如何在首选项 activity 中创建首选项更改的侦听器？

Question

我的应用程序中有首选项 activity，其中包含 ListPreference，因此用户可以为应用程序选择语言。

应用在用户关闭首选项后立即显示新语言activity。

我想为 ListPreference 创建一个侦听器，这样应用程序将在侦听器被触发时重新启动（就在用户从 ListPreference 中选择 language/choose 项目之后）。

我该怎么做？

设置活动：

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

这是我在我的一个项目中设置的共享首选项更改侦听器的一些真正的快速示例代码；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地方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);

Answer 2

一个可能的解决方案是将所有内容放在一起，并在您自己的 GeneralPreferenceFragment.

中实现 OnSharedPreferenceChangeListener 接口

您可以通过声明 GeneralPreferenceFragment 继承自 PreferenceFragment 并实现 SharedPreferences.OnSharedPreferenceChangeListener 接口来做到这一点。这意味着您需要在 GeneralPreferenceFragment.

中为 onSharedPreferenceChanged 定义覆盖

因为首选项只有在相关片段处于活动状态时才会更改，您可以在 onResume 中将片段注册为片段的侦听器（通过 registerOnSharedPreferenceChangeListener），然后在 [=20] 上取消注册=].

下面的示例代码是在 Kotlin 中，而不是在 Java 中，但应该很容易翻译它。

class SettingsActivity : AppCompatActivity() {
    // ...
    class SettingsFragment : PreferenceFragmentCompat(),
                             SharedPreferences.OnSharedPreferenceChangeListener 
    {
        // ...

        override fun onSharedPreferenceChanged(sharedPreferences: SharedPreferences?,
                                               key: String?) {
            if (key == "<something>")
                // do something
        }

        override fun onResume() {
            super.onResume()
            preferenceScreen.sharedPreferences
                ?.registerOnSharedPreferenceChangeListener(this)
        }

        override fun onPause() {
            super.onPause()
            preferenceScreen.sharedPreferences
                ?.unregisterOnSharedPreferenceChangeListener(this)
        }
}

如何在首选项 activity 中创建首选项更改的侦听器？

How to create a Listener to Preferences changes in Preferences activity?

java

android

android-preferences

preferenceactivity

listpreference