觸發onPreferenceClick時如何動態填充ListPreference？

Question

我有一個偏好活動，它的language為ListPreference ，它顯示可用的語言列表。 我可以在調用 onCreate 時填充列表，但我想在用戶單擊它時填充列表。

this is the java code ：

public class SettingsActivity extends PreferenceActivity implements OnPreferenceClickListener {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        try {
            addPreferencesFromResource(R.xml.settings);
        } catch (Exception e) {

        }

    }

    @Override
    public boolean onPreferenceClick(Preference preference) {

        if((preference instanceof ListPreference) && (preference.getKey().equals("language"))){
            ListPreference lp = (ListPreference)preference;
            CharSequence[] entries = { "English", "French" };
            CharSequence[] entryValues = {"1" , "2"};
            lp.setEntries(entries);
            lp.setDefaultValue("1");
            lp.setEntryValues(entryValues);
            return true;
        }
        return false;

    }
}

這是settings.xml （首選項）：

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen
  xmlns:android="http://schemas.android.com/apk/res/android">
    <PreferenceCategory android:title="General Settings">
        <CheckBoxPreference android:key="enabled"  android:title="Application Status" android:summary="Enable or disable the application" />
         <ListPreference 
         android:key="language" 
         android:title="Language"
         android:dialogTitle="Application language" 
         android:summary="Select the Application language"
         />
    </PreferenceCategory>
</PreferenceScreen>

我搜索但沒有找到結果！ 每次單擊該列表時都會發生異常。

Answer 1

您收到異常是因為您的 ListPreference 對象未初始化 - 您要么需要在 XML 中設置entries和entryValues屬性，要么在onCreate()編程方式進行設置。

如果您需要在初始 ListPreference 對象初始化后動態更改列表中的項目，則需要將OnPreferenceClickListener直接附加到 ListPreference 對象。 使用您在 XML 中指定的鍵來獲取首選項的句柄。

由於填充entries和entryValues數組的代碼必須同時在onCreate()和onPreferenceClick中onPreferenceClick ，因此將其提取到單獨的方法setListPreferenceData()以避免重復是有意義的。

public class SettingsActivity extends PreferenceActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        try {
            addPreferencesFromResource(R.xml.settings);
        } catch (Exception e) {

        }

        final ListPreference listPreference = (ListPreference) findPreference("language");

        // THIS IS REQUIRED IF YOU DON'T HAVE 'entries' and 'entryValues' in your XML
        setListPreferenceData(listPreference);

        listPreference.setOnPreferenceClickListener(new OnPreferenceClickListener() {
            @Override
            public boolean onPreferenceClick(Preference preference) {

                setListPreferenceData(listPreference);
                return false;
            }
        });
    }

    protected static void setListPreferenceData(ListPreference lp) {
            CharSequence[] entries = { "English", "French" };
            CharSequence[] entryValues = {"1" , "2"};
            lp.setEntries(entries);
            lp.setDefaultValue("1");
            lp.setEntryValues(entryValues);
    }
}

這是谷歌的DeskClock應用程序的另一個例子：

Answer 2

使用PreferenceFragment & JAVA set key 而不是 PreferenceActivity & XML ，如https://stackoverflow.com/a/13828912/1815624所示，此答案基於：

如果您希望能夠在初始 ListPreference 對象初始化后動態更改列表中的項目，那么您需要將OnPreferenceClickListener直接附加到 ListPreference 對象。 使用您在 JAVA 源中指定的鍵（作為CUSTOM_LIST ）來獲取首選項的句柄。

由於填充entries和entryValues數組的代碼必須同時在onCreate()和onPreferenceClick中onPreferenceClick ，因此將其提取到單獨的方法setListPreferenceData()以避免重復是有意義的。

/**
 * This fragment shows data and sync preferences only. It is used when the
 * activity is showing a two-pane settings UI.
 */
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public static class myCustomPreferenceFragment extends PreferenceFragment {

    final private String CUSTOM_LIST= "custom_list";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.pref_custom_frag);

        PreferenceCategory targetCategory = (PreferenceCategory) findPreference("CUSTOM_FRAG");

        final ListPreference lp = setListPreferenceData((ListPreference) findPreference(CUSTOM_LIST), getActivity());

        lp.setOnPreferenceClickListener(new Preference.OnPreferenceClickListener() {
            @Override
            public boolean onPreferenceClick(Preference preference) {

                setListPreferenceData(lp, getActivity());
                return false;
            }
        });
        setHasOptionsMenu(true);
        targetCategory.addPreference(lp);

        bindPreferenceSummaryToValue(targetCategory);
        bindPreferenceSummaryToValue(lp);
    }

    protected ListPreference setListPreferenceData(ListPreference lp, Activity mActivity) {
        CharSequence[] entries = { "One", "Two", "Three" };
        CharSequence[] entryValues = { "1", "2", "3" };
        if(lp == null)
            lp = new ListPreference(mActivity);
        lp.setEntries(entries);
        lp.setDefaultValue("1");
        lp.setEntryValues(entryValues);
        lp.setTitle("Number Of blahs");
        lp.setSummary(lp.getEntry());
        lp.setDialogTitle("Number of Blah objects");
        lp.setKey(CUSTOM_LIST);
        return lp;
    }

