TabHost 显示一次内容(onCreate)
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【中文标题】TabHost 显示一次内容(onCreate)【英文标题】:TabHost displays content once (onCreate) 【发布时间】:2015-09-03 22:45:51 【问题描述】:我有一个TabHost
在一个navigationDrawer
里面,当我从作为导航抽屉项目存在的TabHost
转到另一个导航抽屉项目并返回@987654326 时,就会出现这个奇怪的问题@它不会显示它的内容,第一次它工作得很好但是当我改变项目并回到它时,它不会显示内容;换句话说,它不会加载子片段,除非我关闭应用程序并重新启动它或更改方向(重新创建片段)。
我第一次打开它时的样子(带有内容)
去另一个navDrawer Item后返回TabHost
TabHost 片段:
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TabHost;
import android.widget.TabWidget;
import java.util.ArrayList;
import info.fds.Emirates.R;
public class MyFragment extends Fragment
private TabHost mTabHost;
private ViewPager mViewPager;
private TabsAdapter mTabsAdapter;
public MyFragment()
@Override
public void onCreate(Bundle instance)
super.onCreate(instance);
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
View v = inflater.inflate(R.layout.fragment_main, container, false);
mTabHost = (TabHost) v.findViewById(android.R.id.tabhost);
mTabHost.setup();
mViewPager = (ViewPager) v.findViewById(R.id.pager);
mTabsAdapter = new TabsAdapter(getActivity(), mTabHost, mViewPager);
return v;
@Override
public void onResume()
super.onResume();
// Here we load the content for each tab.
mTabsAdapter.addTab(mTabHost.newTabSpec("Incident").setIndicator("Incident"), PageOneFragment.class, null);
mTabsAdapter.addTab(mTabHost.newTabSpec("Service Request").setIndicator("Service Request"), PageTwoFragment.class, null);
public static class TabsAdapter extends FragmentPagerAdapter implements TabHost.OnTabChangeListener, ViewPager.OnPageChangeListener
private final Context mContext;
private final TabHost mTabHost;
private final ViewPager mViewPager;
private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();
static final class TabInfo
private final String tag;
private final Class<?> clss;
private final Bundle args;
TabInfo(String _tag, Class<?> _class, Bundle _args)
tag = _tag;
clss = _class;
args = _args;
static class DummyTabFactory implements TabHost.TabContentFactory
private final Context mContext;
public DummyTabFactory(Context context)
mContext = context;
public View createTabContent(String tag)
View v = new View(mContext);
v.setMinimumWidth(0);
v.setMinimumHeight(0);
return v;
public TabsAdapter(FragmentActivity activity, TabHost tabHost, ViewPager pager)
super(activity.getSupportFragmentManager());
mContext = activity;
mTabHost = tabHost;
mViewPager = pager;
mTabHost.setOnTabChangedListener(this);
mViewPager.setAdapter(this);
mViewPager.setOnPageChangeListener(this);
public void addTab(TabHost.TabSpec tabSpec, Class<?> clss, Bundle args)
tabSpec.setContent(new DummyTabFactory(mContext));
String tag = tabSpec.getTag();
TabInfo info = new TabInfo(tag, clss, args);
mTabs.add(info);
mTabHost.addTab(tabSpec);
notifyDataSetChanged();
@Override
public int getCount()
return mTabs.size();
@Override
public Fragment getItem(int position)
TabInfo info = mTabs.get(position);
return Fragment.instantiate(mContext, info.clss.getName(), info.args);
public void onTabChanged(String tabId)
int position = mTabHost.getCurrentTab();
mViewPager.setCurrentItem(position);
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels)
public void onPageSelected(int position)
// Unfortunately when TabHost changes the current tab, it kindly
// also takes care of putting focus on it when not in touch mode.
// The jerk.
// This hack tries to prevent this from pulling focus out of our
// ViewPager.
TabWidget widget = mTabHost.getTabWidget();
int oldFocusability = widget.getDescendantFocusability();
widget.setDescendantFocusability(ViewGroup.FOCUS_BLOCK_DESCENDANTS);
mTabHost.setCurrentTab(position);
widget.setDescendantFocusability(oldFocusability);
public void onPageScrollStateChanged(int state)
PageOneFragment:
public class PageOneFragment extends Fragment
@Override
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
return inflater.inflate(R.layout.pageone_fragment, container, false);
@Override
public void onActivityCreated(Bundle savedInstanceState)
super.onActivityCreated(savedInstanceState);
@Override
public void onAttach(Activity activity)
super.onAttach(activity);
@Override
public void onStart()
super.onStart();
@Override
public void onResume()
super.onResume();
PageTwoFragment
public class PageTwoFragment extends Fragment
@Override
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
return inflater.inflate(R.layout.pagetwo_fragment, container, false);
@Override
public void onActivityCreated(Bundle savedInstanceState)
super.onActivityCreated(savedInstanceState);
@Override
public void onAttach(Activity activity)
super.onAttach(activity);
@Override
public void onStart()
super.onStart();
@Override
public void onResume()
super.onResume();
注意:调试后我注意到PageOneFragment和PageTwoFragment中的onCreateView()
没有被执行。
那么发生了什么以及为什么tabHost
在导航到另一个项目后没有加载其内容?
编辑: 经过数小时痛苦的调试后,我发现我的代码在第二次调用时从未执行休闲方法:
@Override
public Fragment getItem(int position)//never get executed after the second call
TabInfo info = mTabs.get(position);
return Fragment.instantiate(mContext, info.clss.getName(), info.args);
我该如何解决这个问题?
非常感谢任何帮助。
提前致谢。
【问题讨论】:
嗨。请不要发布您的整个代码,只是为了了解您的问题。如果你能创造一个小提琴,那就太好了。 【参考方案1】:这个荒谬的错误花费了我很多时间,而解决方案实际上很简单,问题是我在替换后使用FragmentPagerAdapter
而不是FragmentStatePagerAdapter
,一切正常,希望这对其他人有帮助有类似的问题。
【讨论】:
我在两天前遇到了完全相同的情况!对我来说也花了很多时间!!两天前才在另一个 SO 帖子上找到了这个解决方案!是的,这太荒谬了! (这是我的问题!***.com/q/30885610/2811343)【参考方案2】:在您的代码中,FragmentPageAdapter
将使用活动的FragmentManager
,但是当FragmentPageAdapter
中的instantiateItem
时,它将在活动的FragmentManager
中找到片段。可惜PageOneFragment
和PageTwoFragment
已经在activity的FragmentManager
中,所以没有新创建PageOneFragment
和PageTwoFragment
,FragmentPageAdapter
会在Fragment backstack中使用PageOneFragment
。但是PageOneFragment
是在最后一个FragmentPageAdapter
里面加的,然后就没有内容了。
使用 FragmentPageStateAdapter 代替 FragmentPageAdapter 是一个简单的选择。如果你想在某些时候使用比FragmentPageStateAdapter
更好的FragmentPageAdapter
,你可以这样使用:
public TabsAdapter(Fragment fragment, TabHost tabHost, ViewPager pager)
super(fragment.getChildFragmentManager());
mContext = fragment.getActivity();
mTabHost = tabHost;
mViewPager = pager;
mTabHost.setOnTabChangedListener(this);
mViewPager.setAdapter(this);
mViewPager.setOnPageChangeListener(this);
Log.i("Test", "TabsAdapter super");
使用ChildFragmentManager
。
我认为,如果您删除活动的FragmentManager
中的PageOneFragment
和PageTwoFragment
,也可以。
【讨论】:
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