java - 引用新 fragment 会出现错误

Question

我正在尝试关注this answer但是，当我尝试引用我创建的 Fragment 时，出现以下错误:

Incompatible types.

Required: android.support.v4.app.Fragment
Found: com.john.test.TestFragment

MainActivity.java

package com.john.test;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentManager;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

import com.astuetz.PagerSlidingTabStrip;

public class MainActivity extends AppCompatActivity {

    ViewPager viewPager;
    PagerAdapter pagerAdapter;
    PagerSlidingTabStrip pagerSlidingTabStrip;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewPager = (ViewPager) findViewById(R.id.pager);
        pagerAdapter = new PagerAdapter(getSupportFragmentManager());
        pagerSlidingTabStrip = (PagerSlidingTabStrip) findViewById(R.id.tabs);
        viewPager.setAdapter(pagerAdapter);
        pagerSlidingTabStrip.setViewPager(viewPager);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public class PagerAdapter extends FragmentPagerAdapter {

        public PagerAdapter(FragmentManager fm) {
            super(fm);
        }

        private Fragment f = null;

        @Override
        public Fragment getItem(int position) { // Returns Fragment based on position
            switch (position) {
                case 0:
                    f = new TestFragment();
                    break;
                case 1:
                    // f = new FragmentPageTwo();
                    break;
            }
            return f;
        }

        @Override
        public int getCount() { // Return the number of pages
            return 2;
        }

        @Override
        public CharSequence getPageTitle(int position) { // Set the tab text
            if (position == 0) {
                return "Fragment One";
            }
            if (position == 1) {
                return "Fragment Two";
            }
            return getPageTitle(position);
        }
    }
}

TestFragment.java

package com.john.test;

import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;


/**
 * A simple {@link Fragment} subclass.
 * Activities that contain this fragment must implement the
 * {@link TestFragment.OnFragmentInteractionListener} interface
 * to handle interaction events.
 * Use the {@link TestFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class TestFragment extends Fragment {
    // 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;

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment TestFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static TestFragment newInstance(String param1, String param2) {
        TestFragment fragment = new TestFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    public TestFragment() {
        // Required empty public constructor
    }

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_trending, container, false);
    }

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @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;
    }

    /**
     * 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(Uri uri);
    }

}

Answer 1

您必须从 android.support.v4.app.Fragment 扩展 fragment ，而不是从 android.app.Fragment 扩展。

查看TestFragment的导入。