UIBackdropView

_UIBackdropView is a private class in UIKit.framework (iOS 7.0+), a subclass of UIView, which is used for the popular blur effects.

It uses a CABackdropLayer with a gaussianBlur CAFilter (kCAFilterGaussianBlur) .

Creating Settings

_UIBackdropView uses a _UIBackdropViewSettings object for its setup. There are many ways to create it:

_UIBackdropViewSettings *settings = (_UIBackdropViewSettings *)[[[_UIBackdropViewSettingsSemiLight alloc] init] autorelease];

_UIBackdropViewSettings *settings = [_UIBackdropViewSettings settingsForStyle:2070];

_UIBackdropViewSettings *settings = [_UIBackdropViewSettings settingsForPrivateStyle:2070]; //this only calls settingsForStyle internally, so there are no advantages of using it over settingsForStyle 

_UIBackdropViewSettings *settings = [[[_UIBackdropViewSettings alloc] initWithDefaultsValue] autorelease];

_UIBackdropViewSettings *settings = [_UIBackdropViewSettings settingsForStyle:2030 graphicsQuality:100] ; //can be either 10 or 100, 100 is better. See notes at the bottom

Available settings classes (styles)

Here's a list with known settings classes (subclasses of _UIBackdropViewSettings) available.

Class	Styles	Applications	Comments
_UIBackdropViewSettingsCombiner	3
_UIBackdropViewSettingsNone	-2
_UIBackdropViewSettingsLight	0, 1000, 1003, 2020, 10090, 10100
_UIBackdropViewSettingsDark	0, 1001, 1100, 2030, 11050, 11060	Notification Center Keyboard (Dark) Safari Navigation Bar (Private mode)
_UIBackdropViewSettingsBlur	2	Common blurring
_UIBackdropViewSettingsColorSample	2000
_UIBackdropViewSettingsUltraLight	(iOS 7) 2010 (iOS 8) 2010, 10050, 10060, 10070, 10080, 10110	Alert views and various UI (White)	Fallback of unsupported styles
_UIBackdropViewSettingsLightLow	2029		Optimized version of _UIBackdropViewSettingsLight
_UIBackdropViewSettingsDarkWithZoom	2031
_UIBackdropViewSettingsDarkLow	2039		Optimized version of _UIBackdropViewSettingsDark
_UIBackdropViewSettingsColored	2040		Tint: rgba(0.0196078, 0.0196078, 0.0196078, 1)
	10091		Tint (iOS 7): rgba(0.160784, 1, 0.301961, 1)
			Tint (iOS 8): rgba(0.160784, 1, 0, 1)
			Tint (iOS 9+): rgba(0.160784, 1, 0.301961, 1)
	10092		Tint (iOS 7): rgba(1, 0.0980392, 0.0470588, 1)
			Tint (iOS 8): rgba(1, 0.098039, 0.047059, 1)
			Tint (iOS 9+): rgba(1, 0.0980392, 0.0470588, 1)
	10120		Tint (iOS 7): rgba(0.0313725, 0.262745, 0.560784, 1)
			Tint (iOS 8): rgba(0.031373, 0.262745, 0.560784, 1)
			Tint (iOS 9+): rgba(0.0313725, 0.262745, 0.560784, 1)
_UIBackdropViewSettingsUltraDark	2050, 11070
_UIBackdropViewSettingsAdaptiveLight	2060	Control Center
_UIBackdropViewSettingsSemiLight	2070
_UIBackdropViewSettingsFlatSemiLight	2071
_UIBackdropViewSettingsUltraColored	2080
_UIBackdropViewSettingsPasscodePaddle	3900		iOS 7.1+
_UIBackdropViewSettingsLightKeyboard	3901		iOS 7.1+
_UIBackdropViewSettingsLightEmojiKeyboard	3902		iOS 9.0+
_UIBackdropViewSettingsATVSemiLight	4000		iOS 9.0+
_UIBackdropViewSettingsATVMediumLight	4001		iOS 9.0+
_UIBackdropViewSettingsATVLight	4002		iOS 9.0+
_UIBackdropViewSettingsATVUltraLight	4003		iOS 9.0+
_UIBackdropViewSettingsATVMenuLight	4004		iOS 9.0+
_UIBackdropViewSettingsATVSemiDark	4005		iOS 9.0+
_UIBackdropViewSettingsATVMediumDark	4006		iOS 9.0+
_UIBackdropViewSettingsATVDark	4007		iOS 9.0+
_UIBackdropViewSettingsATVUltraDark	4008		iOS 9.0+
_UIBackdropViewSettingsATVMenuDark	4009		iOS 9.0+
_UIBackdropViewSettingsATVAdaptive	4010		iOS 9.0+
_UIBackdropViewSettingsATVAdaptiveLighten	4011		iOS 9.0+
_UIBackdropViewSettingsATVAccessoryLighten	4012		iOS 9.0+
_UIBackdropViewSettingsATVAccessoryDark	4013		iOS 9.3+

