如何动态填充列表preference当preferenceClick被触发？ [英] How to fill ListPreference dynamically when onPreferenceClick is triggered?

问题描述

我有，有一个 A preference活动语言为目录preference 其中显示可用语言列表。我可以填写列表时的onCreate是所谓的，但我想，以填补名单，当用户点击就可以了。

I have a preference activity that has a language as ListPreference which displays the available language list. I can fill the list when onCreate is called, but I want to fill the list when the user clicks on it.

这是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;

    }
}

这是的settings.xml （preference）：

and this is the settings.xml (preference) :

<?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>

我搜查，但没有发现任何结果！异常发生时我每次单击列表上。

I searched but found no result! An exception occurs every time I click on that list.

推荐答案

您所得到的例外，因为你的列表preference对象未完全初始化 - 你要么需要设置输入和 entryValues​​ 属性在你的XML或做编程的的onCreate（）。

You are getting the exception because your ListPreference object is not fully initialized - you either need to set entries and entryValues attributes in your XML or do it programatically in onCreate().

如果你想要的是能够动态地在最初的名单preference对象已被初始化，则可以更改列表中的项目，您将需要连接在preferenceClickListener 直接到列表preference对象。使用您在XML中指定的键得到一个句柄preference。

If what you want is to be able to change the items in the list dynamically after the initial ListPreference object has been initialized then you will need to attach the OnPreferenceClickListener directly to the ListPreference object. Use the key you have specified in the XML to get a handle to the preference.

由于code来填充输入和 entryValues​​ 阵列将不得不无论是在运行的onCreate（）和在preferenceClick ，是有意义的解压缩到一个单独的方法 - SETLIST preferenceData（），以避免重复。

Since the code to populate the entries and entryValues arrays will have to run both in onCreate() and in onPreferenceClick, it makes sense to extract it to a separate method - setListPreferenceData() in order to avoid duplication.

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);
    }
}

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