當點擊標籤頁時，查看分頁器片段不會被調用？

Question

我已創建ViewPager，其中一個選項卡具有QR碼閱讀器，一個選項卡顯示掃描的QR碼的結果。默認情況下，qr代碼屏幕的結果將彈出，所以當我在掃描qr代碼選項卡上的標籤我只看到該片段的佈局，但掃描儀屏幕不顯示。 當我將默認選項卡設置爲掃描儀時，只有它顯示掃描儀屏幕。下面 是我的視圖尋呼機代碼..

tabLayout = (TabLayout) findViewById(R.id.bottomNavigation); 




    viewPager =(ViewPager)findViewById(R.id.viewPagerHome); 
    tabLayout.setupWithViewPager(viewPager); 



    viewPager.setOffscreenPageLimit(2); 
    view1= (View)findViewById(R.id.view1); 
    view2= (View)findViewById(R.id.view2); 
    view3= (View)findViewById(R.id.view3); 

    //Adding the tabs using addTab() method 
    tabLayout.addTab(tabLayout.newTab().setText("Scan")); 
    tabLayout.addTab(tabLayout.newTab().setText("Candidate")); 
    tabLayout.addTab(tabLayout.newTab().setText("Setting")); 
    viewPager = (ViewPager) findViewById(R.id.viewPagerHome); 

    //Creating our pager adapter 
    adapter = new Pager(getSupportFragmentManager(), tabLayout.getTabCount()); 

    //Adding adapter to pager 
    viewPager.setAdapter(adapter); 
    //Adding onTabSelectedListener to swipe views 
    tabLayout.setOnTabSelectedListener(this); 
    //setUptabIcon(); 


    tabLayout.setTabGravity(TabLayout.GRAVITY_FILL); 



viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() { 
     @Override 
     public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { 

     } 

     @Override 
     public void onPageSelected(int position) { 


      switch(position){ 

       case 0: 

        /* ViewPager viewPager = (ViewPager)findViewById(R.id.viewPagerHome); 
        viewPager.setCurrentItem(0);*/ 


        view1.setBackgroundResource(R.color.red ); 
        view2.setBackgroundResource(R.color.white ); 
        view3.setBackgroundResource(R.color.white); 
        break; 

       case 1: 
        view1.setBackgroundResource(R.color.white); 
        view2.setBackgroundResource(R.color.red); 
        view3.setBackgroundResource(R.color.white); 
        break; 

       case 2: 
        view1.setBackgroundResource(R.color.white ); 
        view2.setBackgroundResource(R.color.white); 
        view3.setBackgroundResource(R.color.red ); 
        break; 

       default: 
        view1.setBackgroundResource(R.color.white ); 
        view2.setBackgroundResource(R.color.red); 
        view3.setBackgroundResource(R.color.white ); 
        break; 
      } 
     } 

     @Override 
     public void onPageScrollStateChanged(int state) { 

     } 
    }); 

    @Override 
public void onTabSelected(TabLayout.Tab tab) { 
    viewPager.setCurrentItem(tab.getPosition()); 

    if(tab.getPosition() == 0){ 


     Fragment childF = new CandidateScanChildFragment(); 
     FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); 
     transaction.replace(R.id.child_scanfragment_container, childF).commit(); 

    } 
} 

ViewPagerAdpater.class

public class Pager extends FragmentStatePagerAdapter { 


int tabCount; 
FragmentManager mFragmentManager; 

private Fragment mFragmentAtPos0; 
//FirstPageListener listener = new FirstPageListener(); 
public Pager(FragmentManager fm, int tabCount) { 
    super(fm); 
    this.tabCount = tabCount; 
} 





public Pager(FragmentManager fragmentManager) { 
    super(fragmentManager); 
    mFragmentManager = fragmentManager; 
} 





    @Override 
public Fragment getItem(int position) { 
    switch (position) { 

     case 0: 
      ScanFragment scanTabFragment = new ScanFragment(); 
      return scanTabFragment; 
     case 1: 
      CandidateFragment candidateTabFragment = new CandidateFragment(); 
      return candidateTabFragment; 
     case 2: 
      SettingFragment settingtabFragment = new SettingFragment(); 
      return settingtabFragment; 
     default: 
      return null; 
    } 
} 



@Override 
public int getCount() { 
    return tabCount; 
} 

@覆蓋 公衆詮釋getItemPosition（Object對象） {

return POSITION_NONE; 
} 

}

Answer 1

請查閱以下代碼

mPager = (ViewPager) findViewById(R.id.mPager); 
tabLayout = (TabLayout) findViewById(R.id.tabLayout); 

setupViewPager(mPager); 
tabLayout.setupWithViewPager(mPager); 

private void setupViewPager(ViewPager viewPager) { 
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager()); 
    adapter.addFragment(new RequestFragment(), getString(R.string.requests)); 
//  adapter.addFragment(new AddedMeFragment(), getString(R.string.added_me)); 
    adapter.addFragment(new FriendsFragment(), getString(R.string.friends)); 
    viewPager.setAdapter(adapter); 
} 


class ViewPagerAdapter extends FragmentPagerAdapter { 
    private final List<Fragment> mFragmentList = new ArrayList<>(); 
    private final List<String> mFragmentTitleList = new ArrayList<>(); 

    public ViewPagerAdapter(FragmentManager manager) { 
     super(manager); 
    } 

    @Override 
    public Fragment getItem(int position) { 
     return mFragmentList.get(position); 
    } 

    @Override 
    public int getCount() { 
     return mFragmentList.size(); 
    } 

    public void addFragment(Fragment fragment, String title) { 
     mFragmentList.add(fragment); 
     mFragmentTitleList.add(title); 
    } 

    @Override 
    public CharSequence getPageTitle(int position) { 
     return mFragmentTitleList.get(position); 
    } 
}