Posts Tagged 'Programming'

CoverFlow Tutorial

Here’s an excellent tutorial on how to, well,

… help you add a cool effect called the “cover flow/open flow” effect to any of your iphone apps. This is cool in two ways actually. One it adds animation kind of effect to your app and the other, its very easy to build too…

It’s based on the OpenFlow project that we actually mentioned in passing before, but if you haven’t checked that out yet this is a great place to start!

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Tip: TCP and SSL

You may have noted in QA1652 that is now possible to use NSStreams for your TCP communication needs even though the iPhone has no NSHost class, by leveraging the NSStream <-> CFStream toll-free bridge; but we’ll bet you didn’t know that you can encrypt them with SSL easily:

… The way that we enable SSL encryption is to simply use setProperty:forKey: on both streams, setting the key NSStreamSocketSecurityLevelKey to a value that specifies the version of SSL to use. If you want to tell NSStream to use the highest version supported in common with the remote connection, specify NSStreamSocketSecurityLevelKey. That’s what you’ll usually want…

However, that’s for a somewhat optimistic value of “easily”:

… This code will work if everything is perfect. However, by default, SSL support in NSStream is a little paranoid. It won’t, for example, use a self-signed certificate or an expired certificate to establish a secure connection. NSStream does a number of validity checks when establishing the secure connection, and if they don’t all pass, the streams appear to be valid, but no data gets sent or received. This is somewhat frustrating…

Read the whole article for further advice and sample code!

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Streaming in OpenAL

For the latest in our “just in case you ever need to know how” notes, here’s what looks like a comprehensive study in

Streaming in OpenAL

streamingHighLevel2.png

Not that there appears to be anything particularly wizardly technical about streaming in OpenAL compared to streaming using any other set of APIs, but hey, it beats having to figure out all the appropriate calls yourself!

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Tip: Grayscale UIImage

Here’s a handy routine to easily convert an UIImage to grayscale, like this:

grayscale.png

- (UIImage *)convertImageToGrayScale:(UIImage *)image

{

  // Create image rectangle with current image width/height

  CGRect imageRect = CGRectMake(0, 0, image.size.width, image.size.height);

  // Grayscale color space

  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();

  // Create bitmap content with current image size and grayscale colorspace

  CGContextRef context = CGBitmapContextCreate(nil, image.size.width, image.size.height, 8, 0, colorSpace, kCGImageAlphaNone);

  // Draw image into current context, with specified rectangle

  // using previously defined context (with grayscale colorspace)

  CGContextDrawImage(context, imageRect, [image CGImage]);

  // Create bitmap image info from pixel data in current context

  CGImageRef imageRef = CGBitmapContextCreateImage(context);

  // Create a new UIImage object

  UIImage *newImage = [UIImage imageWithCGImage:imageRef];

  // Release colorspace, context and bitmap information

  CGColorSpaceRelease(colorSpace);

  CGContextRelease(context);

  CFRelease(imageRef);

  // Return the new grayscale image

  return newImage;

}

That would be a stylish effect for a “please wait” pause or the like, we figure.

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BarTint

Here’s a handy-looking little tool called BarTint for playing with your interface colours:

BarTint is a tool for developers and designers of iPhone apps, to assist in the visualization of the various bar-type objects (toolbars, navbars, segmented controls) when a tint color has been applied to them.

Because of the gloss and caustic shader applied to these objects, when you specify a color, you don’t necessarily get what you think you’re going to get. BarTint takes the guesswork out, letting you see exactly what a color combination looks like on the device, and allows you to forward the Objective-C required to produce that UIColor to yourself over email…

BarTint.jpg

Very nice, very nice. And FREE, no less!

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Generating Barcodes

So, you want to generate barcodes on your iPhone screen?

