ViewPager+FragmentTabhost 解决办法

android viewpager+fragmentTabhost：直接将一个FragmentTabhost 加入到viewPager中，滑动viewPager再次返回之前FragmentTabhost
会出现java.lang.NullPointerException, 是在FragmentState.instantiate 出错。

第一次加载viewPager不会出错，第二次就会出现以上情况，解决办法如下代码：
注：TabsInfo是关键，在getItem方法中需要使用Fragment.instantiate得到一个Fragment

经测试ViewPager + fragment 不会出现以上所说情况，可以在构造的时候传递一个

ArrayList<Fragmet> list,再通过getItem 返回即可，有不正确的地方还请指正...

[1].[图片] 0815_16_24_01.png 跳至 [1] [2]

[2].[代码] [Java]代码 跳至 [1] [2]

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import java.util.ArrayList; 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.FragmentStatePagerAdapter;     //************************自定义pagerAdapter********************** public class MviewPagerAdapter extends FragmentStatePagerAdapter{            private final ArrayList<TabsInfo> lstTabsInfo;      private final Context mContext;      public static class TabsInfo {          private final Class<?> clss_;          private final Bundle args_;          public TabsInfo(Class<?> clss, Bundle args) {              this .clss_ = clss;              this .args_ = args;          }      }      public MviewPagerAdapter(FragmentActivity activity, ArrayList<TabsInfo> lstTabsInfo) {          super (activity.getSupportFragmentManager());          mContext = activity;          this .lstTabsInfo = lstTabsInfo;      }        @Override      public Fragment getItem( int position) {          // TODO Auto-generated method stub          TabsInfo info = lstTabsInfo.get(position);          return Fragment.instantiate(mContext, info.clss_.getName(), info.args_);      }        @Override      public int getCount() {          // TODO Auto-generated method stub          return lstTabsInfo.size();      } }   //*******************应用************************ public class MainActivity extends FragmentActivity implements OnPageChangeListener, OnCheckedChangeListener{      private RadioGroup mRadioGroup;      private ViewPager mViewPager;      private ArrayList<Integer> lstCheckIds;      private ArrayList<TabsInfo> lstTabsInfos;      @Override      protected void onCreate(Bundle savedInstanceState) {          super .onCreate(savedInstanceState);          setContentView(R.layout.activity_main);          mRadioGroup = (RadioGroup)findViewById(R.id.radiogroup);          mRadioGroup.check(R.id.chengzai);          lstCheckIds = new ArrayList<Integer>();          for ( int i= 0 ; i< 5 ; i++) {              lstCheckIds.add(R.id.chengzai+i);          }          mRadioGroup.setOnCheckedChangeListener( this );          mViewPager = (ViewPager)findViewById(R.id.main_viewPager);          lstTabsInfos = new ArrayList<TabsInfo>();          //**********此处为关键代码*************          lstTabsInfos.add( new TabsInfo(FireDisasterFragment. class , null ));          lstTabsInfos.add( new TabsInfo(SuperviseFragment. class , null ));          lstTabsInfos.add( new TabsInfo(Tab1. class , null ));          lstTabsInfos.add( new TabsInfo(Tab2. class , null ));          lstTabsInfos.add( new TabsInfo(Tab1. class , null ));          MviewPagerAdapter adapter = new MviewPagerAdapter( this , lstTabsInfos);          mViewPager.setAdapter(adapter);          mViewPager.setCurrentItem( 0 );          mViewPager.setOnPageChangeListener( this );      }            @Override      public void onCheckedChanged(RadioGroup group, int checkedId) {          // TODO Auto-generated method stub          for ( int i= 0 ; i<lstCheckIds.size(); i++) {              if (lstCheckIds.get(i) == checkedId) {                  mViewPager.setCurrentItem(i);                  break ;              }          }      }            @Override      public void onPageScrollStateChanged( int arg0) {          // TODO Auto-generated method stub                }            @Override      public void onPageScrolled( int arg0, float arg1, int arg2) {          // TODO Auto-generated method stub                }            @Override      public void onPageSelected( int position) {          // TODO Auto-generated method stub          mRadioGroup.check(lstCheckIds.get(position));      }   }   //*********另附上 FireDisasterFragment(FragmentTabhost)关键代码************** @Override      public View onCreateView(LayoutInflater inflater, ViewGroup container,              Bundle savedInstanceState) {          // TODO Auto-generated method stub          Log.e( "fire_oncreateview" , "oncreateview" );                    View view = (View)inflater.inflate(R.layout.firedisaste_layout, container, false );          mTabHost = (FragmentTabHost)view.findViewById(android.R.id.tabhost);          mTabHost.setup(getActivity(), getChildFragmentManager(), R.id.realtabcontent);          View indicator = (View)inflater.inflate(R.layout.tabwidgets_layout, null );          TextView textView = (TextView)indicator.findViewById(R.id.tabwidget_indicator);                    textView.setText( "tabwidget1" );          mTabHost.addTab(mTabHost.newTabSpec( "tab1" ).setIndicator(indicator), Tab3. class , null );                    View indicator1 = (View)inflater.inflate(R.layout.tabwidgets_layout, null );          TextView textView2 = (TextView)indicator1.findViewById(R.id.tabwidget_indicator);          textView2.setText( "tabwidget2" );          mTabHost.addTab(mTabHost.newTabSpec( "tab2" ).setIndicator(indicator1), Tab4. class , null );          return view;      }   //*********************布局代码*************************** <?xml version= "1.0" encoding= "utf-8" ?> <android.support.v4.app.FragmentTabHost      xmlns:android= "http://schemas.android.com/apk/res/android"      android:id= "@android:id/tabhost"      android:layout_width= "match_parent"      android:layout_height= "match_parent" >        <LinearLayout          android:orientation= "vertical"          android:layout_width= "match_parent"          android:layout_height= "match_parent" >            <TabWidget              android:id= "@android:id/tabs"              android:orientation= "horizontal"              android:layout_width= "match_parent"              android:layout_height= "wrap_content"              android:layout_weight= "0" />            <FrameLayout              android:id= "@android:id/tabcontent"              android:layout_width= "0dp"              android:layout_height= "0dp"              android:layout_weight= "0" />            <FrameLayout              android:id= "@+id/realtabcontent"              android:layout_width= "match_parent"              android:layout_height= "0dp"              android:layout_weight= "1" />        </LinearLayout> </android.support.v4.app.FragmentTabHost>