黑魔法——“低版本中使用高版本中出现的类”之技术实现原理详解
UIVisualEffectView是在iOS8上实现毛玻璃效果的系统库，在iOS7上无法使用。XABlurEffect可以实现在iOS7上直接使用UIVisualEffectView来实现毛玻璃效果。
使用方法：直接拷贝导入
直接拷贝导入 直接将XABlurEffect拷贝到工程项目中，无需改动代码。
XAVisualEffectView.h
#import <UIKit/UIKit.h>
typedef NS_ENUM(NSInteger, XABlurEffectStyle) {
XABlurEffectStyleExtraLight,
XABlurEffectStyleLight,
XABlurEffectStyleDark,
XABlurEffectStyleExtraDark,
XABlurEffectStyleRegular,
XABlurEffectStyleProminent
};
NS_ASSUME_NONNULL_BEGIN
@interface XAVisualEffect : NSObject <NSCopying, NSSecureCoding> @end
@interface XABlurEffect : XAVisualEffect
+ (XABlurEffect *)effectWithStyle:(XABlurEffectStyle)style;
@end
@interface XAVibrancyEffect : XAVisualEffect
+ (XAVibrancyEffect *)effectForBlurEffect:(XABlurEffect *)blurEffect;
@end
@interface XAVisualEffectView : UIView <NSSecureCoding>
@property (nonatomic, strong, readonly) UIView *contentView;
@property (nonatomic, copy, nullable) XAVisualEffect *effect;
- (instancetype)initWithEffect:(nullable XAVisualEffect *)effect;
- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder;
@end
NS_ASSUME_NONNULL_END
XAVisualEffectView.m
#import "XAVisualEffectView.h"
#import <objc/runtime.h>
@implementation XAVisualEffect
#pragma mark - NSSecureCoding
+ (BOOL)supportsSecureCoding {
return YES;
}
- (void)encodeWithCoder:(NSCoder *)aCoder {
}
- (instancetype)initWithCoder:(NSCoder *)aDecoder {
if (self = [super init]) {
}
return self;
}
#pragma mark - NSCopying
- (id)copyWithZone:(NSZone *)zone {
return [[self class] allocWithZone:zone];
}
@end
@implementation XABlurEffect
+ (XABlurEffect *)effectWithStyle:(XABlurEffectStyle)style {
XABlurEffect *effect = [[XABlurEffect alloc] init];
objc_setAssociatedObject(effect, _cmd, @(style), OBJC_ASSOCIATION_RETAIN);
return effect;
}
@end
@implementation XAVibrancyEffect
+ (XAVibrancyEffect *)effectForBlurEffect:(XABlurEffect *)blurEffect {
XAVibrancyEffect *effect = [[XAVibrancyEffect alloc] init];
objc_setAssociatedObject(effect, _cmd, blurEffect, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
return effect;
}
@end
@implementation XAVisualEffectView
{
UIToolbar *_toolBar;
}
- (instancetype)initWithEffect:(XAVisualEffect *)effect {
if (self = [super init]) {
[self setEffect:effect];
}
return self;
}
// VisualEffect
- (void)setEffect:(XAVisualEffect *)effect {
if ([effect isMemberOfClass:[XABlurEffect class]]) {
[self setBlurEffect:(XABlurEffect *)effect];
} else if ([effect isMemberOfClass:[XAVibrancyEffect class]]) {
[self setVibrancyEffect:(XAVibrancyEffect *)effect];
}
}
// BlurEffect
- (void)setBlurEffect:(XABlurEffect *)effect {
XABlurEffectStyle style = [objc_getAssociatedObject(effect, @selector(effectWithStyle:)) integerValue];
switch (style) {
case XABlurEffectStyleExtraLight: {
[self effectWithBarStyle:UIBarStyleDefault];
}
break;
case XABlurEffectStyleLight: {
[self effectWithBarStyle:UIBarStyleDefault];
}
break;
case XABlurEffectStyleDark: {
[self effectWithBarStyle:UIBarStyleBlack];
}
break;
case XABlurEffectStyleRegular: {
[self effectWithBarStyle:UIBarStyleDefault];
}
break;
