Activity UI elements not showing

Question

Adding UI elements to my activity changes nothing when app runs - I get an empty activity. I've attached my activity layout, manifest and styles file.

Activity Layout:

<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/activity_main"
android:clickable="false">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="text"
    android:id="@+id/textView"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="75dp"
    android:visibility="visible"
    android:editable="false" />

Manifest looks like:

<?xml version="1.0" encoding="utf-8"?>

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

<application
    android:allowBackup="true"
    android:icon="@mipmap/my_icon"
    android:label="@string/app_name">
    <activity
        android:name=".MainActivity"
        android:theme="@style/myTheme"
        android:label=""
        >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Styles looks like:

<resources>

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

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
</style>

Answer 1

make sure to use the right oncreate() method as we have two methods:

public void onCreate(Bundle savedInstanceState, PersistableBundle persistentState)

and

protected void onCreate(@Nullable Bundle savedInstanceState)