In this post I will be making another view and tell you how to navigate from first view to the one we are going to create now. The new view is a table view and we will learn here how to make a UITableView programatically.
Please refer my previous post as I am going to add code to the same project.
Simple Hello World Application
So, this time we will be creating a complete tableView and populate it with some data. We created a button last time “Hit Me”. We will add code so that when user presses it, the new view gets displayed.
To start, right click on the classes folder in the left column of your xCode and select add>new file.
Chose the “UIViewController subclass” template and name it as MyTableView. This will add 2 files in the project namely MyTableView.h and MyTableView.m.
Now open MyTableView.h and add the follwing code:
As you can see we have added a UITableView object as a property to this viewController class
Now we should create and add this tableView to the view. So open MyTableViewController.m and add the following code to -(void)loadView method.
Most of the lines in code are self explanatory but I will discuss few of them.
aTableView.delegate = self;
aTableView.dataSource = self;
These lines tell that all the delegate methods of tableView will be implemented in this class only. Similarly the data source is set to self.
self.view = aTableView;
Hmmm..this time we have now added a UI element as a subView as we saw in the last post but instead we are making it the base view it self. I did this because I want the table to cover the whole screen in the application, i.e. I am not going to put any other UI elements so why not make it the base view itself. That ways I dont have to define the frame(coordinates and size of table). I will discuss how to add a table view as a sub view in next post where a table will just be covering a small portion of screen and will have its own scroller.
Now, we have created a tableView and made it as the base view. But what does this table display? We are now going to do the same thing now. For that we need to implement the delegate methods of UITableView. If you remember the interface definition in MyTableView.h was like @interface MyTableView : UIViewController {
In triangular brackets we tell that what are the protocols that this class will be adhering to.
I just hope you have read ObjC properly to understand what I said.
Anyways, in the MyTableView.m file add that following code
Now, three methods, which are automatically called define how the table will look like and what data it will display.
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame :CGRectZero reuseIdentifier:MyIdentifier]autorelease];
So what is this dequeReusableCell? Why can’t we just create a cell by alloc and init? We can do that but there is something you should always keep in mind. This method is called every time you scroll the tableView and a new cell which was not visible earlier gets visible. Imagine you have 20 cells in the table and iPhone can display only 19 on full screen. So the 20th cell will be created by cellForRow method only when it gets visible on the screen. But then the first cell will go out of view ryt? When you scroll back to view the first screen, cellForRow method will be called again to to return a cell to be displayed at first place. That’s why we use dequeReusablelCell so that it doesn create a new cell every time.
CAUTION: Do not do anything stupid inside cellForRow method cuz it gets called multiple times.
Finally we have created the view and are ready to use it. What we want is that the new view should appear when we click the “Hit Me” button we created earlier.
So open MyTestProjectViewController.h and modify it to look like this:
We have only defined an instance of MyTableView here, to create it and push it on button click
open MyTestProjectViewControler.m and modify buttonPressed method we created earlier to look like this:
Here we are creating an instance of MyTableView and pushing it over the view which we are looking at now.
If you build this project and run it, you will see the same screen as we saw last time, on pressing the button you will notice that nothing happens. If you chose “navigation based” template when creating the project last time this code would have worked, but since we chose “view based” template its not working. This is the reason why I picked this template so that we can learn how we can programatically do any this we want.
The reason why the new view is not getting pushed is that there is no navigationController attached to the originalView. To do so open MyTestProjectAppDelegate.m and find a method named - (void)applicationDidFinishLaunching:(UIApplication *)application
Add the code to make it look like this
Here we have created a navigation controller and initialized it with the root view as MyTestProjectViewController. So now our original view has a navigation controller and it can push any view over it.
Now if you build and run the project, you can see the new screen containing a tableView on pressing the “Hit Me” button.
In the next post I will be creating a customized view with a table and a few other UI elements on the same page. This will be my favorite post as I could not find this thing using google.
Also I will be creating App Settings in the same project which will work as dataSource for the new view we will be making.
Lemme know if I have been missing something in this post. Till den good luck.
