Help with National Parks Tutorial

[Waldo_De_Villiers]

I am struggling to run this app it keeps saying something about: The operation > cannot accept the arguments: , [0.0], [empty-string]. I think the problem is with the Sort and get list procedure. Any ideas how to fix this will be appreciated?

[Waldo_De_Villiers]

after clicking plot parks the app shows markers but gets no further...
No hidden buttons becomes visible.

[SteveJG]

Thanks for your posts Waldo.

It appears the latest version of Companion 2.63 or the nb189a release on June 19, 2022 broke the code again.
I will attempt to find out what the problem is. Yes I get a similar error .

[SteveJG]

Use the fixed aia. replacement Waldo.

NationalParks3a.aia (17.0 KB).

The aia was corrected in the tutorial too. National Park Tutorial (Markers) updated

The problem was how the new release handled the csvdistanceList differently than pre update.

Does the example work now?

[Ten04]

Hi, so I need help on getting explanation for these super long block codes on why and what does it do.

The blocks are as below

1. The whole block is very confusing, but why is it needed and what does it do?

1. What is the purpose of the minimum value needed for?
2. Why does the selected item, needs to be sorted out?

1. There are a couple distance lists, may i know what are the difference between them and the functions?
2. What does the control "for each number from 1 to length of list by 1" do
3. if the number in marker map list is less than 1 then it will add item in it, is my interpretation correct?
4. Why does global csv has to be joined with the decimal number of user's lat and long?
5. Why does experimental distance CSV has to be converted into the distance csv
6. Then, why will experimental distance CSV be deleted

1. I don't understand why is minimum at the index and what does it do

Thank you so much for helping out, I really want to understand the codes, so that i can start doing a similar project for my own use.

The aia is here
NationalParks3a.aia (17.0 KB)

Credits to @SteveJG

[SteveJG]

@Ten04

The whole block is very confusing, but why is it needed and what does it do?

The Procedure sorts a generic List. See List Sorting On App Inventor | Imagnity . The Procedure is used in the app to determine the Park that is closest (by straight line distance) to the app's user. The app needs to determine how far away each Park is from the app's user. If you are not concerned with which Park is closest, the MinimumValueinList would not be needed. You might wish to re-read the tutorial

@SteveJG

The Tutorial

This tutorial demonstrates how to use the MIT Map component to display a large number of run time location Markers, calculate the distance from the Android device to all the displayed locations and display that information. A bubble sort creates a list of locations in ascending distance from the device. The first item in the calculated and sorted List is the straight-line distance to the closest Marker and location. National Parks was designed on a Tablet. It should display properly on most cell phones. The coding requires use of Responsive Sizing and must be run on a real device.

Provide csv table file of the information required To display a lot of Markers,. The csv, called Destinations.csv in the example National Park app, is stored in the Media. A File control retrieves the csv file stored in Media. The csv information is used to create several Lists. The Lists are manipulated to display the information you want on the OpenStreetMap map tile screen and Marker bubbles.

@Ten04

What does the control "for each number from 1 to length of list by 1" do

The "for each number... "

does several things, notably the involved Block calculates the distance each Park is from the user.

@Ten04

I really want to understand the codes

Load and run the aia, then use DoIt debugger to see what values are evaluated in specific parts of the code.