考虑私有C函数_UICreateScreenUIImage
,该函数返回UIImage
当前设备屏幕的快照:
OBJC_EXTERN UIImage *_UICreateScreenUIImage(void) NS_RETURNS_RETAINED;
我可以将其放在桥接标头中,然后在Swift中访问它,如下所示:
MyApp-Bridging-Header.h
@import UIKit;
UIImage *_UICreateScreenUIImage(void) NS_RETURNS_RETAINED;
MyClass.swift
let image = _UICreateScreenUIImage()
print(image) // <UIImage: 0x7fc4ba6081c0>, {375, 667}
有没有一种方法可以_UICreateScreenUIImage
在不使用桥接头的情况下在纯Swift中访问?
最初的想法是在上创建扩展UIImage
,但是该扩展希望我在扩展中声明函数的主体:
extension UIImage {
public func _UICreateScreenUIImage(_: Void) -> UIImage // "Expected '{' in body of function declaration"
}
无论如何,这种实现都是有缺陷的,因为_UICreateScreenUIImage
上没有方法UIImage
。
在纯Swift中是否可以公开和访问此方法?
人们似乎将我的问题与“如何拍摄屏幕截图”混淆了。那不是我要的 我在问如何访问UIImage *_UICreateScreenUIImage(void);
Swift中的方法。它可以是任何私有方法,例如+(UIImage *)_deviceSpecificImageNamed:(NSString *)name inBundle:(NSBundle *)bundle;
或+(UIImage *)_pu_PhotosUIImageNamed:(NSString *)name;
。
它比您预期的容易得多:
@asmname("_UICreateScreenUIImage")
func _UICreateScreenUIImage() -> UIImage
// That's it – go ahead and call it:
_UICreateScreenUIImage()
碰巧的是,@asmname
实际上只是在2.3版本中将更改为@_silgen_name
,因此准备相应地进行调整:
@_silgen_name("_UICreateScreenUIImage")
func _UICreateScreenUIImage() -> UIImage
据我所知,@_silgen_name
没有提供Objective-C方法的解析。为此,有更强大的Objective-C运行时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)
就处理而言NS_RETURNS_RETAINED
,这不会为您生成。相反,您可以使用的返回类型Unmanaged
,并将其包装在函数中以方便使用:
@_silgen_name("_UICreateScreenUIImage")
func _UICreateScreenUIImage() -> Unmanaged<UIImage>
func UICreateScreenUIImage() -> UIImage {
return _UICreateScreenUIImage().takeRetainedValue()
}
本文收集自互联网,转载请注明来源。
如有侵权,请联系 [email protected] 删除。
我来说两句