title: activity or fragment keeps opening if I implement startActivity or navigate in observe of LiveData
body: <ol>
  <li>ViewModel</li>
  </ol>
  <pre><code>_response.postValue(true)
  </code></pre>
  <ol start="2">
  <li>Activity</li>
  </ol>
  <pre><code>response.observe(this@MyActivity){
      //
      startActivity() // this keeps being called when I return to this fragment from finish() in Other(Next) Activity
  }
  </code></pre>
  <ol start="3">
  <li>Fragment</li>
  </ol>
  <pre><code>response.observes(this@MyFragment){
      //
      findNavController().navigate(R.id.myFragment) // this keeps being called when I return to this fragment from findNavController().popBackStack() in myFragment
  }
  </code></pre>
  <p>Is there any way to prevent recalling this part?
  I think it's good when data does but something related to animation behaves differently from the expectation.</p>
  <p>How can I solve this problem?</p>