case XABlurEffectStyleProminent: {
[self effectWithBarStyle:UIBarStyleDefault];
}
break;
default:
break;
}
}
// VibrancyEffect
- (void)setVibrancyEffect:(XAVibrancyEffect *)effect {
XABlurEffect *blurEffect = objc_getAssociatedObject(effect, @selector(effectForBlurEffect:));
[self setBlurEffect:blurEffect];
}
#pragma mark - setEffect
- (void)effectWithBarStyle:(UIBarStyle)barStyle {
UIToolbar *toolBar = [[UIToolbar alloc] init];
toolBar.barStyle = barStyle;
[self addSubview:toolBar];
_toolBar = toolBar;
[self setLayoutConstraints];
}
#pragma mark - Layout
- (void)setLayoutConstraints {
_toolBar.translatesAutoresizingMaskIntoConstraints = NO;
NSLayoutConstraint *topConstraint = [NSLayoutConstraint constraintWithItem:_toolBar attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeTop multiplier:1.0 constant:0];
NSLayoutConstraint *leftConstraint = [NSLayoutConstraint constraintWithItem:_toolBar attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeLeft multiplier:1.0 constant:0];
NSLayoutConstraint *bottomConstraint = [NSLayoutConstraint constraintWithItem:_toolBar attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeBottom multiplier:1.0 constant:0];
NSLayoutConstraint *rightConstraint = [NSLayoutConstraint constraintWithItem:_toolBar attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeRight multiplier:1.0 constant:0];
[self addConstraints:@[topConstraint, leftConstraint, bottomConstraint, rightConstraint]];
}
#pragma mark - NSSecureCoding
+ (BOOL)supportsSecureCoding {
return YES;
}
- (instancetype)initWithCoder:(NSCoder *)aDecoder {
if (self = [super initWithCoder:aDecoder]) {
_contentView = [aDecoder decodeObjectOfClass:[UIView class] forKey:@"contentView"];
_effect = [aDecoder decodeObjectOfClass:[UIVisualEffect class] forKey:@"effect"];
}
return self;
}
- (void)encodeWithCoder:(NSCoder *)aCoder {
[aCoder encodeObject:_contentView forKey:@"contentView"];
[aCoder encodeObject:_effect forKey:@"effect"];
}
@end
#pragma mark - Runtime Injection
__asm(
".section __DATA,__objc_classrefs,regular,no_dead_strip\n"
#if TARGET_RT_64_BIT
".align 3\n"
"L_OBJC_CLASS_UIVisualEffect:\n"
".quad _OBJC_CLASS_$_UIVisualEffect\n"
".align 3\n"
"L_OBJC_CLASS_UIBlurEffect:\n"
".quad _OBJC_CLASS_$_UIBlurEffect\n"
".align 3\n"
"L_OBJC_CLASS_UIVibrancyEffect:\n"
".quad _OBJC_CLASS_$_UIVibrancyEffect\n"
".align 3\n"
"L_OBJC_CLASS_UIVisualEffectView:\n"
".quad _OBJC_CLASS_$_UIVisualEffectView\n"
#else
".align 2\n"
"_OBJC_CLASS_UIVisualEffect:\n"
".long _OBJC_CLASS_$_UIVisualEffect\n"
".align 2\n"
"_OBJC_CLASS_UIBlurEffect:\n"
".long _OBJC_CLASS_$_UIBlurEffect\n"
".align 2\n"
"_OBJC_CLASS_UIVibrancyEffect:\n"
".long _OBJC_CLASS_$_UIVibrancyEffect\n"
".align 2\n"
"_OBJC_CLASS_UIVisualEffectView:\n"
".long _OBJC_CLASS_$_UIVisualEffectView\n"
#endif
".weak_reference _OBJC_CLASS_$_UIVisualEffect\n"
".weak_reference _OBJC_CLASS_$_UIBlurEffect\n"
".weak_reference _OBJC_CLASS_$_UIVibrancyEffect\n"
".weak_reference _OBJC_CLASS_$_UIVisualEffectView\n"
);
// Constructors are called after all classes have been loaded.
