Modifier le texte d'un bouton sur l'onglet android ou sélectionnez

Question

J'ai un bouton sur une activité à onglets, maintenant chaque activité est balayée ou un autre onglet est sélectionné, je veux changer le texte du bouton en fonction de l'index du fragment. Comment je fais ça?

Je viens de suivre ce tutoriel sur la création d'onglets Android: https://www.youtube.com/watch?v=00LLd7qr9sA Il est essentiellement l'activité à onglets par défaut, il vient de créer un fichier java et XML par fragment.

Ceci est mon main_activity.java

import android.support.design.widget.TabLayout; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 

import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentPagerAdapter; 
import android.support.v4.view.ViewPager; 
import android.os.Bundle; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.widget.Button; 
import android.widget.TextView; 


public class MainActivity extends AppCompatActivity{ 

    private SectionsPagerAdapter mSectionsPagerAdapter; 
    private ViewPager mViewPager; 
    Button buttonChangeMyText; 


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

     buttonChangeMyText= (Button)findViewById(R.id.btnChange); 


     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 
     // 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.container); 
     mViewPager.setAdapter(mSectionsPagerAdapter); 


     anoNa=mViewPager.getCurrentItem(); 


     TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs); 
     tabLayout.setupWithViewPager(mViewPager); 

    } 


    @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_screen, 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 onPageSelected(View v) { 
     TextView tv = (TextView) v.getRootView().findViewById(R.id.textViewSaUna); 
     tv.setText("Welcome To Android"); 
    }*/ 


    /** 
    * 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) { 
      switch (position){ 
       case 0: 
        Tab1_First tab1 = new Tab1_First(); 
        return tab1; 
       case 1: 
        Tab2_Second tab2 = new Tab2_Second(); 
        return tab2; 
       case 2: 
        Tab3_Third tab3 = new Tab3_Third(); 
        return tab3; 
       default: 
        return null; 

      } 

     } 

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

     @Override 
     public CharSequence getPageTitle(int position) { 
      switch (position) { 
       case 0: 
        return "ONE"; 
       case 1: 
        return "TWO"; 
       case 2: 
        return "THREE"; 
      } 
      return null; 
     } 
    }//end ng fragment adapter 
} 

Voici le code java d'un fragment.

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

public class Tab1_Una extends Fragment { 
    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) { 
     View rootView = inflater.inflate(R.layout.tab1_una, container, false); 

     return rootView; 
    } 

} 

Ceci est le fichier XML de l'activité principale.

<?xml version="1.0" encoding="utf-8"?> 
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:app="http://schemas.android.com/apk/res-auto" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:id="@+id/main_content" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:fitsSystemWindows="true" 
    tools:context="com.example.lat.sampletabs.MainScreen"> 

    <android.support.design.widget.AppBarLayout 
     android:id="@+id/appbar" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:paddingTop="@dimen/appbar_padding_top" 
     android:theme="@style/AppTheme.AppBarOverlay"> 

     <android.support.v7.widget.Toolbar 
      android:id="@+id/toolbar" 
      android:layout_width="match_parent" 
      android:layout_height="?attr/actionBarSize" 
      android:background="?attr/colorPrimary" 
      app:layout_scrollFlags="scroll|enterAlways" 
      app:popupTheme="@style/AppTheme.PopupOverlay" 


      > 

     </android.support.v7.widget.Toolbar> 

     <android.support.design.widget.TabLayout 
      android:id="@+id/tabs" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" /> 

    </android.support.design.widget.AppBarLayout> 

    <Button 
     android:id="@+id/btnChange" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_marginLeft="120dp" 
     android:layout_marginTop="500dp" 
     android:text="Change the text"/> 


    <android.support.v4.view.ViewPager 
     android:id="@+id/container" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     app:layout_behavior="@string/appbar_scrolling_view_behavior" /> 


</android.support.design.widget.CoordinatorLayout> 

Answer 1

Vous devez ajouter un OnPageChangeListener à votre mViewPager comme ceci:

mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() { 
     @Override 
     public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { 
      // position = Current tab index being scrolled from 

     } 

     @Override 
     public void onPageSelected(int position) { 
      // position = New tab index 
      switch (position) { 
       case 0: 
        buttonChangeMyText.setText("Some text"); 
        break; 
       case 1: 
        buttonChangeMyText.setText("Some other text"); 
        break; 
       case 2: 
        buttonChangeMyText.setText("Some other other text"); 
        break; 
       // ... 
      } 
     } 

     @Override 
     public void onPageScrollStateChanged(int state) { 
      // state = Tells when the user begins dragging, when the pager is 
      // automatically settling to the current page, or when it is fully stopped/idle. 

     } 
    });