我从片段中获取活动时遇到问题。我在这里阅读了几个主题并且我确信它会起作用，但我仍然在我的片段中的onAttach（）方法中从getActivity（）方法中获取null。
我的代码：
public static class TabsAdapter extends FragmentPagerAdapter implements ActionBar.TabListener, ViewPager.OnPageChangeListener {
private final FragmentActivity mContext;
private final ActionBar mActionBar;
private final ViewPager mViewPager;
private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();
private Fragment mFragment;
static final class TabInfo {
private final Class<?> clss;
private final Bundle args;
TabInfo(Class<?> _class, Bundle _args) {
clss = _class;
args = _args;
}
}
public TabsAdapter(SherlockFragmentActivity activity, ViewPager pager) {
super(activity.getSupportFragmentManager());
mContext = activity;
mActionBar = activity.getSupportActionBar();
mViewPager = pager;
mViewPager.setAdapter(this);
mViewPager.setOnPageChangeListener(this);
}
public void addTab(ActionBar.Tab tab, Class<?> clss, Bundle args) {
TabInfo info = new TabInfo(clss, args);
tab.setTag(info);
tab.setTabListener(this);
mTabs.add(info);
mActionBar.addTab(tab);
notifyDataSetChanged();
}
@Override
public int getCount() {
return mTabs.size();
}
@Override
public Fragment getItem(int position) {
TabInfo info = mTabs.get(position);
FragmentTransaction ft=mContext.getSupportFragmentManager().beginTransaction();
Fragment fragment=Fragment.instantiate(mContext, info.clss.getName(), info.args);
if(mFragment==null || !mFragment.equals(fragment)){
mFragment=fragment;
ft.add(mViewPager.getId(), mFragment);
ft.commit();
}else{
ft.detach(mFragment);
mFragment=fragment;
ft.attach(mFragment);
ft.commit();
}
return mFragment;
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
mActionBar.setSelectedNavigationItem(position);
}
@Override
public void onPageScrollStateChanged(int state) {
}
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
Object tag = tab.getTag();
for (int i = 0; i < mTabs.size(); i++) {
if (mTabs.get(i) == tag) {
mViewPager.setCurrentItem(i);
}
}
}
@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
}
我打电话。
setListAdapter(new CompaniesListAdapter(getActivity(), records));
我的片段中的onAttach（）方法，如多个线程所述。
我已经尝试了几乎所有的东西，但我不能让它返回Activity。非常感谢您的回答。
日志：
07-27 11:30:57.648: E/AndroidRuntime(18378): FATAL EXCEPTION: main
07-27 11:30:57.648: E/AndroidRuntime(18378): java.lang.NullPointerException
07-27 11:30:57.648: E/AndroidRuntime(18378): at com.citysmartgo.cheaptaxi.tabs.support.CompaniesListAdapter.getView(CompaniesListAdapter.java:59)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.AbsListView.obtainView(AbsListView.java:2033)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.ListView.makeAndAddView(ListView.java:1772)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.ListView.fillDown(ListView.java:672)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.ListView.fillFromTop(ListView.java:732)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.ListView.layoutChildren(ListView.java:1625)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.AbsListView.onLayout(AbsListView.java:1863)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.View.layout(View.java:11278)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.ViewGroup.layout(ViewGroup.java:4224)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.View.layout(View.java:11278)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.ViewGroup.layout(ViewGroup.java:4224)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1388)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.View.layout(View.java:11278)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.ViewGroup.layout(ViewGroup.java:4224)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.View.layout(View.java:11278)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.ViewGroup.layout(ViewGroup.java:4224)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.View.layout(View.java:11278)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.ViewGroup.layout(ViewGroup.java:4224)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.View.layout(View.java:11278)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.ViewGroup.layout(ViewGroup.java:4224)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1489)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.os.Handler.dispatchMessage(Handler.java:99)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.os.Looper.loop(Looper.java:137)
07-27 11:30:57.648: E/AndroidRuntime(18378): at android.app.ActivityThread.main(ActivityThread.java:4424)
07-27 11:30:57.648: E/AndroidRuntime(18378): at java.lang.reflect.Method.invokeNative(Native Method)
07-27 11:30:57.648: E/AndroidRuntime(18378): at java.lang.reflect.Method.invoke(Method.java:511)
07-27 11:30:57.648: E/AndroidRuntime(18378): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
07-27 11:30:57.648: E/AndroidRuntime(18378): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
07-27 11:30:57.648: E/AndroidRuntime(18378): at dalvik.system.NativeStart.main(Native Method)
07-27 11:30:58.874: I/Process(18378): Sending signal. PID: 18378 SIG: 9
我的getView方法
@Override
public View getView(int position, View convertView, ViewGroup parrent){
View rowView = convertView;
TaxiCompanyQuoteView cqView = null;
if(rowView == null) {
LayoutInflater inflater = activity.getLayoutInflater();
rowView = inflater.inflate(R.layout.companies_row_layout, null);
cqView=new TaxiCompanyQuoteView();
cqView.company=(TextView) rowView.findViewById(R.id.companies_name);
cqView.company=(TextView) rowView.findViewById(R.id.companies_phone);
cqView.company=(TextView) rowView.findViewById(R.id.companies_price_per_unit);
cqView.company=(TextView) rowView.findViewById(R.id.companies_entering_price);
cqView.company=(TextView) rowView.findViewById(R.id.companies_waiting_price);
rowView.setTag(cqView);
}else{
cqView = (TaxiCompanyQuoteView) rowView.getTag();
}
TaxiCompany currentTaxiCompany = taxiCompanies.get(position);
cqView.company.setText(currentTaxiCompany.getName());
cqView.phone.setText(currentTaxiCompany.getNumber());
cqView.pricePerUnit.setText(currentTaxiCompany.getPricePerUnit());
cqView.waitingPrice.setText(currentTaxiCompany.getEnteringPrice());
cqView.enteringPrice.setText(currentTaxiCompany.getWaitingPrice());
return rowView;
}
答案 0 :(得分：3)
在onAttach()中，尚未准备好使用该活动..请检查fragment lifecycle ..
您可以将代码移至onActivityCreated()而不是
答案 1 :(得分：0)
我建议以下内容。在扩展Fragment的类中为您的上下文创建一个属性：
private FragmentActivity myContext;
重写以下方法，当片段附加到其上下文时会调用该方法。
@Override
public void onAttach(@NonNull Context context) {
myContext = (FragmentActivity) context;
super.onAttach(context);
}