Creating Sample

// Creating blur view using settings object
_UIBackdropViewSettings *settings = [_UIBackdropViewSettings settingsForStyle:2060];

// initialization of the blur view
_UIBackdropView *blurView = [[_UIBackdropView alloc] initWithFrame:CGRectZero
                                              autosizesToFitSuperview:YES settings:settings];
// another way for initialization
_UIBackdropView *blurView = [[_UIBackdropView alloc] initWithSettings:settings];

// or without settings object implementation
_UIBackdropView *blurView = [[_UIBackdropView alloc] initWithStyle:2060];

[someView addSubview:blurView];
[blurView release];

About _UIBackdropViewSettingsColored

You can give it a tint color (in fact, it already has a default tint color, and some styles (10091, 10092, 10120) set their own). Example:

_UIBackdropViewSettings *settings = [[_UIBackdropViewSettingsColored alloc]init];
[settings setTintColor:[UIColor colorWithRed:1 green:0 blue:0 alpha:1];
//now use it somewhere

For iOS 9

_UIBackdropViewSettings *settings = [_UIBackdropViewSettings settingsForPrivateStyle:2040];
[settings setColorTint:[UIColor colorWithRed:1 green:0 blue:0 alpha:1]];
//now use it somewhere

Blurring Sample

There are only two blur qualities available.

• low
• default (Assumed to be "medium")

They correspend to the kCAFilterGaussianBlur's property "inputQuality"

[blurView setBlurRadiusSetOnce:NO];
[blurView setBlurRadius:10.0];
[blurView setBlurHardEdges:3];
[blurView setBlurWithHardEdges:YES];
[blurView setBlurQuality:@"low"];

Tinting Sample

[blurView setRequiresColorStatistics:YES];
[blurView setUsesColorTintView:YES];
UIColor *color = [UIColor cyanColor];
[blurView setColorTint:color]; // or you may use - (void)transitionToColor:(UIColor *)color;
[blurView setColorTintAlpha:0.8];
[blurView setColorTintMaskAlpha:0.7];

About graphics quality

Some styles require higher graphics quality, determined using [UIDevice _graphicsQuality] and might not be suitable for legacy devices. There are two values: 10 and 100. 100 looks better, but needs more resources. On default, iPad2,6, iPad2,7, iPad3,4, iPad3,5, iPad3,6, iPhone4,1, iPhone5,1, iPhone5,2, iPod5,1 get 10, the other devices get 100 (as of iOS 8.1). To manually set a graphic quality to a style, use

[_UIBackdropViewSettings settingsForStyle:2030 graphicsQuality:100]; // request style 2030 at highest graphics quality (100)
[_UIBackdropViewSettings settingsForStyle:2030 graphicsQuality:10]; // request style 2030 at lower graphics quality (10)

Applying blur settings/style

There are several ways for doing this by methods.

Signature	- (void)transitionIncrementallyToPrivateStyle:(NSInteger)style weighting:(CGFloat)weight;
Available in	7.0 –

Signature	- (void)transitionIncrementallyToStyle:(NSInteger)style weighting:(CGFloat)weight;
Available in	7.0 –

Signature	- (void)transitionToSettings:(_UIBackdropViewSettings *)settings;
Available in	7.0 –

Signature	- (void)transitionToPrivateStyle:(NSInteger)style;
Available in	7.0 –

Signature	- (void)transitionToStyle:(NSInteger)style;
Available in	7.0 –

transitionIncrementallyToPrivateStyle and transitionIncrementallyToStyle do the same (transitionIncrementallyToPrivateStyle calls transitionIncrementallyToStyle internally). transitionToSettings and transitionToPrivateStyle are equivalent too.

For example

_UIBackdropViewSettings *newSettings = [_UIBackdropViewSettings settingsForPrivateStyle:0];

// Whatever configuration for the settings

blurView.inputSettings = newSettings;

Getting/Parsing all _UIBackdropView objects at runtime

NSArray *blurViews = [_UIBackdropView allBackdropViews];

for (_UIBackdropView *view in blurViews) {
      NSLog(@"This _UIBackdropView style is: %d", view.style);
     // do any _UIBackdropView configuration here
}