问题描述
考虑私有 C 函数 _UICreateScreenUIImage，它返回当前设备屏幕的 UIImage 快照:
Consider the private C function _UICreateScreenUIImage, which returns a UIImage snapshot of the current device screen:
OBJC_EXTERN UIImage *_UICreateScreenUIImage(void) NS_RETURNS_RETAINED;
我可以把它放在一个桥接头中并像这样在 Swift 中访问它:
I can put this in a bridging header and access it in Swift like so:
MyApp-Bridging-Header.h
MyApp-Bridging-Header.h
@import UIKit;
UIImage *_UICreateScreenUIImage(void) NS_RETURNS_RETAINED;
MyClass.swift
MyClass.swift
let image = _UICreateScreenUIImage()
print(image) // <UIImage: 0x7fc4ba6081c0>, {375, 667}
有没有一种方法可以在不使用桥接头的情况下在纯 Swift 中访问 _UICreateScreenUIImage?
Is there a way I can access _UICreateScreenUIImage in pure Swift without using a bridging header?
最初的想法是在 UIImage 上创建一个扩展，但扩展期望我在扩展中声明函数的主体:
An initial thought was to create an extension on UIImage, but the extension is expecting me to declare the body of the function in the extension:
extension UIImage {
public func _UICreateScreenUIImage(_: Void) -> UIImage // "Expected '{' in body of function declaration"
}
无论如何，这个实现是有缺陷的，因为 _UICreateScreenUIImage 不是 UIImage 上的方法.
This implementation is flawed anyways, as _UICreateScreenUIImage isn't a method on UIImage.
是否可以在纯 Swift 中公开和访问此方法?
Is exposing and accessing this method possible in pure Swift?
人们似乎将我的问题与我如何截屏?"混淆了.这不是我要问的.我在问如何在 Swift 中访问像 UIImage *_UICreateScreenUIImage(void); 这样的方法.它可以是任何私有方法，例如 +(UIImage *)_deviceSpecificImageNamed:(NSString *)name inBundle:(NSBundle *)bundle; 或 +(UIImage *)_pu_PhotosUIImageNamed:(NSString *)名称;.
People seem to be confusing my question with "How do I take a screenshot?" That's not what I'm asking. I'm asking how do I access methods like UIImage *_UICreateScreenUIImage(void); in Swift. It could be any private method, such as +(UIImage *)_deviceSpecificImageNamed:(NSString *)name inBundle:(NSBundle *)bundle; or +(UIImage *)_pu_PhotosUIImageNamed:(NSString *)name;
.
推荐答案
这比你想象的要容易得多:
It's a lot easier than you would expect:
@asmname("_UICreateScreenUIImage")
func _UICreateScreenUIImage() -> UIImage
// That's it – go ahead and call it:
_UICreateScreenUIImage()
事实上，@asmname 实际上刚刚在 2.3 版本中被更改为 @_silgen_name，因此请做好相应调整的准备:
As it happens, @asmname has actually just been changed in the 2.3 builds to @_silgen_name, so be ready to adjust accordingly:
@_silgen_name("_UICreateScreenUIImage")
func _UICreateScreenUIImage() -> UIImage
据我所知，@_silgen_name 不提供 Objective-C 方法的解析.为此，还有更强大的 Objective-C 运行时 API:
To my knowledge, @_silgen_name does not provide resolution of Objective-C methods. For this, there is the evenmore powerful Objective-C runtime API:
let invokeImageNamed: (String, NSTimeInterval) -> UIImage? = {
// The Objective-C selector for the method.
let selector: Selector = "animatedImageNamed:duration:"
guard case let method = class_getClassMethod(UIImage.self, selector)
where method != nil else { fatalError("Failed to look up (selector)") }
// Recreation of the method's implementation function.
typealias Prototype = @convention(c) (AnyClass, Selector, NSString, NSTimeInterval) -> UIImage?
let opaqueIMP = method_getImplementation(method)
let function = unsafeBitCast(opaqueIMP, Prototype.self)
// Capture the implemenation data in a closure that can be invoked at any time.
return { name, interval in function(UIImage.self, selector, name, interval) }
}()
extension UIImage {
// Convenience method for calling the closure from the class.
class func imageNamed(name: String, interval: NSTimeInterval) -> UIImage? {
return invokeImageNamed(name, interval)
}
}
UIImage.imageNamed("test", interval: 0)
就处理 NS_RETURNS_RETAINED 而言，这不会为您生成.相反，您可以使用 Unmanaged 的返回类型，并将其包装在一个函数中以方便您使用:
As far as handling NS_RETURNS_RETAINED, this won't be generated for you. Instead, you can use a return type of Unmanaged, and wrap that in a function to your convenience:
@_silgen_name("_UICreateScreenUIImage")
func _UICreateScreenUIImage() -> Unmanaged<UIImage>
func UICreateScreenUIImage() -> UIImage {
return _UICreateScreenUIImage().takeRetainedValue()
}
这篇关于在不使用桥接头的情况下访问私有 UIKit 函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！