Remove Android App Title Bar

I was able to do this for Android 2.1 devices and above using an App Compatibility library theme applied to the app element in the manifest:

<application
    ...
    android:theme="@style/AppTheme" />

<style name="AppTheme" parent="@style/Theme.AppCompat.Light.NoActionBar">
    ...
   <item name="windowNoTitle">true</item>
   <item name="android:windowNoTitle">true</item>
</style>

Note: You will need to include the com.android.support:appcompat-v7library in your build.gradle file

for Title Bar

requestWindowFeature(Window.FEATURE_NO_TITLE);

for fullscreen

getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);

Place this after

super.onCreate(savedInstanceState);

but before

setContentView(R.layout.xml);

This worked for me.try this

1. In the Design Tab, click on the AppTheme Button

2. Choose the option "AppCompat.Light.NoActionBar"

3. Click OK.

Simple way is to put this in your onCreate():

// Java
getSupportActionBar().hide();

// Kotlin
supportActionBar?.hide()