对于Android 7.0牛轧糖(或更低)，请遵循这篇文章:

在Android中以编程方式改变语言

旧的答案 这包括RTL/LTR支持:

public static void changeLocale(Context context, Locale locale) {
    Configuration conf = context.getResources().getConfiguration();
    conf.locale = locale;
    Locale.setDefault(locale);

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
       conf.setLayoutDirection(conf.locale);
    }

    context.getResources().updateConfiguration(conf, context.getResources().getDisplayMetrics());
}

Resources.updateConfiguration()已经弃用，我已经解决了这个问题，没有创建任何自定义的ContextWrapper。

首先我创建了一个扩展函数

fun Context.setAppLocale(language: String): Context {
    val locale = Locale(language)
    Locale.setDefault(locale)
    val config = resources.configuration
    config.setLocale(locale)
    config.setLayoutDirection(locale)
    return createConfigurationContext(config)
}

然后在活动的attachBaseContext方法中，简单地用新的上下文替换上下文。

override fun attachBaseContext(newBase: Context) {
  super.attachBaseContext(ContextWrapper(newBase.setAppLocale("bn")))
}

/*change language at Run-time*/
//use method like that:
//setLocale("en");
 public void setLocale(String lang) { 
  myLocale = new Locale(lang);         
  Resources res = getResources();         
  DisplayMetrics dm = res.getDisplayMetrics();         
  Configuration conf = res.getConfiguration();         
  conf.locale = myLocale;         
  res.updateConfiguration(conf, dm);         
  Intent refresh = new Intent(this, AndroidLocalize.class);         
  startActivity(refresh); 
 }

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)
    }
}

这里列出的解决方案没有一个对我有用。

如果AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES)，语言没有在android >= 7.0上切换

这个LocaleUtils工作得很好: https://gist.github.com/GigigoGreenLabs/7d555c762ba2d3a810fe

LocaleUtils

public class LocaleUtils {

public static final String LAN_SPANISH      = "es";
public static final String LAN_PORTUGUESE   = "pt";
public static final String LAN_ENGLISH      = "en";

private static Locale sLocale;

public static void setLocale(Locale locale) {
    sLocale = locale;
    if(sLocale != null) {
        Locale.setDefault(sLocale);
    }
}

public static void updateConfig(ContextThemeWrapper wrapper) {
    if(sLocale != null && Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
        Configuration configuration = new Configuration();
        configuration.setLocale(sLocale);
        wrapper.applyOverrideConfiguration(configuration);
    }
}

public static void updateConfig(Application app, Configuration configuration) {
    if(sLocale != null && Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1) {
        //Wrapping the configuration to avoid Activity endless loop
        Configuration config = new Configuration(configuration);
        config.locale = sLocale;
        Resources res = app.getBaseContext().getResources();
        res.updateConfiguration(config, res.getDisplayMetrics());
    }
}
}

将此代码添加到应用程序

public class App extends Application {
public void onCreate(){
    super.onCreate();

    LocaleUtils.setLocale(new Locale("iw"));
    LocaleUtils.updateConfig(this, getBaseContext().getResources().getConfiguration());
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    LocaleUtils.updateConfig(this, newConfig);
}
}

活动中的代码

public class BaseActivity extends AppCompatActivity {
    public BaseActivity() {
        LocaleUtils.updateConfig(this);
    }
}