如何在Xamarin Forms上创建图像选择器? [英] How to create a image picker on Xamarin Forms?

问题描述

有人知道是否可以制作像这样的图像选择器:

Does anybody knows if its possible to make a Image picker like this:

我尝试使用以下插件:

https://github.com/jamesmontemagno/MediaPlugin

https://github.com/matheusneder/Xamarin.Forms.ImagePicker

我不想创建能够执行每个操作的按钮，我想要的是使用单个按钮来建议使用哪个应用程序.这可能吗?

I do not want to create buttons to be able to perform each operation, what I want is that with a single button I suggest which application to use. This is possible?

谢谢.

推荐答案

如果由于Xamarin.Forms不包含此功能而要从手机的图片库中选择一张照片，则必须使用DependencyService访问每个平台上的本机API.

If you want to pick a photo from the phone's picture library, due to Xamarin.Forms does not include this functionality, it is necessary to use DependencyService to access native APIs on each platform.

创建界面:IPhotoPickerService.cs

Create the interface: IPhotoPickerService.cs

public interface IPhotoPickerService
{
    Task<Stream> GetImageStreamAsync();
}

Android实现:

MainActivity.cs

MainActivity.cs

public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
{
    internal static MainActivity Instance { get; private set; }

      ... ...

    // Field, property, and method for Picture Picker
    public static readonly int PickImageId = 1000;

    public TaskCompletionSource<Stream> PickImageTaskCompletionSource { set; get; }

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

        if (requestCode == PickImageId)
        {
            if ((resultCode == Result.Ok) && (intent != null))
            {
                Android.Net.Uri uri = intent.Data;
                Stream stream = ContentResolver.OpenInputStream(uri);

                // Set the Stream as the completion of the Task
                PickImageTaskCompletionSource.SetResult(stream);
            }
            else
            {
                PickImageTaskCompletionSource.SetResult(null);
            }
        }
    }
}

PhotoPickerService.cs

PhotoPickerService.cs

public class PhotoPickerService : IPhotoPickerService
{
    public Task<Stream> GetImageStreamAsync()
    {
        // Define the Intent for getting images
        Intent intent = new Intent();
        intent.SetType("image/*");
        intent.SetAction(Intent.ActionGetContent);

        // Start the picture-picker activity (resumes in MainActivity.cs)
        MainActivity.Instance.StartActivityForResult(
            Intent.CreateChooser(intent, "Select Photo"),
            MainActivity.PickImageId);

        // Save the TaskCompletionSource object as a MainActivity property
        MainActivity.Instance.PickImageTaskCompletionSource = new TaskCompletionSource<Stream>();

        // Return Task object
        return MainActivity.Instance.PickImageTaskCompletionSource.Task;
    }
}

有关IOS，照片选择器的UWP实现的更多信息，您可以查看MS文章. https://docs. microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/dependency-service/photo-picker

For more information about IOS, UWP implementation of photo picker, you could check the MS article. https://docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/dependency-service/photo-picker

然后从链接下载源文件. https://docs.microsoft.com/zh -cn/samples/xamarin/xamarin-forms-samples/dependencyservice/

And download the source file from link. https://docs.microsoft.com/zh-cn/samples/xamarin/xamarin-forms-samples/dependencyservice/

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