我有一个问题,我用谷歌搜索了一遍又一遍,但此时一切似乎都不合逻辑。
我有一个 fragment ,它在主要 Activity 中发生某些事情时开始(我认为这不重要)。
在我有这段代码的 fragment 中,请注意 onCreate 部分,因为错误发生在 testtext.setText(""+parola);
:
public class FinishedFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment FinishedFragment.
*/
// TODO: Rename and change types and number of parameters
public static FinishedFragment newInstance(String param1, String param2) {
FinishedFragment fragment = new FinishedFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
private View rootView;
public FinishedFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ActionBar actionBar = getActivity().getActionBar();
actionBar.hide();
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
TextView testtext = (TextView) getActivity().findViewById(R.id.testtext);
String parola = prefs.getString("prefUserPassword","defaultpass");
testtext.setText(" "+parola);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
rootView = inflater.inflate(R.layout.fragment_finished, container, false);
return rootView;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mListener = (OnFragmentInteractionListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnFragmentInteractionListener");
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
public void onFragmentInteraction(Uri uri);
}
}
这是SettingsActivity.java
:
public class SettingsActivity extends PreferenceActivity
{
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// add the xml resource
addPreferencesFromResource(R.xml.preferences);
ActionBar actionBar = getActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
switch (item.getItemId()) {
case android.R.id.home:
this.finish();
return true;
}
return super.onOptionsItemSelected(item);
}
最佳答案
您正尝试在 onCreateMethod
中设置 UI 元素,此时 View 尚未创建,这就是您的应用程序崩溃的原因。
尝试在 onViewCreated
或 onActivityCreated
方法中设置它们,以便在创建 View 时设置 View 元素。
@Override
public void onViewCreated (View view, Bundle savedInstanceState) {
ActionBar actionBar = getActivity().getActionBar();
actionBar.hide();
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
TextView testtext = (TextView) getActivity().findViewById(R.id.testtext);
String parola = prefs.getString("prefUserPassword","defaultpass");
testtext.setText(" "+parola);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
关于java - fragment 中 getDefaultSharedPreferences 上的 NullPointerException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/25996230/