在开发海外项目的时候，需要实现app内部的中英文切换功能，所有的英文都是内置的，整体思路为：

创建一个sp对象，存储当前系统的语言类型，然后在BaseActivity中对语言进行判断；

//公共Activity

public abstract class BaseActivity extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        setTransparent();
        super.onCreate(savedInstanceState);
        setContentView(initLayout());

        String languageCode = SpUtils.getString(this, Constants.LANGUAGE);
        //从SP中取出来的当前语言类型；中文是："cn"，英文是："en"，对应底下的这个languageCode

        //系统内置的设置app内语言的功能；
        Locale locale = new Locale(languageCode);
        Locale.setDefault(locale);
        Configuration config = new Configuration();
        config.setLocale(locale);
        getResources().updateConfiguration(config, getResources().getDisplayMetrics());
   }

    //设置布局
    protected abstract int initLayout();
}

2、可以新开一个页面，用来set当前的sp中数据（只写代码）

Constants.LANGUAGE:

public static final String LANGUAGE = "application_language";//语言设置

//可以自定义一个String字符串，不用全局变量

//设置语言的方法，通过传入的language判断当前用户选择的是中文还是英文
public void setLanguage(String language) {
            if (language.equals("中文")) {
                switchLanguage("cn");
            } else {
                switchLanguage("en");
            }
    }

//选完之后就可以将app中的语言进行切换

public void switchLanguage(String languageCode) {
        Locale locale = new Locale(languageCode);
        Locale.setDefault(locale);
        Configuration config = new Configuration();
        config.setLocale(locale);
        getResources().updateConfiguration(config, getResources().getDisplayMetrics());
        SpUtils.putString(mContext, Constants.LANGUAGE, languageCode);
//（这个只是SP的工具类，可以不用这个，直接用SP写入，都是一样的，我习惯别名用静态的，不容易写错）
        restartApplication(mContext);
    }


//然后重启app生效

    public static void restartApplication(Context context) {
        Intent intent = context.getPackageManager().getLaunchIntentForPackage(context.getPackageName());
        if (intent != null) {
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            context.startActivity(intent);
        }
        System.exit(0);
    }

SpUtils:

public class SpUtils {

    private static final String spFileName = "app";

    public static String getString(Context context, String strKey) {
        SharedPreferences setPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        String result = setPreferences.getString(strKey, "");
        return result;
    }

    public static String getString(Context context, String strKey,
                                   String strDefault) {
        SharedPreferences setPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        String result = setPreferences.getString(strKey, strDefault);
        return result;
    }

    public static void putString(Context context, String strKey, String strData) {
        SharedPreferences activityPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = activityPreferences.edit();
        editor.putString(strKey, strData);
        editor.commit();
    }

    public static Boolean getBoolean(Context context, String strKey) {
        SharedPreferences setPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        Boolean result = setPreferences.getBoolean(strKey, false);
        return result;
    }

    public static Boolean getBoolean(Context context, String strKey,
                                     Boolean strDefault) {
        SharedPreferences setPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        Boolean result = setPreferences.getBoolean(strKey, strDefault);
        return result;
    }


    public static void putBoolean(Context context, String strKey,
                                  Boolean strData) {
        SharedPreferences activityPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = activityPreferences.edit();
        editor.putBoolean(strKey, strData);
        editor.commit();
    }

    public static int getInt(Context context, String strKey) {
        SharedPreferences setPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        int result = setPreferences.getInt(strKey, -1);
        return result;
    }

    public static int getInt(Context context, String strKey, int strDefault) {
        SharedPreferences setPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        int result = setPreferences.getInt(strKey, strDefault);
        return result;
    }

    public static void putInt(Context context, String strKey, int strData) {
        SharedPreferences activityPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = activityPreferences.edit();
        editor.putInt(strKey, strData);
        editor.commit();
    }

    public static long getLong(Context context, String strKey) {
        SharedPreferences setPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        long result = setPreferences.getLong(strKey, -1);
        return result;
    }

    public static long getLong(Context context, String strKey, long strDefault) {
        SharedPreferences setPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        long result = setPreferences.getLong(strKey, strDefault);
        return result;
    }

    public static void putLong(Context context, String strKey, long strData) {
        SharedPreferences activityPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = activityPreferences.edit();
        editor.putLong(strKey, strData);
        editor.commit();
    }

    public static void cleanSp(Context context) {
        SharedPreferences activityPreferences = context.getSharedPreferences(
                spFileName, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = activityPreferences.edit();
        editor.clear();
        editor.apply();
    }
}