如果你想在你的应用中保持语言变化，你必须做两件事。

首先，创建一个base Activity，让你所有的Activity都从下面扩展:

public class BaseActivity extends AppCompatActivity {

    private Locale mCurrentLocale;

    @Override
    protected void onStart() {
        super.onStart();

        mCurrentLocale = getResources().getConfiguration().locale;
    }

    @Override
    protected void onRestart() {
        super.onRestart();
        Locale locale = getLocale(this);

        if (!locale.equals(mCurrentLocale)) {

            mCurrentLocale = locale;
            recreate();
        }
    }

    public static Locale getLocale(Context context){
        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);

        String lang = sharedPreferences.getString("language", "en");
        switch (lang) {
            case "English":
                lang = "en";
                break;
            case "Spanish":
                lang = "es";
                break;
        }
        return new Locale(lang);
    }
}

注意，我将新语言保存在sharedPreference中。

其次，像这样创建一个应用程序的扩展:

    public class App extends Application {

    @Override
    public void onCreate() {
        super.onCreate();
        setLocale();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        setLocale();
    }

    private void setLocale() {

        final Resources resources = getResources();
        final Configuration configuration = resources.getConfiguration();
        final Locale locale = getLocale(this);
        if (!configuration.locale.equals(locale)) {
            configuration.setLocale(locale);
            resources.updateConfiguration(configuration, null);
        }
    }
}

注意，getLocale()与上面相同。

这是所有! 我希望这能帮助到一些人。

这段代码真的可以工作:

fa = 波斯语，en = 英语

注意:语言代码不能有“-”，必须是2个小写字母

在languageToLoad变量中输入您的语言代码:

import android.app.Activity;
import android.content.res.Configuration;
import android.os.Bundle;

public class Main extends Activity {
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    String languageToLoad  = "fa"; // your language
    Locale locale = new Locale(languageToLoad); 
    Locale.setDefault(locale);
    Configuration config = new Configuration();
    config.locale = locale;
    getBaseContext().getResources().updateConfiguration(config, 
      getBaseContext().getResources().getDisplayMetrics());
    this.setContentView(R.layout.main);
  }
}

2021年6月更新(Kotlin):

class Main : Activity() {
    // Called when the activity is first created.
    public override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        
        val config = resources.configuration
        val lang = "fa" // your language code
        val locale = Locale(lang)
        Locale.setDefault(locale)
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1)
            config.setLocale(locale)
        else
            config.locale = locale

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N)
            createConfigurationContext(config)
        resources.updateConfiguration(config, resources.displayMetrics)

        this.setContentView(R.layout.main)
    }
}

您应该执行一些步骤

首先，您需要更改配置的区域设置

Resources resources = context.getResources();

Configuration configuration = resources.getConfiguration();
configuration.locale = new Locale(language);

resources.updateConfiguration(configuration, resources.getDisplayMetrics());

其次，如果希望更改直接应用于可见的布局，可以直接更新视图，也可以调用activity. rebuild()重新启动当前活动。

你还必须保留你的更改因为在用户关闭你的应用程序之后你就会失去语言更改。

我在我的博客文章中解释了更详细的解决方案，在Android中以编程方式改变语言

基本上，你只需要在你的应用程序类上调用LocaleHelper.onCreate()如果你想动态地改变语言环境你可以调用LocaleHelper.setLocale()

添加LocaleHelper类

public class LocaleHelper{ 
private static final String SELECTED_LANGUAGE = "Locale.Helper.Selected.Language";
public static Context onAttach(Context context) {
    String lang = getPersistedData(context, Locale.getDefault().getLanguage());
    return setLocale(context, lang);
}

public static Context onAttach(Context context, String defaultLanguage) {
    String lang = getPersistedData(context, defaultLanguage);
    return setLocale(context, lang);
}

public static String getLanguage(Context context) {
    return getPersistedData(context, Locale.getDefault().getLanguage());
}
public static Context setLocale(Context context, String language) {
    persist(context, language);

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
        return updateResources(context, language);
    }

    return updateResourcesLegacy(context, language);
}

private static String getPersistedData(Context context, String defaultLanguage) {
    SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
    return preferences.getString(SELECTED_LANGUAGE, defaultLanguage);
}

private static void persist(Context context, String language) {
    SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
    SharedPreferences.Editor editor = preferences.edit();

    editor.putString(SELECTED_LANGUAGE, language);
    editor.apply();
}

@TargetApi(Build.VERSION_CODES.N)
private static Context updateResources(Context context, String language) {
    Locale locale = new Locale(language);
    Locale.setDefault(locale);

    Configuration configuration = context.getResources().getConfiguration();
    configuration.setLocale(locale);
    configuration.setLayoutDirection(locale);

    return context.createConfigurationContext(configuration);
}

@SuppressWarnings("deprecation")
private static Context updateResourcesLegacy(Context context, String language) {
    Locale locale = new Locale(language);
    Locale.setDefault(locale);

    Resources resources = context.getResources();

    Configuration configuration = resources.getConfiguration();
    configuration.locale = locale;
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
        configuration.setLayoutDirection(locale);
    }

    resources.updateConfiguration(configuration, resources.getDisplayMetrics());

    return context;
}
}

在活动或片段中

Context context = LocaleHelper.setLocale(this, App.getSharedPre().getLanguage());
Resource resources = context.getResources();

现在在每个文本上设置文本

TextView tv = findViewById(R.id.tv);
tv.setText(resources.getString(R.string.tv));

这是工作时，我按下按钮改变我的TextView的文本语言。(strings.xml在值-de文件夹)

String languageToLoad = "de"; // your language
Configuration config = getBaseContext().getResources().getConfiguration();
Locale locale = new Locale(languageToLoad);
Locale.setDefault(locale);
config.locale = locale;
getBaseContext().getResources().updateConfiguration(config, getBaseContext().getResources().getDisplayMetrics());
recreate();

对每应用语言偏好的支持刚刚添加到API 33 (Android 13，提拉米苏目前在开发者预览版)。

要改变应用程序的语言环境，只需从LocaleManager调用setApplicationLocales:

// Set app locale to pt-BR (Portuguese, Brazil)
getSystemService(LocaleManager::class.java)
    .applicationLocales = LocaleList(Locale.forLanguageTag("pt-BR"))

详见https://developer.android.com/about/versions/13/features/app-languages#api-impl

我已经写了一篇关于这个功能的文章https://proandroiddev.com/exploring-the-new-android-13-per-app-language-preferences-8d99b971b578