1.需求背景
iOS15上有一个非常好用的scan text (也可以叫live text)功能,如果能加上,用于扫描文本OCR(光学字符识别Optical Character Recognition),直接插入到textField里还是很方便的。
2.为什么目前不支持?
因为我用的自定义textField,没有针对scan text进行适配。我查阅了很多关于iOS15 OCR的资料。但是给textField长按菜单,加上scan text的内容没有找到,大体都说自定义长按菜单需要在
override func canPerformAction(_ action: Selector, withSender sender: Any?) -> Bool
这个函数里去添加对应的action,然后
override func target(forAction action: Selector, withSender sender: Any?) -> Any?
这个函数里也要去做对应方法的实现,才能有对应的功能。
那么scan text对应的是哪个selector方法呢?
UIResponderStandardEditActions这个类里,并没有看到和OCR或者scan text相关的方法。然后我翻阅官方文档,找到了个很类似OCR的API
extension UIResponder {
@available(iOS 15.0, *)
open func captureTextFromCamera(_ sender: Any?)
}
试了下,果然就是这个玩意儿
所以如果你要你的自定义textField或者textview拥有scan text OCR的能力,那么应该如下实现。
3.实现
override func canPerformAction(_ action: Selector, withSender sender: Any?) -> Bool {
if #available(iOS 15.0, *) {
if action == #selector(UIResponderStandardEditActions.paste(_:)) ||
action == #selector(UIResponder.captureTextFromCamera(_:)){
return true
}
} else {
return super.canPerformAction(action, withSender: sender)
}
return super.canPerformAction(action, withSender: sender)
}
override func target(forAction action: Selector, withSender sender: Any?) -> Any? {
if #available(iOS 15.0, *) {
if action == #selector(UIResponderStandardEditActions.paste(_:)) ||
action == #selector(UIResponderStandardEditActions.select(_:)) ||
action == #selector(UIResponderStandardEditActions.selectAll(_:)) ||
action == #selector(UIResponder.captureTextFromCamera(_:)) {
return super.target(forAction: action, withSender: sender)
}
} else {
// Fallback on earlier versions
if action == #selector(UIResponderStandardEditActions.paste(_:)) ||
action == #selector(UIResponderStandardEditActions.select(_:)) ||
action == #selector(UIResponderStandardEditActions.selectAll(_:))
{
return super.target(forAction: action, withSender: sender)
}
}
return nil
}
4.限制
4.1 版本和设备限制
只支持iOS15+,且iPhone Xs及以后的设备。如下是官方说明
For this property to be
true
, the device must have the A12 Bionic chip or later.
所以我们需要判断iOS 系统版本是iOS15,且支持OCR。
4.2 如何判断是否支持live text
一种是ImageAnalyzer.isSupported,如果是iOS 16就用这个判断,需要引入import VisionKit 这个visionKit。
另一种是利用实例化方法, canPerformAction(_:withSender:)
,官方的说法如下:
To determine whether the data scanner runs on the user’s device, pass
captureTextFromCamera(_:)
to thecanPerformAction(_:withSender:)
method.
例如
if UITextField().canPerformAction(#selector(UIResponder.captureTextFromCamera(_:)), withSender: self) { ... }
我之前以为直接用button的实例,来判断就可以了,居然不生效。一直返回false,我还不清楚说明原因。但是用上面这种,直接声明一个UITextField的实例来判断,就正常了,真的神奇。如果是在UIController里面,用下面的代码也可以:
if #available(iOS 15.0, *), self.canPerformAction(#selector(UIResponder.captureTextFromCamera(_:)), withSender: self) {
print("support live text")
button.addTarget(self, action: #selector(UIResponder.captureTextFromCamera(_:)), for: .touchUpInside)
} else {
print("this device is not support live text")
}
所以这个条件,也是有点迷。
5.扩展运用 -- 如何自定义一个按钮,调用scan text识别文字功能?
自定义的按钮,和textField最大的不同,就是textField默认遵循了UIKeyInput
or UITextInput
这两个中的某个协议,所以我们自定定义的按钮,那么我们要自己去遵循至少,这两个之一的协议,然后实现对应的代理方法,否则会崩溃。官方说明如下:
To receive callbacks from the data scanner, the responder should conform to either the
UIKeyInput
orUITextInput
protocol. If it conforms toUIKeyInput
, the scanner calls theinsertText:
protocol method. If it conforms toUITextInput
, the scanner calls thesetMarkedText(_:selectedRange:)
andunmarkText()
protocol methods.
class ViewController: UIViewController, UIKeyInput {
var hasText: Bool = false
override func viewDidLoad() {
super.viewDidLoad()
let button = UIButton.init(frame: CGRect(x: 100, y: 200, width: 100, height: 100))
if #available(iOS 15.0, *), self.canPerformAction(#selector(UIResponder.captureTextFromCamera(_:)), withSender: self) {
print("support live text")
button.addTarget(self, action: #selector(UIResponder.captureTextFromCamera(_:)), for: .touchUpInside)
} else {
print("this device is not support live text")
}
button.backgroundColor = .red
view.addSubview(button)
}
func deleteBackward() {
}
func insertText(_ text: String) {
//ORC scan text的 insert Text 按钮回调
print("OCR 扫描到的文字是: \(text)")
labelTest.text = text
}
}
参考文献:
https://developer.apple.com/documentation/uikit/uiresponder/3778577-capturetextfromcamera?changes=_5
https://developer.apple.com/documentation/visionkit/imageanalyzer/3974561-issupported
https://stackoverflow.com/questions/69702884/how-to-know-a-device-is-available-to-use-capturetextfromcamera-api/73995804#73995804