Android Service 两种启动方式

1.Context.startService()方式启动 

①Context.startService()方式的生命周期： 启动时，startService –> onCreate() –> onStart()停止时，stopService –> onDestroy()如果调用者直接退出而没有停止Service，则Service 会一直在后台运行 Context.startService()方法启动服务，在服务未被创建时，系统会先调用服务的onCreate()方法，接着调用onStart()方法。如果调用startService()方法前服务已经被创建，多次调用startService()方法并不会导致多次创建服务，但会导致多次调用onStart()方法。采用startService()方法启动的服务，只能调用Context.stopService()方法结束服务，服务结束时会调用onDestroy()方法附代码

2.Context.bindService()方式启动：①Context.bindService()方式的生命周期： 绑定时,bindService -> onCreate() –> onBind()调用者退出了，即解绑定时,Srevice就会unbindService –>onUnbind() –> onDestory()Context.bindService()方式启动 Service的方法：绑定Service需要三个参数：bindService(intent, conn, Service.BIND_AUTO_CREATE);第一个：Intent对象第二个：ServiceConnection对象，创建该对象要实现它的onServiceConnected()和 onServiceDisconnected()来判断连接成功或者是断开连接第三个：如何创建Service，一般指定绑定的时候自动创建附代码

 package com.dada.test;

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

 import com.dada.test.BindService.MyBinder;

 public class TestActivity extends Activity {

     private boolean flag;
     private static final String TAG = "TestActivity";
     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);

         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);

         Button btnStart = (Button) findViewById(R.id.btnStart);

         Button btnStop = (Button) findViewById(R.id.btnStop);


         btnStart.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
                 //启动service 方式2
                 bindService();
             }
         });

         btnStop.setOnClickListener(new View.OnClickListener() {

             @Override
             public void onClick(View v) {
  //停止service 方式2
                 unBindService();
             }
         });
     }

     //启动service 方式2
     //
     private void bindService(){
         Intent intent = new Intent(TestActivity.this,BindService.class);
         Log.i(TAG, "bindService()");
         bindService(intent, conn, Context.BIND_AUTO_CREATE);
     }

     private void unBindService(){
         Log.i(TAG, "unBindService() start....");
         if(flag == true){
             Log.i(TAG, "unBindService() flag");
             unbindService(conn);
             flag = false;
         }
     }

 private ServiceConnection conn = new ServiceConnection() {

         @Override
         public void onServiceDisconnected(ComponentName name) {
             // TODO Auto-generated method stub
             Log.i(TAG, "onServiceDisconnected()");
         }

         @Override
         public void onServiceConnected(ComponentName name, IBinder service) {
             // TODO Auto-generated method stub
             Log.i(TAG, "onServiceConnected()");
             MyBinder binder = (MyBinder)service;
             BindService bindService = binder.getService1();
             bindService.MyMethod();
             flag = true;
         }
     };
 }

service

 package com.dada.test;

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

 public class BindService extends Service {

     private static final String TAG = "BindService";
     private MyBinder myBinder = new MyBinder();
     public void MyMethod(){
         Log.i(TAG, "BindService-->MyMethod()");
     }

     @Override
     public IBinder onBind(Intent intent) {
         Log.i(TAG, "BindService-->onBind()");
         return myBinder;
     }

     public class MyBinder extends Binder{

         public BindService getService1(){
             return BindService.this;
         }
     }



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

     @Override
     public void onStart(Intent intent, int startId) {
         Log.i(TAG, "BindService-->onStart()");
         super.onStart(intent, startId);
     }

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

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

 }

运行日志

点击启动

点击停止

没有打出onServiceDisconnected的日志的原因：

注：SDK上是这么说的：This is called when the connection with the service has been 
unexpectedly disconnected -- that is, its process crashed. Because it is running in our same 
process, we should never see this happen.

所以说，只有在service因异常而断开连接的时候，这个方法才会用到

其他

由于Service 的onStart()方法只有在startService()启动Service的情况下才调用，故使用onStart()的时候要注意这点。

与 Service 通信并且让它持续运行

      如果我们想保持和 Service 的通信，又不想让 Service 随着 Activity 退出而退出呢？你可以先 startService() 然后再 bindService() 。当你不需要绑定的时候就执行 unbindService() 方法，执行这个方法只会触发 Service 的 onUnbind() 而不会把这个 Service 销毁。这样就可以既保持和 Service 的通信，也不会随着 Activity 销毁而销毁了。