在Flutter应用程序中使用Android NDK中的AssetManager类

class NativeLib {
    companion object {
        init {
            System.loadLibrary("native-lib")
        }

        external fun readAsset(assetManager: AssetManager, fileName: String): String
    }
}

#include <jni.h>
#include <string>
#include <android/asset_manager.h>
#include <android/asset_manager_jni.h>

extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_myapp_NativeLib_readAsset(JNIEnv* env, jobject thiz, jobject assetManager, jstring fileName) {
    AAssetManager* mgr = AAssetManager_fromJava(env, assetManager);
    const char* file = env->GetStringUTFChars(fileName, nullptr);
    AAsset* asset = AAssetManager_open(mgr, file, AASSET_MODE_BUFFER);
    env->ReleaseStringUTFChars(fileName, file);

    if (asset == nullptr) {
        return env->NewStringUTF("");
    }

    off_t assetLength = AAsset_getLength(asset);
    std::string content(assetLength, '\0');
    AAsset_read(asset, &content[0], assetLength);
    AAsset_close(asset);

    return env->NewStringUTF(content.c_str());
}

import 'dart:ffi';
import 'package:flutter/services.dart';

class NativeAssetReader {
  static const platform = const MethodChannel('com.example.myapp/native_asset_reader');

  static Future<String> readAsset(String fileName) async {
    try {
      final String result = await platform.invokeMethod('readAsset', {'fileName': fileName});
      return result;
    } on PlatformException catch (e) {
      print("Failed to read asset: ${e.message}");
      return '';
    }
  }
}

class MainActivity: FlutterActivity() {
    private val CHANNEL = "com.example.myapp/native_asset_reader"

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL).setMethodCallHandler { call, result ->
            if (call.method == "readAsset") {
                val fileName = call.argument<String>("fileName")
                val content = NativeLib.readAsset(assetManager, fileName!!)
                result.success(content)
            } else {
                result.notImplemented()
            }
        }
    }
}