如何在 FragmentPagerAdapter 中的片段之间传递数据

Question

对于我的学术项目，我想创建一个包含 4 个选项卡的应用程序。第一个将显示最近添加到列表中的游戏，第二个将是搜索表单，第三个将显示搜索结果，最后一个将显示详细信息。我目前已经为TabView 和 4 个选项卡创建了代码。问题是我想执行搜索以获取列表中符合片段 2 搜索条件的项目，但我不知道如何将片段 2 中的数据（textView 数据和微调器）传递给片段3.我的代码如下：

MainActivity.java:

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.design.widget.TabLayout;
import android.view.MenuInflater;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.widget.Button;
import android.widget.Toast;


public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {



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


        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setImageResource(R.drawable.ic_search_white_24dp);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
            }
        });

        //TabLayout function call
        configureTabLayout();

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        switch (item.getItemId()){
            case R.id.menu_exit:
                finish();
                return true;
            case R.id.menu_settings:
                Toast.makeText(this, "Under Construction", Toast.LENGTH_LONG).show();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_camera) {
            // Handle the camera action
        } else if (id == R.id.nav_gallery) {

        } else if (id == R.id.nav_slideshow) {

        } else if (id == R.id.nav_manage) {

        } else if (id == R.id.nav_share) {

        } else if (id == R.id.nav_send) {

        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }




    //Tab Layout function declaration
    private void configureTabLayout() {

        //Getting the tab layout
        TabLayout tabLayout = findViewById(R.id.tab_layout);

        //Adding Tabs
        tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.ic_home_white_24dp));
        tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.ic_search_white_24dp));
        tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.ic_results_white_24dp));
        tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.ic_details_white_24dp));


        //The TabPagerAdapter instance is then
        //assigned as the adapter for the ViewPager and the TabLayout component added
        //to the page change listener
        final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
        final PagerAdapter adapter = new TabPagerAdapter
            (getSupportFragmentManager(), tabLayout.getTabCount());
        viewPager.setAdapter(adapter);


        //Finally, the onTabSelectedListener is configured on the TabLayout instance and
        //the onTabSelected() method implemented to set the current page on the
        //ViewPager based on the currently selected tab number.
        viewPager.addOnPageChangeListener(new     TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
            }
            @Override
            public void onTabUnselected(TabLayout.Tab tab) {
            }
            @Override
            public void onTabReselected(TabLayout.Tab tab) {
            }
        });
    }
}

TabPagerAdapter.java

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

public class TabPagerAdapter extends FragmentPagerAdapter{

    int tabCount;

    public TabPagerAdapter(FragmentManager fm, int numberOfTabs) {
        super(fm);
        this.tabCount = numberOfTabs;
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return new HomeScreenFragment();
            case 1:
                return new SearchFormFragment();
            case 2:
                return new SearchResultsFragment();
            case 3:
                return new DetailsScreenFragment();
            default:
                return null;
        }
    }
    @Override
    public int getCount() {
        return tabCount;
    }
}

SearchFormFragment.java

package gr.pliroforiki_edu.videogamedb;


import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;


/**
 * A simple {@link Fragment} subclass.
 */
public class SearchFormFragment extends Fragment {

    private Button searchButton;
    private EditText gameTitleEditText;

    Spinner spinnerGenre;



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

    @Override
    public View onCreateView(final LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

        View searchFormView = inflater.inflate(R.layout.fragment_search_form, container, false);

        searchButton = searchFormView.findViewById(R.id.searchButton);
        gameTitleEditText = searchFormView.findViewById(R.id.game_title_editText);
        spinnerGenre = searchFormView.findViewById(R.id.genre_spinner);

        ArrayAdapter<CharSequence> genreAdapter = ArrayAdapter.createFromResource(
            getActivity(),
            R.array.game_genres,
            android.R.layout.simple_spinner_item
        );

        genreAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinnerGenre.setAdapter(genreAdapter);


        searchButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String filterGameTitle = gameTitleEditText.getText().toString();
                int filterGenreId = spinnerGenre.getSelectedItemPosition();

                String message = String.format("Game Title: %s\n Genre: %s", filterGameTitle, filterGenreId);
                Toast.makeText(getActivity(),message, Toast.LENGTH_LONG).show();

            }
        });

        // Inflate the layout for this fragment
        //return inflater.inflate(R.layout.fragment_search_form, container, false);
        return searchFormView;

    }

}

SearchResultsFragment.java

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.widget.TextView;


/**
 * A simple {@link Fragment} subclass.
 */
public class SearchResultsFragment extends Fragment {

    TextView infoTextView;
    ListView listViewGames;




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


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

        View searchResultsView = inflater.inflate(R.layout.fragment_search_results, container, false);



        return searchResultsView;
    }

    private void findViews()
    {
        infoTextView = getActivity().findViewById(R.id.info_textView);
        listViewGames = getActivity().findViewById(R.id.games_listView);
    }


