我正在为tab创建一个包含三个片段的活动。我想将对象（在父活动中可用）中的数据设置为片段的子视图。我尝试通过片段的公共方法执行此操作。但是当试图访问视图时，它返回空指针异常并且应用程序崩溃。任何人都可以帮我解决这个问题吗？
家长活动是：
public class EnquiryViewActivity extends AppCompatActivity implements IFragmentToActivity {
private Context mContext;
// Session Manager Class
SessionManagement session;
private RequestQueue requestQueue;
private Gson gson;
//String enquiryId;
int enId, uid;
Enquiry enquiry;
// Alert Dialog Manager
AlertDialogManager alert = new AlertDialogManager();
/* Button btn_MoreEnqDetails, btn_ToSiteVisit, btn_nextEnq2;
EditText etName, etAddress, etSiteAddress, etPhoneNo, etMob, etEmail;
private RadioGroup rgrp_familyType;
private RadioButton radioSelectedFamilyType;
*/
private TabLayout addenqtabLayout;
private ViewPager addenqviewPager;
//Fragments
ContactFragment contactFragment;
RequirementsFragment requirementsFragment;
FollowUpFragment followupFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_enquiry);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
//--------------------------------------------
//Initializing viewPager
addenqviewPager = (ViewPager) findViewById(R.id.addenqviewpager);
addenqviewPager.setOffscreenPageLimit(3);
//Initializing the tablayout
addenqtabLayout = (TabLayout) findViewById(R.id.addenqtablayout);
addenqtabLayout.setupWithViewPager(addenqviewPager);
addenqviewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
addenqviewPager.setCurrentItem(position, false);
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
setupViewPager(addenqviewPager);
//----------------------------------------------
enquiry = new Enquiry();
try {
mContext = this;
enId = getIntent().getIntExtra("EnquiryId", -1);
uid = getIntent().getIntExtra("UserId", -1);
if (enId != -1) {
Log.d("h", "get enqid is " + enId);
enquiry = EnquiryORM.findEnquiryById(mContext, enId);
} else {
Log.d("h", "didn't get bid");
}
/*int position = tabLayout.getSelectedTabPosition();
Fragment fragment = adapter.getFragment(tabLayout
.getSelectedTabPosition());
if (fragment != null) {
switch (position) {
case 0:
((TabFragment1) fragment).onRefresh();
break;
case 1:
((TabFragment2) fragment).onRefresh();
break;
}
}*/
contactFragment.setDataToScreen(enquiry);
contactFragment.disableAllViews();
} catch (NumberFormatException e) {
Log.d("NumberFormatException: ", "some int is null");
Log.d("NumberFormatException: ", e.getMessage());
}
}
//---------------------------------------------------------------
@Override
public void showToast(String msg) {
Toast.makeText(this, msg, Toast.LENGTH_LONG).show();
}
@Override
public void communicateToFragment2() {
/*RequirementsFragment fragment = (RequirementsFragment) adapter.getFragment(1);
if (fragment != null) {
fragment.fragmentCommunication();
} else {
Log.i("log", "Fragment 2 is not initialized");
}*/
}
@Override
public void gotoMoreDetails() {
if (ConnectivityReceiver.isConnected()) {
//fetch and
//send indent to next activity to view more details
//show option to edit details
fetchMoreEnquiryDetails();
} else {
alert.showAlertDialog(EnquiryViewActivity.this, "Network Error", "Internet is not available!\nCannot connect to server", false);
}
}
@Override
public void gotoSiteVisit() {
Intent in = new Intent(EnquiryViewActivity.this, SiteVisitViewActivity.class);
in.putExtra("EnquiryId", enId);
in.putExtra("UserId", uid);
startActivity(in);
}
@Override
public void saveDataContacts(Enquiry enq) {
if (enquiry != null) {
enq.setId(enquiry.getId());
enq.setStatus(enquiry.getStatus());
enq.setUser_id(enquiry.getUser_id());
enq.setEnqstatusnew(enquiry.getEnqstatusnew());
enq.setCreateddate(getDateTime());
}
int enI=(int)EnquiryORM.insertEnquiry(mContext, enq);
enq.setId(enI);
}
//-----------------------------------------------------------------------
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
contactFragment = new ContactFragment();
requirementsFragment = new RequirementsFragment();
