Digital Speedometer

Project, where speed values are generated in background in the Service (SpeedValuesService). Then values are sent to Activity (MainActivity), that has fullscreen custom digital speedometer view (DigitalSpeedometerView). While app is running, device screen won't turn of.

Project consists of 2 modules:

• app module with custom view;
• data-source module with business logic.

This project shows using:

1. AIDL interfaces (Android Interface Definition Language) for interaction between SpeedValuesService and MainActivity, where service is generating speed values, based on time-dependent periodic function (sum of sinuses).

In SpeedValuesService aidl interface ISpeedValuesBinder's method registerCallback(listener: IOnSpeedChangedListener) register listener that is implemented in MainActivity and send new speed values to it.

In MainActivity implemented IOnSpeedChangedListener that listens to speed values changes from service and shows it on view binding.speedometerView.updateSpeed(newSpeed).

2. Custom view, that is based on ConstraintLayout, as the digital speedometer.

       android:id="@+id/speedometerView"
       android:layout_width="0dp"
       android:layout_height="0dp"
       app:backgroundDrawable="@drawable/bg_speedometer_view"
       app:layout_constraintBottom_toBottomOf="parent"
       app:layout_constraintLeft_toLeftOf="parent"
       app:layout_constraintRight_toRightOf="parent"
       app:layout_constraintTop_toTopOf="parent"
       app:speedTextColor="@android:color/holo_blue_light"
       app:speedUnit="kmh"
       app:unitTextColor="@android:color/holo_blue_light" />
   
   

From .xml you can change some parameters:

• speedTextColor
• unitTextColor
• bgColor
• speedTextSize
• unitTextSize
• speedUnit: choose between "kmh" and "mph"
• speedValue
• backgroundDrawable
• disableBackgroundImage
• showUnit

3. SpeedValuesService extends LifecycleService for using lifecycleScope for launching coroutines to calculate and new speed values (using Dispatchers.Default).