从资源中加载语言特定的字符串？

Question

在我的一个 Android 应用程序中，有一次我需要加载特定语言的字符串。例如：

 values:    <string name="txt_help">Help</string>
 values-de: <string name="txt_help">Hilfe</string>
 values-fr: <string name="txt_help">Aider</string>

现在我需要默认（值）文本。

有没有办法用给定的语言“en”加载键“txt_help”？我找不到可以将语言环境设置为附加参数的方法。

或者我可以用给定的语言环境创建一个新的 ResourceManager 并通过这个资源对象读取字符串吗？

提前非常感谢。 hjw

Answer 1

查看the documentation，这看起来很有希望：

Resources standardResources = context.getResources();
AssetManager assets = standardResources.getAssets();
DisplayMetrics metrics = standardResources.getDisplayMetrics();
Configuration config = new Configuration(standardResources.getConfiguration());
config.locale = Locale.US;
Resources defaultResources = new Resources(assets, metrics, config);

换句话说，创建一个配置为标准语言环境的新资源对象。

Answer 2

从my own question 参考this answer 和this answer，我想出了以下自定义类解决方案：

package com.my.package.localisation;

import android.content.Context;
import android.content.res.AssetManager;
import android.content.res.Configuration;
import android.content.res.Resources;
import android.os.Build;
import android.support.annotation.NonNull;
import android.util.DisplayMetrics;

import java.util.Formatter;
import java.util.Locale;

/**
 * Class to manage fetching {@link Resources} for a specific {@link Locale}. API levels less
 * than {@link Build.VERSION_CODES#JELLY_BEAN_MR1} require an ugly implementation.
 * <p/>
 * Subclass extends {@link Resources} in case of further functionality requirements.
 */
public class MyResources {

    private final Context mContext;
    private final AssetManager assetManager;
    private final DisplayMetrics metrics;
    private final Configuration configuration;
    private final Locale targetLocale;
    private final Locale defaultLocale;

    public MyResources(@NonNull final Context mContext, @NonNull final Locale defaultLocale,
                         @NonNull final Locale targetLocale) {

        this.mContext = mContext;
        final Resources resources = this.mContext.getResources();
        this.assetManager = resources.getAssets();
        this.metrics = resources.getDisplayMetrics();
        this.configuration = new Configuration(resources.getConfiguration());
        this.targetLocale = targetLocale;
        this.defaultLocale = defaultLocale;
    }

    public String[] getStringArray(final int resourceId) {

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
            configuration.setLocale(targetLocale);
            return mContext.createConfigurationContext(configuration).getResources().getStringArray(resourceId);
        } else {
            configuration.locale = targetLocale;
            final String[] resourceArray = new ResourceManager(assetManager, metrics, configuration).getStringArray(resourceId);
            configuration.locale = defaultLocale; // reset
            new ResourceManager(assetManager, metrics, configuration); // reset
            return resourceArray;
        }
    }

    public String getString(final int resourceId) {

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
            configuration.setLocale(targetLocale);
            return mContext.createConfigurationContext(configuration).getResources().getString(resourceId);
        } else {
            configuration.locale = targetLocale;
            final String resource = new ResourceManager(assetManager, metrics, configuration).getString(resourceId);
            configuration.locale = defaultLocale; // reset
            new ResourceManager(assetManager, metrics, configuration); // reset
            return resource;
        }
    }

    private final class ResourceManager extends Resources {
        public ResourceManager(final AssetManager assets, final DisplayMetrics metrics, final Configuration config) {
            super(assets, metrics, config);
        }

        /**
         * Return the string array associated with a particular resource ID.
         *
         * @param id The desired resource identifier, as generated by the aapt
         *           tool. This integer encodes the package, type, and resource
         *           entry. The value 0 is an invalid identifier.
         * @return The string array associated with the resource.
         * @throws NotFoundException Throws NotFoundException if the given ID does not exist.
         */
        @Override
        public String[] getStringArray(final int id) throws NotFoundException {
            return super.getStringArray(id);
        }

        /**
         * Return the string value associated with a particular resource ID,
         * substituting the format arguments as defined in {@link Formatter}
         * and {@link String#format}. It will be stripped of any styled text
         * information.
         * {@more}
         *
         * @param id         The desired resource identifier, as generated by the aapt
         *                   tool. This integer encodes the package, type, and resource
         *                   entry. The value 0 is an invalid identifier.
         * @param formatArgs The format arguments that will be used for substitution.
         * @return String The string data associated with the resource,
         * stripped of styled text information.
         * @throws NotFoundException Throws NotFoundException if the given ID does not exist.
         */
        @NonNull
        @Override
        public String getString(final int id, final Object... formatArgs) throws NotFoundException {
            return super.getString(id, formatArgs);
        }

        /**
         * Return the string value associated with a particular resource ID.  It
         * will be stripped of any styled text information.
         * {@more}
         *
         * @param id The desired resource identifier, as generated by the aapt
         *           tool. This integer encodes the package, type, and resource
         *           entry. The value 0 is an invalid identifier.
         * @return String The string data associated with the resource,
         * stripped of styled text information.
         * @throws NotFoundException Throws NotFoundException if the given ID does not exist.
         */
        @NonNull
        @Override
        public String getString(final int id) throws NotFoundException {
            return super.getString(id);
        }
    }
}