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

XML布局：

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <PreferenceCategory
        android:key="CUSTOM_FRAG"
        android:title="Some Options">

    </PreferenceCategory>
</PreferenceScreen>

Answer 3

我解決了擴展 ListPreference 的問題。 這很簡單。

public class DListPref extends ListPreference
{
    public interface LoadingListener
    {
        void setData(ListPreference lp);
    }

    LoadingListener TheLL;

    public void setLoadingListener(LoadingListener l)
    {
        TheLL = l;
    }

    @Override
    protected void onPrepareDialogBuilder(AlertDialog.Builder builder)
    {
        if(TheLL!=null)
        {
            TheLL.setData(this);
        }
        super.onPrepareDialogBuilder(builder);
    }

    //Do not mind the rest of this class, as they are auto-generated boilerplate code.
    public DListPref(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)
    {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    public DListPref(Context context, AttributeSet attrs, int defStyleAttr)
    {
        super(context, attrs, defStyleAttr);
    }

    public DListPref(Context context, AttributeSet attrs)
    {
        super(context, attrs);
    }

    public DListPref(Context context)
    {
        super(context);
    }
}

然后我只是在 XML 中將名稱更改為我的類。

<my.company.DListPref
    android:defaultValue="-1"
    android:key="damn"
    android:title="vegetables"/>

然后我只是在 onCreate 上做了這個。

        DListPref lp = (DListPref) findPreference("damn");

        lp.setLoadingListener(new DListPref.LoadingListener()
        {
            @Override
            public void setData(ListPreference lp)
            {
                lp.setEntries(new String[]{"doge", "wow"});
                lp.setEntryValues(new String[] {"1", "2"});
                lp.setDefaultValue("1");
            }
        });

馬上工作了。 其實，我沒想到會這么容易。

Answer 4

這是我必須做的才能讓我的工作

    public static class MyPreferenceFragment extends PreferenceFragment
{
    @Override
    public void onCreate(final Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.pref_general);
        PreferenceCategory targetCategory = (PreferenceCategory) findPreference("CUSTOM_FRAG");

        //final Preference pref;
        //pref = findPreference("example_list1");
        final ListPreference lp = setListPreferenceDataSocieties((ListPreference) findPreference("custom1"), getActivity());
        final ListPreference lp2 = setListPreferenceDataRoutes((ListPreference) findPreference("custom2"), getActivity());
        final ListPreference lp3 = setListPreferenceDataCoolers((ListPreference) findPreference("custom3"), getActivity());



        setHasOptionsMenu(true);
        targetCategory.addPreference(lp);
        targetCategory.addPreference(lp2);
        targetCategory.addPreference(lp3);

        bindPreferenceSummaryToValue(targetCategory);
        bindPreferenceSummaryToValue(lp);
        bindPreferenceSummaryToValue(lp2);
        bindPreferenceSummaryToValue(lp3);
    }

    protected ListPreference setListPreferenceDataSocieties(ListPreference lp, Activity mActivity) {
        CharSequence[] entries = { "One", "Two", "Three" };
        CharSequence[] entryValues = { "1", "2", "3" };
        if(lp == null)
            lp = new ListPreference(mActivity);
        lp.setEntries(entries);
        lp.setDefaultValue("1");
        lp.setEntryValues(entryValues);
        lp.setTitle("Origin Society");
        lp.setSummary(lp.getEntry());
        lp.setDialogTitle("Registered Societies");
        lp.setKey("society_list");
        return lp;
    }


    protected ListPreference setListPreferenceDataRoutes(ListPreference lp, Activity mActivity) {
        CharSequence[] entries = { "One", "Two", "Three" };
        CharSequence[] entryValues = { "1", "2", "3" };
        if(lp == null)
            lp = new ListPreference(mActivity);
        lp.setEntries(entries);
        lp.setDefaultValue("1");
        lp.setEntryValues(entryValues);
        lp.setTitle("Designated Route");
        lp.setSummary(lp.getEntry());
        lp.setDialogTitle("Available Routes");
        lp.setKey("route_list");
        return lp;
    }
    protected ListPreference setListPreferenceDataCoolers(ListPreference lp, Activity mActivity) {
        CharSequence[] entries = { "One", "Two", "Three" };
        CharSequence[] entryValues = { "1", "2", "3" };
        if(lp == null)
            lp = new ListPreference(mActivity);
        lp.setEntries(entries);
        lp.setDefaultValue("1");
        lp.setEntryValues(entryValues);
        lp.setTitle("Destination Cooler");
        lp.setSummary(lp.getEntry());
        lp.setDialogTitle("Available Coolers");
        lp.setKey("cooler_list");
        return lp;
    }

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

}


boolean first_run = true;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    MyPreferenceFragment frag =  new MyPreferenceFragment();
    getFragmentManager().beginTransaction().replace(android.R.id.content, frag).commit();

}