<== Chapter 9 -- Chapter 11 ==>

Chapter 10 - Main Native C/C++ code part 2

Now that we have got our Gradle working correctly we can now more easily work on our main native code!

Tango_NDK_Tutorial.h

  • The first we do is make sure to include the JNI library and the Tango APIs being used
#include <jni.h>
#include "tango_client_api.h"
#include "tango_support_api.h"  // Optional API
  • To make things easier we also define some logging tools in this demo so we log out to logcat easier
    • Example: LOGI("You will see this part printed out in logcat with value %d", someValue)
    • This works the same as printf formatting
    • With this you will be able to filter out all the Tutorial_TAG logs later so make sure to use a meaningful naming for the tags of your logs to make debugging easier.
      • Change the #define LOG_TAG "Tutorial_TAG" with a different tag if you want
  • The rest of the header is very standard for C++ programmer, but will help fill a few gaps if you are new to that (I would highly suggest learning about standard C++ OOP before getting knee deep in NDK development)
    • Since we included this header in our native-lib.cpp file we need to make sure to declare each function
    • Since we are using a namespace you need to reference this class as NAMESPACE::CLASS or for this case tango_tutorial::Tango_NDK_Tutorial
    • We have a private local instance of TangoConfig tango_config_ which we will use later.

Tango_NDK_Tutorial.cpp

You Made it! If you got here you got through the boring setup and now we can start coding with the Tango API!

  • This file is split into our main Tango usage in the namespace tango_tutorial {} while we create an anonymous namespace above to keep hold of more general items
  • If you are not up to speed with some of the technical aspect going on make sure to checkout the Coding technical Stuff Section

void Tango_NDK_Tutorial::OnCreate

  • We need to first address what to do when our MainActivity calls the onCreate function
  • We call TangoSupport_GetTangoVersion(env, caller_activity, &version); which will return the version of our Tango Core to version
  • We then can compare the version with a minimum version we have set to prevent people with outdated Tango to use our application
    • Note I have yet to find anywhere online what core version are needed to use features, but I figure this is for future ground breaking changes they might add one day.
    • Currently I am running version 16016 as of writing this tutorial

void Tango_NDK_Tutorial::OnTangoServiceConnected

This is where we do all of our setup and get Tango up and running

  • First we need to just run TangoService_setBinder(env, iBinder) which will take the JNIEnv* env, jobject iBinder values passed in

    • This is how Tango takes in the IBinder service value we created in our Java MainActivity.
    • This right here will link the Tango service and we can technically begin using it if it returns TANGO_SUCCESS

  • Next we need to setup our TangoConfig tango_config_ value.

  • Tango comes with many different API features and it would be wasteful to turn them all on if we are not using them all. To save power and processing we tell Tango which feature we want to use in our TangoConfig value
  • There are two ways to set up the TangoConfig
    1. Use a preset TangoConfig Type
      • This what we use for our tutorial demo
      • By calling tango_config_ = TangoService_getConfig(TANGO_CONFIG_DEFAULT); we give our TangoConfig permission to use Motion Tracking but we have turn off Depth Perception and the rest of the settings

    2. We can add each TangoConfig setting one at a time by using the Tango Config Refernce Guide

      • To add Depth Perception we would call ``` // Sets our TangoConfig 'config_enable_depth' configuration on for use TangoConfig_setBool(tango_config_, "config_enable_depth", true);

      // Tells Tango to get depth as pointcloud of type XYZC TangoConfig_setInt32(tango_config_, "config_depth_mode", TANGO_POINTCLOUD_XYZC); `` * Here we make a call first toTangoConfig_setBoolto toggle on the setting and then another toTangoConfig_setInt32to tell what depth mode options we want to include as well * Again, you will need to consult the [Tango Config Reference](https://developers.google.com/tango/apis/c/reference/group/config-params) for knowing what you need to enable and set * Next since we are using the Motion sensor we need to tell Tango about the Frame of Reference being used * More info about that can be found in [Frame of Reference Chapter](../../Section_03_Tango/Tutorials/Chapter_07.md) * Once we set ourTangoCoordinateFramePairto be what we want we need to call theTangoService_connectOnPoseAvailablefunction to set up what do with our position data. * The first two arguments are for telling whichTangoCoordinateFramePairto use * The third argument is where we tell it to call theonPoseAvailablefunction whenever it gets a new set of Motion Tracking position values * The last thing we need to do is set the configurations withTangoService_connect(nullptr, tango_config_)` and we are all connected!

void Tango_NDK_Tutorial::OnPause

If we pause our application we need to take the correct steps to get Tango disconnected correctly. What we need to do is well self documented from good naming conventions on Tango's part.

  • The first thing we call is TangoConfig_free(tango_config_); which will properly free the TangoConfig object
  • It is good memory management practice to set the point to null to prevent it being seen as valid elsewhere in the program
    • tango_config_ = nullptr;
  • Last we call TangoService_disconnect(); where Tango will unbind the service for use we have on it

void onPoseAvailable

This is our callback we set whenever Tango has Pose data available. Again very well sell documented with good naming conventions

  • It returns const TangoPoseData* pose which we can use to print out the value in this case
  • Each pose has its XYZ position and its XYZW orientation.
  • If you want to learn more about what values are in the Pose just check the Pose Reference

<== Chapter 9 -- Chapter 11 ==>