Android开发中处理程序和线程之间的通信技巧

private class CookServer extends Thread {
       private Handler mHandler = new Handler() {
               public void handleMessage(Message msg) {
                     ....
                }
        };

private class CookServer extends Thread {
       public void run() {
             Looper.prepare();
                 // or new Handler(Looper.myLooper())
                 private Handler mHandler = new Handler() {
                       public void handleMessage(Message msg) {
                     ....
                }
        };

private class DeliverServer extends HandlerThread {
      private Handler mHandler;
      public DeliverServer(String name) {
           super(name);
      }
      @Override
      public void onLooperPrepared() {
            mHandler = new Handler(getLooper()) {
                    public void handleMessage(Message msg) {
                        .....
                    }
             };
       }
}

/**
 * How to attach an Handler to a Thread:
 * If you specify Looper object to Handler, i.e. new Handler(Looper), then the handler is attached to the thread owning
 * the Looper object, in which handleMessage() is executed.
 * If you do not specify the Looper object, then the handler is attached to the thread calling new Handler(), in which
 * handleMessage() is executed.
 * In this example, for class CookServer or DeliverServer, if you write this way:
 *     private class CookServer extends Thread {
  private Handler mHandler;
  private Looper mLooper;

  public CookServer() {
   mHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
     ....
    }
       start();
  }
 * then mHandler is attached to thread calling new CookServer(), which is the main thread, so mHandler.handleMessage() will
 * be executed in main thread.
 * To attach mHandler to its own thread, you must put it in run(), or after mLooper is created. For our example, providing
 * mLooper or not won't matter, because new Handler() is called in run(), which is in a new thread.
 */
public class HandlerITCDemo extends ListActivity {
    private static final int COOKING_STARTED = 1;
    private static final int COOKING_DONE = 2;
    private static final int DELIVERING_STARTED = 3;
    private static final int ORDER_DONE = 4;

    private ListView mListView;
    private static final String[] mFoods = new String[] {
 "Cubake",
 "Donut",
 "Eclaire",
 "Gingerbread",
 "Honeycomb",
 "Ice Cream Sanwitch",
 "Jelly Bean",
    };
    private ArrayList mOrderList;
    private TextView mGeneralStatus;
    private Button mSubmitOrder;
    private static Random mRandomer = new Random(47);
    private int mOrderCount;
    private int mCookingCount;
    private int mDeliveringCount;
    private int mDoneCount;

    private Handler mMainHandler = new Handler() {
 @Override
 public void handleMessage(Message msg) {
     switch (msg.what) {
     case COOKING_STARTED:
  mCookingCount++;
  break;
     case COOKING_DONE:
  mCookingCount--;
  break;
     case DELIVERING_STARTED:
  mDeliveringCount++;
  break;
     case ORDER_DONE:
  mDeliveringCount--;
  mDoneCount++;
     default:
  break;
     }
     mGeneralStatus.setText(makeStatusLabel());
 }
    };

    private CookServer mCookServer;
    private DeliverServer mDeliverServer;

    @Override
    protected void onDestroy() {
 super.onDestroy();
 if (mCookServer != null) {
     mCookServer.exit();
     mCookServer = null;
 }
 if (mDeliverServer != null) {
     mDeliverServer.exit();
     mDeliverServer = null;
 }
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 mListView = getListView();
 mOrderList = new ArrayList();
 mGeneralStatus = new TextView(getApplication());
 mGeneralStatus.setText(makeStatusLabel());
 mSubmitOrder = new Button(getApplication());
 mSubmitOrder.setText("Submit order");
 mSubmitOrder.setOnClickListener(new View.OnClickListener() {
     public void onClick(View v) {
  String order = mFoods[mRandomer.nextInt(mFoods.length)];
  mOrderList.add(order);
  mOrderCount = mOrderList.size();
  mGeneralStatus.setText(makeStatusLabel());
  setAdapter();
  mCookServer.cook(order);
     }
 });
 mListView.addHeaderView(mGeneralStatus);
 mListView.addFooterView(mSubmitOrder);
 setAdapter();
 mCookServer = new CookServer();
 mDeliverServer = new DeliverServer("deliver server");
    }

    private String makeStatusLabel() {
 StringBuilder sb = new StringBuilder();
 sb.append("Total: ");
 sb.append(mOrderCount);
 sb.append("    Cooking: ");
 sb.append(mCookingCount);
 sb.append("    Delivering: ");
 sb.append(mDeliveringCount);
 sb.append("    Done: ");
 sb.append(mDoneCount);
 return sb.toString();
    }

    private void setAdapter() {
 final ListAdapter adapter = new ArrayAdapter(getApplication(), android.R.layout.simple_list_item_1, mOrderList);
 setListAdapter(adapter);
    }

    private class CookServer extends Thread {
 private Handler mHandler;
 private Looper mLooper;

 public CookServer() {
     start();
 }

 @Override
 public void run() {
     Looper.prepare();
     mLooper = Looper.myLooper();
     mHandler = new Handler(mLooper, new Handler.Callback() {
  public boolean handleMessage(Message msg) {
      new Cooker((String) msg.obj);
      return true;
  }
     });
     Looper.loop();
 }

 public void cook(String order) {
     if (mLooper == null || mHandler == null) {
  return;
     }
     Message msg = Message.obtain();
     msg.obj = order;
     mHandler.sendMessage(msg);
 }

 public void exit() {
     if (mLooper != null) {
  mLooper.quit();
  mHandler = null;
  mLooper = null;
     }
 }
    }

    private class Cooker extends Thread {
 private String order;
 public Cooker(String order) {
     this.order = order;
     start();
 }

 @Override
 public void run() {
            mMainHandler.sendEmptyMessage(COOKING_STARTED);
            SystemClock.sleep(mRandomer.nextInt(50000));
            mDeliverServer.deliver(order);
            mMainHandler.sendEmptyMessage(COOKING_DONE);
 }
    }

    private class DeliverServer extends HandlerThread {
 private Handler mHandler;

 public DeliverServer(String name) {
     super(name);
     start();
 }

 @Override
 protected void onLooperPrepared() {
     super.onLooperPrepared();
     mHandler = new Handler(getLooper(), new Handler.Callback() {
  public boolean handleMessage(Message msg) {
      new Deliver((String) msg.obj);
      return true;
  }
     });
 }
 public void deliver(String order) {
     if (mHandler == null || getLooper() == null) {
  return;
     }
     Message msg = Message.obtain();
     msg.obj = order;
     mHandler.sendMessage(msg);
 }

 public void exit() {
     quit();
     mHandler = null;
 }
    }

    private class Deliver extends Thread {
 private String order;
 public Deliver(String order) {
     this.order = order;
     start();
 }

 @Override
 public void run() {
     mMainHandler.sendEmptyMessage(DELIVERING_STARTED);
     SystemClock.sleep(mRandomer.nextInt(50000));
     mMainHandler.sendEmptyMessage(ORDER_DONE);
 }
    }
}