table is up to you, but this should get you started.
- (void)sectionPreviousBunttonPress:(id)sender {
...
[sections addObject:section];
[courses addObjectsFromArray:fetchedCourses];
[table reloadData];
}
Related
I have created numerous Xcode projects to see if this was a single project problem but no. The problem that I am getting is that when I populate a UITableVIiew with either local data or data that is stored in a Parse database it does not show.
I have tried re-installing Xcode, cleaning my project and walking through the code/project to see if I'd made a mistake but everything looks in place.
An example is that I created a UITableViewController with a UIImage in the cell and when I build and run the project it does not show up.
Here is an example:
Thanks in advance.
You should implement two required methods of UITableViewDataSource.
Something like that:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return 5;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"cell"];
return cell;
}
This would go quicker if you just posted the available code... Annnnyway...
The reason I ask is because if you've only done this in storyboard, and it's a dynamic table, the table looks to your numberOfRowsInSection method to see if it should be populating the table or not. If this is 0, then you'll get no rows no matter what you put into the storyboard.
Also, if you've got a cell identifier of cell in your cellForRowAtIndexPath, but you haven't identified your storyboard cell as cell, then you'll still get blank cells.
Furthermore, if you have implemented these two methods correctly, you need to ensure that this table is hooked up to that class as it's dataSource, either via storyboard or programatically.
But these are all just guesses because I would need to see code to figure it out.
If you are using a UITableViewController, have you changed the cells to static?
You said you don't have any custom code other than what Xcode provides. That is your problem.
You need to implement the UITableViewDataSource methods in order to install your data into your table view. Xcode does not do that. The code Xcode puts into your view controller tells the table view that there is no data. You need to report that there is at least 1 section, and at least 1 row in that section. You then need to write code for cellForRowAtIndexPath that installs data from your model into your cells.
Nikita lists 2 of the 3 methods that you must implement before you table view will do anything.
I am somewhat new to iOS, but am experienced in Android.
I have an app I am working on and it needs to populate a page with your "history" of past people you've interacted with, and it shows their picture, name, rating, and some other information.
This needs to populate in a vertical list, maybe a table? See the image below...
Now, in android, I would create a custom class with a layout that houses the picture, name, information, rating, and what not in one xml file, and in the activity I would call that class in a for loop, grabbing all the users and then programmatically it would add each view one after another, with their own unique user information until there is no more users to populate with.
How exactly can I do this in iOS and xcode? Do I need to make an XIB and add the picture, name, rating, and info place holders in that, and create a custom class for it that I would use to run in a for loop as well? I am a little stuck on how to do this with iOS.
Any help is much appreciated, and I can provide any additional information! Thanks :)
In iOS, you probably want to use a UITableView, with each row being a custom subclass of UITableViewCell. You can either create the layout for those cells in a separate XIB, or put the whole lot, tableView and "prototype" cells in a storyboard. You can achieve a lot without even subclassing, so fire up a dummy project in XCode and play (using one of Apple's templates gives you a good start). Enjoy.
What you probably want is to use a UITableView.
You don’t do the for-loop yourself. What you do is implement a set of delegate methods that the table view calls back to.
You can create your prototype cell in your XIB or Storyboard. When you add a Table View to the layout, you can then add a cell to that table view, and that cell will be your prototype. It looks like you only need one prototype cell, but you can create as many as you need. In Interface Builder you give the prototype cell a “reuse identifier”, which is just an arbitrary tag you use to refer to the prototype in your code. Your prototype cell can be your own subclass of UITableViewCell, or if you don’t need any custom code in it, you can just use UITableViewCell.
Then you implement several delegate methods. One is where you set the number of sections in the table view; it looks like you will only have on section.
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tv
{
return 1;
}
Then you tell it how many items are in the table view. Assuming you have the objects you want to display in an array, you just return the length of the array.
- (NSInteger)tableView:(UITableView *)tv numberOfRowsInSection:(NSInteger)section
{
return self.objects.count;
}
Then, for each item in the array, cellForRowAtIndexPath will be called. Make that method return the actual cell. You call dequeueReusableCellWithIdentifier to retrieve your prototype cell, using the reuse identifier you assigned in Interface Builder. Then use the corresponding object to set up the UI elements in your cell.
