探寻Android的线程问题

// Version 1
public class IAmAThread extends Thread {
  public IAmAThread() {
    super("IAmAThread");
  }
 
  @Override
  public void run() {
     
// your code (sequence of instructions)
  }
}
// to execute this sequence of instructions in a separate thread.
new IAmAThread().start();
 
// Version 2
public class IAmARunnable implements Runnable {
  @Override
  public void run() {
     
// your code (sequence of instructions)
  }
}
// to execute this sequence of instructions in a separate thread.
IAmARunnable myRunnable = new IAmARunnable();
new Thread(myRunnable).start();
 

> A Handler allows you to send and process Message and Runnable objects associated with a thread's MessageQueue. Each Handler instance is associated with a single thread and that thread's message queue. When you create a new Handler, it is bound to the thread/message queue of the thread that is creating it ― from that point on, it will deliver messages and runnables to that message queue and execute them as they come out of the message queue.

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
}

class LooperThread extends Thread { 
 public Handler mHandler; 
 
 public void run() { 
  Looper.prepare(); //创建本线程的Looper并创建一个MessageQueue
 
  mHandler = new Handler() { 
   public void handleMessage(Message msg) { 
    // process incoming messages here 
   } 
  }; 
 
  Looper.loop(); //开始运行Looper,监听Message Queue 
 } 
}

public class ListProgressDemo extends ListActivity { 
 
 @Override
 public void onCreate(Bundle savedInstanceState) { 
  super.onCreate(savedInstanceState); 
  setContentView(R.layout.listprogress); 
 
  ((Button) findViewById(R.id.load_Handler)).setOnClickListener(new View.OnClickListener(){ 
 
   @Override
   public void onClick(View view) { 
    data = null; 
    data = new ArrayList<string>(); 
 
    adapter = null; 
 
    showDialog(PROGRESS_DIALOG); 
    new ProgressThread(handler, data).start(); 
   } 
  }); 
 } 
 
 @Override
 protected Dialog onCreateDialog(int id) { 
  switch(id) { 
  case PROGRESS_DIALOG: 
     return ProgressDialog.show(this, "", 
     "Loading. Please wait...", true); 
 
  default: return null; 
  } 
 } 
 
 private class ProgressThread extends Thread { 
 
  private Handler handler; 
  private ArrayList<string> data; 
 
  public ProgressThread(Handler handler, ArrayList<string> data) { 
   this.handler = handler; 
   this.data = data; 
  } 
 
  @Override
  public void run() { 
   for (int i=0; i<8; i++) { 
    data.add("ListItem"); //后台数据处理
    try { 
     Thread.sleep(100); 
    }catch(InterruptedException e) { 
      
     Message msg = handler.obtainMessage(); 
     Bundle b = new Bundle(); 
     b.putInt("state", STATE_ERROR); 
     msg.setData(b); 
     handler.sendMessage(msg); 
      
    } 
   } 
   Message msg = handler.obtainMessage(); 
   Bundle b = new Bundle(); 
   b.putInt("state", STATE_FINISH); 
   msg.setData(b); 
   handler.sendMessage(msg); 
  } 
   
 } 
 
 // 此处甚至可以不需要设置Looper，因为Handler默认就使用当前线程的Looper
 private final Handler handler = new Handler(Looper.getMainLooper()) {
 
  public void handleMessage(Message msg) { // 处理Message，更新ListView
   int state = msg.getData().getInt("state"); 
   switch(state){ 
    case STATE_FINISH: 
     dismissDialog(PROGRESS_DIALOG); 
     Toast.makeText(getApplicationContext(), 
       "加载完成!", 
       Toast.LENGTH_LONG) 
       .show(); 
 
     adapter = new ArrayAdapter<string>(getApplicationContext(), 
       android.R.layout.simple_list_item_1, 
       data ); 
        
     setListAdapter(adapter); 
 
     break; 
 
    case STATE_ERROR: 
     dismissDialog(PROGRESS_DIALOG); 
     Toast.makeText(getApplicationContext(), 
       "处理过程发生错误!", 
       Toast.LENGTH_LONG) 
      .show(); 
 
     adapter = new ArrayAdapter<string>(getApplicationContext(), 
       android.R.layout.simple_list_item_1, 
       data ); 
        
      setListAdapter(adapter); 
 
      break; 
 
    default: 
 
   } 
  } 
 }; 
 
 
 private ArrayAdapter<string> adapter; 
 private ArrayList<string> data; 
 
 private static final int PROGRESS_DIALOG = 1; 
 private static final int STATE_FINISH = 1; 
 private static final int STATE_ERROR = -1; 
} 

((Button) findViewById(R.id.load_AsyncTask)).setOnClickListener(new View.OnClickListener(){ 
 
 @Override
 public void onClick(View view) { 
  data = null; 
  data = new ArrayList<string>(); 
 
  adapter = null; 
 
  //显示ProgressDialog放到AsyncTask.onPreExecute()里 
  //showDialog(PROGRESS_DIALOG); 
  new ProgressTask().execute(data); 
 } 
}); 
 
private class ProgressTask extends AsyncTask, Void, Integer> { 
 
/* 该方法将在执行实际的后台操作前被UI thread调用。可以在该方法中做一些准备工作，如在界面上显示一个进度条。*/
@Override
protected void onPreExecute() { 
 // 先显示ProgressDialog
 showDialog(PROGRESS_DIALOG); 
} 
 
/* 执行那些很耗时的后台计算工作。可以调用publishProgress方法来更新实时的任务进度。 */
@Override
protected Integer doInBackground(ArrayList<string>... datas) { 
 ArrayList<string> data = datas[0]; 
 for (int i=0; i<8; i++) { 
  data.add("ListItem"); 
 } 
 return STATE_FINISH; 
} 
 
/* 在doInBackground 执行完成后，onPostExecute 方法将被UI thread调用， 
 * 后台的计算结果将通过该方法传递到UI thread. 
 */
@Override
protected void onPostExecute(Integer result) { 
 int state = result.intValue(); 
 switch(state){ 
 case STATE_FINISH: 
  dismissDialog(PROGRESS_DIALOG); 
  Toast.makeText(getApplicationContext(), 
    "加载完成!", 
    Toast.LENGTH_LONG) 
    .show(); 
 
  adapter = new ArrayAdapter<string>(getApplicationContext(), 
    android.R.layout.simple_list_item_1, 
    data ); 
     
  setListAdapter(adapter); 
 
  break; 
   
 case STATE_ERROR: 
  dismissDialog(PROGRESS_DIALOG); 
  Toast.makeText(getApplicationContext(), 
    "处理过程发生错误!", 
    Toast.LENGTH_LONG) 
   .show();
 
  adapter = new ArrayAdapter<string>(getApplicationContext(), 
    android.R.layout.simple_list_item_1, 
    data );
 
   setListAdapter(adapter);
 
   break;
 
 default:
 
 }
}