OK, well neither do we at the moment, or any time in the past for that matter; but just in case the idea ever comes up, here’s a new library (well, a new port) for you:

Cocoa-Touch-Barcodes

This is a fork of Jeff Lamarche’s Cocoa Barcodes project, with the code modified to work on the iPhone and iPad. In my testing, a CCD and laser scanner can read UPC and Code 128 barcodes directly from the screen w/ no issue…

Handy if you need it!

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Icon template

[UPDATE: Now points to the iPhone 4 savvy version!]

Here’s a handy template for your iPhone and iPad icon design needs:

ists
iPhone-4-icon-PSD.png

- 512 pixels, iTunes Store style (Caution: very ugly. Talk to Apple about that, not me.)


- 512 pixels, iPad style (either have different overlays. Who’d have thought?)


- 512 pixels, iPhone style.


- 72 pixels for iPad home screen.


- 57 pixels for iPhone home screen.


[UPDATE: -114 pixels for iPhone 4 home screen!]

- 48 pixels for iPad Spotlight (with Spotlight background).


- 29 pixels for iPad / iPhone Settings and iPhone Spotlight (with both backgrounds).

Yes, it is getting complicated these days, isn’t it?

h/t: MacFanatic!

UPDATE:

And here is a post about another icon template for Illustrator CS 5; and if you’re wondering about appropriate sizes for icons for Android, Linux, Windows, Safari, or anything else, check out their

Icon Reference Chart

And here is a script, iPhone-Photoshop-JSX-Icon-Exporter, to create all the needed sizes from one 512×512 icon.

And here is iOS Icon Template for Perfectionists, reputedly correcting a corner issue with the above template.

And finally, QA1686 App Icons on iPad and iPhone is where you should go for the current Final Word™!

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Data Entry Screens

Here’s a worth reading post on how to make data entry screens that center the current entry field above the keyboard by simply using a UIScrollView, instead of the mess of hardcoded animation blocks that we’ve been using up ’til now:

How To Create A Data Entry Screen

Couple problems with the code as presented, but read to the end of the comments and apply the keyboard notification responses there and you’re just about good!

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Tip: UINavigationBar Background

So you’ve got this design from the artists for your new navigation-based app, and they want the navigation bar to look exactly like the artwork, a close gradient just doesn’t cut it. What to do? What to do? And if you look around, there are a number of suggestions on how to accomplish this, which are mostly overly complicated and in some places just plain wrong.

But, assuming that all the bars in the app are supposed to look the same which is most likely a safe assumption, why indeed there is an extremely simple way — just make a category to override UINavigationBar’s -drawRect! Easy once you think of it, indeed. And set the bar’s tint color appropriately for your image there too and buttons will respect that; so in our case here, the simple category

@implementation UINavigationBar (TWXUINavigationBar)
- (void)drawRect:(CGRect)rect
{
UIImage *img  = [UIImage imageNamed: @"customnavigationbar.png"];
[img drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
UIColor *topColor = [UIColor colorFromHexValue:0x910011];
self.tintColor = topColor;
}
@end

where the tint color was taken from the top pixel of the .png file, results in

tintedbar.png

Very nice looking, yes? Now that’s a seriously easy way to satisfy those picky artistic types!

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UITableViewCell from nib warning

If you’ve been reading for a while you might recall this post about loading your UITableViewCell layout from a nib. Or perhaps you stumbled across that somewhere else, or even came up with it on your own; well, if you have been doing that, turns out there’s an additional wrinkle you need to be aware of:

… The key here is that the CellIdentifier value must also be entered into Interface Builder, like this:

UITableViewCell-Identifier.png

If you don’t do this, then UITableViewCells will not be reused. (A telltale sign of this is that you’ll see lots of “creating a new cell” log messages.) There is no compiler or runtime warning if you fail to enter this critical piece of information into Interface Builder. So that log statement can be a useful warning…

Yes. Yes, indeed, if you have several thousand items in your list, and you’re loading directly from the nib each time, that could be very very bad. Be careful out there!

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