UIBackdropView

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_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) .[1]

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 calls settingsForStyle internally

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

_UIBackdropViewSettings *settings = [_UIBackdropViewSettings settingsForStyle:2030 graphicsQuality:100] ; // specify graphics quality, usually 10 (minimum quality) or 100 (maximum quality)

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 8.3+
_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];

Overriding _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 = [_UIBackdropViewSettings settingsForStyle:2040];
settings.colorTint = [UIColor colorWithRed:1.0 green:0.0 blue:0.0 alpha:1.0];

Blurring Sample

There are two blur qualities available.

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

They correspend to the kCAFilterGaussianBlur's property "inputQuality"

blurView.blurRadiusSetOnce = NO;
blurView.blurRadius = 10.0;
blurView.blurHardEdges = 3;
blurView.blurWithHardEdges = YES;
blurView.blurQuality = @"low";

Tinting Sample

blurView.requiresColorStatistics = YES;
blurView.usesColorTintView = YES;
UIColor *color = [UIColor cyanColor];
blurView.colorTint = color; // or you may use - (void)transitionToColor:(UIColor *)color;
blurView.colorTintAlpha = 0.8;
blurView.colorTintMaskAlpha = 0.7;

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 <_UIBackdropView *> *blurViews = [_UIBackdropView allBackdropViews];

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

References

  1. https://twitter.com/conradev/status/380905728393117696