__attribute__((constructor)) static void XAVisualEffectViewPatchEntry(void) {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
@autoreleasepool {
// >= iOS8.
if (objc_getClass("UIVisualEffectView")) {
return;
}
Class *visualEffect = NULL;
Class *blurEffect = NULL;
Class *vibrancyEffect = NULL;
Class *visualEffectView = NULL;
#if TARGET_CPU_ARM
__asm("movw %0, :lower16:(_OBJC_CLASS_UIVisualEffect-(LPC0+4))\n"
"movt %0, :upper16:(_OBJC_CLASS_UIVisualEffect-(LPC0+4))\n"
"LPC0: add %0, pc" : "=r"(visualEffect));
__asm("movw %0, :lower16:(_OBJC_CLASS_UIBlurEffect-(LPC1+4))\n"
"movt %0, :upper16:(_OBJC_CLASS_UIBlurEffect-(LPC1+4))\n"
"LPC1: add %0, pc" : "=r"(blurEffect));
__asm("movw %0, :lower16:(_OBJC_CLASS_UIVibrancyEffect-(LPC2+4))\n"
"movt %0, :upper16:(_OBJC_CLASS_UIVibrancyEffect-(LPC2+4))\n"
"LPC2: add %0, pc" : "=r"(vibrancyEffect));
__asm("movw %0, :lower16:(_OBJC_CLASS_UIVisualEffectView-(LPC3+4))\n"
"movt %0, :upper16:(_OBJC_CLASS_UIVisualEffectView-(LPC3+4))\n"
"LPC3: add %0, pc" : "=r"(visualEffectView));
#elif TARGET_CPU_ARM64
__asm("adrp %0, L_OBJC_CLASS_UIVisualEffect@PAGE\n"
"add %0, %0, L_OBJC_CLASS_UIVisualEffect@PAGEOFF" : "=r"(visualEffect));
__asm("adrp %0, L_OBJC_CLASS_UIBlurEffect@PAGE\n"
"add %0, %0, L_OBJC_CLASS_UIBlurEffect@PAGEOFF" : "=r"(blurEffect));
__asm("adrp %0, L_OBJC_CLASS_UIVibrancyEffect@PAGE\n"
"add %0, %0, L_OBJC_CLASS_UIVibrancyEffect@PAGEOFF" : "=r"(vibrancyEffect));
__asm("adrp %0, L_OBJC_CLASS_UIVisualEffectView@PAGE\n"
"add %0, %0, L_OBJC_CLASS_UIVisualEffectView@PAGEOFF" : "=r"(visualEffectView));
#elif TARGET_CPU_X86_64
__asm("leaq L_OBJC_CLASS_UIVisualEffect(%%rip), %0" : "=r"(visualEffect));
__asm("leaq L_OBJC_CLASS_UIBlurEffect(%%rip), %0" : "=r"(blurEffect));
__asm("leaq L_OBJC_CLASS_UIVibrancyEffect(%%rip), %0" : "=r"(vibrancyEffect));
__asm("leaq L_OBJC_CLASS_UIVisualEffectView(%%rip), %0" : "=r"(visualEffectView));
#elif TARGET_CPU_X86
void *pc1 = NULL;
__asm("calll L0\n"
"L0: popl %0\n"
"leal _OBJC_CLASS_UIVisualEffect-L0(%0), %1" : "=r"(pc1), "=r"(visualEffect));
void *pc2 = NULL;
__asm("calll L0\n"
"L0: popl %0\n"
"leal _OBJC_CLASS_UIBlurEffect-L0(%0), %1" : "=r"(pc2), "=r"(blurEffect));
void *pc3 = NULL;
__asm("calll L0\n"
"L0: popl %0\n"
"leal _OBJC_CLASS_UIVibrancyEffect-L0(%0), %1" : "=r"(pc3), "=r"(vibrancyEffect));
void *pc4 = NULL;
__asm("calll L0\n"
"L0: popl %0\n"
"leal _OBJC_CLASS_UIVisualEffectView-L0(%0), %1" : "=r"(pc4), "=r"(visualEffectView));
#else
#error Unsupported CPU
#endif
if (visualEffect && !*visualEffect) {
Class class = objc_allocateClassPair([XAVisualEffect class], "UIVisualEffect", 0);
if (class) {
objc_registerClassPair(class);
*visualEffect = class;
}
}
if (blurEffect && !*blurEffect) {
Class class = objc_allocateClassPair([XABlurEffect class], "UIBlurEffect", 0);
if (class) {
objc_registerClassPair(class);
*blurEffect = class;
}
}
if (vibrancyEffect && !*vibrancyEffect) {
Class class = objc_allocateClassPair([XAVibrancyEffect class], "UIVibrancyEffect", 0);
if (class) {
objc_registerClassPair(class);
*vibrancyEffect = class;
}
}
if (visualEffectView && !*visualEffectView) {
Class class = objc_allocateClassPair([XAVisualEffectView class], "UIVisualEffectView", 0);
if (class) {
objc_registerClassPair(class);
*visualEffectView = class;
}
}
}
});
}
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