followupFragment = new FollowUpFragment();
adapter.addFragment(contactFragment, "CONTACT DETAILS");
adapter.addFragment(requirementsFragment, "REQUIREMENTS");
adapter.addFragment(followupFragment, "FOLLOW-UP");
viewPager.setAdapter(adapter);
}
private void fetchMoreEnquiryDetails() {
// Get a RequestQueue
// RequestQueue requestQueue = MyVolleySingleton.getInstance(this.getApplicationContext()).getRequestQueue();
requestQueue = Volley.newRequestQueue(this);
//create gson instance which is used to parse json
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.excludeFieldsWithoutExposeAnnotation();
//gsonBuilder.setDateFormat("M/d/yy hh:mm a");
gson = gsonBuilder.create();
StringRequest sr = new StringRequest(Request.Method.POST, EndPoints.GET_SELECTED_ENQUIRIES_URL, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Log.d("d", "getting response.........\n" + response);
Toast.makeText(getApplicationContext(), "Selected Enquiry JSON data :" + response, Toast.LENGTH_LONG).show();
//Enquiry detailEnquiry = gson.fromJson(response, Enquiry.class);
//detailEnquiry.setUser_id(uid);
Enquiry detailEnquiry = new Enquiry();
List<Enquiry> enquiryList = Arrays.asList(gson.fromJson(response, Enquiry[].class));
for (Enquiry enqu : enquiryList) {
detailEnquiry = enqu;
}
forwardToViewEnquiryMoreDetails(detailEnquiry);
/*Log.d("e", "All data inserted...now display.........");
List<Enquiry> enqlist= EnquiryORM.getEnquiries(getBaseContext());
for(Enquiry i:enqlist) {
Log.d("e", "enquiry :" +i.getId());
Log.d("e", i.getName()+","+i.getStatus()+","+i.getAddress()+","+i.getUser_id());
}
*/
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.e("EnqViewActivity", error.toString());
Toast.makeText(getApplicationContext(), "Error: " + error.getMessage(), Toast.LENGTH_LONG).show();
}
}) {
@Override
protected Map<String, String> getParams() throws AuthFailureError {
Log.d("d", "inside getparams()...\n");
Map<String, String> params = new HashMap<String, String>();
params.put("enquiryid", String.valueOf(enId));
params.put("userid", String.valueOf(uid));
Log.d("d", "enquiry id to pass:" + enId + "\n");
return params;
}
};
// Add the request to RequestQueue.
// MyVolleySingleton.getInstance(this).addToRequestQueue(sr);
requestQueue.add(sr);
Log.d("d", "Added to queue");
}
//-----------------------------------------------------------------------
private void forwardToViewEnquiryMoreDetails(Enquiry detailedEnquiry) {
Gson mynewgson = new Gson();
String DEnquiryDataObjectAsString = mynewgson.toJson(detailedEnquiry);
Intent toDetail = new Intent(EnquiryViewActivity.this, EnquiryViewMoreActivity.class);
toDetail.putExtra("DetailedEnquiryDataObjectAsString", DEnquiryDataObjectAsString);
startActivity(toDetail);
// close this activity
//finish();
}
private String getDateTime() {
SimpleDateFormat dateFormat = new SimpleDateFormat(
"yyyy-MM-dd HH:mm:ss", Locale.getDefault());
Date date = new Date();
return dateFormat.format(date);
}
//---------------------------------------------------------------
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.view_enq, menu);
return 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.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_add_enquiry) {
startActivity(new Intent(EnquiryViewActivity.this, EnquiryAddActivity.class));
return true;
}
if (id == R.id.action_edit_enquiry) {
// Make all fields editable
contactFragment.enableAllViews();
return true;
}
return super.onOptionsItemSelected(item);
}
}
片段代码是：
public class ContactFragment extends Fragment implements View.OnClickListener {
private IFragmentToActivity mCallback;
Button btn_MoreEnqDetails, btn_ToSiteVisit, btn_nextEnq1;
EditText etName, etAddress, etSiteAddress, etPhoneNo, etMob, etEmail;
public ContactFragment() {
// Required empty public constructor
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_contact, container, false);
