iPhone Game Tutorial (Part 1)

I thought I could share my methods on how I animate and move stuff around on the iPhone for games with you.
As always, these are just my ways of doing it. I'm sure there are better ways but I'm also very sure that there are far worse ways as well.



First comes first:
What do we want to make this app do ?
As a starter I thought it would be cool having a little man being able to run across the screen in an animated fashion.
You'll need the sprites and the background so it looks nicer.

Sprites

Once downloaded we can move on.

Create the Project:
Easy enough. Create a View Based Application. Give it a name and move to the viewController.h.

ViewController.h:
We will need to add a few things here.
Our project is going to need a UIImageView to display our little soldier.
We are also going to need an array to hold our images for the walking animation.
For the movement I like using a timer, so we'll create that too.

As for the functions, we're going to use a button to make the little guy walk across the screen of our iPhone.
So we'll create two functions for that. The name explains itself, right?
The other two void functions will be used by the timer.

@interface AnimateViewController : UIViewController {
UIImageView *player;
NSArray *walkImages;
NSTimer *walkingTimer;
}

-(IBAction)walk;
-(IBAction)stopWalking;
-(void)startMovingForward;
-(void)moveForward;

Moving on the ViewController.m:
First we're going to create our little world for the little guy to walk around on.

Make the application load in Landscape mode

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
return (interfaceOrientation == UIInterfaceOrientationLandscapeLeft);
}

Interface Builder:
Now open the ViewController.xib and click on the gray arrow in the top corner of the view. This will make the view rotate into landscape. Add a UIImageView, have it take the whole screen and display "wof028.png" in it and set the mode to aspect fit.
Don't forget to add a UIButton in the top right corner to make the soldier walk.
Go to the Button Connections and assign the function "Walk" to "Touch Down" and "StopWalking" to "Touch Up Inside".
Save and close the Interface Builder.

Back to .m:
Insert the following in the viewDidLoad:

- (void)viewDidLoad {
[super viewDidLoad];

walkImages = [[NSArray alloc] initWithObjects:
[UIImage imageNamed:@"w1.png"], [UIImage imageNamed:@"w2.png"],
[UIImage imageNamed:@"w3.png"], [UIImage imageNamed:@"w4.png"],
[UIImage imageNamed:@"w5.png"], [UIImage imageNamed:@"w6.png"], nil];

player = [[UIImageView alloc] initWithFrame:CGRectMake(100, 220, 30, 30)];
player.image = [UIImage imageNamed:@"stand.png"];
player.animationDuration = 1.5;
player.contentMode = UIViewContentModeBottomLeft;
[self.view addSubview:player];

}

Here we simply assigned the images to the array. We could do it with a loop too (which is recommendable if you have more than just a few files) but for this example I wanted to show it like this to make it clearer.

We also initiate our ImageView "player" with a frame (CGRect). A frame is just that. A frame that holds the position of our image. Much like a picture frame in real life. If you don't understand the numbers of CGRectMake try altering them and see what happens.
We also assign a standard "standing" pose with the "stand.png" to the player.

The animation duration number is the number of seconds it need to cycle through the whole animation. You'll need to try and see what works good for you. For this example I use 1.5.

The ContentMode sets where the images will be placed every time in the frame. This is important when the sprites are of different sizes. In our case, not so much.

Last, we add the image to our view.

Taking care of the rest:
Add the following:

#pragma mark -
#pragma mark IB Actions

-(IBAction)walk {
[self startMovingForward];
player.animationImages = walkImages;
[player startAnimating];
}

-(IBAction)stopWalking {
[player stopAnimating];
[walkingTimer invalidate];
}

#pragma mark Move it

-(void)startMovingForward {
walkingTimer = [NSTimer scheduledTimerWithTimeInterval:0.125 target:self selector:@selector(moveForward) userInfo:nil repeats:YES];
}

-(void)moveForward {
player.frame = CGRectMake(((player.frame.origin.x)+5), 220, 30, 30);
}

Pragma Mark ??
Pragma Mark can help you organize your code for when it gets very long. Copy the code above and then click on the two arrows pointing up and down at the top back above your code. This will open an index of your methods and the pragma mark text will help you find what you need.

When we tap on the button we'll start the "walk" function. The walk function starts the "moveForward" function, assigns the array walkImages to the property animationImages of our player ImageView and tells the program to start Animating "player".

startMovingForward will just start the timer. We give it an interval to work with and in the selector we tell it to activate "moveForward" on every interval. Don't forget to tell the timer to repeat itself.

moveForward will finally take care of the actual moving of the little soldier. We assign a new frame to player which is the same as the current one but we add 5 pixel to its x axis.

When we lift our finger from the Walking button, the animation and the timer will be stopped.

Build and run the application. See how it goes.

[iPhone] Quartz 2D

Image via Wikipedia

The last week I've been fighting to get some stuff working in Quartz. Actually I've been trying to get Quartz itself to work.
I've now managed and thought I could share:

Open your viewController.xib and add a view inside your view. Size it and move it the way you want it. This is the view that you will use like a tv screen, showing all your Quartz drawing.
(This is the way I am doing it for a specific app. I'm sure you'll find your way that fits your app the most.)

Select the view and press ⌘4 and change the class to, lets say, "QuartzView".
Select File>Write Class File and check the box to create the .h file too.

Once created, the files will be in your project.
in the QuartzView.h:

@interface QuartzView : UIView {
UIColor *color;
}
@end

Switch over to the .m file.
The drawRect method is the one where we'll do all the drawing. The drawing code has to be in this method as far as I know.

