New little (and first) extension

I would submit this my first little extension which is useful for some financial calculations.
It is only in an early stage of dev., because I would like to add more blocks to solve different problems. Moreover, I need feedback and I have just now a problem with the extension icon, which I don’t know how to include in java file from my PC. Can you help me?

Up to date release:

com.tiziano1960.aix (12.0 KB)


Hi, nice begin!

You should include some info about your extension and add screenshots from the blocks :slight_smile:

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congratulations! nice start!

here is a screenshot of the available blocks

you might want to add an icon for the extension like this

Extension icons: Until now, icons needed to be compiled as part of the MIT App Inventor build or hosted externally using an HTTP or HTTPS URL. Now it is possible to include icons in the extension. To do so, create a directory aiwebres in the same package as the extension. Add a PNG file for the icon, and name it in the iconName field of the @DesignerComponent annotation, for example “aiwebres/icon.png”. When the extension is packaged it will be pulled into the AIX and the SimplePaletteItem will correctly load the icon from the MIT App Inventor server.

(taken from
the icon should be 16x16px



Thank you everybody!

Now I’ve published the final release. The link in first post of this topic was updated.
Now it is possible do to a good variety of financial calculations concerning bank operations. All the blocks are self-commented; here they are:

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Great extension, I love Mortgage function mostly. Keep it up :wink:

you might want to follow the naming conventions, which is UpperCamelCase for property, method and event names and lowerCamelCase (i.e. the first letter should be lower case) for parameter names


Thank you!


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Thanks for suggestions and appreciations. I will follow them. Just now I think I can introduce a property which could be set by user , a numerical input, once for all, visible across all the function blocks. It could be e.g. something like “NumberOfDecimals” useful to set the precision of results. But I need an example how to code such a property. Can you please help me?

Properties are for that. Use property to set variable.

there are plenty of examples in the App Inventor sources

for questions about working with the App Inventor Sources you might want to ask in the Open Source Group next time …
there you will also find the experts from the MIT App Inventor team to answer questions…


Et voilà, this is a more polished version, the updated link is in the first post.

Sorry, I had this problem too, I tried to enclose an icon but I had to give up and use an external url. I don’t get this sentence “To do so, create a directory aiwebres in the same package as the extension.”

for questions about working with the App Inventor Sources, please ask in the Open Source Group!forum/app-inventor-open-source-dev
I will be happy to answer the question there

Por favor, você teria um exemplo de como utilizar esta extensão, agradeço sua ajuda.