Android 完全掌握Service

Service

Service生命周期:

1.context.startService() ->onCreate()- >onStartCommand()->Service running--调用context.stopService() ->onDestroy()

 

2.context.bindService()->onCreate()->onBind()->Service running--调用>onUnbind() -> onDestroy()

IBinder	onBind(Intent intent)	该方法时Service子类必须实现的方法.该方法返回一个IBinder对象,通过这个对象与Service组件通信
Void	onCreate()	在该Service被第一次调用后立即调用该方法
Void	onDestroy()	在该Service被关闭前回调该方法
Void	onStartConmmand(Intent intent,int flags,intstartId)	每次调用startService(Intent)方法启动Service时都会回调该方法
Boolean	onUnbind(Intent intent)	当该Service绑定的所有客户端都断开时回调该方法

 

package com.jia.fistservice; import android.app.Service; import android.content.Intent; import android.os.IBinder; import android.util.Log; public class FirstService extends Service {       @Override     public IBinder onBind(Intent intent) {        Log.d("jia", "必须实现的方法--->onBind(Intent intent)");        return null;     }       @Override     public void onCreate() {        Log.d("jia", "Service被创建的时回调该方法--->onCreate()");        super.onCreate();     }       @Override     public int onStartCommand(Intent intent, int flags, int startId) {        Log.d("jia",               "Service被启动时回调该方法--->onStartCommand(Intent intent, int flags, int startId)");        return super.onStartCommand(intent, flags, startId);     }       @Override     public void onDestroy() {        Log.d("jia", "Service被关闭之前回调该方法--->onCreate()");        super.onDestroy();     } }

使用Service需在AndroidManifest.xml文件中进行配置:

<service android:name=".FirstService"></service>

Service两种启动方式:

1. 通过Context的startService()方法:通过该方法启动Service,访问者与Service之间没有关联,即使访问者退出了,Service也仍然运行.
2. 通过Context的bindService()方法:使用该方法启动Service,访问者与Service绑定在一起,访问者一旦退出,Service也就终止了.

创建Service:

多次启动与销毁:

onCreate()方法只在第一次创建Service时启动,之后不会在触发.

onStartCommand()方法在每次启动Service时都会调用.

绑定本地Service并与之通信

如果Service与访问者之间进行方法调用或交换数据,应该使用bindService()和unbindService()方法启动.关闭Service.

bindService(Intent service,ServiceConnection conn,int flags)方法的三个参数如下:

service:通过Intent指定要启动的Service;

conn:该参数是ServiceConnection的对象,该对象用于监听访问者与Service之间的连接情况.当访问者与Service连接成功时调用ServiceConnection对象的onServiceConnected(ComponentName name, IBinder service)方法;当Service与访问者连接异常时,将调用ServiceConnection对象的onServiceDisconnected(ComponentName name)方法

当调用者主动通过unBinderService()方法断开与Service的连接时,ServiceConnection对象的onServiceDisconnected(ComponentName name)方法并不会调用.

flags:指定绑定时是否自动创建Service(如果Service还未创建).该参数可指定为0(不自动创建)或Service.BIND_AUTO_CREATE(自动创建);

 

Service类必须提供onBind(Intent intent)方法,该方法返回的IBinder对象将会传给ServiceConnection对象里onServiceConnected(ComponentName name, IBinder service)方法的service参数,这样访问者就可以通过该IBinder对象与Service进行通信了.

开发时会采用继承Binder(IBinder的实现类)的方式实现自己的IBinder对象.

BindService

package com.jia.bindservice;   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 int count;       private boolean quit;       private MyBinder bind = new MyBinder();       public class MyBinder extends Binder {            public int getCount() {                  return count;            }       }       @Override       public IBinder onBind(Intent intent) {            Log.d("jia", "Service is Binded---->onBind(Intent intent)");            return bind;       }       @Override       public void onCreate() {            super.onCreate();            Log.d("jia", "Service is Created---->onCreate()");            new Thread() {                  public void run() {                       while (!quit) {                             try {                                   Thread.sleep(1000);                             } catch (InterruptedException e) {                             }                             count++;                       }                  };            }.start();       }         @Override       public boolean onUnbind(Intent intent) {            Log.d("jia", "Service is Unbinded---->onUnbind(Intent intent)");            return true;       }       @Override       public void onDestroy() {            super.onDestroy();            this.quit = true;            Log.d("jia", "Service is Destroyed--->onDestroy()");       } }

