在 Android 系统中使用机器学习套件翻译文本

您可以使用机器学习套件实现语言之间的文本互译。机器学习套件目前支持 59 种语言之间的互译。

准备工作

将 Firebase 添加到您的 Android 项目（如果尚未添加）。

将 Android 版机器学习套件库的依赖项添加到您的模块（应用级层）Gradle 文件（通常为 app/build.gradle）：

apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'

dependencies {
  // ...

  implementation 'com.google.firebase:firebase-ml-natural-language:22.0.0'
  implementation 'com.google.firebase:firebase-ml-natural-language-translate-model:20.0.8'
}

翻译文本字符串

为实现字符串在两种语言之间的互译，请执行以下操作：

创建一个 FirebaseTranslator 对象，并使用源语言和目标语言对其进行配置：

Java

// Create an English-German translator:
FirebaseTranslatorOptions options =
        new FirebaseTranslatorOptions.Builder()
                .setSourceLanguage(FirebaseTranslateLanguage.EN)
                .setTargetLanguage(FirebaseTranslateLanguage.DE)
                .build();
final FirebaseTranslator englishGermanTranslator =
        FirebaseNaturalLanguage.getInstance().getTranslator(options);

Kotlin+KTX

// Create an English-German translator:
val options = FirebaseTranslatorOptions.Builder()
        .setSourceLanguage(FirebaseTranslateLanguage.EN)
        .setTargetLanguage(FirebaseTranslateLanguage.DE)
        .build()
val englishGermanTranslator = FirebaseNaturalLanguage.getInstance().getTranslator(options)

如果您不知道输入文本的语言，可以先使用语言识别 API。（但请确保您不会在设备上同时保留太多语言模型。）

确保已将所需的翻译模型下载到设备上。确信模型可用之后，再调用 translate()。

Java

FirebaseModelDownloadConditions conditions = new FirebaseModelDownloadConditions.Builder()
    .requireWifi()
    .build();
englishGermanTranslator.downloadModelIfNeeded(conditions)
      .addOnSuccessListener(
          new OnSuccessListener<Void>() {
            @Override
            public void onSuccess(Void v) {
              // Model downloaded successfully. Okay to start translating.
              // (Set a flag, unhide the translation UI, etc.)
            }
          })
      .addOnFailureListener(
          new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
              // Model couldn’t be downloaded or other internal error.
              // ...
            }
          });

Kotlin+KTX

englishGermanTranslator.downloadModelIfNeeded()
        .addOnSuccessListener {
            // Model downloaded successfully. Okay to start translating.
            // (Set a flag, unhide the translation UI, etc.)
        }
        .addOnFailureListener { exception ->
            // Model couldn’t be downloaded or other internal error.
            // ...
        }

语言模型大小约为 30 MB，因此若非必要，请勿下载。此外，除非用户另行指定，否则应仅使用 WiFi 下载语言模型。您还应删除不需要的模型。请参阅显式管理翻译模型。

确认模型已下载后，将源语言的文本字符串传递至 translate()：

Java

englishGermanTranslator.translate(text)
      .addOnSuccessListener(
          new OnSuccessListener<String>() {
            @Override
            public void onSuccess(@NonNull String translatedText) {
              // Translation successful.
            }
          })
      .addOnFailureListener(
          new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
              // Error.
              // ...
            }
          });

Kotlin+KTX

englishGermanTranslator.translate(text)
        .addOnSuccessListener { translatedText ->
            // Translation successful.
        }
        .addOnFailureListener { exception ->
             // Error.
             // ...
        }

采用配置的目标语言的译文即会传递给成功监听器。

显式管理翻译模型

在您按上文所述使用翻译 API 时，机器学习套件会根据需要自动将特定语言的翻译模型下载到设备。您还可以使用机器学习套件的翻译模型管理 API 来显式管理设备上可用的翻译模型。如果您想提前下载模型或从设备中删除不需要的模型，此方法会非常有用。

Java

FirebaseModelManager modelManager = FirebaseModelManager.getInstance();

// Get translation models stored on the device.
modelManager.getDownloadedModels(FirebaseTranslateRemoteModel.class)
        .addOnSuccessListener(new OnSuccessListener<Set<FirebaseTranslateRemoteModel>>() {
            @Override
            public void onSuccess(Set<FirebaseTranslateRemoteModel> models) {
                // ...
            }
        })
        .addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                // Error.
            }
        });

// Delete the German model if it's on the device.
FirebaseTranslateRemoteModel deModel =
        new FirebaseTranslateRemoteModel.Builder(FirebaseTranslateLanguage.DE).build();
modelManager.deleteDownloadedModel(deModel)
        .addOnSuccessListener(new OnSuccessListener<Void>() {
            @Override
            public void onSuccess(Void v) {
                // Model deleted.
            }
        })
        .addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                // Error.
            }
        });

// Download the French model.
FirebaseTranslateRemoteModel frModel =
        new FirebaseTranslateRemoteModel.Builder(FirebaseTranslateLanguage.FR).build();
FirebaseModelDownloadConditions conditions = new FirebaseModelDownloadConditions.Builder()
        .requireWifi()
        .build();
modelManager.download(frModel, conditions)
        .addOnSuccessListener(new OnSuccessListener<Void>() {
            @Override
            public void onSuccess(Void v) {
                // Model downloaded.
            }
        })
        .addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                // Error.
            }
        });

Kotlin+KTX

val modelManager = FirebaseModelManager.getInstance()

// Get translation models stored on the device.
modelManager.getDownloadedModels(FirebaseTranslateRemoteModel::class.java)
    .addOnSuccessListener { models ->
        // ...
    }
    .addOnFailureListener {
        // Error.
    }

// Delete the German model if it's on the device.
val deModel = FirebaseTranslateRemoteModel.Builder(FirebaseTranslateLanguage.DE).build()
modelManager.deleteDownloadedModel(deModel)
    .addOnSuccessListener {
        // Model deleted.
    }
    .addOnFailureListener {
        // Error.
    }

// Download the French model.
val frModel = FirebaseTranslateRemoteModel.Builder(FirebaseTranslateLanguage.FR).build()
val conditions = FirebaseModelDownloadConditions.Builder()
    .requireWifi()
    .build()
modelManager.download(frModel, conditions)
    .addOnSuccessListener {
        // Model downloaded.
    }
    .addOnFailureListener {
        // Error.
    }