title: Android Camera2 Basics API
body: <p>I am reading the code about Android Camera2 APIs from here:
  <a href="https://github.com/googlesamples/android-Camera2Basic" rel="noreferrer">https://github.com/googlesamples/android-Camera2Basic</a></p>
  
  <p>And it is confusing in this lines:
  <a href="https://github.com/googlesamples/android-Camera2Basic/blob/master/Application/src/main/java/com/example/android/camera2basic/Camera2BasicFragment.java#L570-L574" rel="noreferrer">https://github.com/googlesamples/android-Camera2Basic/blob/master/Application/src/main/java/com/example/android/camera2basic/Camera2BasicFragment.java#L570-L574</a></p>
  
  <p>that the previewRequest builder only add surface, which is the TextureView to show, as target. But the following line actually add both as the targets. As I understand, this should not fire the "OnImageAvailable" Lisenter during preview, no? So why this add the imagereader's surface here?</p>
  
  <p>I tried to removed this imagereader's surface here but got error when I really want to capture an image.....</p>
  
  <p>SOOO CONFUSING!!!</p>