java - Fragment 列表已更改，但 ViewPager 加载已实例化的 Fragment

Question

• 我有一个 ViewPager，一个扩展 FragmentPagerAdapter 的 FragmentAdapter，以及一个扩展 Fragment 的 NewsFragment 的 ArrayList。问题是，当我动态编辑 FragmentList 时，我的 tabLayout 和 FragmentList 包含正确的数据，但 viewPager 没有显示正确的 Fragment。
• 例如，首先，我进入 fragment3，然后在编辑活动中将 fragment3 替换为 fragment#。之后我回到 mainActivity 并发生了坏事。当我进入应该显示片段#的第三个片段时，它实际上显示的是我第一次进入它时实例化的片段3。
• 我认为问题可能是由于活动管理片段的方式，也许片段存储在由片段管理器或其他控制的集合中。有什么难过的。我试图通过一个一个弹出项目来清除fragmentManager，最后问题仍然存在。这是我与问题相关的代码

public class MainActivity extends AppCompatActivity {
    String[] categoriesList = {"娱乐", "军事", "教育", "文化", "健康", "财经", "体育", "汽车", "科技", "社会"};
    ArrayList<ChannelBean> channelBeans;
    ArrayList<ChannelBean> curChannels;
    ArrayList<NewsFragment> newsFragments;
    TabLayout tagBar;
    ViewPager viewPager;
    NewsFragment curFragment = null;
    Button channelManageBtn;

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

        tagBar = (TabLayout) findViewById(R.id.news_tab_layout);
        viewPager = findViewById(R.id.news_view_pager);
        channelManageBtn = findViewById(R.id.moreChannelBtn);
        newsFragments = new ArrayList<>();
        channelBeans = new ArrayList<>();
        curChannels = new ArrayList<>();
        for (String channel : categoriesList) {
            ChannelBean bean = new ChannelBean(channel, true);
            channelBeans.add(bean);
            curChannels.add(bean);
            newsFragments.add(new NewsFragment(channel));
        }


        viewPager.setAdapter(new FragmentAdapter(getSupportFragmentManager(), newsFragments));

        tagBar.setupWithViewPager(viewPager);

        channelManageBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ChannelActivity.startChannelActivity(MainActivity.this, channelBeans);
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == ChannelActivity.REQUEST_CODE && resultCode == ChannelActivity.RESULT_CODE) {
            String jsonStr = data.getStringExtra(ChannelActivity.RESULT_JSON_KEY);

            Gson gson = new Gson();
            channelBeans = gson.fromJson(jsonStr, new TypeToken<ArrayList<ChannelBean>>(){}.getType());
            newsFragments.clear();
            curChannels.clear();
            for (ChannelBean channel : channelBeans) {
                if (channel.isSelect()) {
                    newsFragments.add(new NewsFragment(channel.getName()));
                    curChannels.add(channel);
                }
            }

            viewPager.getAdapter().notifyDataSetChanged();

            tagBar.setupWithViewPager(viewPager);


        }


    }

    class FragmentAdapter extends FragmentPagerAdapter {

        ArrayList<NewsFragment> mNewsFragment;

        public FragmentAdapter(FragmentManager fm, ArrayList<NewsFragment> newsFragments) {
            super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
            mNewsFragment = newsFragments;
        }
        @NonNull
        @Override
        public Fragment getItem(int position) {
            return mNewsFragment.get(position);
        }

        @Override
        public int getCount() {
            return mNewsFragment.size();
        }

        @Nullable
        @Override
        public CharSequence getPageTitle(int position) {
            return mNewsFragment.get(position).getCategories();
        }

        @Override
        public void setPrimaryItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
            curFragment = (NewsFragment) object;
            super.setPrimaryItem(container, position, object);
        }
    }
}

标签： javaandroidandroid-fragmentsandroid-viewpager