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NullpointerException at actionbar in android [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 6 years ago.
I am newbie to android and working on a demo for swipe tabs demo and refering a link,Going step by step,but i stuck at a point,when i run the app,it throws nullpointerexception,Please see below code and help me to figure out please,
main_listing.xml
<?xml version="1.0" encoding="utf-8"?>
<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" />
java
public class MainListingActivity extends FragmentActivity {
ViewPager Tab;
TabPagerAdapter TabAdapter;
ActionBar actionBar;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_listing);
TabAdapter = new TabPagerAdapter(getSupportFragmentManager());
Tab = (ViewPager)findViewById(R.id.pager);
Tab.setOnPageChangeListener(
new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
actionBar = getActionBar();
actionBar.setSelectedNavigationItem(position); }
});
Tab.setAdapter(TabAdapter);
actionBar = getActionBar();
//Enable Tabs on Action Bar
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
ActionBar.TabListener tabListener = new ActionBar.TabListener(){
#Override
public void onTabReselected(android.app.ActionBar.Tab tab,
FragmentTransaction ft) {
// TODO Auto-generated method stub
}
#Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
Tab.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(android.app.ActionBar.Tab tab,
FragmentTransaction ft) {
// TODO Auto-generated method stub
}};
//Add New Tab
actionBar.addTab(actionBar.newTab().setText("Android").setTabListener(tabListener));
actionBar.addTab(actionBar.newTab().setText("iOS").setTabListener(tabListener));
actionBar.addTab(actionBar.newTab().setText("Windows").setTabListener(tabListener));
}
logcat
FATAL EXCEPTION: main
Process: abc.kayraas.com.allaboutcity, PID: 15728
java.lang.RuntimeException: Unable to start activity ComponentInfo{abc.kayraas.com.allaboutcity/abc.kayraas.com.allaboutcity.MainListingActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2404)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2464)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5653)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at abc.kayraas.com.allaboutcity.MainListingActivity.onCreate(MainListingActivity.java:37)
at android.app.Activity.performCreate(Activity.java:5541)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2368)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2464) 
at android.app.ActivityThread.access$900(ActivityThread.java:172) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:146) 
at android.app.ActivityThread.main(ActivityThread.java:5653) 
at java.lang.reflect.Method.invokeNative(Native Method) 
style.xml
<resources>
<style name="MyRadioButtonStyle" parent="#android:style/Widget.CompoundButton.RadioButton">
<item name="android:button">#drawable/radio_selected</item>
</style>
<style name="AppBaseTheme" parent="android:Theme.Light">
</style>
<!-- Application theme. -->
<style name="AppTheme" parent="AppBaseTheme">
<!-- All customizations that are NOT specific to a particular API-level can go here. -->
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>
</resources>
manifest
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme" >
<activity
android:name=".SlashActivity"
android:theme="#android:style/Theme.Holo.Light.DarkActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

try this :
actionBar=getSupportActionBar

try this code. ActionBar actionBar = getSupportActionBar();

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("Home");
//in styles.xml in your AppTheme ,update as
<style name="AppTheme" parent="Theme.AppCompat.NoActionBar">
//in your xml write this at the top :
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:visibility="gone"
android:layout_height="wrap_content"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:visibility="visible"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
this is your current code:
<style name="AppTheme" parent="AppBaseTheme">
<!-- All customizations that are NOT specific to a particular API-level can go here. -->
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>
instead write this:
<style name="AppTheme" parent="Theme.AppCompat.NoActionBar">
<!-- Customize your theme here. -->
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>

In your style.xml change this line:
<style name="AppBaseTheme" parent="android:Theme.Light">
to
<style name="AppBaseTheme" parent="android:Theme.Holo.Light.DarkActionBar">

