title: Error : requestFeature() must be called before adding content
body: <p><strong>Caused by: android.util.AndroidRuntimeException: requestFeature() must be called before adding content</strong></p>
  
  <p><strong>here is my code,</strong></p>
  
  <pre><code>import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.view.Window;
  import android.view.WindowManager;
  
  public class MainActivity extends AppCompatActivity {
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
  
      this.requestWindowFeature(Window.FEATURE_SWIPE_TO_DISMISS);
      this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
  
      setContentView(R.layout.activity_main);
  }}
  </code></pre>