如何从SharedPreferences获取价值？

Question

I have been making application which uses Preferences. I have following PreferenceActivity:

public class PreferencesActivity extends PreferenceActivity{

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

        PreferenceManager.setDefaultValues(this, R.xml.prefences, true);
    }
}

also I have following preferences.xml:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >
    <EditTextPreference android:key="device_id" android:title="Device ID"/>
    <ListPreference android:key="update_time" android:entries="@array/update_keys" android:entryValues="@array/update_values" android:title="Update time" android:defaultValue="28800000"/>
</PreferenceScreen>

and I try to get values from SharedPreferences in onCreate() method my main Activity:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    initializeOtherElements();

    SharedPreferences prefs=PreferenceManager.getDefaultSharedPreferences(getBaseContext());
    Log.e("key", String.valueOf(prefs.getString("device_id", "1")));
}

I have added PreferencesActivity into manifest. But I see "1" in Log always. Where have I made a mistake?

Answer 1

You always see 1 in the log because you have mentioned "1" as the default value to return if "device_id" preference haven't been set. If you set the "device_id" preference to say ABC, ABC will be returned. If you haven't set "device_id" "1" will be returned.