Action Bar isn't displaying in API16

I'm trying to use a navigation drawer in my Main activity.
when i run it in API 23 Emulator , everything looks fine.
But when I run it in API 16 Emulator, my action bar goes away!
Here is my manifest file :
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:theme="#style/AppTheme">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
Here is my styles.xml
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<!-- Customize your theme here. -->
<item name="colorPrimary">#color/line1</item>
<item name="colorPrimaryDark">#color/line1_dark</item>
<item name="colorAccent">#color/isbc</item>
</style>
<style name="AppTheme.NoActionBar">
<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>
</style>
Here is my v21/styles.xml
<style name="AppTheme.NoActionBar">
<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>
<item name="android:windowDrawsSystemBarBackgrounds">true</item>
<item name="android:statusBarColor">#android:color/transparent</item>
</style>
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<!-- Customize your theme here. -->
<item name="colorPrimary">#color/line1</item>
<item name="colorPrimaryDark">#color/line1_dark</item>
<item name="colorAccent">#color/isbc</item>
</style>
And this is my Mainactivity.java
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
NavigationView navigationView = null;
Toolbar toolbar = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MainFragment fragment = new MainFragment();
android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
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.setDrawerListener(toggle);
toggle.syncState();
navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
changeTypeface(navigationView);
}
#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.main, menu);
return true;
}
private void applyFontToItem(MenuItem item, Typeface font) {
SpannableString mNewTitle = new SpannableString(item.getTitle());
mNewTitle.setSpan(new CustomTypefaceSpan("", font, 16), 0 ,
mNewTitle.length(), Spannable.SPAN_INCLUSIVE_INCLUSIVE);
item.setTitle(mNewTitle);
}
private void changeTypeface(NavigationView navigationView) {
FontTypeface fontTypeface = new FontTypeface(this);
Typeface typeface = fontTypeface.getTypefaceAndroid();
MenuItem item;
item = navigationView.getMenu().findItem(R.id.nav_camera);
item.setTitle("لیست ایستگاه ها");
item.setIcon(R.drawable.ic_action_stations);
applyFontToItem(item, typeface);
item = navigationView.getMenu().findItem(R.id.nav_gallery);
item.setTitle("نقشه");
item.setIcon(R.drawable.ic_action_map);
applyFontToItem(item, typeface);
item = navigationView.getMenu().findItem(R.id.nav_slideshow);
item.setTitle("درباره ما");
item.setIcon(R.drawable.ic_action_us);
applyFontToItem(item, typeface);
}
#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) {
MainFragment fragment = new MainFragment();
android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit(); }
else if (id == R.id.nav_gallery) {
MapFragment fragment = new MapFragment();
android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
} else if (id == R.id.nav_slideshow) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
Here is my app_bar_main :
<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_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
<include layout="#layout/fragment_main" />
<FrameLayout
android:id="#+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent"></FrameLayout>
Here is my activity_main.xml
<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">
<include
layout="#layout/app_bar_main"
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.NavigationView
android:id="#+id/nav_view"
android:layout_width="220dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:headerLayout="#layout/nav_header_main"
app:menu="#menu/activity_main_drawer" />
When I run this code in emulator API 21, everything looks fine.
But when I run it in API 16, i get this error:
"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."
I guess it's telling me not to use actionbar, but how can i actually display my navigation drawer if i set windowActionBar to false?
i've tried this topic but it didn't work

