We will be releasing the next version of MIT App Inventor tomorrow, December 19th, at around 10pm EST. This version will include a new companion version 2.56. However, upgrading the companion is only required if you plan to use the new sensors added in this release.
Some highlights of this release include:
Deleted projects go into a separate Trash area similar to the Windows Recycle Bin or macOS Trash Can. App inventors can restore their projects from the Trash area (or permanently delete them).
Autoloading of projects can be disabled using the option under the Settings menu. One can also append ?autoload=false in the URL to disable autoloading in case a large project prevents App Inventor from properly starting.
Ability to manipulate the properties of multiple components by shift-clicking them in the designer. The properties panel will only show those in common, and changing a property in this mode will change it for all selected components.
Four new sensor components for devices that support them: Barometer, Hygrometer, Light Sensor, and Thermometer.
Some default setting changes for new projects: Sizing will be responsive by default and ShowListsAsJson will be true by default
Adaptive icons: Specify an app icon of up to 512x512 and the build server will generate icons for every available icon size needed by Android.
For complete details on all of the changes in this release, please see the release notes.
What is an app icon (launcher icon) size 512x512px required for within the app (project)? As far as I know, this is only needed for the Play Store icon. While this is harmless, it uses more space than required.
The launcher icon can have the following dimensions:
36x36, 48x48, 72x72, 96x96, 144x144 and (max) 192x192 px
LDPI, MDPI, HDPI, XHDPI, XXHDPI and XXXHDPI
Because the app icon is used to generate all of the sizes, having a higher fidelity icon means sharper icons when they are downsampled (if we wanted to be pedantic, 576 is the LCM of the Android variants and would be a better choice than 512 when it comes to scaling). Eventually, for iOS we will also need to provide a 1024x1024 image in the app bundle for the App Store, so it made sense to pin the size to the needs of the various app store platforms (it needs 18 different variants). Note that anyone can also include an icon that's larger than 512x512 (or smaller, as @Diego pointed out), but in the end they will all be sized to the expected values.
For reference, the default App Inventor icon we use in this release is actually 1024x1024, and it is 67 kB. All of the icon variants that get generated are 166 kB, so the icon payload for an app is around 230 kB. Figures will vary depending on how compressible the icon data are.
