如何在“首选项"活动中创建“首选项"更改的侦听器? [英] How to create a Listener to Preferences changes in Preferences activity?

问题描述

我在具有ListPreference的应用程序中具有首选项"活动，因此用户可以为应用程序选择语言.

I have Preferences activity in my app that has ListPreference so the user can choose language for the app.

应用程序在用户关闭首选项"活动后立即显示新语言.

The app displays the new language just after the user close the Preferences activity.

我想为ListPreference创建一个侦听器，以便在触发侦听器时(在用户从ListPreference中选择一种语言/选择项之后)，应用将重新启动.

I want to create a listener to the ListPreference so the app will restart when the Listener is triggers (just after the user choose a language/choose item from the ListPreference).

我该怎么做?

SettingsActivity:

SettingsActivity:

public class SettingsActivity extends AppCompatPreferenceActivity {
/**
 * A preference value change listener that updates the preference's summary
 * to reflect its new value.
 */
private static Preference.OnPreferenceChangeListener sBindPreferenceSummaryToValueListener = new Preference.OnPreferenceChangeListener() {
    @Override
    public boolean onPreferenceChange(Preference preference, Object value) {
        String stringValue = value.toString();

        if (preference instanceof ListPreference) {
            // For list preferences, look up the correct display value in
            // the preference's 'entries' list.
            ListPreference listPreference = (ListPreference) preference;
            int index = listPreference.findIndexOfValue(stringValue);

            // Set the summary to reflect the new value.
            preference.setSummary(
                    index >= 0
                            ? listPreference.getEntries()[index]
                            : null);

        } else {
            // For all other preferences, set the summary to the value's
            // simple string representation.
            preference.setSummary(stringValue);
        }
        return true;
    }
};


/**
 * Binds a preference's summary to its value. More specifically, when the
 * preference's value is changed, its summary (line of text below the
 * preference title) is updated to reflect the value. The summary is also
 * immediately updated upon calling this method. The exact display format is
 * dependent on the type of preference.
 *
 * @see #sBindPreferenceSummaryToValueListener
 */
private static void bindPreferenceSummaryToValue(Preference preference) {
    // Set the listener to watch for value changes.
    preference.setOnPreferenceChangeListener(sBindPreferenceSummaryToValueListener);

    // Trigger the listener immediately with the preference's
    // current value.
    sBindPreferenceSummaryToValueListener.onPreferenceChange(preference,
            PreferenceManager
                    .getDefaultSharedPreferences(preference.getContext())
                    .getString(preference.getKey(), ""));
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setupActionBar();
    setTitle(R.string.action_settings);
}

/**
 * Set up the {@link android.app.ActionBar}, if the API is available.
 */
private void setupActionBar() {
    ActionBar actionBar = getSupportActionBar();
    if (actionBar != null) {
        // Show the Up button in the action bar.
        actionBar.setDisplayHomeAsUpEnabled(true);
    }
}

@Override
public boolean onMenuItemSelected(int featureId, MenuItem item) {
    int id = item.getItemId();
    if (id == android.R.id.home) {
        if (!super.onMenuItemSelected(featureId, item)) {
            NavUtils.navigateUpFromSameTask(this);
        }
        return true;
    }
    return super.onMenuItemSelected(featureId, item);
}

/**
 * This method stops fragment injection in malicious applications.
 * Make sure to deny any unknown fragments here.
 */
protected boolean isValidFragment(String fragmentName) {
    return PreferenceFragment.class.getName().equals(fragmentName)
            || GeneralPreferenceFragment.class.getName().equals(fragmentName);
}

/**
 * This fragment shows general preferences only. It is used when the
 * activity is showing a two-pane settings UI.
 */
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public static class GeneralPreferenceFragment extends PreferenceFragment {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.pref_general);
        setHasOptionsMenu(true);

        // Bind the summaries of EditText/List/Dialog/Ringtone preferences
        // to their values. When their values change, their summaries are
        // updated to reflect the new value, per the Android Design
        // guidelines.
        bindPreferenceSummaryToValue(findPreference("example_text"));
        bindPreferenceSummaryToValue(findPreference(getString(R.string.language_shared_pref_key)));
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == android.R.id.home) {
            Intent intent = new Intent(getActivity(), MainActivity.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            getActivity().finish();
            startActivity(intent);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

}

pref_general.xml:

pref_general.xml:

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">

<ListPreference
    android:defaultValue="@string/language_code"
    android:entries="@array/pref_languages_list_titles"
    android:entryValues="@array/pref_languages_list_values"
    android:key="@string/language_shared_pref_key"
    android:negativeButtonText="@null"
    android:positiveButtonText="@null"
    android:title="@string/pref_title_language" />

</PreferenceScreen>

谢谢！

推荐答案

以下是我在一个项目中设置的共享prefs chaneg监听器的一些快速示例代码.它位于服务的onCreate中，但显然可以检测到来自我应用程序中任何位置的共享首选项更改.

Here is some real quick sample code for a shared prefs chaneg listener I have set-up in one of my projects; it's located in the onCreate of a Service but obviously can detect changes to my shared prefs that originate from anywhere in my app.

private SharedPreferences.OnSharedPreferenceChangeListener listener;


//Loads Shared preferences
prefs = PreferenceManager.getDefaultSharedPreferences(this);

//Setup a shared preference listener for hpwAddress and restart transport
listener = new SharedPreferences.OnSharedPreferenceChangeListener() {
            public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
           if (key.equals(/*key for shared pref you're listening for*/) {
               //Do stuff; restart activity in your case
            }
        };

prefs.registerOnSharedPreferenceChangeListener(listener);

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