Cannot get anything to change color from spinner menu

I am trying to get my spinner menu to respond by changing the color of anything. Can not change color of anything. See picture before selecting green and after. I am learning how to program for android.
Here is my MainActivity.java
package com.romanescotech.mydropdownnavigation;
import android.graphics.Color;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.SpinnerAdapter;
public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {
Spinner spinner;
ArrayAdapter adapter;
Toolbar toolbar;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
spinner = (Spinner) findViewById(R.id.spinnerMy);
adapter = ArrayAdapter.createFromResource(this, R.array.colors, R.layout.support_simple_spinner_dropdown_item);
adapter.setDropDownViewResource(R.layout.support_simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
}
#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);
}
#Override
public void onItemSelected(AdapterView<?> parent , View view, int pos, long id) {
parent.getItemAtPosition(pos);
String[] colors = getResources().getStringArray(R.array.colors);
String selectedColor = colors[pos];
getWindow().getDecorView().setBackgroundColor(Color.parseColor(selectedColor));
spinner.setBackgroundColor(Color.parseColor(selectedColor));
view.setBackgroundColor(Color.parseColor(selectedColor));
}
#Override
public void onNothingSelected(AdapterView<?> parent) {
// do nothing
}
}
Here is my activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<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_width="match_parent"
android:layout_height="match_parent"
android:background="?attr/colorPrimary"
app:popupTheme="#style/AppTheme.PopupOverlay" />
<Spinner
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/spinnerMy"
android:alpha=".8" />
</android.support.design.widget.AppBarLayout>
<include layout="#layout/content_main" />
<android.support.design.widget.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|end"
android:layout_margin="#dimen/fab_margin"
app:srcCompat="#android:drawable/ic_dialog_email" />
Here is my string.xml
<resources>
<string name="app_name">MyDropDownNavigation</string>
<string-array name="colors">
<item>White</item>
<item>Red</item>
<item>Green</item>
<item>Blue</item>
<item>Yellow</item>
</string-array>
<string name="action_settings">Settings</string>
Here is my Manifest file
<?xml version="1.0" encoding="utf-8"?>
<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"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
Here is my 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>
<style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />
<style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />
Here is my other v21/styles xml
<resources>
<style name="AppTheme.NoActionBar">
<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>
<item name="android:windowDrawsSystemBarBackgrounds">true</item>
<item name="android:statusBarColor">#android:color/transparent</item>
</style>
And here is a picture of it running before making selecting
before making selection
Here is after making selection, manues, background everything is the same color.
after making selection
I am guessing my problem lies in this method.
public void onItemSelected(AdapterView<?> parent , View view, int pos, long id) {
parent.getItemAtPosition(pos);
String[] colors = getResources().getStringArray(R.array.colors);
String selectedColor = colors[pos];
getWindow().getDecorView().setBackgroundColor(Color.parseColor(selectedColor));
spinner.setBackgroundColor(Color.parseColor(selectedColor));
view.setBackgroundColor(Color.parseColor(selectedColor));
in the java code

Your program looks correct except for one change. After the View changes, you need to notify so that view gets to know a change has occured and reflects it in the UI. Try calling adapter.notifydatasetchanged at the end of method onItemSelected().
Hope it helps you.

Action Bar not showing because of Intent?

Update:
I fix it by changing MainActivityFragment extends FragmentActivity to MainActivityFragment extends AppCompatActivity.
Thanks Guys.
The Action Bar will show if i don't comment the Intent. If I run the Intent in onCreate MainActivity, the Action Bar doesn't show. How do I show the Action Bar with the Intent. I provide the Intent (Main Activity) and Android Manifest code below.
Link to screenshot:
Non-Intent
Intent
MainActivity.java :
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_main); // this is the start layout
Intent intent = new Intent(this, MainActivityFragment.class);
startActivity(intent);
}
AndroidManifest.xml :
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.romi1.popularmoviesapp">
<uses-permission android:name="android.permission.INTERNET" />
<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">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<dependency>
<groupId>
info.movito
</groupId>
<artifactId>
themoviedbapi
</artifactId>
<version>
1.3
</version>
</dependency>
<activity android:name=".MainActivityFragment"></activity>
<activity android:name=".MoviesDetailAdapter"></activity>
</application>
</manifest>
Style.xml:
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Base.Theme.AppCompat.Light.DarkActionBar">
<!--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>
</resources>
MainActivityFragment :
public class MainActivityFragment extends FragmentActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_main);
movies = new Movies[1000];
jsonParser(json);
moviesAdapter = new MoviesAdapter(this, movies);
setContentView(R.layout.fragment_main);
GridView gridView = (GridView) findViewById(R.id.listView);
gridView.setAdapter(moviesAdapter);
// This for setting what happen when one of the movie is selected
gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
// Make another fragment class for this Adapter
// And figure out away to send the clicked parcelable variable
Movies topRatedMovieJson = moviesAdapter.getItem(i);
Log.v(LOG_TAG, "topRatedMovieJson : " + i);
Log.v(LOG_TAG, "topRatedMovieJson : " + topRatedMovieJson.title.toString());
Intent intent = new Intent(getBaseContext(), MoviesDetailAdapter.class);
intent.putExtra("parcelable", topRatedMovieJson);
startActivity(intent);
}
});
}
}
Update:
I fix it by changing MainActivityFragment extends FragmentActivity to MainActivityFragment extends AppCompatActivity.
Thanks Guys.

