Make App bar and Status bar transparent.

activity_main.xml

<!-- activity_main.xml (root) -->
+ android:fitsSystemWindows="true"

app_bar_main.xml

<!-- app_bar_main.xml -->
<com.google.android.material.appbar.AppBarLayout
    android:paddingTop="24dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@android:color/transparent"
    android:theme="@style/AppTheme.AppBarOverlay"
    app:elevation="0dp">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        app:popupTheme="@style/AppTheme.PopupOverlay" />

</com.google.android.material.appbar.AppBarLayout>

MainActivity.java

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

    // setting status bar
    Window window = this.getWindow();
    window.setFlags(
            WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS,
            WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS);
    window.getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR);

    setContentView(R.layout.activity_main);
    // ...
}

styles.xml

<!-- styles.xml -->
<resources>
  <!-- Base application theme. -->
  <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->
      ...
    <item name="android:windowTranslucentStatus">true</item>
  </style>

  <style name="AppTheme.NoActionBar">
      <item name="windowActionBar">false</item>
      <item name="windowNoTitle">true</item>
      <item name="android:windowTranslucentStatus">true</item>
  </style>
</resources>

v21\styles.xml

<!-- v21\styles.xml -->
<resources>
    <style name="AppTheme.NoActionBar">
        ...
        <item name="android:windowDrawsSystemBarBackgrounds">false</item>
        <item name="android:windowTranslucentStatus">true</item>
    </style>
</resources>