Question

我正在使用标签式活动来显示三个标签问题是，第一个选项卡总是空白，而第二个和第三个选项卡工作。如果我点击第三个，然后点击第一个，第一个加载数据

public class Main2Activity extends AppCompatActivity {

/**
 * The {@link android.support.v4.view.PagerAdapter} that will provide
 * fragments for each of the sections. We use a
 * {@link FragmentPagerAdapter} derivative, which will keep every
 * loaded fragment in memory. If this becomes too memory intensive, it
 * may be best to switch to a
 * {@link android.support.v4.app.FragmentStatePagerAdapter}.
 */
private SectionsPagerAdapter mSectionsPagerAdapter;

/**
 * The {@link ViewPager} that will host the section contents.
 */
private ViewPager mViewPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);

    //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);

    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_main2, 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);
}

/**
 * A placeholder fragment containing a simple view.
 */

/**
 * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
 * one of the sections/tabs/pages.
 */
public static class SectionsPagerAdapter extends FragmentStatePagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a Movies_Fragment (defined as a static inner class below).
        Movies_Fragment fragment =  Movies_Fragment.newInstance(position );
        return fragment;

    }



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




    @Override
    public CharSequence getPageTitle(int position) {
        switch (position) {
            case 0:
                return "Most Popular";
            case 1:
                return "Top Rated";
            case 2:
                return "Top Rated 2";
        }
        return null;
    }
}

}

public class Movies_Fragment extends Fragment {

public static ImageAdapter imageAdapter;


public static Movies_Fragment newInstance(int sectionNumber) {
    Movies_Fragment fragment = new Movies_Fragment();
    Bundle args = new Bundle();
    args.putInt("index", sectionNumber);
    fragment.setArguments(args);

    return fragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setHasOptionsMenu(true);


}

@Override
public void onStart() {
    super.onStart();
    updateMovies();
    //imageAdapter.notifyDataSetChanged();

}

public void updateMovies() {
    FetchMovieTask movieTask = new FetchMovieTask();
    Bundle bundle = getArguments();
    int index = bundle.getInt("index");
    movieTask.execute(index);
}

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    super.onCreateOptionsMenu(menu, inflater);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_movies_, container, false);

    imageAdapter = new ImageAdapter(getActivity());
    GridView gridView = (GridView)rootView.findViewById(R.id.gridView);
    gridView.setAdapter(imageAdapter);

    gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
            MDMovie movie = (MDMovie) imageAdapter.getItem(i);
            Intent intent = new Intent(getActivity(),movieDetailsActivity.class);
            intent.putExtra("movie", movie);
            startActivity(intent);
        }
    });

    return  rootView;
}

}

Answer 1

这也发生在我的一个项目中，我也无法对其进行诊断。我最终使用了这个[脏]黑客。到目前为止它不是解决方案，但它对我们有用。我们基本上在开始时模拟页面更改：

@Override 
protected void onCreate(Bundle savedInstanceState) {
    ...

    // Set up the ViewPager with the sections adapter. 
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);

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

    mViewPager.setCurrentItem(1);
    mViewPager.setCurrentItem(0);
}

选项卡式活动中的第一个片段始终为空白

1 个答案: