Step 1
Click on one of these links, depending on your region.
(For Hong Kong & Macau users) https://fonts.google.com/?subset=chinese-hongkong
(For Mainland China, Singapore and Malaysia users) https://fonts.google.com/?subset=chinese-simplified
(For Taiwan users) https://fonts.google.com/?subset=chinese-traditional
Note: I checked, some of them have file sizes > 5 MB, do not use them!
Step 2
When the new tab is opened, click on a font that you like. It seems that you have wider options if you use Simplified Chinese.
Click 'Download family'.
The system will open a .ZIP file for you. Open it.
(A screenshot of the ZIP file, it's all Chinese)
Drag out the TTF file (the icon with a little A) into the Desktop.
Step 3
Download this extension's AIX file and import it into MIT App Inventor. Drag out 1 of this extension into the Viewer.
Upload the TTF font file into the Media panel in the Designer.
Note: If App Inventor said that the file is too large, use another font.

Then, use this code:




