Adding FilePathConverter class

(Dunno why this wasn't included in previous commit...)

commons/src/main/java/fr/free/nrw/commons/upload/FilePathConverter.java

@@ -0,0 +1,49 @@
+package fr.free.nrw.commons.upload;
+
+
+import android.content.Context;
+import android.database.Cursor;
+import android.net.Uri;
+import android.provider.DocumentsContract;
+import android.provider.MediaStore;
+import android.util.Log;
+
+public class FilePathConverter {
+
+    private Uri uri;
+    private Context context;
+
+    public FilePathConverter(Context context, Uri uri) {
+        this.context = context;
+        this.uri = uri;
+    }
+
+    /**
+     * Gets file path of image from its Uri
+     * May return null
+     */
+    public String getFilePath(){
+        String filePath ="";
+        // Will return "image:x*"
+        String wholeID = DocumentsContract.getDocumentId(uri);
+
+        // Split at colon, use second item in the array
+        String id = wholeID.split(":")[1];
+        String[] column = { MediaStore.Images.Media.DATA };
+
+        // where id is equal to
+        String sel = MediaStore.Images.Media._ID + "=?";
+        Cursor cursor = context.getContentResolver().query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
+                column, sel, new String[]{id}, null);
+
+        int columnIndex = cursor.getColumnIndex(column[0]);
+
+        if (cursor.moveToFirst()) {
+            filePath = cursor.getString(columnIndex);
+        }
+        cursor.close();
+
+        Log.d("Image", "File path: " + filePath);
+        return filePath;
+    }
+}