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Application strength closes on viewPager.setAdapter (adapter)

I have an application page with a viewpager containing two snippets. When my activity pops up, a server request is made to download current data, and then the adapter is installed. But the application crashes with the following error.

Trying to call the virtual method 'void android.support.v4.app.Fragment.setMenuVisibility (boolean)' to reference a null object

During debugging, viewPager.setAdapter (adapter) detected an exception using an exclusive pointer. Neither my viewPager is equal to either my adapter.

I can’t understand why this is happening.

Please, help!! Thanks in advance!

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2

. fragmentPagerAdapter getItem() null .

+18

TabOne.java

package com.example.tabfragment;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class TabOne extends Fragment {


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.tab_one, null);

    return rootView;
}
}

TabTwo.java

package com.example.tabfragment;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class TabTwo extends Fragment {

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.tab_two, null);
    return rootView;
}

}

** xml tab_one.xml tab_two.xml **

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >

<TextView
    android:id="@+id/textview"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true"
    android:gravity="center"
    android:text="@string/tab_2" />

</RelativeLayout>

TabFragmentPageAdapter.java

package com.example.tabfragment;

import java.util.List;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;

public class TabFragmentPageAdapter extends FragmentPagerAdapter {
private Bundle args;
private List<Fragment> fragments;

public TabFragmentPageAdapter(FragmentManager fm, List<Fragment> fragments,
        Bundle args) {
    super(fm);
    this.fragments = fragments;
    this.args = args;
}

@Override
public Fragment getItem(int position) {
    Fragment fragment = fragments.get(position);
    fragment.setArguments(args);
    return fragment;
}

@Override
public int getCount() {
    return fragments.size();
}

@Override
public int getItemPosition(Object object) {
    return POSITION_NONE;
}
}

TabFragments.java

public class TabFragments extends Fragment implements OnPageChangeListener,
    OnTabChangeListener {

public static final int TAB_LOGIN = 0;
public static final int TAB_REG = 1;

private TabHost tabHost;
private int currentTab = TAB_LOGIN;
private ViewPager viewPager;
private TabFragmentPageAdapter pageAdapter;
private List<Fragment> fragments;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_home, null);
    tabHost = (TabHost) rootView.findViewById(android.R.id.tabhost);
    viewPager = (ViewPager) rootView.findViewById(R.id.viewpager);
    viewPager.setOnPageChangeListener(this);
    fragments = new ArrayList<Fragment>();
    fragments.add(new TabOne());
    fragments.add(new TabTwo());


    return rootView;
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    setRetainInstance(true);
    pageAdapter = new TabFragmentPageAdapter(getChildFragmentManager(),
            fragments, getArguments());
    pageAdapter.notifyDataSetChanged();
    viewPager.setAdapter(pageAdapter);
    setupTabs();

}

private void setupTabs() {
    tabHost.setup();
    tabHost.addTab(newTab(R.string.tab_1));
    tabHost.addTab(newTab(R.string.tab_2));


    for (int i = 0; i < tabHost.getTabWidget().getChildCount(); i++) {

        tabHost.getTabWidget().getChildAt(i)
                .setBackgroundColor(Color.parseColor("#304c58"));

        // tabHost.setBackgroundResource(R.drawable.tab_selector);
        final View view = tabHost.getTabWidget().getChildTabViewAt(i);
        final View textView = view.findViewById(android.R.id.title);
        ((TextView) textView).setTextColor(Color.parseColor("#e2ebf0"));

        ((TextView) textView).setSingleLine(true);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            tabHost.getTabWidget().getChildAt(i)
                    .findViewById(android.R.id.icon);
            tabHost.getTabWidget().getChildAt(i).getLayoutParams().height = 75;

        } else {

            if (view != null) {
                // reduce height of the tab
                view.getLayoutParams().height *= 0.77;

                if (textView instanceof TextView) {
                    ((TextView) textView).setGravity(Gravity.CENTER);
                    textView.getLayoutParams().height =  ViewGroup.LayoutParams.MATCH_PARENT;
                    textView.getLayoutParams().width = ViewGroup.LayoutParams.WRAP_CONTENT;
                }
            }
        }

    }
    tabHost.setOnTabChangedListener(TabFragments.this);
    tabHost.setCurrentTab(currentTab);
}

private TabSpec newTab(int titleId) {
    TabSpec tabSpec = tabHost.newTabSpec(getString(titleId));
    tabSpec.setIndicator(getString(titleId));
    tabSpec.setContent(new TabFactory(getActivity()));
    return tabSpec;
}

@Override
public void onPageScrollStateChanged(int position) {

}

@Override
public void onPageScrolled(int position, float arg1, int arg2) {

}

@Override
public void onPageSelected(int position) {
    tabHost.setCurrentTab(position);
}

@Override
public void onTabChanged(String tabId) {
    currentTab = tabHost.getCurrentTab();
    viewPager.setCurrentItem(currentTab);
    updateTab();
}

@SuppressWarnings("unused")
private void updateTab() {
    switch (currentTab) {
    case TAB_LOGIN:
        TabOne login = (TabOne) fragments.get(currentTab);
        break;
    case TAB_REG:
        TabTwo register = (TabTwo) fragments
                .get(currentTab);
        break;
    }
}

class TabFactory implements TabContentFactory {

    private final Context context;

    public TabFactory(Context context) {
        this.context = context;
    }

    @Override
    public View createTabContent(String tag) {
        View v = new View(context);
        v.setMinimumHeight(0);
        v.setMinimumWidth(0);
        return v;
    }

}
}


import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;

public class MainActivity extends ActionBarActivity {

Fragment fragment = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    fragment = new TabFragments();

    Log.i("fragment", "" + fragment.getId());

    if (fragment != null) {
        FragmentManager fm = getSupportFragmentManager();
        fm.beginTransaction().replace(R.id.frame_container, fragment)
                .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE)
                .commit();
    }
}

}

mainactivity.xml

 <?xml version="1.0" encoding="utf-8"?>
 <android.support.v4.widget.DrawerLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent" >  

      <FrameLayout
        android:id="@+id/frame_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
       />
 </android.support.v4.widget.DrawerLayout>

fragment_home.xml

<?xml version="1.0" encoding="utf-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:ts="http://schemas.android.com/apk/res-auto"
android:id="@android:id/tabhost"
android:layout_width="match_parent"
android:layout_height="match_parent" >

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TabWidget
        android:id="@android:id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fadingEdge="none"
        android:background="#394c58"
        android:tabStripEnabled="false" />

    <FrameLayout
        android:id="@android:id/tabcontent"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <android.support.v4.view.ViewPager
            android:id="@+id/viewpager"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </FrameLayout>
</LinearLayout>

</TabHost>
+1

Source: https://habr.com/ru/post/1568738/

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