I/OpenJPEG(18753)：[INFO]没有解码区域参数，将解码区域设置为整个图像。如何解决这个问题？

Question

我在我的颤振项目中添加了一些本机函数，并在调用它时得到了这个错误：

​

I/OpenJPEG(18753): [INFO] Start to read j2k main header (111).
I/OpenJPEG(18753): [INFO] Main header has been correctly decoded.
I/OpenJPEG(18753): [INFO] No decoded area parameters, set the decoded area to the whole image
I/OpenJPEG(18753): [INFO] Header of tile 1 / 1 has been read.
I/OpenJPEG(18753): [INFO] Stream reached its end !


 PlatformException(error, Unsupported value: 'android.graphics.Bitmap@8a5b1cc' of type 'class android.graphics.Bitmap', null, java.lang.IllegalArgumentException: Unsupported value
: 'android.graphics.Bitmap@8a5b1cc' of type 'class android.graphics.Bitmap'
I/flutter (20654):      at io.flutter.plugin.common.StandardMessageCodec.writeValue(StandardMessageCodec.java:292)
I/flutter (20654):      at io.flutter.plugin.common.StandardMethodCodec.encodeSuccessEnvelope(StandardMethodCodec.java:59)
I/flutter (20654):      at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler$1.success(MethodChannel.java:267)
I/flutter (20654):      at com.yapeal.security.MainActivity.convertJp2(MainActivity.kt:163)
I/flutter (20654):      at com.yapeal.security.MainActivity.configureFlutterEngine$lambda-0(MainActivity.kt:70)
I/flutter (20654):      at com.yapeal.security.MainActivity.lambda$Sgujey3khZ1hmf7McHG_B6lCGlU(Unknown Source:0)
I/flutter (20654):      at com.yapeal.security.-$$Lambda$MainActivity$Sgujey3khZ1hmf7McHG_B6lCGlU.onMethodCall(Unknown Source:2)
I/flutter (20654):      at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.j

​

这是我在Kotlin的代码：

​

private fun convertJp2(list: List<Any>, result: MethodChannel.Result) {
        val inputStream: InputStream = ByteArrayInputStream(list.get(0) as ByteArray, 0, list.get(1) as Int)

        var image = JP2Decoder(inputStream).decode()
        result.success(image)
    }

​

我对Kotlin没有经验，所以我不知道如何解决这个问题。此外，我在谷歌也没有发现类似的问题……

Answer 1

StandardMessageCodec是由MethodChannel使用的，它不支持开箱即用Bitmap (https://api.flutter.dev/flutter/services/StandardMessageCodec-class.html)。

您可以扩展StandardMessageCodec并覆盖writeValue以支持它(https://docs.flutter.dev/development/platform-integration/platform-channels#custom-channels-and-codecs)

下面是一个cloud_firestore如何使用自己的编解码器来扩展功能的示例：https://github.com/firebase/flutterfire/blob/master/packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/method_channel/utils/firestore_message_codec.dart

  @override
  void writeValue(WriteBuffer buffer, dynamic value) {
    if (value is DateTime) {
      buffer.putUint8(_kDateTime);
      buffer.putInt64(value.millisecondsSinceEpoch);
    } else if (value is Timestamp) {
      buffer.putUint8(_kTimestamp);
      buffer.putInt64(value.seconds);
      buffer.putInt32(value.nanoseconds);
    } else if (value is GeoPoint) {
      buffer.putUint8(_kGeoPoint);
      buffer.putFloat64(value.latitude);
      buffer.putFloat64(value.longitude);
    } else if (value is DocumentReferencePlatform) {
      buffer.putUint8(_kDocumentReference);
      writeValue(buffer, value.firestore);
      writeValue(buffer, value.path);
    } else if (value is Blob) {
      buffer.putUint8(_kBlob);
      writeSize(buffer, value.bytes.length);
      buffer.putUint8List(value.bytes);
    } else if (value is FieldValuePlatform) {
      MethodChannelFieldValue delegate = FieldValuePlatform.getDelegate(value);
      final int code = _kFieldValueCodes[delegate.type]!;
      buffer.putUint8(code);
      if (delegate.value != null) writeValue(buffer, delegate.value);
    } else if (value is FieldPathType) {
      final int code = _kFieldPathCodes[value]!;
      buffer.putUint8(code);
    } else if (value is FieldPath) {
      buffer.putUint8(_kFieldPath);
      writeSize(buffer, value.components.length);
      for (final String item in value.components) {
        writeValue(buffer, item);
      }
    } else if (value is MethodChannelFirebaseFirestore) {
      buffer.putUint8(_kFirestoreInstance);
      writeValue(buffer, value.app.name);
      writeValue(buffer, value.settings);
    } else if (value is MethodChannelQuery) {
      buffer.putUint8(_kFirestoreQuery);
      writeValue(buffer, <String, dynamic>{
        'firestore': value.firestore,
        'path': value.path,
        'isCollectionGroup': value.isCollectionGroupQuery,
        'parameters': value.parameters,
      });
    } else if (value is Settings) {
      buffer.putUint8(_kFirestoreSettings);
      writeValue(buffer, value.asMap);
    } else if (value == double.nan) {
      buffer.putUint8(_kNaN);
    } else if (value == double.infinity) {
      buffer.putUint8(_kInfinity);
    } else if (value == double.negativeInfinity) {
      buffer.putUint8(_kNegativeInfinity);
    } else {
      super.writeValue(buffer, value);
    }
  }

用途类似：https://github.com/firebase/flutterfire/blob/982bdfb5fbfae4a68e1af6ab62a9bd762891b217/packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/method_channel/method_channel_firestore.dart

  /// The [FirebaseApp] instance to which this [FirebaseDatabase] belongs.
  ///
  /// If null, the default [FirebaseApp] is used.
  /// The [MethodChannel] used to communicate with the native plugin
  static MethodChannel channel = const MethodChannel(
    'plugins.flutter.io/firebase_firestore',
    StandardMethodCodec(FirestoreMessageCodec()),
  );

  /// The [EventChannel] used for query snapshots
  static EventChannel querySnapshotChannel(String id) {
    return EventChannel(
      'plugins.flutter.io/firebase_firestore/query/$id',
      const StandardMethodCodec(FirestoreMessageCodec()),
    );
  }