title: OpenCV 3.0.0 Android native method not found: org.opencv.core.Mat.n_Mat:()J
body: <p>I'm using native android <em>Opencv 3.0.0 library</em> for Xamarin.Android via <strong>Android Java Bindings Library</strong> .<br>
  I'm doing pretty same like this <strong><a href="https://www.youtube.com/watch?v=pFv_1KeMZVs" rel="nofollow">Tutorial</strong></a> and the problem is that i got this exception  </p>
  
  <blockquote>
    <p>Native method not found: org.opencv.core.Mat.n_Mat:()J</p>
  </blockquote>
  
  <p>What can i do to resolve this problem? Any help will be appreciated,thanks!  </p>
  
  <p>My source code of <strong>Main Activity</strong> :  </p>
  
  <pre><code> public class MainActivity : Activity
      {
  
          Mat m;
          Mat grayM;
          ImageView imageView;
          public MainActivity()
          {
              if (!OpenCVLoader.InitDebug())
              {
                  System.Console.WriteLine("GG");
              }
  
          }
  
          protected override void OnCreate(Bundle bundle) 
          {
              base.OnCreate(bundle);
  
              SetContentView(Resource.Layout.Main); 
  
              Button button = FindViewById&lt;Button&gt;(Resource.Id.myButton);
              ImageButton crop = FindViewById&lt;ImageButton&gt;(Resource.Id.crop);
              crop.Visibility = ViewStates.Invisible;
              imageView = FindViewById&lt;ImageView&gt;(Resource.Id.IMG);
  
              if (IsThereAnAppToTakePictures ())
              {
                  CreateDirectoryForPictures ();
  
                  button.Click += delegate 
                      {
                          Intent intent = new Intent (MediaStore.ActionImageCapture);
                          App._file = new File (App._dir, String.Format("myPhoto_{0}.jpg", System.Guid.NewGuid()));
                          intent.PutExtra (MediaStore.ExtraOutput, Android.Net.Uri.FromFile (App._file));
                          StartActivityForResult (intent, 0);
  
                          crop.Visibility = ViewStates.Visible;
                          // SetImg();
                      };
              }
  
              crop.Click += (sender, e) =&gt; 
                  {
                      SetImg();
                  };
          }
  
          void SetImg()
          {
  
              using (Bitmap _img = BitmapFactory.DecodeFile(App._file.Path))
              {
                  if (_img != null)
                  {
                      m = new Mat();
                      grayM = new Mat();
                      Utils.BitmapToMat(_img, m);
                      Imgproc.CvtColor(m, grayM, Imgproc.ColorBgr2gray);
                      Imgproc.CvtColor(grayM, m, Imgproc.ColorGray2bgra);
                      using (Bitmap bit = Bitmap.CreateBitmap(m.Cols(), m.Rows(), Bitmap.Config.Argb8888))
                      {
                          Utils.BitmapToMat(bit,m);
                          imageView.SetImageBitmap(bit);
  
                      }
  
                      m.Release();
                      grayM.Release();
                  }
              }
          }
  
          protected override void OnActivityResult (int requestCode, Result resultCode, Intent data)
          {
              base.OnActivityResult (requestCode, resultCode, data);
  
              // Make it available in the gallery
  
              Intent mediaScanIntent = new Intent (Intent.ActionMediaScannerScanFile);
              Android.Net.Uri contentUri = Android.Net.Uri.FromFile (App._file);
              mediaScanIntent.SetData (contentUri);
              SendBroadcast (mediaScanIntent);
               imageView.SetImageBitmap(BitmapFactory.DecodeFile(contentUri.Path));
  
              // Dispose of the Java side bitmap.
              GC.Collect();
          }
  
          private void CreateDirectoryForPictures ()
          {
              App._dir = new File (
                  Android.OS.Environment.GetExternalStoragePublicDirectory (
                      Android.OS.Environment.DirectoryPictures), "CameraAppDemo");
              if (!App._dir.Exists ())
              {
                  App._dir.Mkdirs( );
              }
          }
  
          private bool IsThereAnAppToTakePictures ()
          {
              Intent intent = new Intent (MediaStore.ActionImageCapture);
              IList&lt;ResolveInfo&gt; availableActivities =
                  PackageManager.QueryIntentActivities (intent, PackageInfoFlags.MatchDefaultOnly);
              return availableActivities != null &amp;&amp; availableActivities.Count &gt; 0;
          }
  
  
      }
      public static class App 
      {
          public static File _file;
          public static File _dir;
          public static Bitmap bitmap;
      }
  }
  </code></pre>
  
  <p>And <strong>Log</strong> of exception:  </p>
  
  <blockquote>
    <p>[MonoDroid] UNHANDLED EXCEPTION: [MonoDroid]
    Java.Lang.UnsatisfiedLinkError: Exception of type
    'Java.Lang.UnsatisfiedLinkError' was thrown. [MonoDroid] at
    System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw ()
    [0x0000b] in
    /Users/builder/data/lanes/2058/58099c53/source/mono/mcs/class/corlib/System.Runtime.ExceptionServices/ExceptionDispatchInfo.cs:61
    [MonoDroid] at Android.Runtime.JNIEnv.CallNonvirtualVoidMethod
    (intptr,intptr,intptr,Android.Runtime.JValue*) [0x00084] in
    /Users/builder/data/lanes/2058/58099c53/source/monodroid/src/Mono.Android/src/Runtime/JNIEnv.g.cs:1029
    [MonoDroid] at Android.Runtime.JNIEnv.FinishCreateInstance
    (intptr,intptr,intptr,Android.Runtime.JValue*) [0x0000b] in
    /Users/builder/data/lanes/2058/58099c53/source/monodroid/src/Mono.Android/src/Runtime/JNIEnv.cs:306
    [MonoDroid] at Android.Runtime.JNIEnv.FinishCreateInstance
    (intptr,intptr,intptr,Android.Runtime.JValue[]) [0x0001d] in
    /Users/builder/data/lanes/2058/58099c53/source/monodroid/src/Mono.Android/src/Runtime/JNIEnv.cs:312
    [MonoDroid] at Org.Opencv.Core.Mat..ctor () [0x000da] in</p>
  </blockquote>