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在多种语言之间互译文本。机器学习套件可以在 50 多种语言之间进行翻译。

试试看

准备工作

  1. 请务必在您的项目级 build.gradle 文件中的 buildscriptallprojects 部分添加 Google 的 Maven 制品库。
  2. 将 Android 版机器学习套件库的依赖项添加到模块的应用级 Gradle 文件(通常为 app/build.gradle):
    dependencies {
      // ...
    
      implementation 'com.google.mlkit:translate:17.0.2'
    }
    

翻译文本字符串

如需将字符串在两种语言之间互译,请执行以下操作:

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

    Kotlin

    // Create an English-German translator:
    val options = TranslatorOptions.Builder()
        .setSourceLanguage(TranslateLanguage.ENGLISH)
        .setTargetLanguage(TranslateLanguage.GERMAN)
        .build()
    val englishGermanTranslator = Translation.getClient(options)

    Java

    // Create an English-German translator:
    TranslatorOptions options =
        new TranslatorOptions.Builder()
            .setSourceLanguage(TranslateLanguage.ENGLISH)
            .setTargetLanguage(TranslateLanguage.GERMAN)
            .build();
    final Translator englishGermanTranslator =
        Translation.getClient(options);

    如果您不知道输入文本的语言,可以使用 Language Identification API 为您提供语言标记。然后,使用 TranslateLanguage.fromLanguageTag() 将该代码转换为 TranslateLanguage

    避免同时在设备上保留过多语言模型。

  2. 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()

    Kotlin

    var conditions = DownloadConditions.Builder()
        .requireWifi()
        .build()
    englishGermanTranslator.downloadModelIfNeeded(conditions)
        .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.
            // ...
        }

    Java

    DownloadConditions conditions = new DownloadConditions.Builder()
        .requireWifi()
        .build();
    englishGermanTranslator.downloadModelIfNeeded(conditions)
        .addOnSuccessListener(
            new OnSuccessListener() {
              @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.
                // ...
              }
            });

    语言模型大约为 30MB,因此请勿不必要地下载语言模型;除非用户另行指定,否则只能使用 Wi-Fi 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

  3. 确认模型已下载后,将源语言中的文本字符串传递给 translate()

    Kotlin

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

    Java

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

    采用您配置的目标语言的译文即会传递给成功监听器。

  4. 确保在不再使用 Translator 对象时调用 close() 方法。

    如果您在 Fragment 或 AppCompatActivity 中使用翻译器,一种简单的方法是对 Fragment 或 AppCompatActivity 调用 LifecycleOwner.getLifecycle(),然后调用 Lifecycle.addObserver。例如:

    Kotlin

    val options = ...
    val translator = Translation.getClient(options)
    getLifecycle().addObserver(translator)

    Java

    TranslatorOptions options = ...
    Translator translator = Translation.getClient(options);
    getLifecycle().addObserver(translator);
    ... use translator ...

    请注意,这假定代码位于实现 LifecycleOwner 的类(例如 Fragment 或 AppCompatActivity)内。

显式管理翻译模型

在您按上述方式使用翻译 API 时,机器学习套件会根据需要自动将特定于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,明确管理您希望在设备上提供的翻译模型。如果您想提前下载模型或从设备中删除不需要的模型,这种方法会非常有用。

Kotlin

val modelManager = RemoteModelManager.getInstance()

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

// Delete the German model if it's on the device.
val germanModel = TranslateRemoteModel.Builder(TranslateLanguage.GERMAN).build()
modelManager.deleteDownloadedModel(germanModel)
    .addOnSuccessListener {
        // Model deleted.
    }
    .addOnFailureListener {
        // Error.
    }

// Download the French model.
val frenchModel = TranslateRemoteModel.Builder(TranslateLanguage.FRENCH).build()
val conditions = DownloadConditions.Builder()
    .requireWifi()
    .build()
modelManager.download(frenchModel, conditions)
    .addOnSuccessListener {
        // Model downloaded.
    }
    .addOnFailureListener {
        // Error.
    }

Java

RemoteModelManager modelManager = RemoteModelManager.getInstance();

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

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

// Download the French model.
TranslateRemoteModel frenchModel =
        new TranslateRemoteModel.Builder(TranslateLanguage.FRENCH).build();
DownloadConditions conditions = new DownloadConditions.Builder()
    .requireWifi()
    .build();
modelManager.download(frenchModel, conditions)
    .addOnSuccessListener(new OnSuccessListener() {
        @Override
        public void onSuccess(Void v) {
            // Model downloaded.
        }
    })
    .addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e) {
            // Error.
        }
    });