Code Snippet: Prevent The iPhone From Sleeping

The code below will prevent the iPhone from dimming its screen and ultimately going to sleep. Use it wisely as you don’t want your application becoming notorious for being a battery hog

[UIApplication sharedApplication].idleTimerDisabled = YES;

How to Save the Contents of an Array to the iPhone’s Filesystem

The simplest way to save user preference/data on iPhone is using NSUserDefaults. Here comes another easy way to save data in filesystem.

In this example, we are going to create an array, fill it with values and then save the contents of the array to the documents directory of our app.

Then, after stopping the program and putting in code, we will retrieve the array from the filesystem. Finally, to prove that it all worked we will use an alert box to inform the user of what is in the array that we stored.

First, in the applicationDidFinishLaunching method put in this code:

//get the documents directory:
NSArray *paths = NSSearchPathForDirectoriesInDomains
(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];

//make a file name to write the data to using the
//documents directory:
NSString *fullFileName = [NSString stringWithFormat:@"%@/newFileArray", documentsDirectory];

//create an array and add values to it:
NSMutableArray *array = [[NSMutableArray alloc] init];
[array addObject:@"First string"];
[array addObject:@"Second string"];
[array addObject:@"Third string"];

//this statement is what actually writes out the array
//to the file system:
[array writeToFile:fullFileName atomically:NO];

Now, your information has been saved to the iPhone’s file system in the documents directory of your app. Here is how you would retrieve the information that you saved:

//get the documents directory:
NSArray *paths = NSSearchPathForDirectoriesInDomains
(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];

//make a file name to write the data to using the
//documents directory:
NSString *fullFileName = [NSString stringWithFormat:@"%@/newFileArray", documentsDirectory];

//retrieve your array by using initWithContentsOfFile while passing
//the name of the file where you saved the array contents.
NSMutableArray *array = [[NSMutableArray alloc] initWithContentsOfFile:fullFileName];
NSLog(@"%@", array);

That's it – a quick and easy way to save information on the iPhone. The array is easily saved and retrieved from iPhone filesystem.

UIAlertView with a TextField within it

Every iphone developer would have seen default alert view with a title, a message and buttons to dismiss the alert view. Today I will show an option to insert an UITextField inside a UIAlerView.

We will basically call a UIAlertView and then add the UITextField programmatically.

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@”Enter Your Name” message:@”message hidden by text field” delegate:self cancelButtonTitle:@”Dismiss” otherButtonTitles:@”OK!”, nil];
UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(12, 45, 260, 25)];
CGAffineTransform myTransform = CGAffineTransformMakeTranslation(0, 60);
[alert setTransform:myTransform];
[myTextField setBackgroundColor:[UIColor whiteColor]];
[alert addSubview:myTextField];
[alert show];
[alert release];
[myTextField release];

We are including a dummy message in the alert view because it's position will be occupied by our textfield. If we didn’t put that sentence then the alerts buttons would go up more and the UITextField will be messed up.

Next thing that we have used is CGAffineTransform. It is used because on focusing on the textfield, keyboard appears and covers some part of our UITextField. Hence this transform ensures that keyboard doesn't covers it up.

Now build and Run the application. You will get a screen as below.

iPhone: How to Open the Mail App With a Pre-Composed HTML Email

Have you ever wanted to open the Mail app with a pre-composed email? Then today’s iPhone development tip is the one for you! This has many uses, but a common one is a tell-a-friend feature in apps. If you attach the code from this tip to a button, you can give your users a way to promote your app to their friends via the iPhone’s built in Mail app.

A Handy Function
The sendEmailTo function, seen below, can be included in any view controller of your app. This function gives you a simple interface to send emails. It allows you to define “to” addresses, “cc” addresses, “bcc” addresses, a subject and a body. The body supports HTML tags.

- (void)sendEmailTo:(NSString*)to withCC:(NSString*)cc withBCC:(NSString*)bcc withSubject:(NSString*)subject withBody:(NSString*)body {
NSString * url = [NSString stringWithFormat:@"mailto:?to=%@&cc=%@&bcc=%@&subject=%@&body=%@",
[to stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding],
[cc stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding],
[bcc stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding],
[subject stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding],
[body stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding]];

[[UIApplication sharedApplication] openURL:[NSURL URLWithString:url]];
}

PS: Running this function in the iPhone Simulator will have no effect because the simulator does not include the iPhone’s Mail app. To see the effects of this function, it must be run on a device.

Example
The following example opens the Mail app and pre-populates the to, cc, bcc and other fields in it.

[self sendEmailTo:@"friend@example.com"
withCC:@"relative@example.com"
withBCC:@"secret-friend@example.com"
withSubject:@"Blog"
withBody:@"Check out my new blog, here."];

You could also leave some of these fields blank if you want user to specify and fill those.

[self sendEmailTo:@""
withCC:@""
withBCC:@""
withSubject:@"Blog"
withBody:@"Check out my new blog, here"];

Sound Format Conversion in iPhone

Since iPhone supports only following data formats for audion files:

* linear PCM
* MA4 (IMA/ADPCM)
* µLaw
* aLaw

You may use the afconvert tool to convert sounds. For example, to convert the 16-bit linear PCM system sound Submarine.aiff to IMA4 audio in a CAF file, use the following command in the Terminal application:

afconvert /System/Library/Sounds/Submarine.aiff ~/Desktop/sub.caf -d ima4 -f caff -v

You can inspect a sound to determine its data format by opening it in QuickTime Player and choosing Show Movie Inspector from the Movie menu.