btn_MoreEnqDetails = (Button) view.findViewById(R.id.btn_MoreEnqDetails);
btn_ToSiteVisit = (Button) view.findViewById(R.id.btn_ToSiteVisit);
btn_nextEnq1 = (Button) view.findViewById(R.id.btn_nextEnq1);
etName = (EditText) view.findViewById(R.id.etClientName);
etAddress = (EditText) view.findViewById(R.id.etAddress);
etSiteAddress = (EditText) view.findViewById(R.id.etSiteAddress);
etPhoneNo = (EditText) view.findViewById(R.id.etPhoneNo);
etMob = (EditText) view.findViewById(R.id.etMob);
etEmail = (EditText) view.findViewById(R.id.etEmail);
btn_MoreEnqDetails.setOnClickListener(this);
btn_ToSiteVisit.setOnClickListener(this);
btn_nextEnq1.setOnClickListener(this);
return view;
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btn_MoreEnqDetails:
mCallback.showToast("Hello from Fragment 1");
break;
case R.id.btn_ToSiteVisit:
mCallback.gotoSiteVisit();
break;
case R.id.btn_nextEnq1:
Enquiry enq=new Enquiry();
enq=getDataFromViews(enq);
mCallback.saveDataContacts(enq);
break;
}
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
try {
mCallback = (IFragmentToActivity) context;
} catch (ClassCastException e) {
throw new ClassCastException(context.toString()
+ " must implement IFragmentToActivity");
}
}
@Override
public void onDetach() {
mCallback = null;
super.onDetach();
}
public void onRefresh() {
Toast.makeText(getActivity(), "Fragment 1: Refresh called.",
Toast.LENGTH_SHORT).show();
}
public void disableAllViews() {
Log.d("EnqViewAct: ", "disabling all views..");
btn_MoreEnqDetails.setEnabled(false);
btn_ToSiteVisit.setEnabled(false);
btn_nextEnq1.setEnabled(false);
etName.setEnabled(false);
etAddress.setEnabled(false);
etSiteAddress.setEnabled(false);
etPhoneNo.setEnabled(false);
etMob.setEnabled(false);
etEmail.setEnabled(false);
}
public void enableAllViews() {
Log.d("EnqViewAct: ", "enabling all views..");
btn_MoreEnqDetails.setEnabled(true);
btn_ToSiteVisit.setEnabled(true);
btn_nextEnq1.setEnabled(true);
etName.setEnabled(true);
etAddress.setEnabled(true);
etSiteAddress.setEnabled(true);
etPhoneNo.setEnabled(true);
etMob.setEnabled(true);
etEmail.setEnabled(true);
}
public void setDataToScreen(Enquiry enquiry) {
Log.d("EbqViewAct","Data to display : "
+enquiry.getId()+","+enquiry.getUser_id()+","+
enquiry.getStatus()+","+enquiry.getEnqstatusnew()+","+
enquiry.getCreateddate()+","+
enquiry.getName()+","+enquiry.getAddress()+","+
enquiry.getSiteaddress()+","+enquiry.getPhone_number()+","+
enquiry.getMobile_number()+","+enquiry.getEmail());
if(enquiry.getName()!=null && enquiry.getName()!="")
{etName.setText(enquiry.getName());}
if(enquiry.getAddress()!=null && enquiry.getAddress()!="")
{etAddress.setText(enquiry.getAddress());}
if(enquiry.getSiteaddress()!=null && enquiry.getSiteaddress()!="")
{etSiteAddress.setText(enquiry.getSiteaddress());}
if(enquiry.getPhone_number()!=null && enquiry.getPhone_number()!="")
{etPhoneNo.setText(enquiry.getPhone_number());}
if(enquiry.getMobile_number()!=null && enquiry.getMobile_number()!="")
{etMob.setText(enquiry.getMobile_number());}
if(enquiry.getEmail()!=null && enquiry.getEmail()!="")
{etEmail.setText(enquiry.getEmail());}
/* if (thisSv.getFamilytype() != null) {
if (thisSv.getFamilytype().equalsIgnoreCase("Nuclear")) {
rgrp_familyType.check(R.id.rbtn_nuclear);
} else if (thisSv.getFamilytype().equalsIgnoreCase("Join")) {
rgrp_familyType.check(R.id.rbtn_join);
} else {
rgrp_familyType.check(R.id.rbtn_nuclear);
}
}*/
}
public Enquiry getDataFromViews(Enquiry enq) {
/*
radioSelectedFamilyType = (RadioButton) findViewById(rgrp_familyType.getCheckedRadioButtonId());
if (radioSelectedFamilyType != null) {
newSv.setFamilytype(radioSelectedFamilyType.getText().toString());
}*/
if ((etName.getText().toString()) != "" && (etName.getText().toString()) != null) {
enq.setName(etName.getText().toString().trim());
}
if ((etAddress.getText().toString()) != "" && (etAddress.getText().toString()) != null) {
