我有一个用户执行此 *** 作的应用：
1 – 打开navigationDrawer并选择一个选项(创建一个片段)(我在这里选择第二个选项);
public voID selectItem(int position) { Fragment fragment = null; switch (position) { case FRAGMENT_OPTION1: ... break; case FRAGMENT_OPTION2: fragment = ControlPanelFragment.newInstance(); break; ... case FRAGMENT_OPTIONN: ... return; default: break; } if (fragment != null) { FragmentManager fragmentManager = getSupportFragmentManager(); fragmentManager.beginTransaction().replace(R.ID.fragment_container,fragment).commitAllowingStateLoss(); }} 2 – 加载所选选项(ControlPanelFragment)：
2.1 – 控制面板有标签和iconpager.对于每个寻呼机页面和每个选项卡,都会创建一个新的片段.我有3个标签和3个页面,因此创建了9个片段;
@OverrIDepublic voID onVIEwCreated(VIEw vIEw,@Nullable Bundle savedInstanceState) { super.onVIEwCreated(vIEw,savedInstanceState); if (savedInstanceState != null) { currentControlPanelOption = savedInstanceState.getInt("currentControlPanelOption",currentControlPanelOption); currentControlPanelTab = savedInstanceState.getInt("currentControlPanelTab",currentControlPanelTab); } setControlPanelTabs(); setIconPager();}@OverrIDepublic voID onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); outState.putInt("currentControlPanelOption",pager.getCurrentItem()); outState.putInt("currentControlPanelTab",mTabHost.getCurrentTab());} 3 – 在setIconPager()中;我有这个代码：
pager = (VIEwPager) vIEw.findVIEwByID(R.ID.pager);cPanelPagerAdapter = new ControlPanelPagerAdapter(getChildFragmentManager());pager.setoffscreenPagelimit(2);pager.setAdapter(cPanelPagerAdapter);
其中ControlPanelPagerAdapter具有以下代码：
public Fragment getItem(int index) { Fragment fragment; switch (index) { case 1: fragment = FragmentA.newInstance(); break; case 2: fragment = FragmentB.newInstance(); break; case 3: fragment = FragmentC.newInstance(); break; default: fragment = null; break; } ... return fragment;} 4 – FragmentA,FragmentB和FragmentC具有几乎相同的代码：
public static FragmentA newInstance() { return new FragmentA();}@OverrIDepublic VIEw onCreateVIEw(LayoutInflater inflater,VIEwGroup container,Bundle savedInstanceState) { VIEw vIEw = inflater.inflate(R.layout.fragment_placeholder,container,false); return vIEw;}@OverrIDepublic voID onVIEwCreated(VIEw vIEw,Bundle savedInstanceState) { super.onVIEwCreated(vIEw,savedInstanceState); if (savedInstanceState == null) { fragmentA_Data = new FragmentADetail[3]; createTabInstance(0); } else { fragmentA_Data = (FragmentADetail[]) savedInstanceState.getSerializable("Data"); return; }}private voID createTabInstance(int tab) { new FragmentADetail(); fragment = FragmentADetail.newInstance(tab); Bundle args = new Bundle(); args.putInt("tab",tab); fragment.setArguments(args); fragmentA_Data[tab] = fragment; FragmentTransaction fragmentTransaction = getChildFragmentManager().beginTransaction(); fragmentTransaction.replace(R.ID.fragment_placeholder,fragmentA_Data[tab]); fragmentTransaction.commitAllowingStateLoss();}public voID getTabData(int tab) { if (fragmentA_Data[tab] == null) { createStoreTimePeriodInstance(tab); } else { if (fragmentA_Data[tab].getArguments() == null) { Bundle args = new Bundle(); args.putInt("tab",tab); fragmentA_Data[tab].setArguments(args); } FragmentTransaction fragmentTransaction = getChildFragmentManager().beginTransaction(); fragmentTransaction.replace(R.ID.fragment_placeholder,fragmentA_Data[tab]); fragmentTransaction.commitAllowingStateLoss(); }}@OverrIDepublic voID onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); outState.putSerializable("data",fragmentA_Data);} 5 – 最后,FragmentADetail有这个代码：
public static FragmentADetail newInstance(int tab) { selectedTab = tab; return new FragmentADetail();}@OverrIDepublic VIEw onCreateVIEw(LayoutInflater inflater,Bundle savedInstanceState) { vIEw = inflater.inflate(R.layout.details_fragment,false); ... if (savedInstanceState != null) { selectedTab = savedInstanceState.getInt("selectedTab"); } ...}public voID getTabData(int tab) { //This is where I'm getting the data that populates the layout}@OverrIDepublic voID onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); outState.putInt("selectedTab",selectedTab);}@OverrIDepublic voID onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); Bundle args = getArguments(); if (args != null) { getTabData(args.getInt("tab")); }} 现在,想象一下我在FragmentA上选择了第三个标签.如果我旋转屏幕,我会有以下事件序列：
> ControlPanelFragment onSaveInstanceState保存当前选项卡和当前片段
> FragmentA onSaveInstanceState保存寻呼机的选项卡片段
> navigationDrawer第二个选项再次被称为fragment = ControlPanelFragment.newInstance();
>调用onConCreated的ControlPanelFragment,我可以获取保存的数据信息,并创建新的寻呼机和标签
>调用FragmentA onVIEwCreated,我可以提取保存的数据
> FragmentADetail onActivityCreated获取保存的数据并正确加载数据(至少我认为)
从现在起第二次调用第二组方法,之前保存的数据被重置,因此它现在显示错误的数据
> ControlPanelFragment onSaveInstanceState但现在savedInstanceState为null
> ControlPanelPagerAdapter getItem被调用实例化3个片段
> FragmentA onSaveInstanceState现在调用它,但savedInstanceState为null
>调用FragmentADetail onActivityCreated但现在tab = 0
有人可以解释一下 – 我怎么能阻止步骤7到10发生？
解决方法 我弄清楚我的问题是什么.当我这样做时：
case FRAGMENT_OPTION2: fragment = ControlPanelFragment.newInstance();break;
我正在创建一个片段,当我旋转屏幕时,再次调用selectItem(int position),因此创建了相同对象的新实例,因此执行了步骤7及其后续步骤.解决方案是检查片段是否已经创建并使用他而不是创建新片段.
我用标签保存了初始片段,然后他们查找了那个标签.如果标签存在,请使用该片段,否则创建一个新片段.
public voID selectItem(int position) { Fragment fragment = null; switch (position) { case FRAGMENT_OPTION1: ... break; case FRAGMENT_OPTION2: fragment = getSupportFragmentManager().findFragmentByTag(String.valueOf(position)); if (fragment == null) { fragment = ControlPanelFragment.newInstance(); } break; ... case FRAGMENT_OPTIONN: ... return; default: break; } if (fragment != null) { FragmentManager fragmentManager = getSupportFragmentManager(); fragmentManager.beginTransaction().replace(R.ID.fragment_container,fragment,String.valueOf(position)).commitAllowingStateLoss(); }} 总结 以上是内存溢出为你收集整理的Android oncreateview调用了两次全部内容，希望文章能够帮你解决Android oncreateview调用了两次所遇到的程序开发问题。
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