java - fragment 刷新？

Question

我的应用程序由两个 fragment 的主要 Activity 组成，我正在使用带有选项卡的 FragmentStatePagerAdapter，我想要的是每次单击第一个 fragment 的选项卡或滑动到它时刷新第一个 fragment ，我尝试了很多解决方案，但没有一个接缝有效，我使用 onStart 和 setUserVisibleHint 因此，如果它们都是 true，则应该刷新 fragment ，但我得到相同的内容。

我的代码如下

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;
        }
    }

<小时/> <小时/>

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

您的代码是正确的。为了在用户可见时刷新 fragment ，您可以使用:

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

在您的代码中，您似乎从未将 isStarted 标志设置为 true，因此您朝自己的腿开枪了;)