对我来说，最好的解决办法是: https://www.bitcaal.com/how-to-change-the-app-language-programmatically-in-android/

package me.mehadih.multiplelanguage;

import androidx.appcompat.app.AppCompatActivity;

import android.content.res.Configuration;
import android.content.res.Resources;
import android.os.Build;
import android.os.Bundle;
import android.util.DisplayMetrics;

import java.util.Locale;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setApplicationLocale("az"); // short name of language. "en" for English
        setContentView(R.layout.activity_main);

    }

    private void setApplicationLocale(String locale) {
        Resources resources = getResources();
        DisplayMetrics dm = resources.getDisplayMetrics();
        Configuration config = resources.getConfiguration();
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
            config.setLocale(new Locale(locale.toLowerCase()));
        } else {
            config.locale = new Locale(locale.toLowerCase());
        }
        resources.updateConfiguration(config, dm);
    }
}

首先为不同的语言创建多个string.xml;然后在onCreate()方法中使用这段代码:

super.onCreate(savedInstanceState);
String languageToLoad  = "fr"; // change your language here
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);

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));

如果你正在使用片段，并且你想在Android中以编程方式更改应用程序语言，请使用此方法

  public void setLocale(Activity activity, String languageCode) {
    Locale locale = new Locale(languageCode);
    Locale.setDefault(locale);
    Resources resources = activity.getResources();
    Configuration config = resources.getConfiguration();
    config.setLocale(locale);
    resources.updateConfiguration(config, resources.getDisplayMetrics());
     SettingsFragment settingsFragment = new SettingsFragment();
     FragmentManager fragmentManager = requireActivity().getSupportFragmentManager();
     FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    activity.overridePendingTransition(0,0);
     fragmentTransaction.replace(R.id.main, settingsFragment).commit();
}

这样叫它

setLocale(requireActivity(),"fr");

只需要用你的片段名改变SettingsFragment，在你调用方法的地方，这基本上是刷新布局来获得视图上的新字符串 如果你想在另一个类上设置这个方法只需像这样添加context

public void setLocale(Activity activity, String languageCode,Context context) {
    Locale locale = new Locale(languageCode);
    Locale.setDefault(locale);
    Resources resources = activity.getResources();
    Configuration config = resources.getConfiguration();
    config.setLocale(locale);
    resources.updateConfiguration(config, resources.getDisplayMetrics());
    SettingsFragment settingsFragment = new SettingsFragment();
    FragmentManager fragmentManager = ((AppCompatActivity) context).getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    activity.overridePendingTransition(0,0);
    fragmentTransaction.replace(R.id.main, settingsFragment).commit();
}

我终于弄清楚如何设置它工作在两个=N安卓版本。

用你自己的抽象类扩展AppCompatActivity，比如:

abstract class MLAppCompatActivity : AppCompatActivity() {
  override fun attachBaseContext(newBase: Context?) {
    super.attachBaseContext(LocaleHelper.wrap(newBase))
  }

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N) {
        LocaleHelper.wrap(this)
    }
  }
}

attachBaseContext在Android >=N版本上被调用，这样activity将使用正确的上下文。在Android <N上，我们必须以另一种方式调用这个函数，在设置内容视图之前。因此，我们重写onCreate函数来设置正确的上下文。 意思是，每当你创建一个新的Activity时，你必须扩展你的抽象类。比如这个:

class TermsActivity : MLAppCompatActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_terms)
  }
}

最后LocaleHelper是这样的:

import android.annotation.TargetApi;
import android.content.Context;
import android.content.ContextWrapper;
import android.content.SharedPreferences;
import android.content.res.Configuration;
import android.content.res.Resources;
import android.os.Build;
import android.util.DisplayMetrics;

import com.at_zone.constants.SharedPreferencesKeys;

import java.util.Locale;

public class LocaleHelper extends ContextWrapper {

    public LocaleHelper(Context base) {
        super(base);
    }

    public static Context wrap(Context context) {
        SharedPreferences sharedPreferences = context.getSharedPreferences(
                SharedPreferencesKeys.SHARED_PREFERENCES, Context.MODE_PRIVATE
        );
        String language = sharedPreferences.getString(SharedPreferencesKeys.CURRENT_LANGUAGE, "default");
        if (!language.equals("default")) {
            Configuration config = context.getResources().getConfiguration();
            if (!language.equals("")) {
                Locale locale = new Locale(language);
                Locale.setDefault(locale);
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
                    setSystemLocale(config, locale);
                } else {
                    setSystemLocaleLegacy(context, config, locale);
                }
                config.setLayoutDirection(locale);
                context = context.createConfigurationContext(config);
            }
            return new LocaleHelper(context);
        }
        return context;
    }

    public static String getSystemLanguage(Context context) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            return getSystemLocale(context).getLanguage().toLowerCase();
        } else {
            return getSystemLocaleLegacy(context).getLanguage().toLowerCase();
        }
    }

    public static Locale getSystemLocaleLegacy(Context context) {
        Configuration config = context.getResources().getConfiguration();
        return config.locale;
    }

    @TargetApi(Build.VERSION_CODES.N)
    public static Locale getSystemLocale(Context context) {
        return context.getResources().getConfiguration().getLocales().get(0);
    }

    public static void setSystemLocaleLegacy(Context context, Configuration config, Locale locale) {
        config.locale = locale;
        Resources res = context.getResources();
        DisplayMetrics dm = res.getDisplayMetrics();
        res.updateConfiguration(config, dm);
    }

    @TargetApi(Build.VERSION_CODES.N)
    public static void setSystemLocale(Configuration config, Locale locale) {
        config.setLocale(locale);
    }

}

在设置内容之前，应该在每个活动中设置区域配置- this.setContentView(r.b ayout.main);