https://github.com/dart-lang/sdk/blob/2.12.0-21.0.dev/samples/ffi/sample_ffi_functions_callbacks.dart

C++

typedef intptr_t (*IntptrBinOp)(intptr_t a, intptr_t b);
// Returns a closure.
// Note this closure is not properly marked as DART_EXPORT or extern "C".
// Used for testing passing a pointer to a closure to Dart.
// TODO(dacoharkes): is this a supported use case?
DART_EXPORT IntptrBinOp IntptrAdditionClosure() {
  std::cout << "IntptrAdditionClosure()\n";
  IntptrBinOp retval = [](intptr_t a, intptr_t b) { return a + b; };
  std::cout << "returning " << &retval << "\n";
  return retval;
}

Dart

typedef NativeIntptrBinOp = IntPtr Function(IntPtr, IntPtr);
typedef NativeIntptrBinOpLookup = Pointer<NativeFunction<NativeIntptrBinOp>>
    Function();

调用

 {
    // Return a c pointer to a c function from a c function.
    Pointer<NativeFunction<NativeIntptrBinOpLookup>> p14 =
        ffiTestFunctions.lookup("IntptrAdditionClosure");
    NativeIntptrBinOpLookup intptrAdditionClosure = p14.asFunction();

    Pointer<NativeFunction<NativeIntptrBinOp>> intptrAdditionPointer =
        intptrAdditionClosure();
    BinaryOp intptrAddition = intptrAdditionPointer.asFunction();
    print(intptrAddition(10, 27));
  }