Bottom_Navigation_Bar

step 1:activity_main.xml

 <TextView
        android:id="@+id/message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="@dimen/activity_horizontal_margin"
        android:layout_marginStart="@dimen/activity_horizontal_margin"
        android:layout_marginTop="@dimen/activity_vertical_margin"
        android:text="@string/title_home"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="0dp"
        android:layout_marginStart="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:menu="@menu/navigation" />

</android.support.constraint.ConstraintLayout>

Step 2:frg1.xml
//aave rete frg2 and frg3 leva only text name change

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView android:layout_height="match_parent"
        android:layout_width="match_parent"
        android:text="Fragment1 Home"/>
</LinearLayout>

Step 3:frg1.java
//aavi rete frg2 and frg3 change karvu 

public class frg1 extends android.app.Fragment {

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

        View view = inflater.inflate(R.layout.frg1, container, false);
        return view;
    }

Step 4:MainActivity.java

public class MainActivity extends AppCompatActivity {

    private TextView mTextMessage;

    private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
            = new BottomNavigationView.OnNavigationItemSelectedListener() {

        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.navigation_home:
                    frg1 f1=new frg1();
                    FragmentManager fm=getFragmentManager();
                    FragmentTransaction ft=fm.beginTransaction();
                    ft.replace(R.id.container,f1);
                    ft.commit();
                    // mTextMessage.setText(R.string.title_home);
                    return true;
                case R.id.navigation_dashboard:

                    frg2 f2=new frg2();
                    FragmentManager fm2=getFragmentManager();
                    FragmentTransaction ft2=fm2.beginTransaction();
                    ft2.replace(R.id.container,f2);
                    ft2.commit();
                    // mTextMessage.setText(R.string.title_dashboard);
                    return true;
                case R.id.navigation_notifications:
                    frg3 f3=new frg3();
                    FragmentManager fm3=getFragmentManager();
                    FragmentTransaction ft3=fm3.beginTransaction();
                    ft3.replace(R.id.container,f3);
                    ft3.commit();
                    //mTextMessage.setText(R.string.title_notifications);
                    return true;
            }
            return false;
        }
    };

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

        mTextMessage = (TextView) findViewById(R.id.message);
        BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
        navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
    }

}

}