问如何在Android中添加片段

EN

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.support.design.widget.TabLayout$Tab android.support.design.widget.TabLayout.newTab()' on a null object reference
                                                                at ca.rev.revcore.MainActivity.onCreate(MainActivity.java:76)

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.TabLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/rev_tablayout"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:theme="@style/RevStyle_PlaceNewBagBttn">

    <android.support.design.widget.TabItem
        android:id="@+id/tabItem"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tab1" />

</android.support.design.widget.TabLayout>

 TabLayout tabLayout = (TabLayout) findViewById(R.id.rev_tablayout);

 tabLayout.addTab(tabLayout.newTab().setText("Upload"));
 tabLayout.addTab(tabLayout.newTab().setText("Pics"));
 tabLayout.addTab(tabLayout.newTab().setText("Vids"));
 tabLayout.addTab(tabLayout.newTab().setText("Papers"));

 tabLayout.getTabAt(0).setIcon(R.drawable.ic_publish_black_24dp);
 tabLayout.getTabAt(1).setIcon(R.drawable.ic_menu_camera);
 tabLayout.getTabAt(2).setIcon(R.drawable.ic_videocam_black_24dp);
 tabLayout.getTabAt(3).setIcon(R.drawable.ic_airplay_black_24dp);