Developing environment

This project is written with Google’s official IDE “Android studio”, with a developing framework called “Jetpack-Compose”.

1. Install IDE: https://developer.android.google.cn/codelabs/basic-android-kotlin-compose-install-android-studio
2. Open the project: Click ‘open’ and open the folder “vibration_data_sensing”

1. Build and run the app on an Android phone: https://developer.android.google.cn/studio/run/device
2. Read the official starter documents for jetpack-compose framework.https://developer.android.google.cn/courses/android-basics-compose/course You don’t need to read all of them, as long as you can understand the file “MainActicity.kt” - what are @Composable functions? Where is the UI defined? Which code runs when the app starts?
3. For sake of time, I don’t recommend learning a new language “Kotlin” and all of its grammar from zero. Do the preparations below, and let ChatGPT do the rest for you. Here is a very helpful AI coding tool: Cursor

Preparations

To start modifying the vibration data collection app, you’ll need these basic knowledge.

• Basic knowledge of object oriented programming.
• The “declaration programming” concept in Jetpack-Compose developing framework.
  • Basically, you’ll find many functions annotated “@Composable” in the code. Such functions describes a mechanism that the app would keep track of some variables. Whenever they changes, the app run some code written in the function and update the changes in the UI component.
  • You don’t have to manually consider every detail of the state shifting. Android automatically monitor and decide when to update the UI. So it is called “declaration”.
• Learn that the MQTT protocol requires a router, a broker, and several client devices. Learn about the publish-subscribe relation between clients.
• Learn about multi-thread operations in mobile apps.
  • Network operations must be put in back-stage threads.
  • To make back-stage threads not mixed with each other (e.g. prevent sending get-gain commands to a sensor while another thread is sending get-rate commands to it), lock is used in the code.

Structure of the code

1. Three salient instances in the code

The app monitors and uses 3 salient instances - broker, devices, files. They are digital twins of devices in the real-world or data in the disk. Let’s look at the definition of their class first.

• Class: Broker

class Broker {
    var reachable by mutableStateOf(false)
    var name by mutableStateOf("Not found")
    var ip by mutableStateOf("Not found")
    var status by mutableStateOf("Please start a broker on port 1883!")
}

There will always be one broker instance in the app, describing the broker’s name, IP, status.