Ndtyjky

I am trying to add a navigation drawer in my application but while i am trying that it shows the following error but if i have commented " getSupportActionBar().setDisplayHomeAsUpEnabled(true);" this line then it won't show any error.

android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference

here is my java code

import android.support.v4.widget.DrawerLayout;

import android.support.v7.app.ActionBarDrawerToggle;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.MenuItem;



public class drawer extends AppCompatActivity {

private DrawerLayout mDrawer;

private ActionBarDrawerToggle mToggle;



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_drawer);

        mDrawer = (DrawerLayout) findViewById(R.id.drawer);

        mToggle = new ActionBarDrawerToggle(this,mDrawer,R.string.Open,R.string.Close);

        mDrawer.addDrawerListener(mToggle);

        mToggle.syncState();

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    }





    @Override

    public boolean onOptionsItemSelected(MenuItem item) {

        if (mToggle.onOptionsItemSelected(item))

        {

            return true;

        }

        return super.onOptionsItemSelected(item);

    }





}

here is my activity_drawer.xml

<?xml version="1.0" encoding="utf-8"?>

<android.support.v4.widget.DrawerLayout

    xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:id="@+id/drawer"

    tools:context=".drawer">

    <LinearLayout

        android:layout_width="match_parent"

        android:layout_height="match_parent"></LinearLayout>



    <android.support.design.widget.NavigationView

        app:headerLayout="@layout/header_drawer"

        android:layout_width="wrap_content"

        android:layout_height="match_parent"

        android:background="@color/colorPrimary"

        app:itemTextColor="@color/grey"

        app:itemIconTint="@color/grey"

        app:menu="@menu/menudrawer"

        android:layout_gravity="start">



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



</android.support.v4.widget.DrawerLayout>

please add

<android.support.v7.widget.Toolbar

    android:id="@+id/toolbar"

    android:layout_width="match_parent"

    android:layout_height="?android:attr/actionBarSize"

    android:background="@color/colorPrimary"

    android:minHeight="?android:attr/actionBarSize"

    android:theme="@style/ThemeOverlay.AppCompat.ActionBar"

    app:title="@string/dashboard" />

instead of

<LinearLayout

    android:layout_width="match_parent"

    android:layout_height="match_parent"></LinearLayout>

and add this in your activity

Toolbar toolbar = findViewById(R.id.toolbar);



if (getSupportActionBar()!=null){

   setSupportActionBar(toolbar);

 }

also, add these to your theme

 <style name=" Your Style">

   <item name="android:windowActionBar">false</item>

   <item name="android:windowNoTitle">true</item>

 </style>

Try this code..
add style into style.xml

    <style name="NoActionBar" parent="Theme.AppCompat.Light.DarkActionBar">

    <item name="android:windowActionBar">false</item>

    <item name="android:windowNoTitle">true</item>

</style>

pass in android manifest into activity..

        <activity android:name=".MainActivity"

        android:theme="@style/NoActionBar">

In your styles.xml use

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<!-- Customize your theme here. -->
</style>

Or provide a toolbar in layout and setSupportActionBar from activity if you want use

Theme.AppCompat.Light.NoActionBar

I think you are missing toolbar in your xml. And you are also missing to set the toolbar in your code..

Toolbar toolbar = findViewById(R.id.toolbar);

setSupportActionBar(toolbar);

<android.support.v7.widget.Toolbar

        android:id="@+id/toolbar"

        android:layout_width="match_parent"

        android:layout_height="?android:attr/actionBarSize"

        android:background="@color/colorPrimary"

        android:minHeight="?android:attr/actionBarSize"

        android:theme="@style/ThemeOverlay.AppCompat.ActionBar"

        local:popupTheme="@style/ThemeOverlay.AppCompat.Light"

        local:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"

        local:title="@string/dashboard" />