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How can I add drawerLayout and not to damage existed LinerLayout style?

I began doing a project without DrawableLayout. I am using mostly LinearLayout. I want to add drawer navigation android, and as I know, I need DrawableLayout.
How can I add this, and not damage everything I have now?

Well don't be afraid. It's not so difficult. Just follow the following steps to get it:-
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#android:color/holo_green_dark">
<!-- put you linear layout here --!>
<android.support.design.widget.NavigationView
android:layout_width="wrap_content"
android:layout_height="match_parent"
app:menu="#menu/navigation_menu"
android:layout_gravity="start"
app:headerLayout="#layout/nav_header"
android:id="#+id/nv">
</android.support.design.widget.NavigationView>
</android.support.v4.widget.DrawerLayout>
Navigation Header:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:background="#color/colorPrimaryDark">
<ImageView
android:layout_width="180dp"
android:layout_height="130dp"
android:layout_marginBottom="15dp"
android:layout_marginTop="15dp"
android:background="#drawable/ic_android_black_24dp"/>
</LinearLayout>
**Create a menu for the navigation drawer**
Right-click the res folder →Select new →Android resource file →Choose ‘menu’ under the resource type drop-down list.
Name the file as ‘navigation_menu.xml’ and copy-paste the following code into the file.
`<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item android:id="#+id/account"
android:icon="#drawable/ic_portrait_black_24dp"
android:title="My Account"/>
<item android:id="#+id/settings"
android:icon="#drawable/ic_brightness_high_black_24dp"
android:title="Settings"/>
<item android:id="#+id/mycart"
android:icon="#drawable/ic_local_grocery_store_black_24dp"
android:title="My Cart"/>
</menu>
** Lastly, in you activity:** <br>
In this last and final step, we will write Java code in the MainActivity.java file.
import android.support.annotation.NonNull;
import android.support.design.widget.NavigationView;
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;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private DrawerLayout dl;
private ActionBarDrawerToggle t;
private NavigationView nv;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dl = (DrawerLayout)findViewById(R.id.activity_main);
t = new ActionBarDrawerToggle(this, dl,R.string.Open, R.string.Close);
dl.addDrawerListener(t);
t.syncState();
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
nv = (NavigationView)findViewById(R.id.nv);
nv.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
int id = item.getItemId();
switch(id)
{
case R.id.account:
Toast.makeText(MainActivity.this, "My Account",Toast.LENGTH_SHORT).show();break;
case R.id.settings:
Toast.makeText(MainActivity.this, "Settings",Toast.LENGTH_SHORT).show();break;
case R.id.mycart:
Toast.makeText(MainActivity.this, "My Cart",Toast.LENGTH_SHORT).show();break;
default:
return true;
}
return true;
}
});
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if(t.onOptionsItemSelected(item))
return true;
return super.onOptionsItemSelected(item);
}
}`

