我有这个问题，我知道有类似的问题也有答案。但是没有人帮助我，我几乎要失去它了。我正在尝试使用gson，wordpress api，片段和凌空构建一个应用程序。每个片段都有请求。但是在这一点上 每个片段中的RequestQueue rQueue = Volley.newRequestQueue（getActivity（））都有问题
我的Tab1片段类
public class Tab1 extends Fragment {
String url = "http://absradiotv.com/wp-json/wp/v2/posts?per_page=10&fields=id,title,featured_image_url";
List<Object> list;
Gson gson;
ProgressDialog progressDialog;
ListView postList;
Map<String,Object> mapPost;
Map<String,Object> mapTitle;
int postID;
String postTitle[];
String postType[];
String postFeaturedMedia[];
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
progressDialog = new ProgressDialog(getActivity(), R.style.MyProgressTheme);
View rootView = inflater.inflate(R.layout.fragment_tab1, container, false);
postList = (ListView)rootView.findViewById(R.id.postList);
progressDialog.setMessage(" ");
progressDialog.setCancelable(true);
progressDialog.setCanceledOnTouchOutside(true);
progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
progressDialog.show();
progressDialog.dismiss();
StringRequest request = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() {
@Override
public void onResponse(String s) {
gson = new Gson();
list = (List) gson.fromJson(s, List.class);
postTitle = new String[list.size()];
postType = new String[list.size()];
postFeaturedMedia = new String[list.size()];
ArrayList<String>listt = new ArrayList<>();
for(int i=0;i<list.size();++i){
mapPost = (Map<String,Object>)list.get(i);
mapTitle = (Map<String, Object>) mapPost.get("title");
postTitle[i] = (String) mapTitle.get("rendered");
postType[i] = (String) mapPost.get("type");
postFeaturedMedia[i] = (String) mapPost.get("featured_image_url");
listt.add(postTitle[i]);
listt.add(postType[i]);
listt.add(postFeaturedMedia[i]);
}
//Here I tried to populate listview with id postList
postList.setAdapter(new ArrayAdapter(getActivity(),android.R.layout.simple_list_item_1, listt));
progressDialog.dismiss();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError volleyError) {
Toast.makeText(getActivity(), "Sorry! An error occured!", Toast.LENGTH_LONG).show();
progressDialog.dismiss();
}
});
//I added a check to test if getActivity returns null, but it doesnt
if(getActivity() != null) {
RequestQueue rQueue = Volley.newRequestQueue(this.getActivity().getApplicationContext());
rQueue.add(request);
}
else
{
Toast.makeText(getActivity(), "A big null issue", Toast.LENGTH_LONG).show();
}
return rootView;
}
}
这是我的PagerAdapter
public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
public PagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
Tab1 tab1 = new Tab1();
return tab1;
case 1:
Tab2 tab2 = new Tab2();
return tab2;
case 2:
Tab3 tab3 = new Tab3();
return tab3;
default:
return null;
}
}
@Override
public int getCount() {
return mNumOfTabs;
}
}
这是我的MainActivity
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
Toolbar toolbar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("");
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
tabLayout.addTab(tabLayout.newTab().setText("LATEST"));
tabLayout.addTab(tabLayout.newTab().setText("POLITICS"));
tabLayout.addTab(tabLayout.newTab().setText("STATE"));
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
final PagerAdapter adapter = new PagerAdapter(getSupportFragmentManager(), tabLayout.getTabCount());
viewPager.setAdapter(adapter);
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main_drawer, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer,toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
return super.onOptionsItemSelected(item);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}