我有这个主要活动：

public class Home extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.home);
        initializeStyle();
    }
    private void initializeStyle() {
        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
        String foobar = prefs.getString("foobar", "hi");
        Log.i("MyActivity", foobar);
    }
// ...
}

而这个PreferenceActivity：

public class Preferences extends PreferenceActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);
    }
}

有了这个XML：

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen
  xmlns:android="http://schemas.android.com/apk/res/android">
<PreferenceCategory 
        android:key="preferences_font"
        android:title="@string/preferences_font">
    <EditTextPreference
            android:title="@string/preferences_font_size"
            android:key="foobar"
            android:defaultValue="12">
    </EditTextPreference>
</PreferenceCategory>
</PreferenceScreen>

Log.i打印“hi”,这意味着这个首选项不存在或我命名错误.

关于我做错了什么的任何想法？

问候,

解决方法:

这可能有助于您重新回到正轨并拥有工作偏好：

XML文件：preferences.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <PreferenceCategory android:title="Preferences Font">
        <EditTextPreference 
            android:title="Select Font Size" 
            android:key="foobar" 
            android:summary="Enter Font Size"
            android:defaultValue="12" />
    </PreferenceCategory>
</PreferenceScreen> 

JAVA FILE 1：Home.java

public class Home extends Activity {

    public SharedPreferences prefs;

    static public String fontPref; //you can make it an int or whatever you need
    static public String myValue; //to store new pref value

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {

         setContentView(R.layout.home);
         initializeStyle();
    } 

    private void initializeStyle() {
       prefs = PreferenceManager.getDefaultSharedPreferences(this);
       fontPref = prefs.getString("foobar", "hi"); //this doesn't actually change the value
       myValue = "This is a test";
       Log.i("MyActivity", foobar); //won't show change yet
    }
}

JAVA FILE 2：Prefernce.java

import android.preference.Preference;
import android.preference.PreferenceActivity;
import android.preference.PreferenceManager;
//... and any other imports

public class Preferences extends PreferenceActivity  implements OnSharedPreferenceChangeListener{

    private SharedPreferences prefs;

    @Override
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);
        //add other stuff here if you need, especially if you might have some
        //prefs that use buttons and need to set up your onClickListener for one
    }

    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPref, String key) {
        Editor editor = sharedPref.edit();
        if(key.equalsIgnoreCase("foobar")){
            Home.fontPref = sharedPref.getString("foobar", "some value");
            editor.putString("foobar", Home.myValue); //where ever or whatever new value is 
        }

        editor.commit();
        Log.i("PrefsActivity", foobar); //should show change now
    }
} 

希望这可以帮助您走上正轨.当然有很多方法可以做这些事情,祝你好运,希望它有所帮助.