刷新android PreferenceFragment

Question

我有CheckBoxPreference一个FragmentPreference.当用户激活复选框时,我会检查是否安装了应用程序,如果没有,我会将首选项重置为false,然后打开Play商店下载应用程序.

基本上一切正常,但我有一个问题来刷新UI.实际上,即使我在打开Play商店之前将首选项设置为false ,当用户返回时,也会检查该框(片段刚刚暂停并恢复,因此忽略了首选项值).

有没有办法"刷新"活动或片段？

Answer 1

使PreferenceFragment实现OnSharedPreferenceChangeListener接口.

在onCreate(),您可以读取首选项值并相应地设置UI.例如:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Load the preferences from an XML resource.
    addPreferencesFromResource(R.xml.shakesql_app_prefs);

    // Initialize pref summary label.

    // Get a reference to the application default shared preferences.
    SharedPreferences sp = getPreferenceScreen().getSharedPreferences();

    // Read the current preference value.
    String listVal =
            sp.getString(getString(R.string.preference_font_size_key),
                    getString(R.string.preference_font_size_default));

    // Look up the textual description corresponding to the
    // preference value and write it into the summary field.
    String listDesc = descriptionFromPref(
            listVal, 
            getResources().getStringArray(
                    R.array.preference_font_size_values), 
                    getResources().getStringArray(
                            R.array.preference_font_size_labels)
                    );
    if (!TextUtils.isEmpty(listDesc)) {
        ListPreference listPref =
                (ListPreference) findPreference(getString(R.string.preference_font_size_key));
        listPref.setSummary(listDesc);
    }
}

然后,在onSharedPreferenceChanged(),更新UI.

public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
    Preference pref = findPreference(key);
    if (pref instanceof ListPreference) {
        // Update display title
        // Write the description for the newly selected preference 
        // in the summary field.
        ListPreference listPref = (ListPreference) pref;
        CharSequence listDesc = listPref.getEntry();
        if (!TextUtils.isEmpty(listDesc)) {
            pref.setSummary(listDesc);
        }
    }        
}

以下是API演示中AdvancedPreferences示例的代码片段,用于强制复选框首选项的值.

// Toggle the value of mCheckBoxPreference.
if (mCheckBoxPreference != null) {
            mCheckBoxPreference.setChecked(!mCheckBoxPreference.isChecked());
}