 

MainActivity

package com.jia.bindservice;   import android.app.Activity; import android.app.Service; import android.content.ComponentName; 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.view.View.OnClickListener; import android.widget.Button; import android.widget.Toast;   public class MainActivity extends Activity {       private Button bind;     private Button unbind;     private Button getServiceStatus;     BindService.MyBinder binder;     // 定义一个ServiceConnection对象     private ServiceConnection conn = new ServiceConnection() {           @Override         public void onServiceDisconnected(ComponentName name) {             Log.d("jia",                     "Service DisConnected--->onServiceDisconnected(ComponentName name)");         }           @Override         public void onServiceConnected(ComponentName name, IBinder service) {             Log.d("jia",                     "Service Connected--->onServiceConnected(ComponentName name, IBinder service)");             binder = (BindService.MyBinder) service;           }     };       @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         bind = (Button) findViewById(R.id.bind);         unbind = (Button) findViewById(R.id.unbind);         getServiceStatus = (Button) findViewById(R.id.getServiceStatus);         final Intent intent = new Intent(this, BindService.class);         bind.setOnClickListener(new OnClickListener() {               @Override             public void onClick(View v) {                 bindService(intent, conn, Service.BIND_AUTO_CREATE);             }         });         unbind.setOnClickListener(new OnClickListener() {               @Override             public void onClick(View v) {                 unbindService(conn);             }         });         getServiceStatus.setOnClickListener(new OnClickListener() {               @Override             public void onClick(View v) {                 Toast.makeText(MainActivity.this,                         "Service的count值为:" + binder.getCount(),                         Toast.LENGTH_SHORT).show();             }         });     }   }

对于Service的onBind()方法所返回的IBinder对象来说,它可被当成该Service组件所返回的代理对象,Service允许客户端通过该IBinder对象来访问Service内部的数据,这样既可实现客户端与Service之间的通信.

当调用unbindService(conn);来断开与Service的绑定时,会先调用onUnbind(Intent intent)方法然后调用onDestroy()方法.

bindService(intent, conn, Service.BIND_AUTO_CREATE)方法与startService(intent)方法不同的是,多次调用bindService()方法不会进行重复绑定,只调用一次onBind(),而对于每次调用startService()方法绑定Service,系统每次都会回调Service的onStartCommand()方法一次.

当Activity调用bindService()绑定一个已启动的Service时,系统只是把Service内部IBinder对象传给Activity,并不会把该Service生命周期完全”绑定”到该Activity,因而当Activity调用unBindeService()方法取消与该Service的绑定时,也只是切断该Activity与Service之间的关联,并不能停止该Service组件.

使用IntentService

Service两个问题:

1. Service不会专门启动一个单独的进程,Service与它所在应用位于同一个进程中.
2. Serivice不是一条新的线程,因此不应该在Service中直接处理耗时的任务.

IntentService具有如下特征:

1. IntentService会创建单独的worker线程来处理所有的Intent请求.
2. IntentService会创建单独的worker线程来处理onHandleIntent()方法实现的代码,无须处理多线程问题.
3. 当所有请求处理完成后,IntentService会自动停止,无须调用stopSelf()方法来停止该Service.
4. 为Service的onBind()方法提供了默认实现,默认实现的onBind()方法返回null.
5. 为Service的onStartCommand()方法提供了默认实现,该实现会将请求Intent添加到队列中.

MyIntentService

package com.jia.intentservicetest;   import android.app.IntentService; import android.content.Intent; import android.util.Log;   public class MyIntentService extends IntentService {       public MyIntentService() {         super("MyIntentService");     }       @Override     protected void onHandleIntent(Intent intent) {         long endTime = System.currentTimeMillis() + 20 * 1000;         Log.d("jia", "MyIntentService---onHandleIntent(Intent intent)");         while (System.currentTimeMillis() < endTime) {             synchronized (this) {                 try {                     wait(endTime - System.currentTimeMillis());                 } catch (InterruptedException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();                 }             }         }         Log.d("jia", "--MyIntentService-耗时任务执行完成---");     }   }