Attempt to invoke virtual method 'void android.support.design [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Null pointer Exception - findViewById()
(12 answers)
Closed 4 years ago.
Im trying to build a free book swap app for months. Got stuck in NavigationView code that points to a null object. I have extracted the full java for your persual. This is my very first call for help.
What i dont understand is, there is:
NavigationView navigationView = findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this)
which is referenced to:
public class MainmainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener
but the error message points to NullPointerException. as below:
java.lang.RuntimeException: Unable to start activity ComponentInfo{booksavenue.co.booksavenue/booksavenue.co.booksavenue.MainmainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.design.widget.NavigationView.setNavigationItemSelectedListener(android.support.design.widget.NavigationView$OnNavigationItemSelectedListener)' on a null object reference
package booksavenue.co.booksavenue;
import android.support.annotation.NonNull;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;
import android.widget.Toast;
public class MainmainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
private DrawerLayout drawer;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
drawer = findViewById(R.id.drawer_layout);
NavigationView navigationView = findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer, toolbar,
R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
new MessageFragment()).commit();
navigationView.setCheckedItem(R.id.nav_message);
}
}
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.nav_message:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
new MessageFragment()).commit();
break;
case R.id.nav_chat:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
new ChatFragment()).commit();
break;
case R.id.nav_profile:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
new ProfileFragment()).commit();
break;
case R.id.nav_share:
Toast.makeText(this, "Share", Toast.LENGTH_SHORT).show();
break;
case R.id.nav_send:
Toast.makeText(this, "Send", Toast.LENGTH_SHORT).show();
break;
}
drawer.closeDrawer(GravityCompat.START);
return true;
}
#Override
public void onBackPressed() {
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
}
initally i thought it is android:theme NoActionBar issue. but seems that it is not the case. Attaching the manifast file for your perusal too
<?xml version="1.0" encoding="utf-8"?>
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity android:name=".SplashscreenActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".MainActivity" />
<activity android:name=".forgetpassActivity" />
<activity android:name=".NewuserActivity" />
<activity android:name=".SecondActivity" />
<activity android:name=".TncActivity" />
<activity
android:name=".MainmainActivity"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
</intent-filter>
</activity>
</application>
**
nav_header.xml
**
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="176dp"
android:background="#color/colorAccent"
android:gravity="bottom"
android:orientation="vertical"
android:padding="16dp"
android:theme="#style/ThemeOverlay.AppCompat.Dark">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#mipmap/ic_launcher_round" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingTop="8dp"
android:text="BooksAvenue"
android:textAppearance="#style/TextAppearance.AppCompat.Body1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="booksavenue#yahoo.com.sg" />
</LinearLayout>
Activity_mainmain.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_layout"
android:fitsSystemWindows="true"
tools:context="booksavenue.co.booksavenue.MainmainActivity"
tools:openDrawer="start">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<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:elevation="4dp"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light" />
<FrameLayout
android:id="#+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
<android.support.design.widget.NavigationView
android:id="#+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
app:headerLayout="#layout/nav_header"
app:menu="#menu/drawer_menu" />
</android.support.v4.widget.DrawerLayout>
styles.xml
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<!-- Customize your theme here. -->
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>
<style name="AppTheme.NoActionBar">
<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>
</style>
</resources>

Open navigation drawer menu in another activity

I have created the navigation drawer menu and now i want it to appear in my main activity.
I have the following code in my main activity:
public class MainActivity extends sideMenu {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FrameLayout contentFrameLayout = (FrameLayout) findViewById(R.id.content_frame);
getLayoutInflater().inflate(R.layout.activity_main, contentFrameLayout);
}}
When i run the app it crashes when entering main activity and it tells this:
**Caused by: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead.**
It specifies the error is in two places:
Menu activity -
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
Main activity -
super.onCreate(savedInstanceState);
If someone can shed some light here i'd be grateful!
EDIT:
Android manifest:
<?xml version="1.0" encoding="utf-8"?>
<!-- To auto-complete the email text field in the login form with the user's emails -->
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.READ_PROFILE" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity
android:name=".LoginActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".MainActivity"
android:theme="#style/AppTheme.NoActionBar">
</activity>
<activity android:name=".Registo" />
<activity android:name=".ListaEmpresas" />
<activity android:name=".ListaFavoritos" />
<activity android:name=".Candidaturas" />
<activity
android:name=".sideMenu"
android:label="#string/title_activity_side_menu"
android:theme="#style/AppTheme.NoActionBar"></activity>
</application>
menu activity code:
public class sideMenu extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_side_menu);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout)
findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open,
R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView)
findViewById(R.id.navigation_view);
navigationView.setNavigationItemSelectedListener(this);
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout)
findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is
present.
getMenuInflater().inflate(R.menu.side_menu, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout)
findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
Menu 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:id="#+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:openDrawer="start">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/content_frame"/>
</LinearLayout>
<include
layout="#layout/app_bar_side_menu"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.NavigationView
android:id="#+id/navigation_view"
android:layout_width="250dp"
android:layout_height="match_parent"
android:layout_gravity="start"
app:headerLayout="#layout/nav_header_side_menu"
app:menu="#menu/activity_side_menu_drawer" />
app_bar_side_menu xml:
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
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"
tools:context="amsi.dei.estg.ipleiria.pt.ima.sideMenu">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:background="?attr/colorPrimary"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
<include layout="#layout/content_side_menu" />
</android.support.design.widget.CoordinatorLayout>
Content_side_menu xml:
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
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"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context="amsi.dei.estg.ipleiria.pt.ima.sideMenu"
tools:showIn="#layout/app_bar_side_menu">
</android.support.constraint.ConstraintLayout>
nav_header_side_menu:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="#dimen/nav_header_height"
android:background="#drawable/side_nav_bar"
android:backgroundTint="#android:color/holo_red_dark"
android:gravity="bottom"
android:orientation="vertical"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:theme="#style/ThemeOverlay.AppCompat.Dark">
<ImageView
android:id="#+id/imageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingTop="#dimen/nav_header_vertical_spacing"
app:srcCompat="#mipmap/ic_launcher_round" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingTop="#dimen/nav_header_vertical_spacing"
android:text="IMA"
android:textAppearance="#style/TextAppearance.AppCompat.Body1" />
<TextView
android:id="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="NOME USER" />
</LinearLayout>