There are 2 ways to do that
1. Change that activity to fragment
2. Add Actionbar to second activity's layout and in your activity.

You can set two style and apply it to your activities.
describe style like this :
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>
<style name="SecondTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>
and apply it to activities :
<activity android:name=".MainActivityFragment" android:theme="#style/SecondTheme"/>
<activity android:name=".MoviesDetailAdapter" android:theme="#style/SecondTheme"/>

This Activity already has an action bar supplied by the window decor?

I am making an Android app using Toolbar with Custom style but when i'm running the app, i'm getting the following error:
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.
Styles.xml
<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/colorPrimary</item>
<item name="android:textColor">#color/textColorPrimary</item>
</style>
<style name="AppTheme.NoActionBar">
<item name="android:textColorSecondary">#color/textColorPrimary</item>
</style>
<style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar"/>
<style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light"/>
<style name="MyMaterialTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorPrimary</item>
</style>
<style name="MyEditTextTheme" parent="Theme.AppCompat.Light.NoActionBar">
<!-- Used for the bottom line when not selected / focused -->
<item name="colorAccent">#color/colorPrimary</item>
<item name="android:textColor">#color/colorPrimary</item>
<item name="android:colorBackground">#color/colorBackground</item>
<item name="android:textStyle">bold</item>
<item name="android:endColor">#color/colorPrimary</item>
<!-- colorControlActivated & colorControlHighlight use the colorAccent color by default -->
</style>
<style name="TabTextAppearance" parent="Theme.AppCompat.Light.DarkActionBar">
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorPrimary</item>
<item name="android:colorBackground">#color/colorBackground</item>
<item name="android:textAllCaps">false</item>
<item name="android:textStyle">bold</item>
</style>
MainActivity:
public class MainActivity extends AppCompatActivity {
private TabLayout tabLayout;
private ViewPager viewPager;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.content_information_category1);
Toolbar toolbar=(Toolbar)findViewById(R.id.toolbar_information);
setSupportActionBar(toolbar);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(new TodayInformationFragment(), "Today");
adapter.addFragment(new ThisWeekInformationFragment(), "This Week");
adapter.addFragment(new ThisMonthInformationFragment(), "This Month");
adapter.addFragment(new AllyearInformationFragment(), "All");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
#Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
#Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
#Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
}

Clearly error says:
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
Use this in your Styles:
<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>
Updated:
Android studio's default example is like this, take a look at the AppTheme.NoActionBar:
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.NoActionBar">
<!-- 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>
<style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />
<style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />
</resources>
And in your Manifest:
<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"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
And make sure your Toolbar implemented correctly.
For example, with AppbarLayout:
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#android:color/transparent"
app:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbarmain"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#color/ColorPrimary"
app:layout_collapseMode="pin"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light"
app:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar" />

Just go to your Manifest file and in the specific activity add
android:theme="#style/AppTheme.NoActionBar"/>

in my case that happened because the phone was in dark mode and I didn't provide a dark mode for my app maybe. it works fine after disabling the dark mode.

in my case i was testing on mobile which was in dark theme i got this and the following code done work for me
<style name="Theme.QrCodeScanner"
parent="Theme.MaterialComponents.DayNight.NoActionBar">
set this in both themes.xm and themes.xml(night)
or if you want it for a specific activty then do the following in your manifest in specific activity
android:theme="#style/AppTheme.NoActionBar"/>