Perform Lazy Loading with Image Cache(HJCache)


Hi,

I am going to explain you how to perform lazy loading with Image Cache using HJCache.It will cache your images according to your requirements. I have perform caching for 1 week.Now i am showing you the steps for achieving you task very simple way.

Step 1:Drag and Drop HJcache Classes into your Project(I have already Provided)

step 2: In Application Delegate Import “HJObjManager.h” file and Make an Object of It.

Step 3:In Application Delegate.m file @synthesize the Object write the following code for Image caching.

Step 4: Now import “HJManagedImageV.h” where you want to implement the lazy loading.

Step 5. Make the custom cell and Take UIView instead of UIImageview in your Custom cell and inherit  Class “HJManagedImageV” as shown here.

Step 6: In use the Object of HJManagedImageV and provide the URL from your Array/Dictionary other things are managed by HJcache Object it self.

Now your task is getting completed.You can have the complete code by Clicking Here

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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 drawingcontextslayers… 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