Your theme already has an ActionBar so you will have to convert it to NoActionBar.
For Whole App:
Open the styles.xml and make sure the last line of the parent has a word NoActionBar for example :
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar"> <!-- changed .DarkActionBar to .NoActionBar -->
<!-- Customize your theme here. -->
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
For An Activity:
Or you can just change it for one particular activity in the Manifest like by adding this atrribute in the Manifest :
android:theme="#style/Theme.AppCompat.Light.NoActionBar"

use this theme.
<style name="AppTheme.NoActionBar">
<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>
</style>

getActionBar().setDisplayHomeAsUpEnabled(true), -> java.lang.NullPointerException Impossible to resolve

I have the following problem:
getActionBar().setDisplayHomeAsUpEnabled(true);
java.lang.NullPointerException
I know that there are many post with the same problem, but this one i can resolve. I tried all solution that I found, but no one help me, I work this Fragment and Drawer (Android)
this is the code : MainActivity.java
package com.example.erik.test2;
import android.app.Activity;
import android.os.Bundle;
import android.support.design.widget.NavigationView;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private DrawerLayout mDrawer;
private Toolbar toolbar;
private ActionBarDrawerToggle mDrawerToggle;
#Override
protected void onCreate(Bundle savedInstanceState) {
//requestWindowFeature(Window.FEATURE_ACTION_BAR);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set a Toolbar to replace the ActionBar.
toolbar = (Toolbar) findViewById(R.id.toolbar);
//setSupportActionBar(toolbar);
// getSupportActionBar().setDisplayHomeAsUpEnabled(true);
// Find our drawer view
mDrawer = (DrawerLayout) findViewById(R.id.drawer_layout);
NavigationView nvDrawer = (NavigationView) findViewById(R.id.nvView);
setupDrawerContent(nvDrawer);
//---- Open Drawer on clic icon BUT CAUSE NULLPOINT EXEPTION--- //
//*
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);//*/
/*
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);//*/
//*
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawer, R.drawable.logo_tam, R.string.ouverture, R.string.fermeture) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(R.string.titre);
invalidateOptionsMenu();
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(R.string.titre_apres_ouverture);
invalidateOptionsMenu();
}
};
mDrawer.setDrawerListener(mDrawerToggle); //*
//-----------------------------------------------------------------------------------------------------------------
/*
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawer, R.drawable.logo_tam, R.string.ouverture, R.string.fermeture ) {
public void onDrawerClosed(View view) {
super.onDrawerClosed(view);
getActionBar().setTitle("Fermer");
}
public void onDrawerOpened(View drawerView) {
super.onDrawerOpened(drawerView);
getActionBar().setTitle("Ouvert");
}
};
// Set the drawer toggle as the DrawerListener
mDrawer.setDrawerListener(mDrawerToggle);*/
// getActionBar().setDisplayHomeAsUpEnabled(true);
//getActionBar().setHomeButtonEnabled(true);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// The action bar home/up action should open or close the drawer.
switch (item.getItemId()) {
case android.R.id.home:
mDrawer.openDrawer(GravityCompat.START);
return true;
}
return super.onOptionsItemSelected(item);
}
// Make sure this is the method with just `Bundle` as the signature
#Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
}
private void setupDrawerContent(NavigationView navigationView) {
navigationView.setNavigationItemSelectedListener(
new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
selectDrawerItem(menuItem);
return true;
}
});
}
public void selectDrawerItem(MenuItem menuItem) {
// Create a new fragment and specify the planet to show based on
// position
Fragment fragment = null;
Class fragmentClass;
switch(menuItem.getItemId()) {
case R.id.nav_first_fragment:
fragmentClass = FirstFragment.class;
break;
case R.id.nav_second_fragment:
fragmentClass = SecondFragment.class;
break;
case R.id.nav_third_fragment:
fragmentClass = ThirdFragment.class;
break;
default:
fragmentClass = FirstFragment.class;
}
try {
fragment = (Fragment) fragmentClass.newInstance();
} catch (Exception e) {
e.printStackTrace();
}
// Insert the fragment by replacing any existing fragment
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.flContent, fragment).commit();
// Highlight the selected item, update the title, and close the drawer
menuItem.setChecked(true);
setTitle(menuItem.getTitle());
mDrawer.closeDrawers();
}
}
code of styles.xml (I already try to change theme to Theme.AppCompat.Light but it doesn't work)
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
<!-- Customize your theme here. -->
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>
</resources>
code of toolbar.xml
<android.support.v7.widget.Toolbar
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/toolbar"
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:fitsSystemWindows="true"
android:minHeight="?attr/actionBarSize"
app:theme="#style/Theme.AppCompat.Light"
android:background="?attr/colorPrimaryDark">
</android.support.v7.widget.Toolbar>
Code activity_main.xml
<!-- This DrawerLayout has two children at the root -->
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- This LinearLayout represents the contents of the screen -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<!-- The ActionBar displayed at the top -->
<!-- <include
layout="#layout/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content" /> -->
<!-- The main content view where fragments are loaded -->
<FrameLayout
android:id="#+id/flContent"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
<!-- The navigation drawer that comes from the left -->
<!-- Note that `android:layout_gravity` needs to be set to 'start' -->
<android.support.design.widget.NavigationView
android:id="#+id/nvView"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:background="#android:color/white"
app:menu="#menu/drawer_view"
app:headerLayout="#layout/nav_header"
/>
</android.support.v4.widget.DrawerLayout>
and code of manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.erik.test2">
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity
android:name=".MainActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
I tried many options with the Theme but it doesn't work in my ActivityMain in the comment you can see all the tests that I tried.

