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samples/experimental/pedometer/README.md

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# FFIgen + JNIgen pedometer
This is a demo for some of our tooling around
calling platform APIs directly from dart code.
This repository represents a demo of a plugin that leverages FFIgen & JNIgen.
There is also an example pedometer app that
uses the bindings generated from these tools.
- [FFIgen](https://pub.dev/packages/ffigen) is used to generate
bindings for C, Objective-C and Swift APIs.
- [JNIgen](https://pub.dev/packages/jnigen) is used to generate
bindings for Java and Kotlin APIs.
**These tools are both experimental and are currently a work in progress.**
If you find any issues or have feedback,
please file it on the corresponding GitHub repositories.
## Re-generating bindings
The bindings that allow the Dart code to call the platform code have
already been generated in the [`\lib` folder](./lib).
You can regenerate them by following the steps below:
### FFIgen
Configuration of FFIgen for the
[CoreMotion framework](https://developer.apple.com/documentation/coremotion)
is in the [`ffigen.yaml` file](./ffigen.yaml).
FFIgen currently does not support autogenerating code to handle callbacks.
So, there are a few extra steps needed to
appropriately handle callbacks in Objective-C.
You can read more about this limitation on
[dart.dev]((https://dart.dev/guides/libraries/objective-c-interop#callbacks-and-multithreading-limitations).
```bash
dart run ffigen --config ffigen.yaml
```
### JNIgen
Configuration of JNIgen for the
[HealthConnect API](https://developer.android.com/guide/health-and-fitness/health-connect)
is in the [`jnigen.yaml` file](./jnigen.yaml).
1. Build an Android APK file from the example app.
Currently, JNIgen requires at least one APK build
to obtain the classpaths of Android Gradle libraries.
```bash
cd example && flutter build apk
```
2. Return to the `/pedometer` directory and run `jnigen`:
```bash
cd .. && dart run jnigen --config jnigen.yaml
```
## Running the example app
The example app is located in the [`/example`](./example) directory,
and the following commands assume they are being run from that location.
Note that step counting is only available on physical devices.
### iOS
- Run `flutter run` and choose your physical device.
- Allow the *pedometer* app access to step counting.
### Android
- Make sure that [Google Fit](https://play.google.com/store/apps/details?id=com.google.android.apps.fitness)
is installed (to ensure that steps are being counted).
- Run `flutter run` and choose your physical device.
- Install [Health Connect](https://play.google.com/store/apps/details?id=com.google.android.apps.healthdata)
and grant access to Google Fit and the *jni_demo* app.
## Project structure
* `src`: Contains the native source code, and a `CMakeLists.txt` file for
building that source code into a dynamic library.
* `lib`: Contains the Dart code that defines the API of the plugin and
calls into the native code using `dart:ffi`.
* platform folders (`ios` etc.): Contain the build files for
building and bundling the native code library with the platform application.
* `example`: Contains the native source code for building
that source code into a dynamic library.