android服务是执行在UI主线程的。一下是代码demo:

package com.example.testservice;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        startService(new Intent(MainActivity.this,ServiceTest.class));
    }


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

package com.example.testservice;

import android.app.Service;
import android.content.Intent;
import android.os.Handler;
import android.os.IBinder;
import android.os.Looper;
import android.os.Message;
import android.util.Log;
import android.widget.Toast;

public class ServiceTest extends Service {
private Handler mHandler=new Handler(){

	@Override
	public void handleMessage(Message msg) {
		switch (msg.what) {
		case 1:
			new Thread(){
				@Override
				public void run() {
					Log.i("服务", "第2个线程");
					Looper.prepare();
					for(int i=10;i<20;i++){
						Toast.makeText(getApplicationContext(), i+"",0).show();
						try {
							//Thread.sleep(1000);
						} catch (Exception e) {
							// TODO: handle exception
						}
						
						
					}
					mHandler.sendEmptyMessage(2);
					Looper.loop();
				};
			}.start();
			
			break;
		case 2:
			new Thread(){
				@Override
				public void run() {
					Log.i("服务", "第3个线程");
					Looper.prepare();
					for(int i=20;i<30;i++){
						Toast.makeText(getApplicationContext(), i+"",0).show();
						try {
							//Thread.sleep(1000);
						} catch (Exception e) {
							// TODO: handle exception
						}
						
						
					}
					mHandler.sendEmptyMessage(3);
					Looper.loop();
				};
			}.start();
			break;
			
		case 3:
			 onDestroy();
			break;

		default:
			break;
		}
		super.handleMessage(msg);
	}
	
	
};
	public ServiceTest() {
		// TODO Auto-generated constructor stub
	}

	@Override
	public IBinder onBind(Intent intent) {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public void onCreate() {
		Log.i("服务", "onCreate()");
		super.onCreate();
		new Thread(){
			@Override
			public void run() {
				Log.i("服务", "第一个线程");
				Looper.prepare();
				for(int i=0;i<10;i++){
					Toast.makeText(getApplicationContext(), i+"",0).show();
					try {
						//Thread.sleep(1000);
					} catch (Exception e) {
						// TODO: handle exception
					}
					
					
				}
				mHandler.sendEmptyMessage(1);
				Looper.loop();
			};
		}.start();
	}

	@Override
	public int onStartCommand(Intent intent, int flags, int startId) {
		Log.i("服务", "onStartCommand");
		
		
		return super.onStartCommand(intent, flags, startId);
	}

	@Override
	public void onDestroy() {
		Log.i("服务", "onDestroy()");
		super.onDestroy();
		stopSelf();
	}
	

}