Bad Approach
Use deprecated code . Avoid calling ActionBarActivity .
Advice
Since the version 22.1.0, the class ActionBarActivity is deprecated.
You should use AppCompatActivity.
You are getting
getActionBar().setDisplayHomeAsUpEnabled(true);
java.lang.NullPointerException
Comment out this line At First .
<include
layout="#layout/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
2ndly , You can use getSupportActionBar() instead getActionBar() & add null checking
if (getSupportActionBar() != null)
{
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
You can change your theme because you are using NoActionBar
parent="Theme.AppCompat.Light.NoActionBar"
Using the Toolbar to replace an ActionBar is pretty straight forward
and begins with making sure that the activity extends
ActionBarActivity. Also make sure that the theme for this activity is
a child of either Theme.AppCompat.NoActionBar or
Theme.AppCompat.Light.NoActionBar.
Please check #SO Answer What to use instead of getSupportActionBar()
and
https://developer.android.com/intl/pt-br/reference/android/support/v7/widget/Toolbar.html

getActionBar().setDisplayHomeAsUpEnabled(true); is giving NullPointerException because in your styles.xml you have given parent Theme.AppCompat.Light.NoActionBar which means there is no ActionBar.
Solution:
Change your style with the style given below in your styles.xml
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<!-- Customize your theme here. -->
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>
</style>
Now in your MainAcitivity use this code
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
Let me know if this helps you.

