Question

我在我的应用中有一个包含ListPreference的偏好设置活动，因此用户可以选择该应用的语言。

应用在用户关闭“偏好设置”活动后立即显示新语言。

我想创建一个ListPreference的监听器，以便在监听器触发时（在用户从ListPreference中选择语言/选择项目之后）重启应用程序。

我该怎么做？

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：

<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!!!

Answer 1

以下是我在其中一个项目中设置的共享prefs chaneg监听器的一些真实快速示例代码;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的更改。

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);

如何在“首选项”活动中创建“首选项”的“侦听器”更改？

1 个答案: