片段刷新？

Question

my app consist of main activity with tow fragments and I,m using FragmentStatePagerAdapter with tabs, what I want is to refresh the first fragment every time I click the first fragment's tab or slide to it, I've tried many solutions but non of them seams to work, Im using onStart and setUserVisibleHint so if they both are true the fragment should be refreshed but I'm getting the same content.

my code is below

public class MainActivity extends AppCompatActivity {

    TabLayout tabLayout;
    ViewPager viewPager;
    CustomAdapter adapter;

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

        getSupportActionBar().setElevation(0f);


        viewPager = (ViewPager) findViewById(R.id.viewpager);
        viewPager.setAdapter(new CustomAdapter(getSupportFragmentManager(), getApplicationContext()));

        tabLayout = (TabLayout) findViewById(R.id.tab);
        tabLayout.setupWithViewPager(viewPager);

        tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
            }

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

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

            }
        });


        }
    }




    class CustomAdapter extends FragmentStatePagerAdapter {

        private String[] fragments  = {"Fragment1","Fragment2"};


        public CustomAdapter(FragmentManager supportFragmentManager, Context applicationContext) {
            super(supportFragmentManager);
        }


        @Override
        public Fragment getItem(int position) {
            switch (position){
                case 0:
                    return new Fragment1();
                case 1:
                    return new Fragment2();
                default:
                    return null;
            }
        }

        @Override
        public int getCount() {
            return fragments.length;
        }
        @Override
        public CharSequence getPageTitle(int position){

            return fragments[position];
        }

        @Override
        public int getItemPosition(Object object) {
            return POSITION_NONE;
        }
    }

---

---

public class Fragment1 extends Fragment {


    private Boolean isVisible = false;
    private Boolean isStarted = false;

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

  // Fragments code 

        return rootView;
    }



    @Override
    public void onResume() {
        super.onResume();

    }

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        isVisible = isVisibleToUser;
        if (isVisible && isStarted) {
            refrehList();
            Log.i("Tag", "reloading fragment");
        }

    }

    @Override
    public void onStart() {
        super.onStart();
        isStarted = true;

    }
    @Override
    public void onStop() {
        super.onStop();
        isStarted = false;
    }

    public void refrehList() {
        android.support.v4.app.FragmentTransaction ft = getFragmentManager().beginTransaction();
        ft.detach(this).attach(this).commit();

    }
}

Answer 1

Your code is correct. In order to refresh the fragment when it becomes visible to the user, you use:

  @Override
    public void setUserVisibleHint(boolean visible) {
        super.setUserVisibleHint(visible);
        if (visible) {
            Log.i("Tag", "reloading fragment");
        }
    }

In your code, it seems that you never set the isStarted flag to true and so you shoot yourself in the leg ;)

Answer 2

If you want to change content of same fragment knowing its position add listener to viewpager

Handler handler =new Handler();
viewpager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
      @Override
      public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

      }

  @Override public void onPageSelected(int position) {
    if(position==0)
      //handler to ensure that method is called after frament creation (rare bag with state restoration)
      handler.post(new Runnable() {
        @Override public void run() {
          if(yourFragment!=null)
            yourFragment.refreshMethod();

        }
      });
  }

      @Override public void onPageScrollStateChanged(int state) {

      }
    });

Also call int on your tabReselected(Tab tab) method While you always want to update only first fragment it is wise to keep external reference to it. Generally i recommend to use map to keep references to all fragments with position as a key.