public class MonitorService extends DynamicEngine {

    ...
    
    /**
     * This method will be called on initializing the service so that we can get the current
     * charging, headset and dock state.
     *
     * @param charging {@code true} if the device is charging or connected to a power source.
     * @param headset {@code true} if the device is connected to a headset or a audio output
     *                device.
     * @param docked {@code true} if the device is docked.
     */
    @Override
    public void onInitialize(boolean charging, boolean headset, boolean docked) {
        super.onInitialize(charging, headset, docked);

        // TODO: Do any work here.        
    }

    /**
     * This method will be called when call state is changed. 
     * Either on call or the device is idle.
     *
     * @param call {@code true} if the device is on call.
     *             Either ringing or answered.
     */
    @Override
    public void onCallStateChange(boolean call) {
        super.onCallStateChange(call);

        // TODO: Do any work here.        
    }

    /**
     * This method will be called when screen state is changed. 
     * Either the device screen is off or on.
     *
     * @param screenOff {@code true} if the device screen is off.
     */
    @Override
    public void onScreenStateChange(boolean screenOff) {
        super.onScreenStateChange(screenOff);

        // TODO: Do any work here.        
    }

    /**
     * This method will be called when lock state is changed. 
     * Either the device is in the locked or unlocked state independent of the PIN, 
     * password or any other security lock.
     *
     * @param locked {@code true} if the device is in the locked state or the lock screen is shown.
     */
    @Override
    public void onLockStateChange(boolean locked) {
        super.onLockStateChange(locked);

        // TODO: Do any work here.        
    }

    /**
     * This method will be called when headset state is changed. 
     * Either the device is connected to a audio output device or volume is routed through 
     * the internal speaker.
     *
     * @param connected {@code true} if the device is connected to a headset or a audio output
     *                  device.
     */
    @Override
    public void onHeadsetStateChange(boolean connected) {
        super.onHeadsetStateChange(connected);

        // TODO: Do any work here.        
    }

    /**
     * This method will be called when charging state is changed. 
     * Either the device is connected to a power source using the battery.
     *
     * @param charging {@code true} if the device is charging or connected to a power source.
     */
    @Override
    public void onChargingStateChange(boolean charging) {
        super.onChargingStateChange(charging);

        // TODO: Do any work here.        
    }

    /**
     * This method will be called when dock state is changed. 
     * Either the device is docked or not.
     *
     * @param docked {@code true} if the device is docked.
     */
    @Override
    public void onDockStateChange(boolean docked) {
        super.onDockStateChange(docked);

        // TODO: Do any work here.  
    }
    
    ...
}

public class MonitorService extends DynamicEngine {

    ...
    
    /**
     * Enable or disable the foreground app monitor task.
     *
     * @param running {@code true} to start monitoring the foreground app and receive
     *                listener callback.
     */
    setAppMonitorTask(boolean running);
    
    ...
    
    /**
     * This method will be called when foreground app is changed. 
     * Use it to provide the app specific functionality in the app.
     *
     * @param dynamicAppInfo The dynamic app info of the foreground package.
     */
    @Override
    public void onAppChange(@Nullable DynamicAppInfo dynamicAppInfo) {
        super.onAppChange(dynamicAppInfo);

        // TODO: Do any work here.
    }
    
    ...
}

public class MonitorService extends DynamicEngine {

    ...
    
    /**
     * This method will be called when an app package is added or changed. 
     * Useful to show a notification if an app is updated or a new app is installed.
     *
     * @param dynamicAppInfo The dynamic app info of the updated or added package.
     * @param newPackage {@code true} if the package is newly added.
     */
    @Override
    public void onPackageUpdated(@Nullable DynamicAppInfo dynamicAppInfo, boolean newPackage) {
        // TODO: Do any work here.
    }

    /**
     * This method will be called when an app package is removed. 
     * Useful to show some work when a package is removed.
     *
     * @param packageName The package which was removed.
     */
    @Override
    public void onPackageRemoved(@Nullable String packageName) {
        // TODO: Do any work here.
    }
    
    ...
}

public class DynamicPriority {
    
    ...

    /**
     * Default priority for the events.
     *
     * 1. Call (highest)
     * 2. Lock
     * 3. Headset
     * 4. Charging
     * 5. Dock
     * 6. App (lowest)
     */
    
    /**
     * Save events priority.
     *
     * @param context The context to get shared preferences.
     * @param eventsPriority ArrayList containing events priority.
     */
    public static void saveEventsPriority(@NonNull Context context, 
        @NonNull ArrayList<String> eventsPriority);
    
    /**
     * Get saved events priority after checking the device for telephony and per app 
     * functionality.
     *
     * @param context The context to get shared preferences.
     *
     * @return The saved events priority.
     */
    public static @NonNull ArrayList<String> getEventsPriority(@NonNull Context context);
    
    /**
     * Reset events priority to default.
     *
     * @param context The context to get shared preferences.
     */
    public static void resetPriority(@NonNull Context context);
    
    ...

}

public abstract class DynamicEngine {
    ...
    
    /**
     * Retrieve the current ongoing events.
     *
     * @return The list of current ongoing events.
     */
    protected @NonNull ArrayList<String> getCurrentEvents();
    
    /**
     * Get the event with highest priority.
     *
     * @return The highest priority event that has been occurred.
     */
    protected @DynamicEvent String getHighestPriorityEvent();

    ...
}