}

我想通过片段归档以下内容：

ListActivity.java

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;


public class ListActivity extends AppCompatActivity {

private TextView textViewInfo;
private ListView listViewBooks;

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

    // Animation when this Activity appears
    overridePendingTransition(R.anim.pull_in_from_right, R.anim.hold);

    // Get user filters from Intent
    Intent intent = getIntent();

    String filterAuthor = intent.getStringExtra("AUTHOR");
    String filterTitle = intent.getStringExtra("TITLE");
    int filterGenreId = intent.getIntExtra("GENREID", 0);

    findViews();

    // Show user filters for information
    String message = String.format("Author: %s\nTitle: %s\nGenreId: %d",
            filterAuthor, filterTitle, filterGenreId);
    textViewInfo.setText(message);

    DataStore.LoadBooks(filterAuthor, filterTitle, filterGenreId);

    //Complex Object Binding
    ListAdapter booksAdapter = new SimpleAdapter(
            this,
            DataStore.Books,
            R.layout.list_item,
            new String[]{DataStore.KEY_TITLE, DataStore.KEY_AUTHOR, DataStore.KEY_GENRENAME},
            new int[]{R.id.book_item_title, R.id.book_item_author, R.id.book_item_genre}
    );

    listViewBooks.setAdapter(booksAdapter);

    listViewBooks.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Intent detailsIntent = new Intent(ListActivity.this, DetailsActivity.class);
            detailsIntent.putExtra(DataStore.KEY_POSITION, position);
            startActivity(detailsIntent);
        }
    });
}

@Override
protected void onPause(){
    overridePendingTransition(R.anim.hold, R.anim.push_out_to_right);
    super.onPause();
}

private void findViews(){
    textViewInfo = findViewById(R.id.textViewInfo);
    listViewBooks = findViewById(R.id.listViewBooks);
}


}

Mainactivity.java

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;



public class MainActivity extends AppCompatActivity {

private EditText textAuthor;
private EditText textTitle;
private EditText textGenre;
private Button buttonSearch;
private Spinner spinnerGenre;

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

    DataStore.Init(getApplicationContext());

    textAuthor = findViewById(R.id.editTextAuthor);
    textTitle= findViewById(R.id.editTextAuthor);
    buttonSearch = findViewById(R.id.buttonSearch);
    spinnerGenre = (Spinner) findViewById(R.id.spinnerGenre);

    ArrayAdapter<CharSequence> genreAdapter = ArrayAdapter.createFromResource(
            this,
            R.array.book_genres,
            android.R.layout.simple_spinner_item
    );

    genreAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinnerGenre.setAdapter(genreAdapter);

    buttonSearch.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String filterAuthor = textAuthor.getText().toString();
            String filterTitle = textTitle.getText().toString();
            int filterGenreId = spinnerGenre.getSelectedItemPosition();

            Intent intent = new Intent(MainActivity.this, ListActivity.class);
            intent.putExtra("AUTHOR", filterAuthor);
            intent.putExtra("TITLE", filterTitle);
            intent.putExtra("GENREID", filterGenreId);
            startActivity(intent);
        }
    });
}
}

Answer 1

试试这个

使用 bundle 在两个片段之间传递值

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

public class TabPagerAdapter extends FragmentPagerAdapter{

int tabCount;

 public TabPagerAdapter(FragmentManager fm, int numberOfTabs) {
super(fm);
this.tabCount = numberOfTabs;
}

 @Override
public Fragment getItem(int position) {
switch (position) {
    case 0:
        return  new HomeScreenFragment();
    case 1:
        return new SearchFormFragment();
    case 2:
       Fragment fragment = new SearchResultsFragment()
     Bundle args = new Bundle();
     args.putString("Key", "Value");
     fragment.setArguments(args);
        return fragment;

    case 3:
        return new DetailsScreenFragment();
    default:
        return null;
   }
}

    @Override
     public int getCount() {

   return tabCount;

   }
   }

在 SearchResultsFragment 的 onCreateView(....) 中

 String value = getArguments().getString("Key");

---

 public class SearchResultsFragment extends Fragment {

TextView infoTextView;
ListView listViewGames;

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


  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
                     Bundle savedInstanceState) {

   View searchResultsView = 
  inflater.inflate(R.layout.fragment_search_results, container, false);
    String value = getArguments().getString("Key");


   return searchResultsView;
 }
 private void findViews(){

 infoTextView = getActivity().findViewById(R.id.info_textView);
listViewGames = getActivity().findViewById(R.id.games_listView);
 }
 }

它会帮助你

Answer 2

您可以通过多种方式在片段之间传递对象/值。在您的情况下，最简单的解决方案是将这些值委托给控股Activity，即MainActivity。

MainActivity：

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.design.widget.TabLayout;
import android.view.MenuInflater;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.widget.Button;
import android.widget.Toast;


public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {
//these will hold your values
String filterGameTitle;
int filterGenreId;

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


    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setImageResource(R.drawable.ic_search_white_24dp);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

    //TabLayout function call
    configureTabLayout();

