Why can't I remove Action Bar in the Android app?

Question

I created a clean app in Android Studio, and made some changes to the standard theme:

<resources>

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
</style>

But after checking on the mobile device, the app crashes, saying the following: Images

Can someone help me explain what's going on here?

Answer 1

Use default theme and remove action bar programmatically using this

  requestWindowFeature(Window.FEATURE_NO_TITLE);
        ActionBar actionBar = getSupportActionBar();
        if (actionBar != null) {
            actionBar.hide();
        }

How to use?

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        ActionBar actionBar = getSupportActionBar();
        if (actionBar != null) {
            actionBar.hide();
        }

        setContentView(R.layout.activity_main);
    }
}

To remove Status bar & action bar use this

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        ActionBar actionBar = getSupportActionBar();
        if (actionBar != null) {
            actionBar.hide();
        }
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
              WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.activity_main);
    }
}

Answer 2

Use this instead

<style name="AppTheme" parent="Theme.AppCompat.Light">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
</style>

<style name="NoActionBarTheme" parent="AppTheme">
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
</style>

use NoActionBarTheme in your manifest