使用Xamarin.Forms访问摄像头-Java 学习之路

是否有人能够提供一个关于如何使用Xamarin.Forms 1.3.x访问相机的简短，自包含的示例？只需调用本机相机应用程序并检索生成的图片就会很棒 . 在Xamarin.Forms页面上显示实时视图真棒！

我已经尝试过使用Xamarin.Mobile和Xamarin.Forms.Labs，但我无法在这两个平台上使用任何解决方案（现在专注于Android和iOS） . 网上发现的大多数代码片段（包括stackoverflow）都是不完整的，例如没有显示IMediaPicker对象的实现或者锚定拍照方法的位置 .

4 回答

我终于为iOS和Android创建了最低限度的解决方案 .

共享项目

首先，让我们看一下共享代码 . 为了在共享 App 类和特定于平台的代码之间轻松交互，我们在 public static App 中存储了静态 Instance ：

public static App Instance;

此外，我们将显示 Image ，稍后将填充内容 . 所以我们创建一个成员：

readonly Image image = new Image();

在 App 构造函数中，我们存储 Instance 并创建页面内容，这是一个简单的 button 和前面提到的 image ：

public App()
{
   Instance = this;

   var button = new Button {
       Text = "Snap!",
       Command = new Command(o => ShouldTakePicture()),
   };

   MainPage = new ContentPage {
       Content = new StackLayout {
       VerticalOptions = LayoutOptions.Center,
           Children = {
                    button,
                    image,
           },
       },
   };
}

按钮的单击处理程序调用事件 ShouldTakePicture . 它是一个公共成员，特定于平台的代码部分稍后将分配给它 .

public event Action ShouldTakePicture = () => {};

最后，我们提供了一种显示捕获图像的公共方法：

public void ShowImage(string filepath)
{
    image.Source = ImageSource.FromFile(filepath);
}

Android项目

在Android上我们修改 MainActivity . 首先，我们为捕获的图像文件定义路径：

static readonly File file = new File(Environment.GetExternalStoragePublicDirectory(Environment.DirectoryPictures), "tmp.jpg");

在 OnCreate 的末尾，我们可以使用创建的 App 的静态 Instance 并分配一个匿名事件处理程序，它将启动一个新的 Intent 来捕获图像：

App.Instance.ShouldTakePicture += () => {
   var intent = new Intent(MediaStore.ActionImageCapture);
   intent.PutExtra(MediaStore.ExtraOutput, Uri.FromFile(file));
   StartActivityForResult(intent, 0);
};

最后但同样重要的是，我们的活动必须对生成的图像做出反应 . 它只是将其文件路径推送到共享 ShowImage 方法 .

protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
   base.OnActivityResult(requestCode, resultCode, data);
   App.Instance.ShowImage(file.Path);
}

就是这样！只是不要忘记在“AndroidManifest.xml”中设置“Camera”和“WriteExternalStorage”权限！

iOS项目

对于iOS实现，我们创建了一个自定义渲染器 . 因此，我们添加一个新文件“CustomContentPageRenderer”并在using语句后面添加相应的程序集属性：

[assembly:ExportRenderer(typeof(ContentPage), typeof(CustomContentPageRenderer))]

CustomContentPageRenderer 继承自 PageRenderer ：

public class CustomContentPageRenderer: PageRenderer
{
    ...
}

我们覆盖 ViewDidAppear 方法并添加以下部分 .

创建一个新的图像选择器控制器参考相机：

var imagePicker = new UIImagePickerController { SourceType = UIImagePickerControllerSourceType.Camera };

一旦 ShouldTakePicture 事件被引发，就会出现图像选择器控制器：

App.Instance.ShouldTakePicture += () => PresentViewController(imagePicker, true, null);

拍摄照片后，将其保存到 MyDocuments 文件夹并调用共享 ShowImage 方法：

imagePicker.FinishedPickingMedia += (sender, e) => {
            var filepath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "tmp.png");
var image = (UIImage)e.Info.ObjectForKey(new NSString("UIImagePickerControllerOriginalImage"));
            InvokeOnMainThread(() => {
                image.AsPNG().Save(filepath, false);
                App.Instance.ShowImage(filepath);
            });
            DismissViewController(true, null);
        };

最后，我们需要处理取消图像处理过程：

imagePicker.Canceled += (sender, e) => DismissViewController(true, null);

回复于 2024-05-06T23:48:01+08:00

试试James Montemagno的MediaPlugin .

只需输入并运行 Install-Package Xam.Plugin.Media -Version 2.6.2 即可使用_2464215安装插件，或者转到Manage NuGet Packages...并输入 Xam.Plugin.Media 并安装插件 . （必须在所有项目中安装插件 - 包括客户端项目）

将提示readme.txt并按照其中的说明进行操作 . 之后，add the following codes（根据需要）到您的共享项目 . 上述readme.txt文件中要遵循的说明如下 .

