Android: Remote service services (including Aidl & IPC Tutorials)

Objective

• Service as one of the four major Android components, the application is very extensive
• This article describes one of the common uses of the service: remote service
  

If you are not aware of the service, it is recommended to read another article I wrote:
Android Four components: the most comprehensive analysis in service history

Directory

1. The difference between a remote service and a local service

• The biggest difference between remote services and local services is that the remote service is not in the same process as the caller (that is, the remote service is running in another process), while the local service is running in the same process as the caller
• The detailed differences between the two are as follows:

2. Usage Scenarios

Multiple applications share the same background service (remote service)

A remote service that communicates across processes with components of multiple applications (four components)

3. Specific Use

• In order for the remote service to cross-process communication (IPC) with the components of multiple applications (four components), the use of aidl

  1. Ipc:inter-process communication, i.e. cross-process communication
  2. Aidl:android Interface definition Language, the Android interface definition language, is used to communicate across processes between a service and multiple application components. This enables multiple applications to share the same service functionality.

• In multi-process communication, there are two process roles (in the simplest case): Server side and Client

• The following are the specific use steps for the two process roles:
  server-side (Service)
  Step 1: Create a new definition Aidl file and declare the interface that the service needs to provide to the client
  Step 2: Implement the interface methods defined in Aidl in the service subclass and define the life cycle methods (Oncreat, Onbind (), BlaBla)
  Step 3: Register Services & claims as remote services in Androidmainfest.xml

  clients (client)
  Step 1: Copy the Aidl file from the server to the directory
  Step 2: Use the Stub.asinterface interface to get the binder for the server and invoke the interface methods provided by the service as needed
  Step 3: Specify the service name and package for the server by intent, bind the remote service

Next, I'll use a concrete example to describe the usage of the remote service

4. Concrete examples

• Instance Description: Remote service for client remotely calling server side
• Specific use:

4.1 Server-side (Service)

Create a new server-side project: Service-server

It will be better if you look at the demo first: Github_remoteservice_server

Step 1. Create a new Aidl file

Step 2. Define the content (method) that the service needs to communicate with the activity in the new Aidl file, and compile (make Project)

// 在新建的AIDL_Service1.aidl里声明需要与Activity进行通信的方法package scut.carson_ho.demo_service;interface AIDL_Service1 {    void AIDL_Service();}//AIDL中支持以下的数据类型//1. 基本数据类型//2. String 和CharSequence//3. List 和 Map ,List和Map 对象的元素必须是AIDL支持的数据类型;//4. AIDL自动生成的接口（需要导入-import）//5. 实现android.os.Parcelable 接口的类（需要导入-import)

Step 3: Implement the interface methods defined in Aidl in the service subclass and define the life cycle methods (Oncreat, Onbind (), BlaBla)
Myservice.java

 Public  class myservice extends Service {    //Instantiate stub class for Aidl (subclass of Binder)Aidl_service1.stub Mbinder =NewAidl_service1.stub () {//Override the method defined in the interface        @Override         Public void Aidl_service()throwsremoteexception {System.out.println ("Client successfully communicates with remote background through Aidl"); }    };//rewriting related methods to service life cycle    @Override     Public void onCreate() {Super. OnCreate (); System.out.println ("Oncreat () executed."); }@Override     Public int Onstartcommand(Intent Intent,intFlagsintStartid) {System.out.println ("Onstartcommand () executed.");return Super. Onstartcommand (Intent, flags, Startid); }@Override     Public void OnDestroy() {Super. OnDestroy (); System.out.println ("Ondestory () executed."); }@Nullable    @Override     PublicIBinderOnbind(Intent Intent) {System.out.println ("Onbind () executed.");//In Onbind () returns binder of stub types that inherit from binder, very important        returnMbinder; }@Override     Public Boolean Onunbind(Intent Intent) {System.out.println ("Onunbind () executed.");return Super. Onunbind (Intent); }}

Step 4: Register Services & claims as remote services in Androidmainfest.xml

<service            android:name=".MyService"            android:process=":remote" //将本地服务设置成远程服务            android:exported="true"      //设置可被其他进程调用            >            //该Service可以响应带有scut.carson_ho.service_server.AIDL_Service1这个action的Intent。            //此处Intent的action必须写成“服务器端包名.aidl文件名”            <intent-filter>                <action android:name="scut.carson_ho.service_server.AIDL_Service1"/>            </intent-filter>        </service>

At this point, the server side (remote service) is complete.

