Xamarin从图库路径中选择图像为空 [英] Xamarin Choose Image From Gallery Path is Null

问题描述

使用此食谱尝试从图库中选择图片，然后将其上传到s3， 我的路径总是返回null.

using this recipe to try and choose an image from the gallery and then upload it to s3 but my path always returns null.

private string _imgPath;
        public void InitializeMediaPicker()
        {
                Intent = new Intent();
                Intent.SetType("image/*");
                Intent.SetAction(Intent.ActionGetContent);
                StartActivityForResult(Intent.CreateChooser(Intent, "Select Picture"), 1000);
        }

        public string GetImage()
        {
            InitializeMediaPicker();

            return _imgPath;
        }

        protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
        {
            if ((requestCode != 1000) || (resultCode != Result.Ok) || (data == null)) return;
            var uri = data.Data;
            _imgPath = GetPathToImage(uri);
        }

        private string GetPathToImage(Android.Net.Uri uri)
        {
            string path = null;
            // The projection contains the columns we want to return in our query.
            var projection = new[] { Android.Provider.MediaStore.Images.Media.InterfaceConsts.Data };
            using (var cursor = ManagedQuery(uri, projection, null, null, null))
            {
                if (cursor == null) return path;
                var columnIndex = cursor.GetColumnIndexOrThrow(Android.Provider.MediaStore.Images.Media.InterfaceConsts.Data);
                cursor.MoveToFirst();
                path = cursor.GetString(columnIndex);
            }
            return path;
        }

推荐答案

这是从这个答案.

在清单中包含WRITE_EXTERNAL_STORAGE权限，此代码才能正常工作.

Include the WRITE_EXTERNAL_STORAGE permission in your manifest for this code to work.

public delegate void OnImageResultHandler(bool success, string imagePath);

protected OnImageResultHandler _imagePickerCallback;
public void GetImage(OnImageResultHandler callback)
{
    if (callback == null) {
        throw new ArgumentException ("OnImageResultHandler callback cannot be null.");
    }

    _imagePickerCallback = callback;
    InitializeMediaPicker();
}

public void InitializeMediaPicker()
{
    Intent = new Intent();
    Intent.SetType("image/*");
    Intent.SetAction(Intent.ActionGetContent);
    StartActivityForResult(Intent.CreateChooser(Intent, "Select Picture"), 1000);
}

protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
    if ((requestCode != 1000) || (resultCode != Result.Ok) || (data == null)) {
        return;
    }

    string imagePath = null;
    var uri = data.Data;
    try {
        imagePath = GetPathToImage(uri);
    } catch (Exception ex) {
        // Failed for some reason.
    }

    _imagePickerCallback (imagePath != null, imagePath);
}

private string GetPathToImage(Android.Net.Uri uri)
{
    string doc_id = "";
    using (var c1 = ContentResolver.Query (uri, null, null, null, null)) {
        c1.MoveToFirst ();
        String document_id = c1.GetString (0);
        doc_id = document_id.Substring (document_id.LastIndexOf (":") + 1);
    }

    string path = null;

    // The projection contains the columns we want to return in our query.
    string selection = Android.Provider.MediaStore.Images.Media.InterfaceConsts.Id + " =? ";
    using (var cursor = ManagedQuery(Android.Provider.MediaStore.Images.Media.ExternalContentUri, null, selection, new string[] {doc_id}, null))
    {
        if (cursor == null) return path;
        var columnIndex = cursor.GetColumnIndexOrThrow(Android.Provider.MediaStore.Images.Media.InterfaceConsts.Data);
        cursor.MoveToFirst();
        path = cursor.GetString(columnIndex);
    }
    return path;
}

用法示例:

Button button = FindViewById<Button> (Resource.Id.myButton);

button.Click += delegate {
    GetImage(((b, p) => {
        Toast.MakeText(this, "Found path: " + p, ToastLength.Long).Show();
    }));
};

我使用了回调方法，而不是返回GetImage的路径，因为调用方法将在OnActivityResult被调用之前完成执行，因此返回的路径将永远无效.

I've used a callback instead of returning the path for GetImage as the calling method would finish executing before OnActivityResult is called so the path returned would never be valid.

这篇关于Xamarin从图库路径中选择图像为空的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！