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 UIKit

struct ImagePicker: UIViewControllerRepresentable {
    @Binding var selectedImage: UIImage?
    @Environment(\.presentationMode) var presentationMode
    var sourceType: UIImagePickerController.SourceType = .camera

    class Coordinator: NSObject, UINavigationControllerDelegate, UIImagePickerControllerDelegate {
        let parent: ImagePicker

        init(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.coordinator
        picker.sourceType = sourceType
        return 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 SwiftUI

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()
    }
}

解释

1. 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。

2. 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

1. 打开你的 Xcode 项目。

2. 在项目导航中，找到并点击你的 Info.plist 文件。

3. 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>NSCameraUsageDescriptionkey>
<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：

1. 打开 Info.plist 文件。
2. 点击右键选择 “Add Row”。
3. 在新行的键列中输入 NSCameraUsageDescription。
4. 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 UIKit

struct ImagePicker: UIViewControllerRepresentable {
    @Binding var selectedImage: UIImage?
    @Environment(\.presentationMode) var presentationMode
    var sourceType: UIImagePickerController.SourceType = .camera

    class Coordinator: NSObject, UINavigationControllerDelegate, UIImagePickerControllerDelegate {
        let parent: ImagePicker

        init(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.coordinator
        picker.sourceType = sourceType
        return 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()
    }
}

通过添加 NSCameraUsageDescription，应用在请求访问相机时会向用户显示一条提示，解释为什么需要访问相机，从而避免因未声明权限而导致的崩溃。