java - 找不到符号方法 findPreference(String)

Question

我有一个 fragment ，我尝试从列表中获取我的设置值，购买它时找不到 findPreference 方法，为什么？

package com.cetabo.trackingpoint;

import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.res.Resources;
import android.os.Bundle;
import android.preference.ListPreference;
import android.preference.Preference;
import android.preference.PreferenceManager;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
import java.util.Timer;
import java.util.TimerTask;

import com.cetabo.trackingpoint.dummy.DummyContent;
import com.cetabo.trackingpoint.util.DetectionLocation;

import java.util.Date;

/**
 * A fragment representing a list of Items.
 * <p/>
 * Large screen devices (such as tablets) are supported by replacing the ListView
 * with a GridView.
 * <p/>
 * Activities containing this fragment MUST implement the {@link OnFragmentInteractionListener}
 * interface.
 */
public class PlacesFragment extends Fragment implements AbsListView.OnItemClickListener {

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    /**
     * The fragment's ListView/GridView.
     */
    private AbsListView mListView;
    ImageView imageView;

    /**
     * The Adapter which will be used to populate the ListView/GridView with
     * Views.
     */
    private ListAdapter mAdapter;

    // TODO: Rename and change types of parameters
    public static PlacesFragment newInstance(String param1, String param2) {
        PlacesFragment fragment = new PlacesFragment();
        Bundle args =  new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    /**
     * Mandatory empty constructor for the fragment manager to instantiate the
     * fragment (e.g. upon screen orientation changes).
     */
    public PlacesFragment() {
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }

        // TODO: Change Adapter to display your content
//        mAdapter = new ArrayAdapter<>(getActivity(), android.R.layout.simple_list_item_1, android.R.id.text1, DummyContent.ITEMS);
    }

    String[] test ={"test","test"};
    String text = "Central Park";
    Date data = new Date();

    //---HERE IS MY PROBLEM---
    ListPreference listPreference = (ListPreference) findPreference("sync_frequency");
    //------------------------    

//    Resources res = getResources();
//    String[] time = res.getStringArray(R.array.pref_example_list_values);
//    ArrayAdapter<String> adapter = ArrayAdapter.createFromResource(this, R.array.pref_sync_frequency_values, android.R.layout.simple_spinner_item);

      public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_place, container, false);
         Context ctx = view.getContext();
         DetectionLocation detectionLocation = new DetectionLocation(ctx);
        CustomListAdapter adapter=new CustomListAdapter(getActivity(),test,String.valueOf(detectionLocation.getLongitude()+"  "+detectionLocation.getLatitude()),data);
        mListView = (AbsListView) view.findViewById(android.R.id.list);
        mListView.setAdapter(adapter);


        // Set OnItemClickListener so we can be notified on item clicks
        mListView.setOnItemClickListener(this);

        return view;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
//        try {
//            mListener = (OnFragmentInteractionListener) activity;
//        } catch (ClassCastException e) {
//            throw new ClassCastException(activity.toString()
//                    + " must implement OnFragmentInteractionListener");
//        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }


    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        if (null != mListener) {
            // Notify the active callbacks interface (the activity, if the
            // fragment is attached to one) that an item has been selected.
            mListener.onFragmentInteraction(DummyContent.ITEMS.get(position).id);
        }
    }

    /**
     * The default content for this Fragment has a TextView that is shown when
     * the list is empty. If you would like to change the text, call this method
     * to supply the text it should use.
     */
    public void setEmptyText(CharSequence emptyText) {
        View emptyView = mListView.getEmptyView();

        if (emptyView instanceof TextView) {
            ((TextView) emptyView).setText(emptyText);
        }
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * <p/>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        public void onFragmentInteraction(String id);
    }

}

Answer 1

因为，

如果您使用的是 API 级别 11+ 设备，

findPreference() 是来自 PreferenceFragment 的方法。或者/否则，它将来自 PreferenceActivity。

有关更多信息，请查看http://developer.android.com/reference/android/preference/PreferenceActivity.html