안 드 로 이 드 의 Handler 비동기 통신 체 제 를 깊이 이해 하 다.

public class TestActivity extends Activity {
 
// ...
// all standard stuff
 
@Override
public void onCreate(Bundle savedInstanceState) {
 
  
// ...
  
// all standard stuff
 
  
// we're creating a new handler here
  
// and we're in the UI Thread (default)
  
// so this Handler is associated with the UI thread
  Handler mHandler = new Handler();
 
  
// I want to start doing something really long
  
// which means I should run the fella in another thread.
  
// I do that by sending a message - in the form of another runnable object
 
  
// But first, I'm going to create a Runnable object or a message for this
  Runnable mRunnableOnSeparateThread = new Runnable() {
    @Override
    public void run () {
 
      
// do some long operation
      longOperation();
 
      
// After mRunnableOnSeparateThread is done with it's job,
      
// I need to tell the user that i'm done
      
// which means I need to send a message back to the UI thread
 
      
// who do we know that's associated with the UI thread?
      mHandler.post(new Runnable(){
        @Override
        public void run(){
          
// do some UI related thing
          
// like update a progress bar or TextView
          
// ....
        }
      });
 
 
    }
  };
 
  
// Cool but I've not executed the mRunnableOnSeparateThread yet
  
// I've only defined the message to be sent
  
// When I execute it though, I want it to be in a different thread
  
// that was the whole point.
 
  new Thread(mRunnableOnSeparateThread).start();
}
 
}

// the below code is inside a TextWatcher
// which implements the onTextChanged method
// I've simplified it to only highlight the parts we're
// interested in
 
private long lastChange = 0;
 
@Override
public void onTextChanged(final CharSequence chars,
             int start, int before, int count) {
 
    
// The handler is spawned from the UI thread
    new Handler().postDelayed(
 
      
// argument 1 for postDelated = message to be sent
      new Runnable() {
        @Override
        public void run() {
 
          if (noChangeInText_InTheLastFewSeconds()) {
            searchAndPopulateListView(chars.toString()); 
// logic
          }
        }
      },
 
      
// argument 2 for postDelated = delay before execution
      300);
 
    lastChange = System.currentTimeMillis();
}
 
 
private boolean noChangeInText_InTheLastFewSeconds() {
  return System.currentTimeMillis() - lastChange >= 300
}