[英]Camera access with Xamarin.Forms
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,但我无法在两个平台上使用任何解决方案(现在专注于Android和iOS)。 Web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。
我终于为iOS和Android创建了最低限度的解决方案。
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
存储了一个静态Instance
:
public static App Instance;
此外,我们将显示一个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
和上述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);
}
在Android上,我们修改了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
结束时,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的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!
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 };
一旦引发ShouldTakePicture
事件,就呈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
文件夹并调用共享的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);
试试James Montemagno的MediaPlugin 。
您可以使用Package Manager Console安装插件,只需键入并运行Install-Package Xam.Plugin.Media -Version 2.6.2
或者转到Manage NuGet Packages ...并键入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, 将以下代码 (根据需要)添加到共享项目中。 上述readme.txt文件中要遵循的说明如下。
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!
将名为xml的新文件夹添加到Resources文件夹中,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!
您的应用程序需要在Info.plist中为NSCameraUsageDescription
和NSPhotoLibraryUsageDescription
提供密钥才能访问设备的摄像头和照片/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>
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");
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
public interface ICameraProvider
{
Task<CameraResult> TakePhotoAsync();
Task<CameraResult> PickPhotoAsync();
}
private Command AttachImage
{
var camera = await DependencyService.Get<ICameraProvider>().TakePhotoAsync();
}
[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;
}
}
这是我需要在我的应用程序中运行异步摄像头捕获所需的:
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
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;
}
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;
}
}
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