需要一个使用 MonoDroid 和 MVVMCross 拍照的例子

问题描述

谁能给我一个拍摄照片并使用MVVMCross存储的例子?

Can anyone point me to an example of take a Photo and store it using MVVMCross?

我一直在寻找，但只找到了这个:

I have been searching but only have found this:

• Monodroid 用相机拍照(不实施MVVMCross)

• Monodroid Take a picture with Camera (Doesn't Implement MVVMCross)

视频录制(这是视频，我无法让它工作:S)

Video Recording (It's Video and i can't make it work :S)

官方配方示例(它有效，但没有实现 MVVMCross)

The Oficialy Recipe Example (It Works but does not implement MVVMCross)

谢谢！！！

已解决！谢谢！
未来参考:(使用主分支)
感谢 Stuart，我只是更改了代码以适应我的现实

using Cirrious.MvvmCross.ExtensionMethods;
using Cirrious.MvvmCross.Interfaces.Platform.Tasks;
using Cirrious.MvvmCross.Interfaces.ServiceProvider;
using SIGEP.DummyService;
using SIGEP.Mobile.Core.Interfaces;


namespace SIGEP.Mobile.Core.Models
{
 public class PhotoService : IMvxServiceConsumer<IMvxPictureChooserTask>
{
    private const int MaxPixelDimension = 1024;
    private const int DefaultJpegQuality = 92;

    public void GetNewPhoto()
    {
        this.GetService<IMvxPictureChooserTask>().TakePicture(
            MaxPixelDimension,
            DefaultJpegQuality,
            HandlePhotoAvailable,
            () => { /* cancel is ignored */ });

    }

    public event EventHandler<PhotoStreamEventArgs> PhotoStreamAvailable;

    private void HandlePhotoAvailable(Stream pictureStream)
    {
        var handler = PhotoStreamAvailable;
        if (handler != null)
        {
            handler(this, new PhotoStreamEventArgs() { PictureStream = pictureStream, OnSucessGettingPhotoFileName = OnSucessGettingPhotoFileName });
        }
    }



    public static void TakePhoto(Action<string> successFileName, Action<Exception> error)
    {
        var service = new PhotoService();
        service.OnSucessGettingPhotoFileName = successFileName;
        service.OnError = error;
        service.GetNewPhoto();
        service.PhotoStreamAvailable += new EventHandler<PhotoStreamEventArgs>(service_PhotoStreamAvailable);
    }

    static void service_PhotoStreamAvailable(object sender, PhotoStreamEventArgs e)
    {
        //grava pra ficheiro!!!
        var directory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
        var filename = Path.Combine(directory, "photo.jpeg");
        string saveTo = filename;
        FileStream writeStream = new FileStream(saveTo, FileMode.Create, FileAccess.Write);
        ReadWriteStream(e.PictureStream, writeStream);

        e.OnSucessGettingPhotoFileName(filename);

    }
    private static void ReadWriteStream(Stream readStream, Stream writeStream)
    {
        int Length = 256;
        Byte[] buffer = new Byte[Length];
        int bytesRead = readStream.Read(buffer, 0, Length);
        // write the required bytes
        while (bytesRead > 0)
        {
            writeStream.Write(buffer, 0, bytesRead);
            bytesRead = readStream.Read(buffer, 0, Length);
        }
        readStream.Close();
        writeStream.Close();
    }

    public Action<string> OnSucessGettingPhotoFileName { get; set; }
    public Action<Exception> OnError { get; set; }
}

[Serializable]
[ComVisible(true)]
public class PhotoStreamEventArgs : EventArgs
{
    public Stream PictureStream { get; set; }

    public Action<string> OnSucessGettingPhotoFileName { get; set; }
}
}

推荐答案

我通常使用内置的 IMvxPictureChooserTask 实现一个服务(如果使用 vNext，这是在插件中):

I generally implement a service using the built-in IMvxPictureChooserTask (this is in a Plugin if using vNext):

using Cirrious.MvvmCross.ExtensionMethods;
using Cirrious.MvvmCross.Interfaces.Platform.Tasks;
using Cirrious.MvvmCross.Interfaces.ServiceProvider;

public class PhotoService
    : IMvxServiceConsumer<IMvxPictureChooserTask>
    , IPhotoService
{
    private const int MaxPixelDimension = 1024;
    private const int DefaultJpegQuality = 92;

    public void GetNewPhoto()
    {
        Trace.Info("Get a new photo started.");

        this.GetService<IMvxPictureChooserTask>().TakePicture(
            MaxPixelDimension,
            DefaultJpegQuality,
            HandlePhotoAvailable,
            () => { /* cancel is ignored */ });
    }

    public event EventHandler<PhotoStreamEventArgs> PhotoStreamAvailable;

    private void HandlePhotoAvailable(Stream pictureStream)
    {
        Trace.Info("Picture available");
        var handler = PhotoStreamAvailable;
        if (handler != null)
        {
            handler(this, new PhotoStreamEventArgs() { PictureStream = pictureStream });
        }
    }
}

我通常在启动时将此服务注册为单例，然后从 ViewModel ICommand 处理程序调用它.

I generally register this service as a singleton during startup, and then call it from a ViewModel ICommand handler.

使用此服务的一个应用是 Blooor 示例 - 请参阅 BaseEditProductViewModel.cs - 这不是一个样本与我有任何关系，但我相信它同时带来了拍照和 ZXing - 两者都使用外部服务.

One app which uses this service is the Blooor sample - see BaseEditProductViewModel.cs - this isn't a sample I had anything to do with, but I believe it brings in both Picture taking and ZXing - both using external services.

一个警告:在 MonoDroid 上，您可以看到一些奇怪的/意外的 Activity/ViewModel 生命周期行为 - 基本上您可以看到您拍摄照片的 Activity 在照片拍摄期间从内存中卸载/擦除.如果您的应用发生这种情况，那么您可能需要开始查看以下问题:Saving Android Activity状态使用保存实例状态 - 这不会在 MvvmCross 中自动处理(目前).

One warning: On MonoDroid, you can see some strange/unexpected Activity/ViewModel lifecycle behaviour - basically you can see that the Activity you take the photo from is unloaded/wiped from memory during the photo taking. If this happens to your app then you'll probably need to start looking at questions like: Saving Android Activity state using Save Instance State - this isn't automatically handled in MvvmCross (yet).

我相信 Blooor 示例可能会遇到此问题 - 但用户是否会在正常的应用程序使用中看到它是有争议的.

I believe the Blooor sample might suffer from this issue - but whether a user would ever see it in normal app use is debatable.

作为 IMvxPictureChooserTask 服务的替代方案，您还可以考虑使用来自 Xamarin.Mobile 的一些跨平台 API - 请参阅MvvmCross vnext :monodroid 在插件中使用 VideoView 作为可能的起点 - 或者仅适用于 Android，您可以轻松地实现你自己的.

As an alternative to the IMvxPictureChooserTask service, you can also look at using some of the cross-platform APIs from Xamarin.Mobile - see MvvmCross vnext : monodroid use a VideoView inside a plugin for a possible starting place - or for Android only you can easily implement your own.

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