Service代码示例

 package com.homily.training.service;

 import android.app.Service;
 import android.content.Intent;
 import android.os.Binder;
 import android.os.IBinder;
 import android.support.annotation.Nullable;
 import android.util.Log;

 import com.homily.training.test.service.ICallbackResult;

 /**
  * Created by Rubert on 2016/7/6.
  */
 public class BindService extends Service{

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

     private MBinder mMBinder;
     private ICallbackResult mICallbackResult;
     private boolean unBindTarget = false;

     @Nullable
     @Override
     public IBinder onBind(Intent intent) {
         Log.i(TAG, "============onBind==================");
         return mMBinder;
     }
     @Override
     public void onCreate() {
         super.onCreate();
         Log.i(TAG, "============onCreate==================");
         mMBinder = new MBinder();
     }

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

     @Override
     public void onDestroy() {
         unBindTarget = true;
         super.onDestroy();
         Log.i(TAG, "============onDestroy==================");
     }

     @Override
     public boolean onUnbind(Intent intent) {
         Log.i(TAG, "============onUnbind==================");
         unBindTarget = true;//该处代码需要这么写是因为，Service中开启了线程。如果该Service直接onUnbind了，但是线程没有停止，并且如果再次bind该Service时，程序会再次重新实例化一个线程，并之前的线程也会一直运行下去，除非该app销毁。
         return super.onUnbind(intent);
     }

     public class MBinder extends Binder {
         public void start(){
             Log.i(TAG, "============MBinder-start==================");
             new Thread(new Runnable() {
                 @Override
                 public void run() {

                     while (true) {
                         if(unBindTarget) {
                             break;
                         }
                         Log.i(TAG, Thread.currentThread().getName() + "============MBinder-start-run==================");
                         mICallbackResult.OnBackResult(null);
                         try {
                             Thread.currentThread().sleep(5000);
                         } catch (InterruptedException e) {
                             e.printStackTrace();
                         }
                     }
                 }
             }).start();
         }

         public void bind(ICallbackResult result) {
             mICallbackResult = result;
         }

     }

 }

 package com.homily.training.service;

 import android.app.Service;
 import android.content.Intent;
 import android.os.IBinder;
 import android.support.annotation.Nullable;
 import android.util.Log;

 /**
  * Created by Rubert on 2016/7/6.
  */
 public class StartService extends Service{

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

     @Nullable
     @Override
     public IBinder onBind(Intent intent) {
         Log.i(TAG, "============onBind==================");
         return null;
     }

     @Override
     public void onCreate() {
         super.onCreate();
         Log.i(TAG, "============onCreate==================");
     }

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

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

     @Override
     public boolean onUnbind(Intent intent) {
         Log.i(TAG, "============onUnbind==================");
         return super.onUnbind(intent);
     }
 }

 package com.homily.training.test.service;

 import android.app.Activity;
 import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
 import android.content.ServiceConnection;
 import android.os.Binder;
 import android.os.Bundle;
 import android.os.IBinder;
 import android.util.Log;
 import android.view.View;
 import android.widget.Button;

 import com.homily.training.R;
 import com.homily.training.service.BindService;
 import com.homily.training.service.StartService;

 /**
  * Created by Rubert on 2016/7/6.
  * 主要验证startService 启动后再次启动；以及bindService绑定后，解绑再次绑定的情况。
  */
 public class ServiceMainAct extends Activity implements View.OnClickListener{

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

     Button startServiceBtn;
     Button closeServiceBtn;
     Button bindServiceBtn;
     Button unbindServiceBtn;
     BindService.MBinder mMBinder;
     boolean IsBinder = false;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.service_layout);
         startServiceBtn = (Button)findViewById(R.id.startService);
         closeServiceBtn = (Button)findViewById(R.id.closeService);
         bindServiceBtn = (Button)findViewById(R.id.binService);
         unbindServiceBtn = (Button)findViewById(R.id.unbinService);

         startServiceBtn.setOnClickListener(this);
         closeServiceBtn.setOnClickListener(this);
         bindServiceBtn.setOnClickListener(this);
         unbindServiceBtn.setOnClickListener(this);
     }

     ServiceConnection mConnection = new ServiceConnection(){
         @Override
         public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
             Log.i(TAG, "=============onServiceConnected==================");
             mMBinder = (BindService.MBinder)iBinder;
             mMBinder.bind(mICallbackResult);
             mMBinder.start();
             IsBinder = true;
         }
         @Override
         public void onServiceDisconnected(ComponentName componentName) {
             Log.i(TAG, "=============onServiceDisconnected==================");
             IsBinder = false;
         }
     };

     ICallbackResult mICallbackResult = new ICallbackResult(){
         @Override
         public void OnBackResult(Object result) {
             Log.i(TAG, "=============result==================");
         }
     };

     @Override
     public void onClick(View view) {
         switch (view.getId()) {
             case R.id.startService:
                 Intent sintent = new Intent(ServiceMainAct.this, StartService.class);
                 startService(sintent);
                 break;
             case R.id.closeService:
                 Intent cintent = new Intent(ServiceMainAct.this, StartService.class);
                 stopService(cintent);
                 break;
             case R.id.binService:
                 Intent service = new Intent(ServiceMainAct.this, BindService.class);
                 bindService(service, mConnection, Context.BIND_AUTO_CREATE);
                 break;
             case R.id.unbinService:
                 if(mConnection != null && IsBinder)
                 unbindService(mConnection);
                 break;
         }

     }

 }

 package com.homily.training.test.service;

 /**
  * Created by Rubert on 2016/7/6.
  */
 public interface ICallbackResult {
     void OnBackResult(Object result);
 }

<application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

        <service android:name="com.homily.training.service.StartService" />
        <service android:name="com.homily.training.service.BindService" />

<activity android:name=".test.service.ServiceMainAct">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
</application>

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical"
     >

     <Button
         android:id="@+id/startService"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:text="startService"
         />
     <Button
         android:id="@+id/closeService"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:text="closeService"
         />

     <Button
         android:id="@+id/binService"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:text="binService"
         />
     <Button
         android:id="@+id/unbinService"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:text="unbinService"
         />

 </LinearLayout>

Android开发的过程中，每次调用startService(Intent)的时候，都会调用该Service对象的onStartCommand(Intent,int,int)方法，然后在onStartCommand方法中做一些处理。然后我们注意到这个函数有一个int的返回值，这篇文章就是简单地讲讲int返回值的作用。

从Android官方文档中，我们知道onStartCommand有4种返回值：

 

START_STICKY：如果service进程被kill掉，保留service的状态为开始状态，但不保留递送的intent对象。随后系统会尝试重新创建service，由于服务状态为开始状态，所以创建服务后一定会调用onStartCommand(Intent,int,int)方法。如果在此期间没有任何启动命令被传递到service，那么参数Intent将为null。

 

START_NOT_STICKY：“非粘性的”。使用这个返回值时，如果在执行完onStartCommand后，服务被异常kill掉，系统不会自动重启该服务。

 

START_REDELIVER_INTENT：重传Intent。使用这个返回值时，如果在执行完onStartCommand后，服务被异常kill掉，系统会自动重启该服务，并将Intent的值传入。

 

START_STICKY_COMPATIBILITY：START_STICKY的兼容版本，但不保证服务被kill后一定能重启。