SwiftUI调用相机拍照

在 SwiftUI 中实现拍照功能，需要结合 UIViewControllerRepresentable 和 UIImagePickerController 来实现相机功能。下面是一个详细的示例，展示如何使用 SwiftUI 来实现拍照功能：

1. 创建一个 `ImagePicker` 组件

首先，创建一个 UIViewControllerRepresentable 结构，用于包装 UIImagePickerController。

import SwiftUI
import UIKitstruct ImagePicker: UIViewControllerRepresentable {@Binding var selectedImage: UIImage?@Environment(\.presentationMode) var presentationModevar sourceType: UIImagePickerController.SourceType = .cameraclass Coordinator: NSObject, UINavigationControllerDelegate, UIImagePickerControllerDelegate {let parent: ImagePickerinit(parent: ImagePicker) {self.parent = parent}func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {if let image = info[.originalImage] as? UIImage {parent.selectedImage = image}parent.presentationMode.wrappedValue.dismiss()}func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {parent.presentationMode.wrappedValue.dismiss()}}func makeCoordinator() -> Coordinator {Coordinator(parent: self)}func makeUIViewController(context: Context) -> UIImagePickerController {let picker = UIImagePickerController()picker.delegate = context.coordinatorpicker.sourceType = sourceTypereturn picker}func updateUIViewController(_ uiViewController: UIImagePickerController, context: Context) {}
}

2. 使用 `ImagePicker` 组件

接下来，在你的主视图中使用 ImagePicker 组件来实现拍照功能。

import SwiftUIstruct ContentView: View {@State private var isImagePickerPresented = false@State private var selectedImage: UIImage?var body: some View {VStack {if let selectedImage = selectedImage {Image(uiImage: selectedImage).resizable().scaledToFit().frame(width: 300, height: 300)} else {Text("No Image Selected").frame(width: 300, height: 300).background(Color.gray)}Button(action: {isImagePickerPresented = true}) {Text("Take Photo").padding().background(Color.blue).foregroundColor(.white).cornerRadius(10)}.padding()}.sheet(isPresented: $isImagePickerPresented) {ImagePicker(selectedImage: $selectedImage)}}
}struct ContentView_Previews: PreviewProvider {static var previews: some View {ContentView()}
}

解释

ImagePicker 组件：
- UIViewControllerRepresentable 协议用来将 UIImagePickerController 引入 SwiftUI。
- makeUIViewController 和 updateUIViewController 方法创建和更新 UIImagePickerController。
- Coordinator 类作为 UIImagePickerController 的代理，处理图片选择和取消操作。
ContentView：
- 使用 @State 属性包装变量 isImagePickerPresented 来控制 ImagePicker 的显示。
- 使用 @State 属性包装变量 selectedImage 来存储选取的图片。
- 当点击 “Take Photo” 按钮时，显示 ImagePicker。
- sheet 修饰符用于在 isImagePickerPresented 为 true 时呈现 ImagePicker。

通过这种方式，你可以在 SwiftUI 应用中实现拍照功能。请注意，拍照功能只能在真实设备上使用，因为模拟器不支持摄像头。

在 iOS 应用中访问相机需要在 Info.plist 文件中添加 NSCameraUsageDescription 键，以告知用户为什么需要访问相机。否则，应用在尝试访问相机时会崩溃。

添加 `NSCameraUsageDescription` 到 `Info.plist`

打开你的 Xcode 项目。
在项目导航中，找到并点击你的 Info.plist 文件。
在 Info.plist 中，添加一个新的键值对：
- 键：NSCameraUsageDescription
- 值：解释你的应用需要使用相机的原因，比如 “This app requires access to the camera to take photos.”

示例：

<key>NSCameraUsageDescription</key>
<string>This app requires access to the camera to take photos.</string>

如果你使用 Xcode 的图形化界面，可以按以下步骤操作：

打开 Info.plist 文件。
点击右键选择 “Add Row”。
在新行的键列中输入 NSCameraUsageDescription。
在值列中输入对用户的说明，比如 “This app requires access to the camera to take photos.”

更新后的示例代码

完成上述步骤后，你可以重新运行之前的代码：

import SwiftUI
import UIKitstruct ImagePicker: UIViewControllerRepresentable {@Binding var selectedImage: UIImage?@Environment(\.presentationMode) var presentationModevar sourceType: UIImagePickerController.SourceType = .cameraclass Coordinator: NSObject, UINavigationControllerDelegate, UIImagePickerControllerDelegate {let parent: ImagePickerinit(parent: ImagePicker) {self.parent = parent}func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {if let image = info[.originalImage] as? UIImage {parent.selectedImage = image}parent.presentationMode.wrappedValue.dismiss()}func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {parent.presentationMode.wrappedValue.dismiss()}}func makeCoordinator() -> Coordinator {Coordinator(parent: self)}func makeUIViewController(context: Context) -> UIImagePickerController {let picker = UIImagePickerController()picker.delegate = context.coordinatorpicker.sourceType = sourceTypereturn picker}func updateUIViewController(_ uiViewController: UIImagePickerController, context: Context) {}
}struct ContentView: View {@State private var isImagePickerPresented = false@State private var selectedImage: UIImage?var body: some View {VStack {if let selectedImage = selectedImage {Image(uiImage: selectedImage).resizable().scaledToFit().frame(width: 300, height: 300)} else {Text("No Image Selected").frame(width: 300, height: 300).background(Color.gray)}Button(action: {isImagePickerPresented = true}) {Text("Take Photo").padding().background(Color.blue).foregroundColor(.white).cornerRadius(10)}.padding()}.sheet(isPresented: $isImagePickerPresented) {ImagePicker(selectedImage: $selectedImage)}}
}struct ContentView_Previews: PreviewProvider {static var previews: some View {ContentView()}
}