Android-语言设置流程分析_android localepicker getallassetlocales

    以Android5.1工程源码为基础,从设置app入手来分析和学习语言切换的过程:

    一、语言设置界面：

    首先在设置app中找到语言设置这个Preference，目前设置中界面大多都是Fragment，先找到语言和输入法的PreferenceScreen，与其对应的Fragment是InputMethodAndLanguageSettings.java，在其onCreate()方法中，首先是增加语言设置的preference：     

addPreferencesFromResource(R.xml.language_settings);

找到language_settings.xml，可发现如下代码：    

<PreferenceScreen
            android:key="phone_language"
            android:title="@string/phone_language"
            android:fragment="com.android.settings.LocalePicker"
            />

于是断定LocalePicker就是语言设置的Fragment，它是ListFragment的子类，继承于framework中LocalePicker,并实现了父类的一个接口，其回调方法是onLocaleSelected()，Locale中文含义大致是语言环境，所以可推测这是设置语言后的一个回调方法，不确定的话，可打断点测试一下。然而此类中并没有关于语言设置界面数据适配的太多逻辑， 只是通过父类的方法创建了一个view:    

 @Override
    public View onCreateView(
            LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        final View view = super.onCreateView(inflater, container, savedInstanceState);
        final ListView list = (ListView) view.findViewById(android.R.id.list);
        Utils.forcePrepareCustomPreferencesList(container, view, list, false);
        return view;
    }

   所以更多逻辑应该在framework中的LocalePicker.java中。既然是ListFragment，那就必须有Adapter,在此类中有构建了一个Adapter：

 /**
     * Constructs an Adapter object containing Locale information. Content is sorted by
     * {@link LocaleInfo#label}.
     */
    public static ArrayAdapter<LocaleInfo> constructAdapter(Context context) {
        return constructAdapter(context, R.layout.locale_picker_item, R.id.locale);
    }
    public static ArrayAdapter<LocaleInfo> constructAdapter(Context context,
            final int layoutId, final int fieldId) {
        boolean isInDeveloperMode = Settings.Global.getInt(context.getContentResolver(),
                Settings.Global.DEVELOPMENT_SETTINGS_ENABLED, 0) != 0;
        //获取系统支持语言的信息
        final List<LocaleInfo> localeInfos = getAllAssetLocales(context, isInDeveloperMode);
        final LayoutInflater inflater =
                (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        return new ArrayAdapter<LocaleInfo>(context, layoutId, fieldId, localeInfos) {
            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                View view;
                TextView text;
                if (convertView == null) {
                    view = inflater.inflate(layoutId, parent, false);
                    text = (TextView) view.findViewById(fieldId);
                    view.setTag(text);
                } else {
                    view = convertView;
                    text = (TextView) view.getTag();
                }
                LocaleInfo item = getItem(position);
                text.setText(item.toString());
                text.setTextLocale(item.getLocale());
                return view;
            }
        };
    }

而此方法通过getAllAssetLocales()方法获取系统支持语言的信息：

public static List<LocaleInfo> getAllAssetLocales(Context context, boolean isInDeveloperMode) {
        final Resources resources = context.getResources();
        //获取系统所支持的语言
        final String[] locales = Resources.getSystem().getAssets().getLocales();
        List<String> localeList = new ArrayList<String>(locales.length);
        Collections.addAll(localeList, locales);
 
        // Don't show the pseudolocales unless we're in developer mode. 
        if (!isInDeveloperMode) {
            localeList.remove("ar-XB");
            localeList.remove("en-XA");
        }
 
        Collections.sort(localeList);
        final String[] specialLocaleCodes = resources.getStringArray(R.array.special_locale_codes);
        final String[] specialLocaleNames = resources.getStringArray(R.array.special_locale_names);
 
        final ArrayList<LocaleInfo> localeInfos = new ArrayList<LocaleInfo>(localeList.size());
        for (String locale : localeList) {
            final Locale l = Locale.forLanguageTag(locale.replace('_', '-'));
            if (l == null || "und".equals(l.getLanguage())
                    || l.getLanguage().isEmpty() || l.getCountry().isEmpty()) {
                continue;
            }
 
            if (localeInfos.isEmpty()) {
                if (DEBUG) {
                    Log.v(TAG, "adding initial "+ toTitleCase(l.getDisplayLanguage(l)));
                }
                localeInfos.add(new LocaleInfo(toTitleCase(l.getDisplayLanguage(l)), l));
            } else {
                // check previous entry:
                //  same lang and a country -> upgrade to full name and
                //    insert ours with full name
                //  diff lang -> insert ours with lang-only name
                final LocaleInfo previous = localeInfos.get(localeInfos.size() - 1);
                if (previous.locale.getLanguage().equals(l.getLanguage()) &&
                        !previous.locale.getLanguage().equals("zz")) {
                    if (DEBUG) {
                        Log.v(TAG, "backing up and fixing " + previous.label + " to " +
                                getDisplayName(previous.locale, specialLocaleCodes, specialLocaleNames));
                    }
                    previous.label = toTitleCase(getDisplayName(
                            previous.locale, specialLocaleCodes, specialLocaleNames));
                    if (DEBUG) {
                        Log.v(TAG, "  and adding "+ toTitleCase(