OnFragmentInteractionListener

尝试通过片段连接从sqlite数据库填充的listview。 在下面粘贴的代码中，您会看到我的交换机中有一个案例块，因为我只是想在我有更多片段之前让它工作。

我得到的例外’……必须实现OnFragmentInteractionListener’

public class MainActivity extends AppCompatActivity { private DrawerLayout mDrawer; private Toolbar toolbar; private NavigationView mNVDrawer; private ActionBarDrawerToggle drawerToggle; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //Set a Toolbar to replace the ActionBar. toolbar = (Toolbar) findViewById(R.id.toolbar); setSupportActionBar(toolbar); mDrawer = (DrawerLayout) findViewById(R.id.drawer_layout); drawerToggle = setupDrawerToggle(); mDrawer.setDrawerListener(drawerToggle); //Find our drawer view mNVDrawer = (NavigationView) findViewById(R.id.nvView); //Setup drawer view setupDrawerContent(mNVDrawer); } private ActionBarDrawerToggle setupDrawerToggle() { return new ActionBarDrawerToggle(this, mDrawer, toolbar, R.string.drawer_open, R.string.drawer_close); } private void setupDrawerContent(NavigationView navigationView) { navigationView.setNavigationItemSelectedListener( new NavigationView.OnNavigationItemSelectedListener() { @Override public boolean onNavigationItemSelected(MenuItem menuItem) { selectDrawerItem(menuItem); return true; } }); } public void selectDrawerItem(MenuItem menuItem) { //Creat a new fragment and specify the planet to show based on //position Fragment fragment = null; Class fragmentClass; switch (menuItem.getItemId()) { case R.id.nav_first_fragment: fragmentClass = AllQuestionsFragment.class; break; default: fragmentClass = AllQuestionsFragment.class; } try { fragment = (Fragment) fragmentClass.newInstance(); } catch (Exception e) { e.printStackTrace(); } //Insert the fragment by replacing any existing fragment FragmentManager fragmentManager = getSupportFragmentManager(); fragmentManager.beginTransaction().replace(R.id.flContent, fragment).commit(); //Highlight the selected item, update the title, and close the drawer menuItem.setChecked(true); setTitle(menuItem.getTitle()); mDrawer.closeDrawers(); } @Override public boolean onOptionsItemSelected(MenuItem item) { //The action bar home/up action should open or close the drawer switch (item.getItemId()) { case android.R.id.home: mDrawer.openDrawer(GravityCompat.START); return true; } if (drawerToggle.onOptionsItemSelected(item)){ return true; } return super.onOptionsItemSelected(item); } @Override protected void onPostCreate(Bundle savedInstanceState) { super.onPostCreate(savedInstanceState); //Sync the toggle state after onRestoreInstanceState has occurred drawerToggle.syncState(); } @Override public void onConfigurationChanged (Configuration newConfig) { super.onConfigurationChanged(newConfig); //Pass any configuration change to the drawer toggles } 

}

 public class AllQuestionsFragment extends android.support.v4.app.Fragment { // TODO: Rename parameter arguments, choose names that match // the fragment initialization parameters, eg 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; private DataBaseHelper mDBHelper; private Cursor mCursor; private QuestionAdapter adapter; private static Context mContext; public AllQuestionsFragment() { // Required empty public constructor } /https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/*https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* Use this factory method to create a new instance of https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* this fragment using the provided parameters. https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* @param param1 Parameter 1. https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* @param param2 Parameter 2. https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* @return A new instance of fragment AllQuestionsFragment. https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/*/ // TODO: Rename and change types and number of parameters public static AllQuestionsFragment newInstance(String param1, String param2) { AllQuestionsFragment fragment = new AllQuestionsFragment(); Bundle args = new Bundle(); args.putString(ARG_PARAM1, param1); args.putString(ARG_PARAM2, param2); fragment.setArguments(args); return fragment; } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (getArguments() != null) { mParam1 = getArguments().getString(ARG_PARAM1); mParam2 = getArguments().getString(ARG_PARAM2); } mContext = getActivity().getApplicationContext(); ListView mListView = (ListView) getView().findViewById(R.id.list_view); mDBHelper = new DataBaseHelper(mContext); mDBHelper.createDataBase(); try { mDBHelper.openDataBase(); } catch (SQLException e) { e.printStackTrace(); } mCursor = mDBHelper.getCursor(); getActivity().startManagingCursor(mCursor); adapter = new QuestionAdapter(mCursor); mListView.setAdapter(adapter); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Inflate the layout for this fragment return inflater.inflate(R.layout.fragment_all_questions, 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(Context context) { super.onAttach(context); if (context instanceof OnFragmentInteractionListener) { mListener = (OnFragmentInteractionListener) context; } else { throw new RuntimeException(context.toString() + " must implement OnFragmentInteractionListener"); } } @Override public void onDetach() { super.onDetach(); mListener = null; } /https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/*https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* This interface must be implemented by activities that contain this https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* fragment to allow an interaction in this fragment to be communicated https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* to the activity and potentially other fragments contained in that https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* activity. https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* 
 https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/* See the Android Training lesson Communicating with Other Fragments for more information. https://stackoverflow.com/questions/34730938/onfragmentinteractionlistener/*/ public interface OnFragmentInteractionListener { // TODO: Update argument type and name void onFragmentInteraction(Uri uri); } class QuestionAdapter extends CursorAdapter { QuestionAdapter(Cursor c) { super(mContext, c); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { LayoutInflater inflater = getActivity().getLayoutInflater(); View row = inflater.inflate(R.layout.list_view_row, parent, false); QuestionHolder holder = new QuestionHolder(row); row.setTag(holder); return row; } @Override public void bindView(View view, Context context, Cursor cursor) { QuestionHolder holder = (QuestionHolder) view.getTag(); holder.populateFrom(cursor, mDBHelper); } } static class QuestionHolder { private TextView txt = null; QuestionHolder(View row) { txt = (TextView) row.findViewById(R.id.tv_question); } void populateFrom(Cursor c, DataBaseHelper r) { txt.setText(r.getName(c)); } } } 

错误信息

 01-11 15:08:24.539 6491-6491/com.example.victor.nattest4 E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.victor.nattest4, PID: 6491 java.lang.RuntimeException: com.example.victor.nattest4.MainActivity@cedfc0a must implement OnFragmentInteractionListener at com.example.victor.nattest4.AllQuestionsFragment.onAttach(AllQuestionsFragment.java:119) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1019) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248) at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1613) at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:517) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5421) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:914) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:707) 

Answer 1

更改

 public class MainActivity extends AppCompatActivity { 

至

 public class MainActivity extends AppCompatActivity implements AllQuestionsFragment.OnFragmentInteractionListener { 

如日志中所述，

com.example.victor.nattest4.MainActivity@cedfc0a必须实现 OnFragmentInteractionListener

＆ 覆盖 onFragmentInteraction(Uri uri)方法。

编辑：

您需要在片段的onCreateView方法中初始化布局，而不是在onCreate ：

 @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 View rootView = inflater.inflate(R.layout.fragment_all_questions, container, false); ListView mListView = (ListView) rootView.findViewById(R.id.list_view); mContext = getActivity().getApplicationContext(); mDBHelper = new DataBaseHelper(mContext); mDBHelper.createDataBase(); try { mDBHelper.openDataBase(); } catch (SQLException e) { e.printStackTrace(); } mCursor = mDBHelper.getCursor(); getActivity().startManagingCursor(mCursor); adapter = new QuestionAdapter(mCursor); mListView.setAdapter(adapter); return rootView; }