4.2 Clients (client)

Project to create a new client: Service-client

It will be better if you look at the demo first: github_remoteservice_client

Step 1: Copy the package containing the Aidl file from the server to the client directory (Project/app/src/main) and compile

Note: Remember to copy intact!! Don't change anything!

Step 2: Define the "Bind service" button in the main layout file
Mainactivity.xml

<?xml version= "1.0" encoding= "Utf-8"?><Relativelayout xmlns:android="Http://schemas.android.com/apk/res/android"    Xmlns:tools="Http://schemas.android.com/tools"    Android:layout_width="Match_parent"    Android:layout_height="Match_parent"    Android:paddingbottom="@dimen/activity_vertical_margin"    Android:paddingleft="@dimen/activity_horizontal_margin"    Android:paddingright="@dimen/activity_horizontal_margin"    Android:paddingtop="@dimen/activity_vertical_margin"    Tools:context="Scut.carson_ho.service_client. Mainactivity ">    <buttonandroid:layout_centerinparent="true"android:id="@+id/ Bind_service "android:layout_width="match_parent "android:layout_height=" Wrap_content "android:text="binding service " />                                        </relativelayout>

Step 3: In the Mainactivity.java

• Use the Stub.asinterface interface to obtain the binder for the server;
• Service binding is performed by specifying the server name and package of the service by intent;
• Invoke the interface methods provided by the service as needed.

Mainactivity.java

 Public  class mainactivity extends appcompatactivity {        PrivateButton Bindservice;//define AIDL interface variables        PrivateAidl_service1 Maidl_service;//Create anonymous class for Serviceconnection        PrivateServiceconnection connection =NewServiceconnection () {//Override Onserviceconnected () method and Onservicedisconnected () method            //Call when activity is associated with service and disassociate            @Override             Public void onservicedisconnected(componentname name) {            }//Called when activity is associated with a service            @Override             Public void onserviceconnected(componentname name, IBinder service) {//Use the AIDLService1.Stub.asInterface () method to get the IBinder object returned by the server side                //Convert IBinder object to Maidl_service interface objectMaidl_service = AIDL_Service1.Stub.asInterface (Service);Try{//The interface method defined in the Myaidlservice.aidl file is invoked through the object to enable cross-process communicationMaidl_service.aidl_service (); }Catch(RemoteException e)                {E.printstacktrace (); }            }        };@Override        protected void onCreate(Bundle savedinstancestate) {Super. OnCreate (Savedinstancestate);            Setcontentview (R.layout.activity_main); Bindservice = (Button) Findviewbyid (R.id.bind_service);//Set button for binding serviceBindservice.setonclicklistener (NewView.onclicklistener () {@Override                 Public void OnClick(View v) {//Specify the service name and package of the server by intent and bind to the remote service                    The //parameter is identical to the server-side action, which is "server package name. Aidl Interface file name"Intent Intent =NewIntent ("Scut.carson_ho.service_server. Aidl_service1 ");remote service cannot be bound by implicit intent only after//android5.0                    //need to specify the package name through the Setpackage () methodIntent.setpackage ("Scut.carson_ho.service_server");//Bind service, incoming intent and Serviceconnection objectsBindservice (Intent, connection, context.bind_auto_create);        }            }); }    }

4.3 Test results

From the above test results can be seen:

• The printed statements run in separate processes (see the package name in front of the statement);
• The client invokes a method of the server-side service

That is , the client and the server are communicating across processes

4.4 Demo Address

• Client: Github_remoteservice_client
• Service side: Github_remoteservice_server
  

5. Summary

• This article provides a comprehensive overview of the remote service in the Android component service

• If you also want to know more about the service, please visit the following articles:

  Android Four components: the most comprehensive analysis in service history
  The most comprehensive analysis of android:service life cycle
  Android: (Local, communication, foreground, remote) service use comprehensive introduction
  Android: Remote service services (including Aidl & IPC Tutorials)
  Android Multithreading comprehensive analysis: Intentservice usage & source code

• The next step is to continue with the knowledge of Android development and to be interested in continuing to follow Carson_ho's Android development notes.

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Android: Remote service services (including Aidl & IPC Tutorials)