enq.setAddress(etAddress.getText().toString().trim());
}
if ((etSiteAddress.getText().toString()) != "" && (etSiteAddress.getText().toString()) != null) {
enq.setSiteaddress(etSiteAddress.getText().toString().trim());
}
if ((etPhoneNo.getText().toString()) != "" && (etPhoneNo.getText().toString()) != null) {
enq.setPhone_number(etPhoneNo.getText().toString().trim());
}
if ((etMob.getText().toString()) != "" && (etMob.getText().toString()) != null) {
enq.setMobile_number(etMob.getText().toString().trim());
}
if ((etEmail.getText().toString()) != "" && (etEmail.getText().toString()) != null) {
enq.setEmail(etEmail.getText().toString().trim());
}
return enq;
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
}
}
界面是：
public interface IFragmentToActivity {
void showToast(String msg);
void communicateToFragment2();
void gotoMoreDetails();
void gotoSiteVisit();
void saveDataContacts(Enquiry enq);
}
PagerAdapter是：
public class ViewPagerAdapter extends FragmentStatePagerAdapter {
private final SparseArray<WeakReference<Fragment>> instantiatedFragments = new SparseArray<>();
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
@Override
public int getItemPosition(Object object){
return super.getItemPosition(object);
}
//--------------------------------------------------------
@Override
public Object instantiateItem(final ViewGroup container, final int position) {
final Fragment fragment = (Fragment) super.instantiateItem(container, position);
instantiatedFragments.put(position, new WeakReference<>(fragment));
return fragment;
}
@Override
public void destroyItem(final ViewGroup container, final int position, final Object object) {
instantiatedFragments.remove(position);
super.destroyItem(container, position, object);
}
@Nullable
public Fragment getFragment(final int position) {
final WeakReference<Fragment> wr = instantiatedFragments.get(position);
if (wr != null) {
return wr.get();
} else {
return null;
}
}
}
错误日志是：
12-25 11:09:46.931 3136-3136/com.example.anjana.decorightkitchen E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.anjana.decorightkitchen, PID: 3136
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.anjana.decorightkitchen/com.example.anjana.decorightkitchen.activity.EnquiryViewActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.EditText.setText(java.lang.CharSequence)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.EditText.setText(java.lang.CharSequence)' on a null object reference
at com.example.anjana.decorightkitchen.fragment.ContactFragment.setDataToScreen(ContactFragment.java:149)
at com.example.anjana.decorightkitchen.activity.EnquiryViewActivity.onCreate(EnquiryViewActivity.java:140)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
注意：查询对象值正在正确地进入片段。 enqName.setText（＆＃34; hai＆＃34;）在片段的onCreateView（）内正常工作。 但是当enqName.setText（＆＃34; hai＆＃34;）放入片段的公共方法，并从onCreateView（）调用该方法时，再次发生nullpointer异常。
答案 0 :(得分：0)
来自您的代码和错误日志
void android.widget.EditText.setText(java.lang.CharSequence)' on a null object reference
finViewByID或您的
ID名称(R.id.checkthis) Enable而非Visibility.Gone。您已经检查了enquiry对象。它运作良好。所以我认为这些可能会导致NullPointerException
答案 1 :(得分：0)
也许你正在寻找这样的东西。
Fragment home = getSupportFragmentManager().findFragmentById(R.id.content_frame);
if (home instanceof HomeFragment) {
((HomeFragment)home).setData(data);
}
答案 2 :(得分：-1)
要在创建时将数据发送到片段，您可以在创建片段时为片段设置参数，而不是像以后那样检索片段：
public static ContactFragment newInstance(String data, int data2) {
ContactFragment fragment = new ContactFragment();
Bundle bundle = new Bundle();
bundle.putString("someData", data);
bundle.putInt("otherData", data2);
fragment.setArguments(bundle);
return fragment;
}
当您调用片段时，请使用以下构造函数：
ContactFragment fragment = ContactFragment.newInstance("firstData",1200);
在您的片段中，您可以在任意位置检索数据：
int variable = getArguments().getInt("otherData");
String string = getArguments().getString("someData");
希望这会有所帮助。