passing index Parameters for Flann matcher using opencv on android

Question

I'm trying to customize the Flann matcher in opencv by editing the index parameters, but I'm using java for android, and I don't know how exactly it works.
I found this answer but I don't know how to apply it in a correct way here is the code I've tried

    String yamlParam="%YAML:1.0\n"
            + "indexParams:\n"
            + "   -\n"
            + "      name: algorithm\n"
            + "      type: 23\n"
            + "      value: 1\n"
            + "   -\n"
            + "      name: trees\n"
            + "      type: 4\n"
            + "      value: 4\n";

    File outputF = File.createTempFile("FlannfDetectorParams", ".YAML", outputDir);
    writeToFile(outputF,yamlParam);
    descriptorMatcher.read(outputF.getPath());

and here's the error I'm getting

OpenCV Error: Assertion failed (sp.type() == FileNode::SEQ) in virtual void cv::FlannBasedMatcher::read(const cv::FileNode &)

Answer 1

You have to use the full format of the yml configuration file:

%YAML:1.0
---
format: 3
indexParams:
   -
      name: algorithm
      type: 23
      value: 1
   -
      name: trees
      type: 4
      value: 4
searchParams:
   -
      name: checks
      type: 4
      value: 32
   -
      name: eps
      type: 5
      value: 0.
   -
      name: sorted
      type: 15
      value: 1

Answer 2

I have the same question in Android SDK 28 and OpenCV 4.5.2.

You should use the external story use absolute path.