一个类中的活动中的Android处理程序不接收来自不同类的线程的消息

Question

在以下代码中，我无法接收从我的活动中的线程发送的消息。什么似乎是错的？甚至可以这样做吗？我不想将处理程序对象作为参数传递。

package com.example.mindentropy.testhandler;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;


public class MainActivity extends Activity {
    private static final String TAG = "MAINACTIVITY";

    private ActivityHandler activityHandler;
    private TestThread testThread;


    static class ActivityHandler extends  Handler {

        @Override
        public void handleMessage(Message msg) {
            Log.d(TAG, "In handler");
            super.handleMessage(msg);
        }
    }


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        activityHandler = new ActivityHandler();
        testThread = new TestThread();
        testThread.start();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}


class TestThread extends Thread {

    private static final String TAG = "TESTTHREAD";
    private final Handler UI_HANDLER = new Handler(Looper.getMainLooper());

    public void run() {
        while(true) {
            Message message = new Message();
            Log.d(TAG,"Sending message");
            UI_HANDLER.sendMessage(message);
            try {
                Thread.sleep(1000<<1);

            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        }
    }
}