读取 assets 中的图片
Future _readImage(String imgPath, {int w = 44, int h = 44}) async {
dart_ui.FrameInfo? frameInfo;
ByteData byteData = await rootBundle.load(imgPath);
dart_ui.Codec codec = await dart_ui.instantiateImageCodec(
byteData.buffer.asUint8List(),
targetWidth: w,
targetHeight: h);
frameInfo = await codec.getNextFrame();
setState(() {
_uiImage = frameInfo?.image;
});
}