Question

我正在使用ViewPager和FragmentStatePagerAdapter。我的应用程序中有以下结构：

在索引0片段A
在索引1到7片段B：
每个片段B有4个按钮：
按钮C（加载片段c）
D（加载片段d）
E（加载片段e）
F（加载片段f）

ViewPager设置时默认加载Fragment C. 我想要实现的目标如下： - 单击按钮D应使用与按钮关联的片段替换当前片段。这个完成了问题是当按下按钮时，当前片段被替换，前一个和下一个片段也被替换。我怎样才能避免这种情况发生？

这是我的FragmentStatePageAdapter

 public class SectionsPagerAdapter extends FragmentStatePagerAdapter {

    private final FragmentManager mFragmentManager;
    private Fragment mFragmentAtPos0;
    public FirstPageListener listener = new FirstPageListener();
    private final class FirstPageListener implements
            ChannelPageFragmentListener {
        public void onSwitchToNextFragment() {
            mFragmentManager.beginTransaction().remove(mFragmentAtPos0)
                    .commit();
            if (mFragmentAtPos0 instanceof LatestPostFragment) {
                mFragmentAtPos0 = new LiveLoungeFragment(listener);
            } else { // Instance of NextFragment
                mFragmentAtPos0 = new LatestPostFragment(listener);
            }
            notifyDataSetChanged();
        }

        public void searchFields() {
            if (mFragmentAtPos0 instanceof LatestPostFragment) {
                ((LatestPostFragment) mFragmentAtPos0).reloadData("", false);
            }
            notifyDataSetChanged();
        }
    }
    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
        mFragmentManager = fm;
    }

    @Override
    public Fragment getItem(int position) {
        Fragment fragment = null;
        String tag = null;
        if(position == 0)
        {
            Log.i("Latest Posts","getItem pos : 0");
            tag = DASHBOARD_FRAGMENT;
            fragment = new DashboardFragment();
        }
        else
        {
            Log.i("Latest Posts","getItem pos : " + position);

            if(label.equalsIgnoreCase("latest"))
            {
                fragment = new LatestPostFragment(listener);
                mFragmentAtPos0 = fragment;
                Log.i("Latest Posts","getItem latest");
            }
        else if(label.equalsIgnoreCase("events"))
            {
                fragment = new LiveLoungeFragment(listener);
                mFragmentAtPos0 = fragment;
                Log.i("Latest Posts","getItem events");
                label = "latest";
            }
               fragment = mFragmentAtPos0;
            showDrawerIcon();
        }
        return fragment;
    }

    @Override
    public int getItemPosition(Object object)
    {
        Log.i("Latest Posts","getItemPosition : " + object.toString());
        if (object instanceof LatestPostFragment) {
            Log.i("Latest Posts","getItemPosition latestpost");

            return POSITION_NONE;
        }
        if (object instanceof LiveLoungeFragment) {
            Log.i("Latest Posts","getItemPosition livelounge");

            return POSITION_NONE;
        }
        return POSITION_UNCHANGED;
    }

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

    @Override
    public CharSequence getPageTitle(int position) {
        Log.i(TAG,"title : " + position);

        return channels.get(position).getSport().name();
    }
}`

这是按钮的触发器：

((Button) findViewById(R.id.latest)).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                label = "latest";
                sub_pressed = true;
                sub_position = "current";
                currentPosition = mViewPager.getCurrentItem();
                getCategoryFromName((String) mSectionsPagerAdapter.getPageTitle(currentPosition).toString());
                LatestPostFragment.firstPageListener.onSwitchToNextFragment();
            }
        });((Button) findViewById(R.id.events)).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                label = "events";
                sub_pressed = true;
                sub_position = "current";
                currentPosition = mViewPager.getCurrentItem();
                getCategoryFromName((String) mSectionsPagerAdapter.getPageTitle(currentPosition).toString());
                LatestPostFragment.firstPageListener.onSwitchToNextFragment();
            }
        });

基本上按下按钮时，会调用onSwitchToNextFragment的监听器并调用notifyDataSetChanged。

这是来自getItemPosition的日志

04-28 10：24：46.940 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItemPosition：LatestPostFragment {395c1afe＃0 id = 0x7f0a008a} 04-28 10：24：46.940 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItemPosition latestpost 04-28 10：24：46.940 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItemPosition：LatestPostFragment {1ae5125f＃2 id = 0x7f0a008a} 04-28 10：24：46.940 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItemPosition latestpost 04-28 10：24：46.940 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItemPosition：LatestPostFragment {139bf4ac＃1 id = 0x7f0a008a} 04-28 10：24：46.940 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItemPosition latestpost 04-28 10：24：46.946 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItem pos：3 04-28 10：24：46.946 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItem latest 04-28 10：24：46.946 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItem pos：2 04-28 10：24：46.946 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItem latest 04-28 10：24：46.946 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItem pos：4 04-28 10：24：46.946 5127-5127 / com.breathesport.breathesportapp I /最新帖子：getItem latest

我的猜测是getItemPosition无法理解哪一个是currentFragment，我可能在我的实现中做错了。我希望有人可以提供帮助

FragmentStatepageAdapter在调用notifyDataSetChanged时更新当前的上一个和下一个片段

0 个答案: