什麼時候使用startService？

答：APP在後臺長時間執行並執行業務的時候，可以用服務，主要是看服務的特點（在後臺長時間執行）；

Service相關程式碼：

package liudeli.service1.service;

import android.app.Service;

import android.content.Intent;
import android.os.IBinder;
import android.util.Log;

public class MyService4 extends Service {

    private final
 
 static String TAG = MyService4.class.getSimpleName();

    private final static int RUN = 1;
    private final static int NOT_RUN = 0;

    private int runState;

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onStart(Intent intent, int
 
 startId) {
        super.onStart(intent, startId);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        runState = RUN;
        new Thread(new BackgroundRun()).start();
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    
 
public void onDestroy() {
        super.onDestroy();
        runState = NOT_RUN;
    }

    /**
     * startService 不能直接執行耗時操作，需要通過非同步去執行耗時操作，Service只負責長時間到在後臺服務執行
     * Service是開啟主執行緒的，Service與Activity很類似，都是開啟執行主執行緒的
     */
    class BackgroundRun implements Runnable {

        @Override
        public void run() {
            while (runState == RUN) {
                Log.d(TAG, "Background Run ......");
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

MainActivity4相關程式碼：

    public void startService(View view) {
        startService(new Intent(this, MyService4.class));
    }

    public void stopService(View view) {
        stopService(new Intent(this, MyService4.class));
    }

Log日誌，Service去啟動執行緒一秒執行一次：

12-06 22:54:07.489 8204-8301/liudeli.service1 D/MyService4: Background Run ......
12-06 22:54:08.490 8204-8301/liudeli.service1 D/MyService4: Background Run ......
12-06 22:54:09.495 8204-8301/liudeli.service1 D/MyService4: Background Run ......
12-06 22:54:10.500 8204-8301/liudeli.service1 D/MyService4: Background Run ......
12-06 22:54:11.507 8204-8301/liudeli.service1 D/MyService4: Background Run ......
12-06 22:54:12.508 8204-8301/liudeli.service1 D/MyService4: Background Run ......
12-06 22:54:13.509 8204-8301/liudeli.service1 D/MyService4: Background Run ......