BlankFragment.newInstance ("", "") - Обязательно: android.support.v4.app.Fragment - при использовании android.app.Fragment

Question

Я использую Android Studio 1.2.1.1 для изучения Android-программирования. Я создал новый проект с фрагментами и BlankFragments-class.

Но когда я использую newInstance(String param1, String param2) -Метод BlankFragment-Class в классе MainActivity-Class, компилятор говорит мне, что android.support.v4.app.Fragment не требуется.

Проблема заключается в том, что новый BlankFragment-Class использует android.app.Fragment, а MainActivity использует android.support.v4.app.Fragment. Но если я изменю import в классе MainActivity, я буду получать новые ошибки.

Это действительно расстраивает, потому что это структуры по умолчанию в Android Studio, насколько я знаю.

Основная деятельность:

package de.immozukunft.scouttools; 

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.Gravity; 
import android.view.LayoutInflater; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.TextView; 


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. 
    */ 
    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 three 
     // 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). 

      switch (position){ 
       case 0: 
        return PlaceholderFragment.newInstance(position + 1); 
       break; 
       case 1: 
        return BlankFragment.newInstance("",""); 
       break; 
       case 2: 
        return PlaceholderFragment.newInstance(position + 1); 
       break; 
       default: 
        return PlaceholderFragment.newInstance(position + 1); 
      } 

     } 

     @Override 
     public int getCount() { 
      // Show 3 total pages. 
      return 3; 
     } 

     @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); 
      } 
      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"; 

     /** 
     * 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_main, container, false); 
      return rootView; 
     } 
    } 

} 

BlankFragments:

package de.immozukunft.scouttools; 

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

    public BlankFragment() { 
     // 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_blank, 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

Я не могу просто заменить android.support.v4.app.Fragment с android.app.Fragment в MainActivity

Да, вы можете. Заменить:

import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentTransaction; 
import android.support.v4.app.FragmentPagerAdapter; 

с:

import android.app.Fragment; 
import android.app.FragmentManager; 
import android.app.FragmentTransaction; 
import android.support.v13.app.FragmentPagerAdapter; 

Обратите внимание, что последняя строка потребует от вас быть в зависимости от support-v13 в файле build.gradle; если у вас есть зависимость от support-v4, замените это на support-v13.

Вам также необходимо будет заменить getSupportFragmentManager() на номер getFragmentManager(), где он будет отображаться в вашем коде. Могут быть и другие изменения, кроме тех, но это должно закрыть вас.

Here is sample project, который использует собственные фрагменты API уровня 11+ с ViewPager.

Но если я изменю импорт в классе MainActivity, я буду продолжать получать новые ошибки.

Никогда не делайте такое заявление, что в Stack Overflow вопрос — или любой поддержки ситуации — без объяснения какие ошибки.