模拟器错误：Android.Database.CursorIndexOutOfBounds异常：'Index 0 requested, with a size of 0'

Question

我正在尝试开发一个 ocr 应用程序，它从图库中挑选图像并执行 Ocr 我的代码适用于真实设备，但是使用模拟器时，从图库中选择图像时它会抛出 Android.Database.CursorIndexOutOfBoundsException.请帮助我解决我的模拟器错误提前感谢。

Activity.cs
public 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 = ContentResolver.Query(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;
}
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
SetContentView(Resource.Layout.GalleryPage);
// Create your application here
txtView = FindViewById<TextView>(Resource.Id.txtView);
_imageView = FindViewById<ImageView>(Resource.Id.imageView1);
Button button = FindViewById<Button>(Resource.Id.MyButton);
button.Click += delegate
{
Intent = new Intent();
Intent.SetType("image/*");
Intent.SetAction(Intent.ActionGetContent);
StartActivityForResult(Intent.CreateChooser(Intent, "Select Picture"), PickImageId);
}; 
}
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
if ((requestCode == PickImageId) && (resultCode == Result.Ok) && (data != null))
{
Android.Net.Uri uri = data.Data;
var path = GetPathToImage(uri);
System.Diagnostics.Debug.WriteLine("Image path == " + path);
//  Bitmap bitmap = BitmapFactory.DecodeFile(path);
Bitmap bitmap =  loadAndResizeBitmap.Coversionandresize(path,4032,3024);
ColorMatrix matrix = new ColorMatrix();
matrix.SetSaturation(0);
_imageView.SetColorFilter(new ColorMatrixColorFilter(matrix));
_imageView.SetImageBitmap(bitmap);
TextRecognizer txtRecognizer = new TextRecognizer.Builder(ApplicationContext).Build();
if (!txtRecognizer.IsOperational)
{
Log.Error("Error", "Detector dependencies are not yet available");
}
else
{
Frame frame = new Frame.Builder().SetBitmap(bitmap).Build();
SparseArray items = txtRecognizer.Detect(frame);
StringBuilder strBuilder = new StringBuilder();
for (int i = 0; i < items.Size(); i++)
{
TextBlock item = (TextBlock)items.ValueAt(i);
strBuilder.Append(item.Value);
strBuilder.Append("/n");
//  strBuilder.Append(Environment.NewLine);
}
txtView.Text = strBuilder.ToString();
}
}
}
}

}

Android.Database.CursorIndexOutOfBoundsException："请求索引 0，大小为 0">

Answer 1

我的一个应用程序使用了此功能，您可以尝试以下代码：

欠条.cs

public class IOUtil
{
public static string getPath(Context context, Android.Net.Uri uri)
{
bool isKitKat = Build.VERSION.SdkInt >= BuildVersionCodes.Kitkat;
// DocumentProvider
if (isKitKat && DocumentsContract.IsDocumentUri(context, uri))
{
// ExternalStorageProvider
if (isExternalStorageDocument(uri))
{
var docId = DocumentsContract.GetDocumentId(uri);
string[] split = docId.Split(':');
var type = split[0];
if ("primary".Equals(type, StringComparison.OrdinalIgnoreCase))
{
return Android.OS.Environment.ExternalStorageDirectory + "/" + split[1];
}
// TODO handle non-primary volumes
}
// DownloadsProvider
else if (isDownloadsDocument(uri))
{
string id = DocumentsContract.GetDocumentId(uri);
Android.Net.Uri contentUri = ContentUris.WithAppendedId(
Android.Net.Uri.Parse("content://downloads/public_downloads"), long.Parse(id));
return getDataColumn(context, contentUri, null, null);
}
// MediaProvider
else if (isMediaDocument(uri))
{
var docId = DocumentsContract.GetDocumentId(uri);
string[] split = docId.Split(':');
var type = split[0];
Android.Net.Uri contentUri = null;
if ("image".Equals(type))
{
contentUri = MediaStore.Images.Media.ExternalContentUri;
}
else if ("video".Equals(type))
{
contentUri = MediaStore.Video.Media.ExternalContentUri;
}
else if ("audio".Equals(type))
{
contentUri = MediaStore.Audio.Media.ExternalContentUri;
}
var selection = "_id=?";
var selectionArgs = new string[] {
split[1]
};
return getDataColumn(context, contentUri, selection, selectionArgs);
}
}
// MediaStore (and general)
else if ("content".Equals(uri.Scheme, StringComparison.OrdinalIgnoreCase))
{
return getDataColumn(context, uri, null, null);
}
// File
else if ("file".Equals(uri.Scheme, StringComparison.OrdinalIgnoreCase))
{
return uri.Path;
}
return null;
}
public static string getDataColumn(Context context, Android.Net.Uri uri, string selection,
string[] selectionArgs)
{
ICursor cursor = null;
var column = "_data";
string[] projection = {
column
};
try
{
cursor = context.ContentResolver.Query(uri, projection, selection, selectionArgs,
null);
if (cursor != null && cursor.MoveToFirst())
{
int column_index = cursor.GetColumnIndexOrThrow(column);
return cursor.GetString(column_index);
}
}
finally
{
if (cursor != null)
cursor.Close();
}
return null;
}
/**
* @param uri The Uri to check.
* @return Whether the Uri authority is ExternalStorageProvider.
*/
public static bool isExternalStorageDocument(Android.Net.Uri uri)
{
return "com.android.externalstorage.documents".Equals(uri.Authority);
}
/**
* @param uri The Uri to check.
* @return Whether the Uri authority is DownloadsProvider.
*/
public static bool isDownloadsDocument(Android.Net.Uri uri)
{
return "com.android.providers.downloads.documents".Equals(uri.Authority);
}
/**
* @param uri The Uri to check.
* @return Whether the Uri authority is MediaProvider.
*/
public static bool isMediaDocument(Android.Net.Uri uri)
{
return "com.android.providers.media.documents".Equals(uri.Authority);
}
public static byte[] readFile(string file)
{
try
{
return readFile(new File(file));
}
catch (Exception ex)
{
System.Diagnostics.Debug.Write(ex);
return new byte[0];
}
}
public static byte[] readFile(File file)
{
// Open file
var f = new RandomAccessFile(file, "r");
try
{
// Get and check length
long longlength = f.Length();
var length = (int)longlength;
if (length != longlength)
throw new IOException("Filesize exceeds allowed size");
// Read file and return data
byte[] data = new byte[length];
f.ReadFully(data);
return data;
}
catch (Exception ex)
{
System.Diagnostics.Debug.Write(ex);
return new byte[0];
}
finally
{
f.Close();
}
}
}

有关更多详细信息，您可以查看： ca 如何从 Intent.CreateChooser(Intent， "Select Any File"( 作为字节的选定文件中获取数据