- (UITableViewCell *)tableView:(UITableView *)tv cellForRowAtIndexPath:(NSIndexPath *)i
{
UITableViewCell *cell = [tv dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:i];
Thingy *item = self.objects[i.row];
cell.textLabel.text = item.name;
return cell;
}
That should be enough to get you started with the documentation, now that you have the overview of what you need to implement.
The first thing you have to do in switching from Android to iOS is to learn the terminology. Then you'll know what to search for on Google, SO, etc.
What's you're looking to do is create a UITableView.
Here is a link to a super basic 'how-to' to get you started with tableviews.
http://www.appcoda.com/uitableview-tutorial-storyboard-xcode5/
Once you've got the basics down, you'll want to take that a step further with learning how to customize the UITableViewCell within your tableview, so you can accomplish the look you've detailed in the question.
http://www.appcoda.com/customize-table-view-cells-for-uitableview/
I'm not sure I can help anymore than that at the moment. Jump in, learn tableviews, and start searching on OS to answer the million other questions you'll have a long the way.
Good luck!
So I'm using the required protocol methods from UITableViewDataSource to display rows on my application. It's working fine and everything but the book I'm learning from doesn't show me exactly how these rows are being updated.
In the method below there is no for loop so I'm wondering if the updating of the rows is done in a for loop in the background or something?
If not is it just updating all rows at once? So let's say in the other required method tableView:numberOfRowsInSection: I'm returning an int with the value of 5. Doe's the method below just take that info and say ok you have 5 rows I'll set the textLabel text for each of them in one go?
I'd like to get a deeper understanding of this.
Code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Create an instance of UITableViewCell, with the default appearance/style and name
// a reuseIdentify, used to identify cells with the same content
UITableViewCell *cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:#"UITableViewCell"];
// Use the index path row number to grab the BNRItem out of the allItems an
BNRItem *p = [[[BNRItemStore sharedStore] allItems] objectAtIndex:[indexPath row]];
// Set text label of cell using the BNRItem stored in "P".
[[cell textLabel] setText:[p description]];
return cell;
}
Kind regards
The method is called by the table view whenever it feels it needs to update a cell. So, if you have five rows on screen, it will call it for those five rows (and maybe a couple of extra). Then, as you scroll, it will call it for rows that are about to appear on the screen. Cells that have scrolled off screen will be added to the reuse pool, limiting the total number of sub views that need to be created fresh and added to the table.
This is a common pattern in Cocoa; to adapt an existing control (like a table), you wouldn't subclass it, you'd configure a separate object (in this case, the datasource) which implements various methods. When the control needs to know something, it calls the relevant method on your specially configured object. It's basically the delegate pattern, except a table view already has a delegate, and the data source does a slightly different job.
By the look of your sample code you're using the Big Nerd Ranch book - their Mac OS X book had one of the best descriptions of subclassing versus delegation that I've read. Something like:
Robocop is a subclassed human. Every part has been replaced with a custom one. Michael Knight uses a powerful delegate object (KITT) instead.
Which do you think is the more lightweight and flexible design?
jrturton covered the answer pretty well.
I would like to add some thoughts.
You are thinking procedurally: Write a for-loop that fills your UI with content from an array.
iOS is an event-driven OS, and Objective C is an object-oriented language. Events happen in the OS, and in response messages get sent to objets.
A table view is an autonomous object that does things on it's own. When a table view is added to the current screen's view hierarchy, it wakes up and figures out what content to display by asking the data source how many sections of data it has, and how many rows per section. It also asks how tall each cell should be. Once it has that information, it decides which items it should display, and asks the data source for cells to display.
If the user scrolls the table view it will recycle cells as they go off-screen and ask the data source to configure new cells for newly exposed data.
tableView:numberOfRowsInSection is sent to the delegate of a UITableView to find out how many rows it needs to have in a given section.
My question is, when and how often is this method called?
The method is called very first time the tableview is getting loaded and if you are more interested in the delegates then put a breakpoint and check when and where which delegate is called and how many times.