适用于Android项目

在您的BaseActivity或MainActivity（对于Xamarin.Forms）中添加以下代码：

public override void OnRequestPermissionsResult(int requestCode, string[] permissions, Permission[] grantResults)
{
    PermissionsImplementation.Current.OnRequestPermissionsResult(requestCode, permissions, grantResults);
}

您还必须添加一些其他配置文件以遵守新的严格模式：

将以下内容添加到< application >标记内的AndroidManifest.xml中：

<provider android:name="android.support.v4.content.FileProvider" 
          android:authorities="YOUR_APP_PACKAGE_NAME.fileprovider" 
          android:exported="false" 
          android:grantUriPermissions="true">
    <meta-data android:name="android.support.FILE_PROVIDER_PATHS" 
               android:resource="@xml/file_paths"></meta-data>
</provider>

YOUR_APP_PACKAGE_NAME必须设置为您的应用包名称！

在Resources文件夹中添加一个名为xml的新文件夹，并添加一个名为 file_paths.xml 的新XML文件

添加以下代码：

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="my_images" path="Android/data/YOUR_APP_PACKAGE_NAME/files/Pictures" />
    <external-path name="my_movies" path="Android/data/YOUR_APP_PACKAGE_NAME/files/Movies" />
</paths>

YOUR_APP_PACKAGE_NAME必须设置为您的应用包名称！

适用于iOS项目

您的应用需要在Info.plist中包含 NSCameraUsageDescription 和 NSPhotoLibraryUsageDescription 的密钥才能访问设备的相机和照片/视频库 . 如果您正在使用库的视频功能，则还必须添加 NSMicrophoneUsageDescription . 当提示用户提供访问这些设备功能的权限时，将为用户显示为每个密钥提供的字符串 .

如：

<key>NSCameraUsageDescription</key>
<string>This app needs access to the camera to take photos.</string>
<key>NSPhotoLibraryUsageDescription</key>
<string>This app needs access to photos.</string>
<key>NSMicrophoneUsageDescription</key>
<string>This app needs access to microphone.</string>

对于共享项目

要简单地打开相机，保存照片并显示带有文件路径的警报，请在共享项目中输入以下内容 .

if (!CrossMedia.Current.IsCameraAvailable || !CrossMedia.Current.IsTakePhotoSupported)
{
    await DisplayAlert("No Camera", ":( No camera avaialble.", "OK");
    return;
}

var file = await CrossMedia.Current.TakePhotoAsync(new Plugin.Media.Abstractions.StoreCameraMediaOptions
{
    PhotoSize = Plugin.Media.Abstractions.PhotoSize.Medium,
    Directory = "Sample",
    Name = "test.jpg"
});

if (file == null)
    return;

await DisplayAlert("File Location", file.Path, "OK");

回复于 2024-05-06T23:48:01+08:00

这就是我需要在我的应用程序中运行异步摄像头捕获：

在iOS中：

public async Task<string> TakePicture()
{
    if (await AuthorizeCameraUse())
    {
        var imagePicker = new UIImagePickerController { SourceType = UIImagePickerControllerSourceType.Camera };

        TaskCompletionSource<string> FinishedCamera = new TaskCompletionSource<string>();

        // When user has taken picture
        imagePicker.FinishedPickingMedia += (sender, e) => {
            // Save the file
            var filepath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "tmp.png");
            var image = (UIImage)e.Info.ObjectForKey(new NSString("UIImagePickerControllerOriginalImage"));
            image.AsPNG().Save(filepath, false);

            // Close the window
            UIApplication.SharedApplication.KeyWindow.RootViewController.DismissViewController(true, null);

            // Stop awaiting
            FinishedCamera.SetResult(filepath);
        };

        // When user clicks cancel 
        imagePicker.Canceled += (sender, e) =>
        {
            UIApplication.SharedApplication.KeyWindow.RootViewController.DismissViewController(true, null);
            FinishedCamera.TrySetCanceled();
        };

        // Show the camera-capture window
        UIApplication.SharedApplication.KeyWindow.RootViewController.PresentViewController(imagePicker, true, null);

        // Now await for the task to complete or be cancelled
        try
        {
            // Return the path we've saved the image in
            return await FinishedCamera.Task;
        }
        catch (TaskCanceledException)
        {
            // handle if the user clicks cancel
        }
    }

    return null;
}

如果您需要授权例程，请确保您也在 info.plist 中填写相机使用，这里是获得授权的功能：

public static async Task<bool> AuthorizeCameraUse()
{
    var authorizationStatus = AVCaptureDevice.GetAuthorizationStatus(AVMediaType.Video);

    if (authorizationStatus != AVAuthorizationStatus.Authorized)
    {
        return await AVCaptureDevice.RequestAccessForMediaTypeAsync(AVMediaType.Video);
    }
    else
        return true;
}