Lets start filling in some code in the drawRect method then and try to draw a line.
First, we set the color for our line and retrieve the context. The context is like your canvas where you'll be drawing. All the drawing is done in a context. As we'll only have one context, I'll call it (who would have guessed) "context" :

color = [UIColor redColor];
CGContextRef context = UIGraphicsGetCurrentContext();

Then, we set some properties of the line we're going to draw. They are pretty self explanatory. You always define the context (which we cleverly called "context") and the specific attribute of the property.

CGContextSetLineWidth(context, 2.0); // We set a 2px thick line.
CGContextSetStrokeColorWithColor(context, color.CGColor);
CGContextSetFillColorWithColor(context, color.CGColor);
//This settings want a CGColor and not a UIColor. Good for us, UIColor has a property that returns the color as a CGColor.

Now that we've set the properties of the line we're about to draw, lets prepare the actual movement required to draw a line.

We'll create 2 CGPoints which basically just group an X & Y coordinate of the screen in one variable.

CGPoint startingPoint = CGPointMake(20.0, 20.0);
CGPoint finishingPoint = CGPointMake(80.0, 80.0);

Now, we move our virtual drawing hand (with the pencil we've defined earlier) to the starting point and then make it move to the finishing point. We then just have to say to actually draw that line and to update our view. 4 lines of code.

CGContextMoveToPoint(context, startingPoint.x, startingPoint.y);
CGContextAddLineToPoint(context, finishingPoint.x, finishingPoint.y);
CGContextStrokePath(context);
[self setNeedsDisplay];

Right, so that's the basics. I'll probably go into more details once I've figured it out better myself soon.

[iPhone] Saving Simple Data

Image by Steve Rhodes via Flickr

This tutorial will show you an easy way of saving simple bits of data so that they can be continue to be used next time the app is started on your iPhone.

Imagine you wanted to save some user settings. In this example I have a UISlider and a UISegmentedControler which I want the user to be able to set, but the iPhone should remember the settings and display them in their last state whenever the iPhone App is restarted.

In the .h file add:

float sliderValue;
float segmentValue; // Use these values to adjust your UI Elements

// You will also need the following methods:
-(NSString *)dataFilePath;
-(void)applicationWillTerminate:(NSNotification *)notification;

In the .m file add:

-(void)viewDidLoad
{
NSString *filePath = [self dataFilePath];
if([[NSFileManager defaultManager] fileExistsAtPath:filePath])
{
NSArray *array = [[NSArray alloc] initWithContentsOfFile:filePath];
sliderValue = [[array objectAtIndex:0] floatValue];
segmentValue = [[array objectAtIndex:1] floatValue];
[array release];
}

UIApplication *app = [UIApplication sharedApplication];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillTerminate:) name:UIApplicationWillTerminateNotification object:app];
[super viewDidLoad];
}

Above: This is where we load the date if there is any from the last save on the iPhone. First, we check to see if the data file does already exist. If it doesn't, then we don't bother about it. If it does however, we instantiate an array with the contents of the file and add the content to our variable as a float. Remember to save and load them in the same order so you don't mix things up. After having done that, we add some extra code to subscribe to the Notification so that it calls the saving process before quiting the app.

-(NSString *)dataFilePath
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
return [documentsDirectory stringByAppendingPathComponent:@"data.plist"];
}

Above: What this method does is return the full path of the the data file (data.plist). It does that by finding the documents directory on the iPhone/iPod Touch device and appending (adding) "data.plist"

-(void)applicationWillTerminate:(NSNotification *)notification
{
NSMutableArray *array = [[NSMutableArray alloc] init];
[array addObject: [NSNumber numberWithFloat:sliderValue]];
[array addObject: [NSNumber numberWithFloat:segmentValue]];
[array writeToFile:[self dataFilePath] atomically: YES];
[array release];
}

Above: The method will be called when, as you might have guessed, the application will get terminated/closed. Here is where you should add all the data you want to keep for the next time the iPhone loads the Application.

[iPhone] Removing the Keyboard when done.

Image by _snapp via Flickr

Let me continue with the easy stuff to fill up the Blog a little more.
Today I'll go through how to make the keyboard move out of the way once you are done editing the field.

There are two basic ways of doing it. One, is pressing the DONE key on the keyboard. The other way is tapping with your finger anywhere else on the screen.

Lets clarify:

UITextField *myTextField;
UITextField *myOtherTextField;

-(IBAction)backgroundClick:(id)sender;
-(IBAction)doneEditing:(id)sender;

Using the DONE key:

To make it return with the Done key start by adding the following code:

-(IBAction)doneEditing:(id)sender
{
[sender resignFirstResponder];
}

Any controller can be called to resign the First Responder status. With this simple function done lets set WHEN it will be called.
Open Interface Builder and single click on one of the Text Fields and click ⌘2 to open up the connections inspector.

Connect the Did End on Exit event with the doneEditing function by dragging the little circle symbol next to the event name to the File's Owner.

Repeat this for the other text field to show that you don't need a separate function for every field and try it out.

By tapping it away:

Some keyboard layouts don't have a DONE key. Or even if they have, a lot of people prefere to just tapp it away instead of tapping the small button in the corner. For these situations there is a quick and easy way of solving the problem.

Add the following code:

-(IBAction)backgroundClick:(id)sender
{
[myTextField resignFirstResponder];
[myOtherTextField resignFirstResponder];
}

Can you already guess? Lets see.

Save it again and go back to to Interface Builder.
Drag a Round Rect Button over your view and resize it so that it covers ALL of your view.
Now Select Layout > Send to Back and don't deselect the button anymore. The Button is now behind everything else you are showing.

Press ⌘1 and change the type to Custom.
You now have an invisible button in you back layer. Only thing missing now is to connect the Did touch up inside event to the action backgroundClick and you're done.

Notice that you can ask all of your fields to resign First Responder even if they don't currently have it and it won't cause any problem.