Get rid of unnecessary root layouts for fullscreen activities

Question

How to get rid of unnecessary root layouts for fullscreen activities?

I have a simple fullscreen activity. The layout inspector shows a large hierarchy of root layouts provided by Android, that I don't need in fullscreen.

Can I get rid of them?

• If YES, how?
• If NO, why not?

The testing setup

Open Android Studio. Create a new project. Accept the default settings. Choose "Empty Activity". You get this manifest:

<application     android:allowBackup="true"     android:icon="@mipmap/ic_launcher"     android:label="@string/app_name"     android:roundIcon="@mipmap/ic_launcher_round"     android:supportsRtl="true"     android:theme="@style/AppTheme">     <activity android:name=".MainActivity">         <intent-filter>             <action android:name="android.intent.action.MAIN" />              <category android:name="android.intent.category.LAUNCHER" />         </intent-filter>     </activity> </application> 

You get this layout/activity_main.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="com.blcknx.myapplication.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> 

Call Tools > Android > Layout Inspector to see the generated root templates.

To make it fullscreen, just add an id HelloWorld to the TextView in the layout and update MainActivity.java:

public class MainActivity extends AppCompatActivity {      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         TextView layout = findViewById(R.id.HelloWorld);         layout.setSystemUiVisibility(                 View.SYSTEM_UI_FLAG_LOW_PROFILE                         | View.SYSTEM_UI_FLAG_FULLSCREEN                         | View.SYSTEM_UI_FLAG_LAYOUT_STABLE                         | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY                         | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION                         | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION         );     } } 

The flags are hiding the navigation, but they don't remove the unused layouts.

Your answer

Use a simple TextView. Show it fullscreen. Check by Tools > Android > Layout Inspector how far you removed the root layouts. Show a screenshot. Show your code.

Answer 1

You can get rid of action_bar_container having changed your activity's theme from DarkActionBar to NoActionBar:

<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">     ... </style> 

Then you'll get following tree:

If you want to go even more and get rid of ContentFrameLayout, than you can do this:

      override fun onCreate(savedInstanceState: Bundle?) {         super.onCreate(savedInstanceState)          val contentView = findViewById(android.R.id.content)         val parent = contentView.parent as ViewGroup         parent.removeView(contentView)         LayoutInflater.from(this).inflate(R.layout.activity_main, parent)     }  

This will be the view hierarchy tree:

Not sure whether you should remove android.R.id.content view, maybe some libraries are assuming that there should exist such a view.

As to action_mode_bar_stubs: you should not be concerned about them, as long as those are ViewStubs, which do not affect overall performance, because they are lazily inflated into view hierarchy.