在Android中：

private TaskCompletionSource<bool> _tcs_NativeCamera;

public async Task<string> TakePicture()
{
    _tcs_NativeCamera = new TaskCompletionSource<bool>();

    // Launch the camera activity
    var intent = new Intent(MediaStore.ActionImageCapture);
    intent.PutExtra(MediaStore.ExtraOutput, Android.Net.Uri.FromFile(cameraCaptureFilePath));

    NextCaptureType = stype;

    StartActivityForResult(intent, SCAN_NATIVE_CAMERA_CAPTURE_ASYNC);

    // Wait here for the activity return (through OnActivityResult)
    var Result = await _tcs_NativeCamera.Task;

    // Return the camera capture file path
    return Result != Result.Canceled ? cameraCaptureFilePath : null;
}

protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
    base.OnActivityResult(requestCode, resultCode, data);

    switch (requestCode)
    {
        case SCAN_NATIVE_CAMERA_CAPTURE_ASYNC:
            _tcs_NativeCamera.SetResult(resultCode);
            break;
    }
}

回复于 2024-05-06T23:48:01+08:00

以下是如何在Xamarin Forms跨Xamarin iOS上完成的 .

这是一个很好的基础，但它需要首先渲染一个Page，你可以在其中为它指定UIApplication，以便为Camera / Photo Picker控制器提供UIView .

https://stackoverflow.com/a/28299259/1941942

便携式项目

public interface ICameraProvider
{
    Task<CameraResult> TakePhotoAsync();
    Task<CameraResult> PickPhotoAsync();
}

private Command AttachImage 
{
    var camera = await DependencyService.Get<ICameraProvider>().TakePhotoAsync();
}

iOS项目

[assembly: Xamarin.Forms.Dependency(typeof(CameraProvider))]

public class CameraProvider : ICameraProvider
{
    private UIImagePickerController _imagePicker;
    private CameraResult _result;
    private static TaskCompletionSource<CameraResult> _tcs;

    public async Task<CameraResult> TakePhotoAsync()
    {
        _tcs = new TaskCompletionSource<CameraResult>();

        _imagePicker = new UIImagePickerController { SourceType = UIImagePickerControllerSourceType.Camera };

        _imagePicker.FinishedPickingMedia += (sender, e) =>
        {
            _result = new CameraResult();
            var filepath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "tmp.png");
            var image = (UIImage)e.Info.ObjectForKey(new NSString("UIImagePickerControllerOriginalImage"));

            _result.ImageSource = ImageSource.FromStream(() => new MemoryStream(image.AsPNG().ToArray())); 
            _result.ImageBytes = image.AsPNG().ToArray();
            _result.FilePath = filepath;

            _tcs.TrySetResult(_result);
            _imagePicker.DismissViewController(true, null);
        };

        _imagePicker.Canceled += (sender, e) =>
        {
            UIApplication.SharedApplication.KeyWindow.RootViewController.DismissViewController(true, null);
        };

        await UIApplication.SharedApplication.KeyWindow.RootViewController.PresentViewControllerAsync(_imagePicker, true);

        return await _tcs.Task; 
    }

    public async Task<CameraResult> PickPhotoAsync()
    {
        _tcs = new TaskCompletionSource<CameraResult>();

        _imagePicker = new UIImagePickerController
        {
            SourceType = UIImagePickerControllerSourceType.PhotoLibrary,
            MediaTypes = UIImagePickerController.AvailableMediaTypes(UIImagePickerControllerSourceType.PhotoLibrary)
        };

        _imagePicker.FinishedPickingMedia += (sender, e) =>
        {

            if (e.Info[UIImagePickerController.MediaType].ToString() == "public.image")
            {
                var filepath = (e.Info[new NSString("UIImagePickerControllerReferenceUrl")] as NSUrl);
                var image = (UIImage)e.Info.ObjectForKey(new NSString("UIImagePickerControllerOriginalImage"));
                //var image = e.Info[UIImagePickerController.OriginalImage] as UIImage;

                _result.ImageSource = ImageSource.FromStream(() => new MemoryStream(image.AsPNG().ToArray()));
                _result.ImageBytes = image.AsPNG().ToArray();
                _result.FilePath = filepath?.Path;
            }

            _tcs.TrySetResult(_result);
            _imagePicker.DismissViewController(true, null);
        };

        _imagePicker.Canceled += (sender, e) =>
        {
            UIApplication.SharedApplication.KeyWindow.RootViewController.DismissViewController(true, null);
        };

        await UIApplication.SharedApplication.KeyWindow.RootViewController.PresentViewControllerAsync(_imagePicker, true);

        return await _tcs.Task;
    }
}

回复于 2024-05-06T23:48:01+08:00

使用Xamarin.Forms访问摄像头

4 回答

共享项目

Android项目

iOS项目

适用于Android项目

适用于iOS项目

对于共享项目

在iOS中：

在Android中：

便携式项目

iOS项目

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