The error started to appear only after I started using fragments in the project
here is my code..
public class MainActivity extends AppCompatActivity {
private Toolbar toolbar;
private ViewPager mPager;
private SlidingTabLayout mTabs;
private MyPagerAdapter adapter;
public static final int product_result = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.app_bar);
setSupportActionBar(toolbar);
assert getSupportActionBar() != null;
getSupportActionBar().setDisplayShowHomeEnabled(true);
NavigationDrawerFragment navigationDrawerFragment = (NavigationDrawerFragment)
getSupportFragmentManager().findFragmentById(R.id.fragment_nav_drawer);
navigationDrawerFragment.setUp(R.id.fragment_nav_drawer, (DrawerLayout) findViewById(R.id.drawer_layout), toolbar);
mPager = (ViewPager) findViewById(R.id.pager);
adapter = new MyPagerAdapter(getSupportFragmentManager());
mPager.setAdapter(adapter);
mTabs = (SlidingTabLayout) findViewById(R.id.tabs);
mTabs.setDistributeEvenly(true);
mTabs.setCustomTabView(R.layout.custom_tab_view, R.id.tabText);
int bgColor = ContextCompat.getColor(this, R.color.colorPrimary);
mTabs.setBackgroundColor(bgColor);
mTabs.setSelectedIndicatorColors(ContextCompat.getColor(MainActivity.this, R.color.colorAccent));
mTabs.invalidate();
mTabs.setViewPager(mPager);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
if (id == R.id.navigate) {
startActivity(new Intent(this, SubActivity.class));
}
if (id == R.id.TabActivity) {
startActivity(new Intent(this, ActivityUsingTabLibrary.class));
}
if (id == R.id.VectorTest) {
startActivity(new Intent(this, VectorTestActivity.class));
}
return super.onOptionsItemSelected(item);
}
class MyPagerAdapter extends FragmentStatePagerAdapter {
int icons[] = {R.drawable.home, R.drawable.hot_article, R.drawable.dizzy_person};
public MyPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
Fragment fragment = null;
switch(position){
case product_result:
fragment = FragmentProduct.newInstance("","");
break;
}
return fragment;
}
@Override
public CharSequence getPageTitle(int position) {
Drawable drawable = ResourcesCompat.getDrawable(getResources(), icons[position], null);
drawable.setBounds(0, 0, 36, 36);
ImageSpan imageSpan = new ImageSpan(drawable);
SpannableString spannableString = new SpannableString(" ");
spannableString.setSpan(imageSpan, 0, spannableString.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
return spannableString;
}
@Override
public int getCount() {
return 3;
}
}
}
this is my fragment.class where im passing jsonObject toast.
public class FragmentProduct extends Fragment {
public static final String product_url = "http://oasisgroups.com/oApp/product.php";
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private String mParam1;
private String mParam2;
private VolleySingleton volleySingleton;
private ImageLoader imageLoader;
private RequestQueue requestQueue;
public FragmentProduct() {
// Required empty public constructor
}
public static FragmentProduct newInstance(String param1, String param2) {
FragmentProduct fragment = new FragmentProduct();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
public static String getRequestUrl(int limit) {
return product_url + "&limit=" + limit;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
volleySingleton = VolleySingleton.getInstance();
requestQueue = volleySingleton.getmRequestQueue();
JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, getRequestUrl(10),
new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
L.t(getActivity(), response.toString());
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
requestQueue.add(request);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_product, container, false);
}
}
stackTrace
02-29 12:10:01.047 17100-17100/com.mydesign.rockstar.materialdesignexample E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.mydesign.rockstar.materialdesignexample, PID: 17100
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.Fragment.setMenuVisibility(boolean)' on a null object reference
at android.support.v4.app.FragmentStatePagerAdapter.instantiateItem(FragmentStatePagerAdapter.java:116)
at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:870)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1086)
at android.support.v4.view.ViewPager.populate(ViewPager.java:952)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1474)
at android.view.View.measure(View.java:18804)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:901)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18804)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:940)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643)
at android.view.View.measure(View.java:18804)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2112)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1228)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1464)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1119)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6060)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
at android.view.Choreographer.doCallbacks(Choreographer.java:670)
at android.view.Choreographer.doFrame(Choreographer.java:606)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
at android.os.Handler.handleCallback(Handler.java:746)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5443)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
i also seen this same problem in this link and i apply his solution but it wont work for me.. im still stuck, help me. so check my code and suggest me where what i missing.
oh yes.. i finally found my mistake.. first of all there is no mistake in my code. everything is right.
i have three tab layout and im passing only for one tablayout and other two are getting null, so i must have to apply three switch case statement.
public Fragment getItem(int position) {
Fragment fragment = null;
switch(position){
case product_result:
fragment = FragmentProduct.newInstance("","");
break;
}
return fragment;
}
instead
public Fragment getItem(int num) {
Fragment fragment = null;
switch (num) {
case TAB_PRODUCT_RESULT:
fragment = FragmentProduct.newInstance("", "");
break;
case TAB_SECOND:
fragment = MyFragment.getInstance(num);
break;
case TAB_THIRD:
fragment = MyFragment.getInstance(num);
break;
}
return fragment;
}
thats it..
I think the problem is in the public Fragment getItem(int position)
method of your MyPagerAdapter
. Your code snippet below is returning null
fragments.
Fragment fragment = null;
switch(position){
case product_result:
fragment = FragmentProduct.newInstance("","");
break;
}
return fragment;
You only get a real fragment for the position 0
, because product_result
is initialized to 0
. In all other cases it returns null. Modify the above snippet of code to always return a fragment instance that is not null.
I had similar problem, I tried to remove null fragment and this cause error. Null check solved problem. Check your fragment transactions. You can't add null fragment.
Fragment fragment = null;
if (fragment != null)
getSupportFragmentManager().beginTransaction()
.add(R.id.container, fragment, "id").commit();
First You Have To Add Adapter in your Activity like this
------- This is Adding number of tab layout according to size of data ------------
for (FirstModel firstModel : list_editdata) {
tabLayout.addTab(tabLayout.newTab().setText(firstModel.getTitle()));
}
**/////Set an Adapter**
SectionAdapter mSectionAdapter = new SectionAdapter(getSupportFragmentManager());
viewPager.setAdapter(mSectionAdapter);
now Add An Adapter in Activity : I take One Fragments and use in switch case repeatedly This Will automatically regenerate according to your tab layout numbers in Activity
public class SectionAdapter extends FragmentPagerAdapter {
private String[] tabTitles = new String[]{"", "", "", ""};
public SectionAdapter (FragmentManager fm) {
super(fm);
}
@Override
public CharSequence getPageTitle(int position) {
return tabTitles[position];
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
Tab1 tab1 = new Tab1();
return tab1 ;
case 1:
Tab1 tab2 = new Tab1();
return tab2 ;
case 2:
Tab1 tab3 = new Tab1();
return tab3 ;
case 3:
Tab1 tab4 = new Tab1();
return tab4 ;
}
return null;
}
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