Изменение вкладок в Android Studio

Question

Я новичок в Android-программировании и студии Android. В основном, я создаю приложение Memo от Android Studio, созданное Tabbed Activity (вкладки Action Bar (с помощью viewpager)), а затем создал 4 класса и макета фрагмента, все коды автоматически генерируются Android Studio. Но я застревают в Tab меняется ......

package com.example.user.memoapp; 

import java.util.Locale; 

import android.support.v7.app.ActionBarActivity; 
import android.support.v7.app.ActionBar; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentTransaction; 
import android.support.v4.app.FragmentPagerAdapter; 
import android.os.Bundle; 
import android.support.v4.view.ViewPager; 
import android.view.LayoutInflater; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.ViewGroup; 

public class MainActivity extends ActionBarActivity implements ActionBar.TabListener { 

/** 
* The {@link android.support.v4.view.PagerAdapter} that will provide 
* fragments for each of the sections. We use a 
* {@link FragmentPagerAdapter} derivative, which will keep every 
* loaded fragment in memory. If this becomes too memory intensive, it 
* may be best to switch to a 
* {@link android.support.v4.app.FragmentStatePagerAdapter}. 
*/ 
SectionsPagerAdapter mSectionsPagerAdapter; 

/** 
* The {@link ViewPager} that will host the section contents. 
*/ 
static ViewPager mViewPager; 

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

    // Set up the action bar. 
    final ActionBar actionBar = getSupportActionBar(); 
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); 

    // Create the adapter that will return a fragment for each of the four 
    // primary sections of the activity. 
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager()); 

    // Set up the ViewPager with the sections adapter. 
    mViewPager = (ViewPager) findViewById(R.id.pager); 
    mViewPager.setAdapter(mSectionsPagerAdapter); 

    // When swiping between different sections, select the corresponding 
    // tab. We can also use ActionBar.Tab#select() to do this if we have 
    // a reference to the Tab. 
    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() { 
     @Override 
     public void onPageSelected(int position) { 
      actionBar.setSelectedNavigationItem(position); 
     } 
    }); 

    // For each of the sections in the app, add a tab to the action bar. 
    for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) { 
     // Create a tab with text corresponding to the page title defined by 
     // the adapter. Also specify this Activity object, which implements 
     // the TabListener interface, as the callback (listener) for when 
     // this tab is selected. 
     actionBar.addTab(
       actionBar.newTab() 
         .setText(mSectionsPagerAdapter.getPageTitle(i)) 
         .setTabListener(this)); 
     } 

} 


@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); 
} 

@Override 
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) { 
    // When the given tab is selected, switch to the corresponding page in 
    // the ViewPager. 
    mViewPager.setCurrentItem(tab.getPosition()); 
} 

@Override 
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) { 
} 

@Override 
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) { 
} 

/** 
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to 
* one of the sections/tabs/pages. 
*/ 
public class SectionsPagerAdapter extends FragmentPagerAdapter { 

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

    @Override 
    public Fragment getItem(int position) { 
     // getItem is called to instantiate the fragment for the given page. 
     // Return a PlaceholderFragment (defined as a static inner class below) 
     return PlaceholderFragment.newInstance(position + 1); 
    } 

    @Override 
    public int getCount() { 
     // Show 4 total pages. 
     return 4; 
    } 

    @Override 
    public CharSequence getPageTitle(int position) { 
     Locale l = Locale.getDefault(); 
     switch (position) { 
      case 0: 
       return getString(R.string.title_section1).toUpperCase(l); 
      case 1: 
       return getString(R.string.title_section2).toUpperCase(l); 
      case 2: 
       return getString(R.string.title_section3).toUpperCase(l); 
      case 3: 
       return getString(R.string.title_section4).toUpperCase(l); 
     } 
     return null; 
    } 
} 

/** 
* A placeholder fragment containing a simple view. 
*/ 
public static class PlaceholderFragment extends Fragment { 
    /** 
    * The fragment argument representing the section number for this 
    * fragment. 
    */ 
    private static final String ARG_SECTION_NUMBER = "section_number"; 

    public int mPage; 
    /** 
    * Returns a new instance of this fragment for the given section 
    * number. 
    */ 
    public static PlaceholderFragment newInstance(int sectionNumber) { 
     PlaceholderFragment fragment = new PlaceholderFragment(); 
     Bundle args = new Bundle(); 
     args.putInt(ARG_SECTION_NUMBER, sectionNumber); 
     fragment.setArguments(args); 
     return fragment; 
    } 

    public PlaceholderFragment() { 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
      View rootView = inflater.inflate(R.layout.fragment_all, container, false); 
      return rootView; 

