This project demonstrates how to create an Android/iOS Home Widget or macOS Today Widget rendered by pure Flutter.
All widget examples in this project are full functional, including widget configure and update.
Flutter engine on iOS takes too much memory and may only works on Simulator.
This project uses 2 different of methods to render a widget.
1. UI Mode
In UI Mode, flutter engine is initialized with a separate main Dart function and run a separate App to display UI of widget.
The UI is rendered by the background renderer, a Bitmap of UI screenshot will be taken and show in the widget.
PROs:
Simple, write code as normal flutter app.
CONs:
Slow, Flutter side of runApp is slow, and a 200ms delay should be manually set after setState, because you have to wait for UI refresh.
It can takes >6 seconds in Debug mode on an old Android phone.
Fortunately, it only takes ~1 second in Release mode, so the speed is still acceptable.
2. Image Mode
In Image Mode, flutter engine is initialized with a separate main Dart function and listen a MethodChannel.
The handler of MethodChannel will draw a image by a dart Canvas and return the bytes array to native side.
When the widget request to update, it convert the bytes to Bitmap and show.
PROs:
Fast, only a few of codes is executed, bitmap is transferred via memory.
No need to wait for render, the image is drawn realtime.
Moreover, you can write your own Encoder of MethodChannel to boost the speed of the exchange of data.
CONs:
Difficult to write code, the whole content is drawn by Canvas.