I am trying to make the swipeable tab layout in android but getting null value in action bar

Question

I am trying to make the two tab layout for {profile} and {Child} which should be swipeable too. I have created the layout and fragment for both of them and on Main Activity layout, I have put

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent">

And in my Main Activity.java class my code is

import android.support.v4.view.ViewPager;
import android.os.Bundle;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;


public class MainActivity extends AppCompatActivity implements ActionBar.TabListener {
private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ActionBar actionBar;

// Tab titles
private String[] tabs = {"Profile", "Child"};

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

    // Initialization
    viewPager = (ViewPager) findViewById(R.id.pager);

    actionBar = (ActionBar) getSupportActionBar();

    mAdapter = new TabsPagerAdapter(getSupportFragmentManager());

But here in actionBar, I am getting null value, so program execute with null pointer at that point. Due to what reason, null might be coming in getActionBar.

Answer 1

Change your activity theme to @style/Theme.AppCompat or define toolbar in your layout:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:minHeight="?attr/actionBarSize"
        android:background="?attr/colorPrimary" />

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

</RelativeLayout>

And set custom action bar:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_edit);

    Toolbar toolbar = (Toolbar) findViewById(toolbar);
    setSupportActionBar(toolbar);

    actionBar = (ActionBar) getSupportActionBar();
}

ActionBar tabs is deprecated and not working since API 21. You should use PagerSlidingTabStrip library.