title: parameter assignment of callback method in android
body: <p>There are some callback methods in android, like "onCreate" or "onClick".</p>
  
  <p>I have a question about them.
  When those callback methods show up in programs,
  their parameters are not assigned by programmer.
  Should they be assigned first?</p>
  
  <p>For example,</p>
  
  <pre><code>Bundle  saveInstanceState = something; 
  //assign parameter saveInstanceState first. (yet not assigned in real case)
  public void onCreate(Bundle saveInstanceState) {
  // do something .....
  };
  </code></pre>
  
  <p>or </p>
  
  <pre><code>View v = something; 
  //assign parameter v first. (yet not assgned in real case)
  public void onClick(View v)  {
  // do something .....
  };
  </code></pre>
  
  <p>All the codes I have read so far don't assign "saveInstanceState"(of onCreate) or 
  "v"(of onClick) by the programmers.</p>
  
  <p>Does that mean "android will assign those parameters of callback methods itself"?
  If so, are all parameters of all callback methods the same case? </p>
  
  <p>For example, "data and camera in onPictureTaken(byte[] data, Camera camera) {};",
  are they assigned by android system automatically and programmer doesn't need to assign them?</p>
  
  <p>I can't find relative details in android developer website so far.
  If a parameter is assigned by system, not by programmer, 
  why is there no relative guideline or note about that in android developer website document?</p>
  
  <p>Thanks for reply.</p>