AndroidManifest.xml

<activity android:name=".MainActivity" android:theme="@android:style/Theme.Black.NoTitleBar"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity>

Activity.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" tools:context=".MainActivity"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Hello World!" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" /> </android.support.constraint.ConstraintLayout>

You need to use the Theme.AppCompat theme with this activity.

    1 answer 1

    Your Activity is a descendant of AppCompatActivity (MainActivity extends AppCompatActivity) and it should use a theme from the Theme.AppCompat namespace.

    Will suit you:

      android:theme="@style/Theme.AppCompat.Light.NoActionBar"