单击选项卡时不调用查看寻呼机片段

Question

我创建了ViewPager，其中一个选项卡具有QR码阅读器，一个选项卡显示扫描的QR码的结果。 默认情况下，将弹出QR码屏幕的结果，因此当我在"扫描QR码"选项卡上单击时，我只能看到该片段的布局，但扫描仪屏幕没有显示。当我将默认选项卡设置为扫描仪时，只有它显示扫描仪屏幕。下面是我的查看寻呼机代码。

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;
}

@Override public int getItemPosition(Object object( {

    return POSITION_NONE;
}

}

Answer 1

检查下面的代码

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);
    }
}