片段在重新附加时创建/恢复重复的视图

and*_*_su 6 android fragment android-fragments android-viewpager

我在6页ViewPagerOffscreenPageLimit=2(容易重现我的错误).
6页中的所有数据均来自服务器.在onCreateView,我向服务器发送请求,并在从服务器获取数据时刷新UI.

当我选择第一个选项卡并快速更改为最后一次时,某些寻呼机显示错误.那时我mMainLayout的片段中的字段不为空.

例如,ListView我的第一页有一个.当页面错误时,另一个ListView位于右侧ListView的顶部.当我尝试滚动ListView时,只移动了正确的一个(底部一个).

我知道我的响应监听器持有mMainLayout和其他一些视图的参考,我在方法onCreateView中创建了一个新的mMainLayout,我认为片段在重新连接/恢复时使用新的mMainLayout并丢弃旧的(或从容器中删除) .但是我错了.

我知道FragmentPagerAdapter附加/重新附加片段instantiateItem和分离destroyItem.适配器没有删除片段.适配器没有制作新片段.片段保持视图并查看状态本身.

我从容器中删除mMainLayout并将我的片段中的所有视图设置为null onDestroyView并且不保存任何内容onSaveInstanceState.但仍然很容易重现这个bug.

活动:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    registerReceiver(receiver, new IntentFilter("com.souyidai.intent.action.log_fragment"));
    FragmentManager fragmentManager = getFragmentManager();
    mResources = getResources();
    mMainPagerAdapter = new MainPagerAdapter(fragmentManager);
    mPager = (ViewPager) findViewById(R.id.pager);
    mPager.setAdapter(mMainPagerAdapter);
    mPager.setOffscreenPageLimit(CACHE_SIZE);
    mIndicator = (TabPageIndicator) findViewById(R.id.indicator);
    mIndicator.setViewPager(mPager);
    ...
}

private class MainPagerAdapter extends FragmentPagerAdapter {
    public MainPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        MainConfig.TabItem tab = mTabs.get(position);
        String tabType = tab.getTabType();
        String code = tab.getCode();
        MainConfig.TabItem.SubTabItem subTabItem = tab.getSubitem().get(0);
        Fragment fragment = MainFragment.newInstance(code, subTabItem);
        return fragment;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        MainConfig.TabItem tab = mTabs.get(position);
        return tab.getTitle();
    }

    @Override
    public int getCount() {
        return mTabs.size();
    }
}
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分段:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    mContainer = container;
    mMainLayout = inflater.inflate(R.layout.fragment_main, container, false);
    ...
}


@Override
public void onDestroyView() {
    super.onDestroyView();
    mContainer.removeView(mMainLayout);
    mContainer = null;
    mMainLayout = null;
    mSwipeRefreshLayout = null;
    mListView = null;
    mHeaderLayout = null;
    mFooterLayout = null;
    ...
}
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android.support.v13.app.FragmentPagerAdapter

@Override
public Object instantiateItem(ViewGroup container, int position) {
    if (mCurTransaction == null) {
        mCurTransaction = mFragmentManager.beginTransaction();
    }

    final long itemId = getItemId(position);

    // Do we already have this fragment?
    String name = makeFragmentName(container.getId(), itemId);
    Fragment fragment = mFragmentManager.findFragmentByTag(name);
    if (fragment != null) {
        if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
        mCurTransaction.attach(fragment);
    } else {
        fragment = getItem(position);
        if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
        mCurTransaction.add(container.getId(), fragment,
                makeFragmentName(container.getId(), itemId));
    }
    if (fragment != mCurrentPrimaryItem) {
        FragmentCompat.setMenuVisibility(fragment, false);
        FragmentCompat.setUserVisibleHint(fragment, false);
    }

    return fragment;
}
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我发现这个:

Android片段onCreateView在彼此之上创建重复的视图

但我只创建了新片段FragmentPagerAdapter.getItem.所以我们是不同的.

我通过删除mMainLayout的所有子节点来解决这个问题,如果在方法onCreateView中mMainLayout不为null .一切都很好.但我仍然对这个错误发生的原因感到困惑?

我做了一些测试.
1.尝试添加一个片段两次,app崩溃和日志说:java.lang.IllegalStateException:已添加片段:...
2.尝试连接片段两次,系统不调用Fragment.onCreateFragment.onCreateView

Qam*_*mar 3

这种情况的发生是由于instantiateItem() 我注意到的一件事的自定义实现。您正在搞乱检查片段是否已添加。

@Override
public Object instantiateItem(ViewGroup container, int position) {
    if (mCurTransaction == null) {
        mCurTransaction = mFragmentManager.beginTransaction();
    }

    final long itemId = getItemId(position);

    // Do we already have this fragment?
    String name = makeFragmentName(container.getId(), itemId);
    Fragment fragment = mFragmentManager.findFragmentByTag(name);
    if (fragment != null) {
        if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
        //make sure you are not attaching already added fragment
        //try with comment and uncomment two lines below
        //if(!fragment.isAdded())
        //mCurTransaction.attach(fragment);
    } else {
        fragment = getItem(position);
        if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
        mCurTransaction.add(container.getId(), fragment,
                makeFragmentName(container.getId(), itemId));
    }
    if (fragment != mCurrentPrimaryItem) {
        FragmentCompat.setMenuVisibility(fragment, false);
        FragmentCompat.setUserVisibleHint(fragment, false);
    }

    return fragment;
}
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不知道为什么你要创建类成员字段mMainLayout

//try to go with default
View view = inflater.inflate(R.layout.fragment_main, container, false);
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