    } 

} 

}

Я попытался изменить GetItem() на что-то вроде этого:

@Override 
    public Fragment getItem(int position) { 
     // getItem is called to instantiate the fragment for the given page. 
     // Return a PlaceholderFragment (defined as a static inner class below) 
     //return PlaceholderFragment.newInstance(position + 1); 

     switch(position){ 
      case 0: 
       return new All(); 
      case 1: 
       return new Urgent(); 
      case 2: 
       return new Late(); 
      case 3: 
       return new Done(); 
      default: 
       return null; 
     } 

    } 

Но это даже не работа , сказал: «К сожалению, MemoApp остановился». Вот коды класса 4 фрагмента, все они генерируются Android Studio, в основном то же самое .... All.java:

package com.example.user.memoapp; 

import android.app.Activity; 
import android.net.Uri; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentTransaction; 



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

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

public All() { 
    // 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_all, 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); 
} 

} 

Urgent.java

package com.example.user.memoapp; 

import android.app.Activity; 
import android.net.Uri; 
import android.os.Bundle; 
import android.support.v4.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 Urgent.OnFragmentInteractionListener} interface 
* to handle interaction events. 
* Use the {@link Urgent#newInstance} factory method to 
* create an instance of this fragment. 
*/ 
public class Urgent 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 Urgent. 
*/ 
// TODO: Rename and change types and number of parameters 
public static Urgent newInstance(String param1, String param2) { 
    Urgent fragment = new Urgent(); 
    Bundle args = new Bundle(); 
    args.putString(ARG_PARAM1, param1); 
    args.putString(ARG_PARAM2, param2); 
    fragment.setArguments(args); 
    return fragment; 
} 

public Urgent() { 
    // 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_urgent, 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); 
} 

} 

Late .java,

package com.example.user.memoapp; 

import android.app.Activity; 
import android.net.Uri; 
import android.os.Bundle; 
import android.support.v4.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 Late.OnFragmentInteractionListener} interface 
* to handle interaction events. 
* Use the {@link Late#newInstance} factory method to 
* create an instance of this fragment. 
*/ 
public class Late 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 Late. 
*/ 
// TODO: Rename and change types and number of parameters 
public static Late newInstance(String param1, String param2) { 
    Late fragment = new Late(); 
    Bundle args = new Bundle(); 
    args.putString(ARG_PARAM1, param1); 
    args.putString(ARG_PARAM2, param2); 
    fragment.setArguments(args); 
    return fragment; 
} 

public Late() { 
    // 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_late, 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); 
} 

} 

Done.java:

package com.example.user.memoapp; 

import android.app.Activity; 
import android.net.Uri; 
import android.os.Bundle; 
import android.support.v4.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 Done.OnFragmentInteractionListener} interface 
* to handle interaction events. 
* Use the {@link Done#newInstance} factory method to 
* create an instance of this fragment. 
*/ 
public class Done 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 Done. 
*/ 
// TODO: Rename and change types and number of parameters 
public static Done newInstance(String param1, String param2) { 
    Done fragment = new Done(); 
    Bundle args = new Bundle(); 
    args.putString(ARG_PARAM1, param1); 
    args.putString(ARG_PARAM2, param2); 
    fragment.setArguments(args); 
    return fragment; 
} 

public Done() { 
    // 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_done, 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); 
} 

} 

Извините за очень долгое скучное кодирования ...

Answer 1

Как LogCat говорит, вы назначаете ваш MainActivity к All.mListener, который является OnFragmentInteractionListener, но MainActivity не реализует этот интерфейс

Так что вам нужно чтобы MainActivity реализовать OnFragmentInteractionListener:

public class MainActivity extends ActionBarActivity implements 
      ActionBar.TabListener, OnFragmentInteractionListener { 
    // ... all your Activity code ... 

    @Override 
    public void onFragmentInteraction(Uri uri) { 
     // ... implement communication here ... 
    } 
} 

Это позволит предотвратить приложение от сбоя, но все же вам нужно будет осуществлять связь между фрагментами и деятельностью. Измените параметры, требуемые функцией onFragmentInteraction(), если вам нужно отправить что-то еще или удалить интерфейс и любую ссылку на mListener, если вам не требуется такое общение.

Удачи вам!