[...] of NewGen, Part 1 iPhone Tutorial: UITableView & Navigation Mar [...]
[...] Navigating from one view to another [...]
[...] Navigating from one view to another [...]
[...] Navigating from one view to another [...]
First, thank for the tutorial.
Second, you might have meant to do this, but I got lost in the section above …
“As you can see we have added a UITableView object as a property to this viewController class
Now we should create and add this tableView to the view. So open MyTableViewController.m and add the following code to -(void)loadView method.”
I think “MyTableViewController.m” should have been “MyTableView.m”, or at least by adding the code to “MyTableView.m” got it to run.
-Shayne
Well my bad..I get confused somtimez too
thanks for d correction..ll reflect the changes soon
Thanks for the example, this is my first app that I’m trying, I’m still new in the development of iPhone apps, but I’m eager to learn, I do find 10 errors after typed in your code, can you assist me please
thanks, let me know
Hello Pierre
What errors is it showing?
The following are needed in MyTableView.h
1. Add missing @synthesize
2. Add initWithFrame as loadView calls for it in tableView = alloc/initWithFrame
3. Change // (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section // as your code returns a non-void function
#import “MyTableView.h”
@implementation MyTableView
@synthesize aTableView;
@synthesize dataForMyTable;
- (id)initWithFrame:(CGRect)frame Style:(UITableViewStyle)aStyle {
self = [super init];
if (self != nil) {
//do some initialization
}
return self;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
int secCount;
switch (section) {
case 0:
secCount = [dataForMyTable count];
case 1:
secCount = 2;
}
return secCount;
}
//memory management, may be necessary for MyTableView
- (void)dealloc {
[tableView release];
[dataForMyTable release];
[super dealloc];
}
//check for some deprecated codes in beta version
hi! I will have to take back the “initWithFrame” in MyTableView.m .. no need for that for below to work.. I mistyped “Style:UITableViewStyleGrouped” instead of style: UITableViewStyleGrouped (small “s”) which gave me the error about no method found..
this line works with or withouth the “initWithFrame”.
aTableView = [[UITableView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame] style:UITableViewStyleGrouped];
[...] Navigating from one view to another [...]
[...] iPhone Tutorial: UITableView & Navigation iPhone Development: Using SQLite3 database Mar 29 [...]
When I am debugging this line of code in loadView (MyTableView.m), I am getting this error message.
Debugging line:
aTableView = [[UITableView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame] Style:UITableViewStyleGrouped];
Error message:
*** -[UITableView initWithFrame:Style:]: unrecognized selector sent to instance 0×538230
Please advise.
thanks,
Jason
as such it should not happen, I will verify this tomorrow when i reach my workstation.
you can for now just use [UITableView alloc] initWithFrame]
and set the style in a separate line of code.
HI,
Thanks for the tutorial, but I can’t get it to work,
Could you post the source, so I can check it with mine.
Thanks
Verdrive
add in viewcontroller.h :
#import “MyTableView.h”
and
@property (nonatomic,retain) MyTableView *nextView;
add in viewcontroller.m after @implementation:
@synthesize nextView;
and all works great…
Nice tutorial.
It helped me doing stuff using interface builder.
This tutorial provided the answer to a problem I was having. Thank you, very well done.
Thank you, I regularly read your blog, I have some questions for you, let me know if you want to contact me by e-mail
When I am debugging this line of code in my application, no error message but when press showInfo2 button i got this warning: TERMINATING_DUE_TO_UNCAUGHT_EXCEPTION…
Can u take a look my code..
—————————————————————————————————–
-(IBAction) showInfo2:(id)sender
{
ProjectAppDelegate *delegate = (ProjectAppDelegate *) [[UIApplication sharedApplication] delegate];
RootViewController *secondView = [[RootViewController alloc ] initWithNibName:@”RootViewController” bundle:nil];
[delegate switchView:self.view toView:secondView.tableView];
}
——————————————————————————————–
Thank you so much for providing such a nice article.It helped me a lot.
But,after building this application,i found a warning that ’setText:’ is deprecated & unused variable ‘nvc’.
Please ,push me out of this situation.