iPhone Development 101

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iPhone Device & Screen Sizes and Resolutions

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To get the screen dimensions (in points) of the current device:

Objective-C:

CGRect screenBounds = [[UIScreen mainScreen] bounds]; // Macros: #define screen_width [ [ UIScreen mainScreen ] bounds ].size.width #define screen_height [ [ UIScreen mainScreen ] bounds ].size.height

Swift:

let screenBounds = UIScreen.main.bounds let screen_width = screenBounds.width let screen_height = screenBounds.height

To get the screen scale:

Objective-C:

CGFloat screenScale = [[UIScreen mainScreen] scale];

Swift:

let screenScale = UIScreen.main.scale

Non-retina devices have a scale of 1.0. Retina devices have a scale of 2.0 or 3.0.

Some dimensions common to all screen sizes:

Status Bar
20 pts
Navigation Bar 44 pts
Nav Bar/Toolbar Icon 20 x 20 pts (transparent PNG)
Tab Bar 49 pts
Tab Bar Icon 30 x 30 pts (transparent PNGs)

Points vs. Pixels

Apple introduced retina displays starting with the iPhone 4. You don't have to modify your code to support high-res displays; the iOS coordinate system uses points rather than pixels, so the dimensions and position in points of all UI elements remains the same across all devices.

iOS supports high resolution displays via the scale property on UIScreen, UIView, UIImage, and CALayer classes. If you load an image from a file whose name includes the @2x modifier, its scale property is set to 2.0. Similarly an image with a @3x modifier has a scale of 3.0. Otherwise the scale defaults to 1.0.

Retina Graphics

To support high-resolution graphics on devices with retina displays, you need @2x and @3x sized images:

@1x:
button.png
60 x 20
@2x:
button@2x.png
120 x 40
@3x:
button@3x.png
180 x 60

To refer to an image in your code (or in Interface Builder), just use the filename of the standard sized image. iOS will automatically detect and use the @2x or @3x version if the device supports it:

Objective-C:

imageView.image = [UIImage imageNamed: @"button.png"];

Swift:

imageView.image = UIImage(named: @"button.png")

Adjusting Sizes

Click here to see how to adjust View Frames and Bounds.

Additional References

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