Check if asset exist in flutter

问题

How I can check if a specific asset exists in Flutter. I'm trying to load some images and sound files and I need to handle the case when these assets do not exist.

I need to check the existence because I have audio files and images for numbers from 1 to 1000. When I build my widgets I use a loop from 1 to 1000 to build it. and there are possibilities that the required file ( the image or the sound for the current number ) does not exist in the assets.

回答1:

I assume that you are using the AssetBundle class to load your data using the load method which takes ByteData, and when you use this method, it will throws an exception if the asset is not found.

回答2:

Following Raouf suggestion I handled the case where the assets not exist.

Image loader widget:

Future<Image> _buildImage() async {
  String path = "assets/images/contents/${content.id}.jpg";
  return rootBundle.load(path).then((value) {
    return Image.memory(value.buffer.asUint8List());
  }).catchError((_) {
    return Image.asset(
      "assets/images/null.png",
      height: 250.0,
    );
  });
}

Using the Image widget inside my build method:

FutureBuilder(
          future: _buildImage(),
          builder: (BuildContext context, AsyncSnapshot<Image> snapshot) {
            if (snapshot.connectionState == ConnectionState.done)
              return snapshot.data;
            else
              return Image.asset("assets/images/null.png");
          },
        ),
      ),

来源：https://stackoverflow.com/questions/52908923/check-if-asset-exist-in-flutter