Android Kotlin MLKit翻译库异常：翻译文本为Null且日志报版本警告

我在Android Kotlin项目中使用MLKit进行文本翻译，运行时无直接错误，但翻译结果始终为Null，相关日志如下：

W/LibraryVersion: Failed to get app version for libraryName: shared-installation-id 
D/TransportRuntime.JobInfoScheduler: Scheduling upload for context TransportContext(cct, VERY_LOW, MSRodHRwczovL2ZpcmViYXNlbG9nZ2luZy5nb29nbGVhcGlzLmNvbS92MGNjL2xvZy9iYXRjaD9mb3JtYXQ9anNvbl9wcm90bzNc) with jobId=-653056373 in 86400000ms(Backend next call timestamp 0). Attempt 1 
W/LibraryVersion: Failed to get app version for libraryName: shared-remote-config 
D/MLKit RemoteConfigRestC: Got remote config. 
I/TetheringManager: registerTetheringEventCallback:com.example.agrithonapp 
D/TransportRuntime.SQLiteEventStore: Storing event with priority=VERY_LOW, name=FIREBASE_ML_SDK for destination cct 
D/TransportRuntime.JobInfoScheduler: Upload for context TransportContext(cct, VERY_LOW, MSRodHRwczovL2ZpcmViYXNlbG9nZ2luZy5nb29nbGVhcGlzLmNvbS92MGNjL2xvZy9iYXRjaD9mb3JtYXQ9anNvbl9wcm90bzNc) is already scheduled. Returning... 
D/TransportRuntime.SQLiteEventStore: Storing event with priority=VERY_LOW, name=FIREBASE_ML_SDK for destination cct 
D/TransportRuntime.JobInfoScheduler: Upload for context TransportContext(cct, VERY_LOW, MSRodHRwczovL2ZpcmViYXNlbG9nZ2luZy5nb29nbGVhcGlzLmNvbS92MGNjL2xvZy9iYXRjaD9mb3JtYXQ9anNvbl9wcm90bzNc) is already scheduled. Returning... 
D/TransportRuntime.SQLiteEventStore: Storing event with priority=VERY_LOW, name=FIREBASE_ML_SDK for destination cct 
D/TransportRuntime.JobInfoScheduler: Upload for context TransportContext(cct, VERY_LOW, MSRodHRwczovL2ZpcmViYXNlbG9nZ2luZy5nb29nbGVhcGlzLmNvbS92MGNjL2xvZy9iYXRjaD9mb3JtYXQ9anNvbl9wcm90bzNc) is already scheduled. Returning... 
D/TransportRuntime.SQLiteEventStore: Storing event with priority=VERY_LOW, name=FIREBASE_ML_SDK for destination cct 
D/TransportRuntime.JobInfoScheduler: Upload for context TransportContext(cct, VERY_LOW, MSRodHRwczovL2ZpcmViYXNlbG9nZ2luZy5nb29nbGVhcGlzLmNvbS92MGNjL2xvZy9iYXRjaD9mb3JtYXQ9anNvbl9wcm90bzNc) is already scheduled. Returning... 

排查与解决步骤 #

• 确认翻译模型已成功下载
  MLKit离线翻译依赖对应语言对的模型，若模型未下载或下载失败，翻译会返回Null。添加模型下载监听，确认状态：

  val translatorOptions = TranslatorOptions.Builder()
      .setSourceLanguage(TranslateLanguage.ENGLISH)
      .setTargetLanguage(TranslateLanguage.CHINESE)
      .build()
  val translator = Translation.getClient(translatorOptions)
  
  val downloadListener = object : ModelDownloadListener {
      override fun onModelDownloaded(conditions: ModelDownloadConditions?) {
          // 模型就绪，可执行翻译
      }
  
      override fun onModelDownloadFailed(conditions: ModelDownloadConditions?, e: Exception?) {
          e?.printStackTrace() // 打印下载失败原因
      }
  }
  
  translator.downloadModelIfNeeded(ModelDownloadConditions.Builder().build())
      .addOnSuccessListener { /* 下载完成回调 */ }
      .addOnFailureListener { it.printStackTrace() }
  

• 校验输入文本合法性
  确保传入翻译的文本非空且非空白，空输入会导致MLKit返回Null：

  val input = "需要翻译的文本"
  if (input.isBlank()) {
      // 处理空输入逻辑
      return
  }
  
  translator.translate(input)
      .addOnSuccessListener { result ->
          // 处理翻译结果
      }
      .addOnFailureListener { it.printStackTrace() }
  

• 检查依赖与配置正确性
  确认MLKit翻译依赖版本兼容，避免版本冲突：

  dependencies {
      implementation 'com.google.mlkit:translate:17.0.1'
  }
  

  同时确保google-services.json已正确放置在项目根目录，且与Firebase项目绑定。

• 处理日志中的警告信息
  日志中Failed to get app version警告需确保AndroidManifest.xml中正确配置应用版本：

  <manifest ...>
      <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="34" />
      <application ...>
          <meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version" />
      </application>
  </manifest>
  

  至于TransportRuntime相关日志，属于Firebase传输组件的正常调度逻辑，不会影响翻译功能，可忽略。

内容的提问来源于stack exchange，提问作者Malhar