you have two ways:
1. use getSupportActionBar() instead getActionBar()
2. change your activity to extend ActionBarActivity

do it in this way
// Set a Toolbar to replace the ActionBar.
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Find our drawer view
mDrawer = (DrawerLayout) findViewById(R.id.drawer_layout);
NavigationView nvDrawer = (NavigationView) findViewById(R.id.nvView);
setupDrawerContent(nvDrawer);
//---- Open Drawer on clic icon BUT CAUSE NULLPOINT EXEPTION--- //
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
also change your layout
<!-- This LinearLayout represents the contents of the screen -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<!-- The ActionBar displayed at the top -->
<include
layout="#layout/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<!-- The main content view where fragments are loaded -->
<FrameLayout
android:id="#+id/flContent"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
<!-- The navigation drawer that comes from the left -->
<!-- Note that `android:layout_gravity` needs to be set to 'start' -->
<android.support.design.widget.NavigationView
android:id="#+id/nvView"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:background="#android:color/white"
app:menu="#menu/drawer_view"
app:headerLayout="#layout/nav_header"
/>

you are not getting action bar, uncomment following code from your xml.
<!-- <include
layout="#layout/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content" /> -->
Also use default theme currently you are using NoActionBar

You are using AppCompat.So, use this:
getSupportActionBar().setDisplayHomeAsUpEnabled(true);

As you are using AppCompactActivity which is in support library. so you need to get ActionBar instance using getSupportActionBar()
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
Since you have given NoActionBar theme. uncomment the toolbar include related you need to add toolbar.Either give Theme with ActionBar not NoActionBar. or Give Toolbar in layout and add it.
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- This LinearLayout represents the contents of the screen -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<!-- The ActionBar displayed at the top -->
<include
layout="#layout/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<!-- The main content view where fragments are loaded -->
<FrameLayout
android:id="#+id/flContent"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
<!-- The navigation drawer that comes from the left -->
<!-- Note that `android:layout_gravity` needs to be set to 'start' -->
<android.support.design.widget.NavigationView
android:id="#+id/nvView"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:background="#android:color/white"
app:menu="#menu/drawer_view"
app:headerLayout="#layout/nav_header"
/>
</android.support.v4.widget.DrawerLayout>

When I am running my first android app using Genymotion emulator its giving error unfortunately "app name" has stopped. Please help me

I am giving the details of all my files below.Please check them and let me know where I am doing the mistake due to which the error that the "unfortunately "app name" has stopped" error is coming when I am running my first android app using android SDK. Since I am a beginner in android development Please explain the solution nicely.
My MainActivity.java file :
package com.example.sunny.myfirstapp;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
public class MainActivity extends Activity {
TextView textView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView=(TextView)findViewById(R.id.greetings_view);
}
public void showGreetings(View view)
{
String message= "welcome to my app";
textView.setText(message);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
My activity_main.xml file is as follows:
<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"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
tools:context=".MainActivity"
android:id="#+id/greetings_view">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="greetings here"
android:id="#+id/greetings_view"
/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="show greetings"
android:layout_below="#+id/greetings_view"
android:onClick="My button"
android:id="#+id/greetings_view"
/>
</RelativeLayout>
My AndroidManifest.xml file :
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.sunny.myfirstapp"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="5"
android:targetSdkVersion="22" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.sunny.myfirstapp.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
My logcat :
06-26 10:37:23.137 31265-31265/? D/dalvikvm﹕ Late-enabling CheckJNI
06-26 10:37:24.013 31265-31265/com.example.sunny.myfirstapp D/AndroidRuntime﹕ Shutting down VM
06-26 10:37:24.021 31265-31265/com.example.sunny.myfirstapp W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xa62be288)
06-26 10:37:24.025 31265-31265/com.example.sunny.myfirstapp E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sunny.myfirstapp/com.example.sunny.myfirstapp.MainActivity}: java.lang.ClassCastException: android.widget.RelativeLayout cannot be cast to android.widget.TextView

all your views have the same ID greetings_view, elements must have no ID (blank) or different IDs.
ps.: in the future, the relevant log cat is the Stacktrace, is the part that have the direct message related to your crash. The log you posted is just some random stuff from your phone.

just try like this , it will Work
package com.example.sunny.myfirstapp;
public class MainActivity extends Activity {
TextView textView;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView=(TextView)findViewById(R.id.greetings_view);
String message= "welcome to my app";
textView.setText(message);
}
}
Remove from android:id="#+id/greetings_view" Relative Layout , You given that id in Two places TextvieW and Relative Layout
simple textview xml
<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"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TextView
android:id="#+id/greetings_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="" />
</RelativeLayout>