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How to get the total of a list in Sketchware

This tutorial covers how to get the total value of items at a specific key of a listmap.

Prerequisites:

A listmap with logic already set up. This tutorial assumes you already have a listmap and want to calculate the total. If you do not know how to set up a listmap then you should check out my tutorial on how to create your own record keeping app.

Add a linear

Add a linear H

Add a textview to the linear. This will display our total.

Add a textview


Go to the events tab


Click event tab


Add a more block as shown below


Name your block and then click add

Name your moreblock

Open the more block

Open moreblock

In your more block, create 2 number variables "n" and "total". 

Open block selector

Click 'add variable' and name your variables 'total' and 'n'

create variables


NB- If you already have a variable named n or total, then give it another name. In my case I called my total variable, "total1"

Then place your blocks to get the total like this:



In my example, I get the total and display it as a string in the decimal format 0.00

I also use a 'shared preferences' component to save this total on the device storage. You can leave this out if you do not need it. 

Also remember that list keys are case sensitive... so calling the wrong key might crash your app.

The next step is displaying the total

You might want to show your total when a button is clicked or when your app starts. In the following example I placed my logic on start. That works if I already have items on my list when the app starts. This calls that moreblock logic when the app starts. If you want to show the total when a button is clicked, place your logic onButtonClick.

More block onStart


Get the total number of items in a list



Use the length of list block to get how many items a specific list is holding
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Comments

Tonyx 67 said…
Hi hi found this tutorial and it is just what I needed for my app, I just can't complete it because I noticed that the code works with an add operation but if I multiply, or divide, or subtract, it always results in zero .. What am I doing wrong? Thanks so much
15 March 2021 at 07:50
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