Question

我有ViewPager显示片段：SearchFragment，FriendFragment。我正在努力做的是将SearchFragment更改为ChatFragment

replace-fragment-inside-a-viewpager/中有很多反馈但我在使这些解决方案有效方面遇到了一些麻烦。

我认为我创建界面的方式可能有问题，我有一些麻烦让它可以从ViewPager调用<center>

我现在到达了

的地步

java.lang.NullPointerException：尝试调用虚方法 “android.support.v4.app.FragmentTransaction android.support.v4.app.FragmentManager.beginTransaction（）'为null 对象参考在 com.example.ashaneen.firebaseapp.adapters.MainScreenAdapter $ 1.onFragmentChange（MainScreenAdapter.java:44）在 com.example.ashaneen.firebaseapp.fragments.SearchFragment $ 4.onComplete（SearchFragment.java:132）

MainScreenAdapter.class

SearchActivity.newInstance(new MyListener {...} )

SearchFragment.class

public class MainScreenAdapter extends FragmentPagerAdapter implements SearchFragment.MyListener {

    private static final String TAG = "MainScreenAdapter";

    private FragmentManager fragmentManager;
    private Fragment fragment1;


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



    @Override
    public Fragment getItem(int position)
    {
        switch (position)
        {
            case 0:
                if (fragment1 == null)
                {
                    fragment1 = SearchFragment.newInstance(new SearchFragment.MyListener() {
                        @Override
                        public void onFragmentChange() {
                            fragmentManager.beginTransaction().remove(fragment1).commit();
                            fragment1 = ChatFragment.newInstance();
                            notifyDataSetChanged();
                        }
                    });
                }
                return fragment1;
            case 1:
                return new FriendsFragment();
            default:
                return new ChatFragment();
        }
    }

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

    }

Answer 1

尝试更改此

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

到

public MainScreenAdapter(FragmentManager fm) {
    super(fm);
    fragmentManager = fm;
}

更改ViewPager中显示的片段

1 个答案: