title: Start Activity from two different package
body: <p>I have a project with two package <em>first.pack</em> and <em>second.pack</em>, with two different Activity. I'm trying to start the second Activity from the first one with that code</p>
  
  <pre><code>Intent intent = new Intent(Intent.ACTION_MAIN); 
        intent.setComponent(new ComponentName("second.pack", "second.pack.SecondActivity")); 
        startActivity(intent);
  </code></pre>
  
  <p>The strange thing is that this code had worked for a while, but after i unistalled and reinstalled the application, it's started to return me the following error:</p>
  
  <pre><code>Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {second.pack/second.pack.SecondActivity}; have you declared this activity in your AndroidManifest.xml?
  </code></pre>
  
  <p>Where am i wrong?</p>