Below are the instances when that function will get called,
For the first time when table is loaded
the time you reload the table data
the time you add/update/delete your row or sections dynamically.
The method - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section is a protocol method of the UITableViewDataSource - protocol. It will be called
the very first time your table view is loaded based on that you have set the dataSource properly, e.g.
self.yourTableView.dataSource = self;
If you are interested in updating your table again at a later time you can call
[self.yourTableView reloadData];
in order to reload the entire table. If you are only interested in reloading a part of your table you can do something similar to
NSIndexSet *reloadSet = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, [self numberOfSectionsInTableView:self.yourTableView])];
[self.yourTableView reloadSections:reloadSet withRowAnimation:UITableViewRowAnimationAutomatic];
Hope it helps!
My question is, when and how often is this method called?
Short Answer : When your UITableView needs to update something.
Long Answer : Delegates Methods generally called themselves however it may be called multiple times when your UITableView needs to update something. By default, it's called very first time the tableview is getting loaded or updated (reloaded).
It depends on how often user will scroll UITable view to section and how many sections there are. This value, which is returned by this function and is casched. Method will need be revoked if you will update content of table view (filtering results, or updating data via reloadData).
Best thing for you will be to add logging to this function and check this yourself.
I have a question regarding a design convention.. See I have this tableview filled with editable information. Editable as in changing the text in the right detail of the cell, not as in deleting or moving a cell. I wonder how to design/model this, the only Apple product that I know has this feature is the contacts app. The solution there is to make lots and lots of groups, but this does not fit my problem at all, partly since I already have groups. The simplest way would just be to have the right detail be a text field and enable it in edit mode, but that would of course be a stupid solution since no visual feedback is given..
Any ideas on how to design/model this, or how Apple would like to have it?
EDIT:
To be more clear in what I mean, this is a screenshot explaining what I have said. Once again, my problem is how to show the table cells when they are in edit mode. All values are changeable, and none of them have any kind of presets to choose from, they are all based on text written by the user. This part of the app is basically a CRM system, where you can edit all the information about yourself.
What you are trying to do is pretty standard for Dynamic Prototype cells (as opposed to the Static Cells you probably used to make that screenshot). You're best bet is probably going to be to just watch a couple of these tutorials.
To give a quick summary, you're going to put all the strings you want to show in the Value part of your screenshot into an NSArray. There are UITableViewDelegate and UITableViewDataSource methods that will automatically handle putting the ith item in the array into the ith cell (so the 3 item in the array will go into the 3rd cell, etc.). To allow the user to edit things, you're going to want to make a whole new second screen (this is where you're UITextfields will be). When the user goes back from the second screen to your table screen, you replace items in the array with whatever the user entered in the UITextfield, then tell the UITableViewDelegate methods to reload the table with the new Values.
Most of the tutorials I linked to probably aren't going to have anything about having multiple Groups, so I'll add a bit on that here (what follows will probably only make sense if you watch the tutorials first, so I'd suggest following along with the tutorials, then coming back here afterward and making the changes I'm about to suggest). The NSIndexPath that is sent to the tableView:cellForRowAtIndexPath method contains information on the cell row and section. Each "Group" is it's own section (I'm really not sure why Apple decided to use two different names for the same thing, but so it goes). The easiest way to do this is to have different arrays for each section (so you'll have lines for NSMutableArray *firstSectionArray = [[NSMutableArray alloc] init];, NSMutableArray *secondSectionArray = [[NSMutableArray alloc] init];, and so on). Then, at the very top of your tableView:cellForRowAtIndexPath method, you put some if statements in to see what section of the table you are "building", and use values from the correct array accordingly. Something like:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.section == 0)
{
// bunch of stuff from the tutorials here to create "cell"
[cell.detailTextLabel.text = firstSectionArray objectAtIndex:indexPath.row];
// bunch more stuff
}
else if (indexPath.section == 1)
{
// bunch of stuff from the tutorials here to create "cell"
[cell.detailTextLabel.text = secondSectionArray objectAtIndex:indexPath.row];
// bunch more stuff
}
// else if (keep going for however many sections you have)
return cell;
}