Flutter中open_file_plus编译失败：PluginRegistry.Registrar找不到符号

我正在开发一款Flutter移动应用，需要在应用内创建PDF后打开它。使用最新版本open_file_plus: ^3.4.1+1时，编译始终出现PluginRegistry.Registrar相关构建错误。

保存并打开PDF的代码 #

openFile() async {
    String storeNameForInvoice = '${storeName.value} - $date';
    final invoicesPath = await getTargetDirectoryPath();
    final file = File("$invoicesPath/$storeNameForInvoice.pdf");
    await file.writeAsBytes(await pdf.save());
    await saveInvoiceToFirestore();
    loadInvoicesToCurrentInvoice(storeName.value);

    await OpenFile.open(file.path);
}

配置详情 #

1. Gradle版本 (gradle-wrapper.properties) #

distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
distributionUrl=https\://services.gradle.org/distributions/gradle-8.9-all.zip

2. 编译与Target SDK版本 (build.gradle 应用级) #

compileSdk = 34
targetSdk = 34

3. Settings.gradle配置 #

pluginManagement {
    def flutterSdkPath = {
        def properties = new Properties()
        file("local.properties").withInputStream { properties.load(it) }
        def flutterSdkPath = properties.getProperty("flutter.sdk")
        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
        return flutterSdkPath
    }()

    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")

    repositories {
        google()
        mavenCentral()
        gradlePluginPortal()
    }
}

plugins {
    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
    id "com.android.application" version "7.3.0" apply false
    id "com.google.gms.google-services" version "4.3.15" apply false
    id "org.jetbrains.kotlin.android" version "1.9.0" apply false
}

include ":app"

错误信息 #

C:\Users\MQ\AppData\Local\Pub\Cache\hosted\pub.dev\open_file_plus-3.4.1+1\android\src\main\java\com\joutvhu\openfile\OpenFilePlusPlugin.java:66: error: cannot find symbol
    public static void registerWith(PluginRegistry.Registrar registrar) {
                                                  ^
  symbol:   class Registrar
  location: interface PluginRegistry
1 error

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':open_file_plus:compileDebugJavaWithJavac'.
> Compilation failed; see the compiler error output for details.

* Try:
> Run with --info option to get more log output.
> Run with --scan to get full insights.

BUILD FAILED in 1m 20s
Error: Gradle task assembleDebug failed with exit code 1

补充信息 #

已尝试flutter upgrade、flutter clean、flutter pub upgrade、flutter pub outdated等操作，但问题仍存在。测试open_file、url_launcher等同类库也出现相似错误。

问题 #

1. PluginRegistry.Registrar错误的成因是什么？
2. 如何解决该问题以成功在Flutter应用中打开PDF？

解答 #

错误成因 #

PluginRegistry.Registrar是Flutter旧版插件API的接口，在Flutter 3.10+版本中，该接口已被废弃并移除，改用新的FlutterPlugin API实现插件注册。你使用的open_file_plus: ^3.4.1+1版本的Android端代码仍在使用旧的注册方式，与当前Flutter版本不兼容，导致编译报错。

解决方法 #

方法一：升级到兼容新版Flutter的插件版本

检查open_file_plus的最新版本，确认是否已适配新版Flutter插件API。在pubspec.yaml中更新依赖：

dependencies:
  open_file_plus: ^最新兼容版本

更新后执行flutter pub get，再重新编译项目。

方法二：修改插件的Android代码（临时方案）

如果暂时没有兼容版本，可以手动修改本地缓存的插件代码：

1. 打开错误提示中的文件路径：C:\Users\MQ\AppData\Local\Pub\Cache\hosted\pub.dev\open_file_plus-3.4.1+1\android\src\main\java\com\joutvhu\openfile\OpenFilePlusPlugin.java
2. 删除旧的registerWith方法，替换为新版Flutter插件注册逻辑：

import io.flutter.embedding.engine.plugins.FlutterPlugin;
import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
import io.flutter.plugin.common.MethodChannel.Result;

public class OpenFilePlusPlugin implements FlutterPlugin, MethodCallHandler {
  private MethodChannel channel;

  @Override
  public void onAttachedToEngine(FlutterPlugin.FlutterPluginBinding flutterPluginBinding) {
    channel = new MethodChannel(flutterPluginBinding.getBinaryMessenger(), "open_file_plus");
    channel.setMethodCallHandler(this);
  }

  @Override
  public void onMethodCall(MethodCall call, Result result) {
    // 保留原有的方法处理逻辑
  }

  @Override
  public void onDetachedFromEngine(FlutterPlugin.FlutterPluginBinding binding) {
    channel.setMethodCallHandler(null);
  }
}

3. 同时修改android/src/main/AndroidManifest.xml，移除旧的<meta-data>注册项（如果有），确保插件通过新方式注册。

方法三：使用替代插件

如果上述方法无效，可以尝试使用已适配新版Flutter的文件打开插件，比如filex或open_filex，这些插件通常已更新到新的插件API。

内容的提问来源于stack exchange，提问作者Muhammad Qazmouz