我有两个名为School.java和SchoolDetails.java的活动。在SchoolDetails活动下，我通过实现可滑动的选项卡使用了片段。我使用intent将一个值从Schools.java传递给SchoolDetails.java。现在我想设置从Schools接收的该值.java到在SchoolDetails.java活动的一个片段内的textField。我收到了以下错误。
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Intent.getStringExtra(java.lang.String)' on a null object reference
这就是我在Schools.java中所做的所有事情，我将学校的名称传递给SchoolDetails
School.java
import android.app.ProgressDialog;
import android.content.Intent;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.android.volley.toolbox.JsonArrayRequest;
import com.example.user.educationhunt.adapter.CustomListAdapter;
import com.example.user.educationhunt.fragment.About;
import com.example.user.educationhunt.pojos.AppController;
import com.example.user.educationhunt.pojos.OurSchool;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
public class School extends AppCompatActivity{
// Log tag
private static final String TAG = School.class.getSimpleName();
// Billionaires json url
private static final String url = "http://myeducationhunt.com/public/schools";
private ProgressDialog pDialog;
private List<OurSchool> ourSchoolsListItems = new ArrayList<OurSchool>();
private ListView listView;
private CustomListAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_school);
ActionBar actionBar=getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setTitle("Schools");
listView = (ListView) findViewById(R.id.list);
adapter = new CustomListAdapter(this, ourSchoolsListItems);
listView.setAdapter(adapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
OurSchool ourSchool=new OurSchool();
Intent i=new Intent(School.this,SchoolDetails.class);
i.putExtra("id", ourSchoolsListItems.get(position).schoolId);
i.putExtra("name", ourSchoolsListItems.get(position).schoolName);
i.putExtra("location", ourSchoolsListItems.get(position).schoolLocation);
i.putExtra("logo", ourSchoolsListItems.get(position).schoolLogo);
i.putExtra("email", ourSchoolsListItems.get(position).schoolEmail);
i.putExtra("website", ourSchoolsListItems.get(position).schoolEmail);
i.putExtra("created_at", ourSchoolsListItems.get(position).createdAt);
i.putExtra("updated_at", ourSchoolsListItems.get(position).updatedAt);
startActivity(i);
}
});
pDialog = new ProgressDialog(this);
// Showing progress dialog before making http request
pDialog.setMessage("Loading…");
pDialog.show();
// Creating volley request obj
JsonArrayRequest billionaireReq = new JsonArrayRequest(url,
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
Log.d(TAG, response.toString());
hidePDialog();
// Parsing json
for (int i = 0; i < response.length(); i++) {
try {
JSONObject obj = response.getJSONObject(i);
OurSchool ourSchool = new OurSchool();
ourSchool.schoolId=obj.getInt("id");
ourSchool.schoolName=obj.getString("name");
ourSchool.schoolLocation=obj.getString("location");
ourSchool.schoolLogo=obj.getString("logo");
ourSchool.schoolEmail=obj.getString("email");
ourSchool.schoolWebsite=obj.getString("website");
ourSchool.createdAt=obj.getString("created_at");
ourSchool.updatedAt=obj.getString("updated_at");
// adding schools to ourSchool list
ourSchoolsListItems.add(ourSchool);
} catch (JSONException e) {
e.printStackTrace();
}
}
adapter.notifyDataSetChanged();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
hidePDialog();
}
});
// Adding request to request queue
AppController.getInstance().addToRequestQueue(billionaireReq);
}
@Override
public void onDestroy() {
super.onDestroy();
hidePDialog();
}
private void hidePDialog() {
if (pDialog != null) {
pDialog.dismiss();
pDialog = null;
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
onBackPressed();
return true;
case R.id.schoolSearch:
default:
return super.onOptionsItemSelected(item);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.search, menu);
return true;
}
}
SchoolDetails.java
package com.example.user.educationhunt;
import android.content.Intent;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import com.example.user.educationhunt.fragment.About;
import com.example.user.educationhunt.fragment.Admission;
import com.example.user.educationhunt.fragment.FeeStructure;
import com.example.user.educationhunt.fragment.Majors;
import com.example.user.educationhunt.pojos.OurSchool;
import org.junit.runner.Describable;
import java.util.ArrayList;
import java.util.List;
public class SchoolDetails extends AppCompatActivity{
private Toolbar toolbar;
private TabLayout tabLayout;
private ViewPager viewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_school_details);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
About aboutFragment= (About) getSupportFragmentManager().findFragmentById(R.id.aboutFragment);
aboutFragment.aboutSchoolName.setText("name:"+ getIntent().getStringExtra("name"));
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(new About(), "ABOUT US");
adapter.addFragment(new Admission(), "ADMISSION");
// adapter.addFragment(new Majors(), "MAJORS");
adapter.addFragment(new FeeStructure(), "FEE");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
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);
}
}
}
最后这是我的About Fragment
package com.example.user.educationhunt.fragment;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import com.example.user.educationhunt.R;
import com.example.user.educationhunt.School;
import com.example.user.educationhunt.SchoolDetails;
import com.example.user.educationhunt.pojos.OurSchool;
import com.google.android.gms.maps.CameraUpdate;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapView;
import com.google.android.gms.maps.MapsInitializer;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import org.junit.runner.Describable;
import java.io.Serializable;
/**
* A simple {@link Fragment} subclass.
*/
public class About extends Fragment implements OnMapReadyCallback{
MapView mapView;
GoogleMap map;
public TextView aboutSchoolName,aboutSchoolLocation,aboutSchoolNumber,aboutSchoolEmail,aboutSchoolWebsite,aboutSchoolCategory;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v = inflater.inflate(R.layout.fragment_about, container, false);
aboutSchoolName= (TextView) v.findViewById(R.id.about_school_name);
aboutSchoolLocation= (TextView) v.findViewById(R.id.about_school_location);
aboutSchoolNumber= (TextView) v.findViewById(R.id.about_school_number);
aboutSchoolCategory= (TextView) v.findViewById(R.id.about_school_category);
aboutSchoolEmail= (TextView) v.findViewById(R.id.about_school_email);
aboutSchoolWebsite= (TextView) v.findViewById(R.id.about_school_website);
// School school=new School();
// aboutSchoolName.setText("name:"+ school.getIntent().getStringExtra("name"));
// Gets the MapView from the XML layout and creates it
mapView = (MapView) v.findViewById(R.id.mapview);
mapView.onCreate(savedInstanceState);
// Gets to GoogleMap from the MapView and does initialization stuff
map = mapView.getMap();
map.getUiSettings().setMyLocationButtonEnabled(false);
map.setMyLocationEnabled(true);
// Needs to call MapsInitializer before doing any CameraUpdateFactory calls
MapsInitializer.initialize(this.getActivity());
// Updates the location and zoom of the MapView
CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(new LatLng(27.6933, 85.3211), 15);
map.animateCamera(cameraUpdate);
onMapReady(map);
return v;
}
@Override
public void onResume() {
mapView.onResume();
super.onResume();
}
@Override
public void onDestroy() {
super.onDestroy();
mapView.onDestroy();
}
@Override
public void onLowMemory() {
super.onLowMemory();
mapView.onLowMemory();
}
@Override
public void onMapReady(GoogleMap map) {
map.addMarker(new MarkerOptions()
.position(new LatLng(27.6933, 85.3211))
.title("St. Xavier's College"));
}
}
有人可以帮我吗？
尝试从Activity的Intent中获取额外内容，然后通过使用参数实例化任何额外的数据到片段。遵循此步骤，Android Fragment中的何处/如何getIntent（）。getExtras（）？
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我来说两句