Uint8List 图像为 null - Flutter

Question

我正在尝试将图像编码为 Uint8List，但它给了我一个 null

  List<int> bytes;
  I.Image _img;

  @override
  void initState() {
    super.initState();
    WidgetsFlutterBinding.ensureInitialized();
    String file = 'lib/graphics/logo.png';
    readFileAsync(file);
  }

  Future<dynamic> readFileAsync(String filePath) async {
    var imageData = await rootBundle.load('lib/graphics/logo.png');
    bytes = Uint8List.view(imageData.buffer);
    _img = I.decodeImage(bytes);
  }

并从小部件树中调用它

Container(
  child: Image.memory(_img.getBytes()),
),

错误

I/flutter (26125): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (26125): The following NoSuchMethodError was thrown building LayoutBuilder:
I/flutter (26125): The method 'getBytes' was called on null.
I/flutter (26125): Receiver: null
I/flutter (26125): Tried calling: getBytes()

Answer 1

你得到一个空值，因为 load 方法是一个 Future 而你不需要在你的构建方法上等待它。

您必须检查 _img 是否为 null 并显示另一个小部件，如 Text 或 CircularProgressIndicator 如果它是：

Container(
  child: _img ? Image.memory(_img.getBytes()) : Text('loading...'),
),

之后，您需要在 readFileAsync 方法中调用 setState() 方法来重建您的小部件：

setState() {
  _img = I.decodeImage(bytes);
}

Uint8List 图像为 null - Flutter

Image is null with Uint8List - Flutter

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