How to remove title bar from the android activity?

you just add this style in your style.xml file which is in your values folder

<style name="AppTheme.NoActionBar" parent="Theme.AppCompat.Light.DarkActionBar">
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
    <item name="android:windowFullscreen">true</item>
</style>

After that set this style to your activity class in your AndroidManifest.xml file

android:theme="@style/AppTheme.NoActionBar"

Edit:- If you are going with programmatic way to hide ActionBar then use below code in your activity onCreate() method.

if(getSupportedActionbar()!=null)    
     this.getSupportedActionBar().hide();

and if you want to hide ActionBar from Fragment then

getActivity().getSupportedActionBar().hide();

AppCompat v7:- Use following theme in your Activities where you don't want actiobBar Theme.AppComat.NoActionBar or Theme.AppCompat.Light.NoActionBar or if you want to hide in whole app then set this theme in your <application... /> in your AndroidManifest.

In Kotlin:

add this line of code in your onCreate() method or you can use above theme.

supportActionBar?.hide()

i hope this will help you more.

Try this:

this.getSupportActionBar().hide();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    try
    {
        this.getSupportActionBar().hide();
    }
    catch (NullPointerException e){}

    setContentView(R.layout.activity_main);
}

You can try:

<activity android:name=".YourActivityName"
          android:theme="@style/Theme.Design.NoActionBar">

that works for me

In your Android Manifest file make sure that the activity is using this (or a) theme (that is based on) @style/Theme.AppCompat.NoActionBar This removes the ActionBar completely, but won't make your activity fullscreen. If you want to make your activity fullscreen only use this theme

@android:style/Theme.NoTitleBar.Fullscreen

Or you could change

this.requestWindowFeature(Window.FEATURE_NO_TITLE);

to

requestWindowFeature(Window.FEATURE_NO_TITLE);
 getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);

This is what I use to get fullscreen at runtime

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
                mDecorView = getWindow().getDecorView();
                mDecorView.setSystemUiVisibility(
                        View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                                | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                                | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                                | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION // hide nav bar
                                | View.SYSTEM_UI_FLAG_FULLSCREEN // hide status bar
                                | View.SYSTEM_UI_FLAG_IMMERSIVE);
            }

To exit fullscreen I use this

mDecorView = getWindow().getDecorView();
mDecorView.setSystemUiVisibility(
                    View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                            | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                            | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);