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

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

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    switch (item.getItemId()){
        case R.id.menu_exit:
            finish();
            return true;
        case R.id.menu_settings:
            Toast.makeText(this, "Under Construction", Toast.LENGTH_LONG).show();
            return true;
            default:
                return super.onOptionsItemSelected(item);
    }
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_camera) {
        // Handle the camera action
    } else if (id == R.id.nav_gallery) {

    } else if (id == R.id.nav_slideshow) {

    } else if (id == R.id.nav_manage) {

    } else if (id == R.id.nav_share) {

    } else if (id == R.id.nav_send) {

    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}




//Tab Layout function declaration
private void configureTabLayout() {

    //Getting the tab layout
    TabLayout tabLayout = findViewById(R.id.tab_layout);

    //Adding Tabs
    tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.ic_home_white_24dp));
    tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.ic_search_white_24dp));
    tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.ic_results_white_24dp));
    tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.ic_details_white_24dp));


    //The TabPagerAdapter instance is then
    //assigned as the adapter for the ViewPager and the TabLayout component added
    //to the page change listener
    final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
    final PagerAdapter adapter = new TabPagerAdapter
            (getSupportFragmentManager(), tabLayout.getTabCount());
    viewPager.setAdapter(adapter);


    //Finally, the onTabSelectedListener is configured on the TabLayout instance and
    //the onTabSelected() method implemented to set the current page on the
    //ViewPager based on the currently selected tab number.
    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            viewPager.setCurrentItem(tab.getPosition());
        }
        @Override
        public void onTabUnselected(TabLayout.Tab tab) {
        }
        @Override
        public void onTabReselected(TabLayout.Tab tab) {
        }
    });
}
}

SearchFormFragment：

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;


/**
 * A simple {@link Fragment} subclass.
 */
public class SearchFormFragment extends Fragment {

private Button searchButton;
private EditText gameTitleEditText;

Spinner spinnerGenre;



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

@Override
public View onCreateView(final LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View searchFormView = inflater.inflate(R.layout.fragment_search_form, container, false);

    searchButton = searchFormView.findViewById(R.id.searchButton);
    gameTitleEditText = searchFormView.findViewById(R.id.game_title_editText);
    spinnerGenre = searchFormView.findViewById(R.id.genre_spinner);

    ArrayAdapter<CharSequence> genreAdapter = ArrayAdapter.createFromResource(
            getActivity(),
            R.array.game_genres,
            android.R.layout.simple_spinner_item
    );

    genreAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinnerGenre.setAdapter(genreAdapter);


    searchButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String filterGameTitle = gameTitleEditText.getText().toString();
            int filterGenreId = spinnerGenre.getSelectedItemPosition();
            ((MainActivity)getActivity()).filterGameTitle = filterGameTitle;
            ((MainActivity)getActivity()).filterGenreId = filterGenreId;
            String message = String.format("Game Title: %s\n Genre: %s", filterGameTitle, filterGenreId);
            Toast.makeText(getActivity(),message, Toast.LENGTH_LONG).show();

        }
    });

    // Inflate the layout for this fragment
    //return inflater.inflate(R.layout.fragment_search_form, container, false);
    return searchFormView;

}

}

搜索结果片段：

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.widget.TextView;


/**
 * A simple {@link Fragment} subclass.
 */
public class SearchResultsFragment extends Fragment {

TextView infoTextView;
ListView listViewGames;

String filterGameTitle;
int filterGenreId;

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

@Override
public void onAttach(Context context)
{
    filterGameTitle = ((MainActivity)getActivity()).filterGameTitle;
    filterGenreId = ((MainActivity)getActivity()).filterGenreId;

    super.onAttach(context);
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View searchResultsView = inflater.inflate(R.layout.fragment_search_results, container, false);

    return searchResultsView;
}

private void findViews()
{
    infoTextView = getActivity().findViewById(R.id.info_textView);
    listViewGames = getActivity().findViewById(R.id.games_listView);
}


}

Answer 3

您可以使用接口将您的搜索字符串从片段 2 发送到您的活动，并且您可以从中调用片段 3 中的所有方法，因为片段3 对象将在您的活动中可供您使用，您可以在您的 fragment3 并从您的活动中调用它。 或者，您可以使用事件总线之类的东西来避免设置界面所需的样板代码。

看看这个事件总线回购https://github.com/greenrobot/EventBus 在您想要搜索字符串的位置注册事件总线，在您的情况下，像这样在 Fragment3 中注册事件总线

  @Override
 public void onStart() {
 super.onStart();
 EventBus.getDefault().register(this);
 }

 @Override
 public void onStop() {
 super.onStop();
 EventBus.getDefault().unregister(this);
 }

在你的 Fragment 3 中创建一个这样的函数

    @Subscribe
public void onSearchEvent(String searchString){
 //you will get your search string here
}

现在从你想发送searchString的地方回到fragment2，你必须在你想发送searchString的地方放下面的代码，这个发布的searchString将被fragment 3在其onSearchEvent方法中接收

EventBus.getDefault().post(searchString);