getImage static method
绘制时需要用到 ui.Image 的对象,通过此方法进行转换
Implementation
static Future<ui.Image> getImage(String asset) async {
ByteData data = await rootBundle.load("packages/flutter_weather_bg_null_safety/$asset");
Codec codec = await ui.instantiateImageCodec(data.buffer.asUint8List());
FrameInfo fi = await codec.getNextFrame();
return fi.image;
}