How to take screenshots within your Application.

iPhone / iPod touch allows you to make screenshots (saves the contents as an image) by pressing both home and power button, although many users don’t know this functionality. If you go to your camera roll or sync photos with your computer, every screenshot you make is an image 320 x 480 px.

Today I will show you how to make a screenshot of arbitrary size using Quartz. What does arbitrary size mean? Well you can not only save the smaller part of your screen, but, if you for example have bigger view than 320×480 px you can save it all, not only the visible part.

Before you start, you have to add the QuartzCore framework to the project.

#import <QuartzCore/QuartzCore.h>

You can add this line in either header (.h) or implementation file (.m).

Now it’s time to add the method which will make a screenshot and explain how it works:

-(void)saveToCameraRoll {
	UIGraphicsBeginImageContext(self.view.bounds.size);
	[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
	UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
	UIGraphicsEndImageContext();
	UIImageWriteToSavedPhotosAlbum(viewImage, self, nil, nil); 

	/* 
	flashView.alpha = 1;
	[UIView beginAnimations:nil context:NULL];
	[UIView setAnimationDuration:0.5];
	flashView.alpha = 0;
	[UIView commitAnimations];
	UIAlertView *alert= [[UIAlertView alloc] initWithTitle:nil message:@"Photo saved to your camera roll" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
	[alert show];
	[alert release];
	*/
}

I’ve implemented the saveToCameraRoll method were first five lines do everything you need. It’s quite difficult to discuss it, as long as I never mentioned about Quartz drawing, contexts, layers… But, first line creates the context of our view (UIViewController’s self.view) size. Using that context’sframe (it’s not frame properly speaking) it contents is rendered (2nd line) and saved to anviewImage. 4th line is closing the context as we do not need it anymore, and the 5th line putsviewImage to the Camera Roll.

How about the part in the comment ( /* and */ )? Well it’s my idea how to copy the animation iPhone uses while making the screenshot using home and power buttons. I created the flashView – simple white view of the same size of my self.view most time 100% transparent. When the userdecides to create a screenshot using a button I provided in the application, flashView become visible and during half a second it’s transparent again. And the alert to inform what has just happen.

Please remember that above method saves the whole self.view and all it’s subviews. So whatever is a subview of self.view will be saved as well. You can change the alpha property of anything you don’t want to save and reveal what’s behind it, and after screenshot was made bring alpha to normal. While making a screenshot as long as it will be one procedure – one task user won’t see any changes in interface. Example:

-(void)saveToCameraRoll {	topView.alpha = 0;

	UIGraphicsBeginImageContext(self.view.bounds.size);
	[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
	UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
	UIGraphicsEndImageContext();
	UIImageWriteToSavedPhotosAlbum(viewImage, self, nil, nil); 
	topView.alpha = 1;

}

As always (don’t thank me) I provided an sample project. It alows you to make screenshot of whole iPhone screen (320 x 480 px), only central part (320 x 240 px) and again the whole iPhone screen without button on the bottom.

 

Thanks goes to http://chris-software.com/

You can get the source code from here

 

Day-13 for iOS development

Click here for Lecture 13 which includes  UIView Animation, UISegmentedControl, Accelerometer ,  UIAlertView ,UIActionSheet  and  NSTimer.

How to use UIAlertView in your Application?

Hello Friends now we are moving forward with some development side.Today I am going to explain usage of UIAlertView.

Here is a example for this:

UIAlertView *simpleAlert = [[UIAlertView alloc] initWithTitle:@”Simple Alert” message:@”Alert’s message” delegate:self cancelButtonTitle:@”OK” otherButtonTitles:nil];

[simpleAlert show];

[simpleAlert release];

Here simpleAlert is an object for UIAlertView class.Using initWithTitle we can set the title for Alert and with message:@”” we can set the appropriate message for it.We have to set the delegate for it and provide the cancelButtonTitle here OK is provided here.

using [simpleAlert show] alert is prompted and user can get the Alert to his screen.using release keyword we have freed the memory which we have used using alloc keyword.

Grab the code from Here

In File Menu Click on Download Original tab for Grab this Code.