title: Android Studio Navigation bar showing Apps's name is missing?
body: <p>When I launch the apps in Emulator, I realize the Navigation bar which shows apps name is missing. May I know what's going on?</p>
  
  <pre><code>public class MainActivity extends Activity implements OnClickListener {
  
  EditText first_name;
  EditText last_name;
  Button button_submit;
  
  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      first_name = (EditText) findViewById(R.id.first_name);
      last_name = (EditText) findViewById(R.id.last_name);
      button_submit = (Button) findViewById(R.id.button_submit);
      button_submit.setOnClickListener(this);
  
  }
  @Override
  public void onClick(View v) {
      Intent intent = new Intent(this, ViewActivity.class);
      intent.putExtra("first_name", first_name.getText().toString());
      intent.putExtra("last_name", last_name.getText().toString());
      startActivity(intent);
    }
  }
  </code></pre>
  
  <p><strong>Manifest.xml</strong></p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="com.yuqk.intent_usage"&gt;
  
  &lt;application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:supportsRtl="true"
      android:theme="@style/AppTheme"&gt;
      &lt;activity android:name=".MainActivity"&gt;
          &lt;intent-filter&gt;
              &lt;action android:name="android.intent.action.MAIN" /&gt;
  
              &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
          &lt;/intent-filter&gt;
      &lt;/activity&gt;
      &lt;activity android:name=".ViewActivity"&gt;&lt;/activity&gt;
  &lt;/application&gt;
  </code></pre>
  
  <p></p>
  
  <p><strong>Style.xml</strong></p>
  
  <pre><code>&lt;resources&gt;
  &lt;!-- Base application theme. --&gt;
  &lt;style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar"&gt;
      &lt;!-- Customize your theme here. --&gt;
      &lt;item name="colorPrimary"&gt;@color/colorPrimary&lt;/item&gt;
      &lt;item name="colorPrimaryDark"&gt;@color/colorPrimaryDark&lt;/item&gt;
      &lt;item name="colorAccent"&gt;@color/colorAccent&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  
  <p></p>
  
  <p>Please refer the the screenshot for reference.. Thanks!</p>
  
  <p><a href="https://i.stack.imgur.com/Hxhdq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Hxhdq.png" alt="screenshot"></a></p>