MIT App Inventor 2 ZIP Code Search is a free and open source Android app. Search for the zip code of the desired address by selecting the displayed prefecture, city, and town area. The tutorial for creating this application and the source code are available at the following URL.
https://appinventor.tmsoftwareinc.com/archives/809

How to use:
* Launch the app. It takes some time for the state menu display to initialize the database at the first startup. After the second time, the prefecture menu will be displayed immediately.
* Select the desired province.
* Select the city you want.
* Select the desired town area.
* The postal code of the desired address is displayed.
* If you want to search again, press the reset button.

This app was developed with MIT App Inventor 2 Japanese version.