如何在 Xamarin Forms 上创建图像选择器？

Question

有人知道是否可以制作这样的图像选择器：

我试过以下插件：

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，我想要的是通过单个按钮来建议使用哪个应用程序。这可能吗？

谢谢。

Answer 1

您可以通过 xf 依赖服务在 Android 上使用 Intent.SetComponent：

Xf:

public interface IShare
{
    void Share();
}

安卓：

[assembly: Dependency(typeof(ShareImage))]
namespace AndroidShareSample.Droid
{
    public class ShareImage : Activity, IShare
    {
        public void Share()
        {
            var appPackageName = "com.sample.app";
            var intent = new Intent(Intent.ActionPick, Android.Provider.MediaStore.Images.Media.ExternalContentUri);
            var resInfos = CrossCurrentActivity.Current.Activity.PackageManager.QueryIntentActivities(intent,0);
            intent.SetComponent(new ComponentName(appPackageName, resInfos.FirstOrDefault(x=> x.ActivityInfo.PackageName == appPackageName).ActivityInfo.Name));
            Forms.Context.StartActivity(Intent.CreateChooser(intent, "Select Image"));
        }
    }
}

Answer 2

如果你想从手机的图片库中挑选一张照片，由于Xamarin.Forms不包含这个功能，需要使用DependencyService来访问各个平台的原生API。

创建接口： IPhotoPickerService.cs

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

Android 实现：

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

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;
    }
}

更多关于IOS、UWP实现照片选择器的信息，可以查看MS文章。 https://docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/dependency-service/photo-picker

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