Android四大元件之Service:遠端service

遠端service

AIDL

每個應用程式都運作在自己的獨立程序中，
并且可以啟動另一個應用程序的服務，
而且經常需要在不同的程序間傳遞資料對象。

在Android平台，一個程序不能直接通路另一個程序的記憶體空間，
是以要想對話，需要将對象分解成作業系統可以了解的基本單元(例如基本資料類型)，
并且有序的通過程序邊界。

AIDL (Android Interface Definition Language) 
  用于生成可以在Android裝置上兩個程序之間
  進行程序間通信(interprocess communication, IPC)的代碼。

如果在一個程序中（例如Activity）要調用另一個
程序中（例如Service）對象的操作，就可以使用AIDL生成可序列化的參數。

練習例子

首先定義AIDL接口
這個AIDL接口和接口的類很像,我們可以先定義一個這樣的接口
然後再進行适當的修改就可以了

建立檔案：IStudentService.aidl

  package com.example.service;
  import com.example.service.Student;
  interface IStudentService 
  {
    Student getStudentById(int id);
  }

編寫AIDL需要注意:
1.接口名和aidl檔案名相同.
2.接口和方法前不用加通路權限修飾符public,private,protected等,也不能用final,static.
3.aidl預設支援的類型包話java基本類型(int,long,boolean等)和(String,List,Map,CharSequence),
  使用這些類型時不需要import聲明.對于List和Map中的元素類型必須是aidl支援的類型.
  如果使用自定義類型作為參數或傳回值,自定義類型必須實作Parcelable接口.
4.自定義類型和aidl生成的其它接口類型在aidl描述檔案中,應該顯式import,
  即便在該類和定義的包在同一個包中.
5.在aidl檔案中所有非Java基本類型參數必須加上in、out、inout标記,
  以指明參數是輸入參數、輸出參數還是輸入輸出參數.
6.Java原始類型預設的标記為in,不能為其它标記.

然後建立自定義類型Student

package com.example.service;

import android.os.Parcel;
import android.os.Parcelable;
import android.util.Log;

public class Student implements Parcelable
{

  private int id;
  private String name;
  private double price;

  @Override
  public int describeContents()
  {
    return 0;
  }
  
  // 将目前對象的屬性資料打成包: 寫到包對象中
  @Override
  public void writeToParcel(Parcel dest, int flags)
  {
    Log.e("TAG", "打包 writeToParcel()");
    // id
    dest.writeInt(id);
    // name
    dest.writeString(name);
    // price
    dest.writeDouble(price);
  }
  
  // 添加一個靜态成員,名為CREATOR,該對象實作了Parcelable.Creator接口
  public static final Parcelable.Creator<Student> CREATOR = new Parcelable.Creator<Student>()
  {
    
    // 解包: 讀取包中的資料并封裝成對象
    @Override
    public Student createFromParcel(Parcel source)
    {
      Log.e("TAG", "解包 createFromParcel()");
      // id
      int id = source.readInt();
      // name
      String name = source.readString();
      // price
      double price = source.readDouble();
      
      return new Student(id, name, price);
    }
    
    // 傳回一個指定大小的對象容器
    @Override
    public Student[] newArray(int size)
    {
      return new Student[size];
    }
  };
  
  public Student(int id, String name, double price)
  {
    super();
    this.id = id;
    this.name = name;
    this.price = price;
  }

  public Student()
  {
    super();
  }

  public int getId()
  {
    return id;
  }

  public void setId(int id)
  {
    this.id = id;
  }

  public String getName()
  {
    return name;
  }

  public void setName(String name)
  {
    this.name = name;
  }

  public double getPrice()
  {
    return price;
  }

  public void setPrice(double price)
  {
    this.price = price;
  }

  @Override
  public String toString()
  {
    return "Student [id=" + id + ", name=" + name + ", price=" + price+ "]";
  }
}

然後定義自定義類型的AIDL接口 

建立檔案：Student.aidl

package com.example.service;
parcelable Student;

然後會自動生成一個通信接口類
粘出來給看看吧

/*
 * This file is auto-generated.  DO NOT MODIFY.
 * Original file: E:\\Android\\WorkSpace\\Service\\src\\com\\example\\service\\IStudentService.aidl
 */
package com.example.service;

public interface IStudentService extends android.os.IInterface
{
  /** Local-side IPC implementation stub class. */
  public static abstract class Stub extends android.os.Binder implements
      com.example.service.IStudentService
  {
    private static final java.lang.String DESCRIPTOR = "com.example.service.IStudentService";

    /** Construct the stub at attach it to the interface. */
    public Stub()
    {
      this.attachInterface(this, DESCRIPTOR);
    }

    /**
     * Cast an IBinder object into an com.example.service.IStudentService
     * interface, generating a proxy if needed.
     */
    public static com.example.service.IStudentService asInterface(
        android.os.IBinder obj)
    {
      if ((obj == null))
      {
        return null;
      }
      android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
      if (((iin != null) && (iin instanceof com.example.service.IStudentService)))
      {
        return ((com.example.service.IStudentService) iin);
      }
      return new com.example.service.IStudentService.Stub.Proxy(obj);
    }

    @Override
    public android.os.IBinder asBinder()
    {
      return this;
    }

    @Override
    public boolean onTransact(int code, android.os.Parcel data,
        android.os.Parcel reply, int flags)
        throws android.os.RemoteException
    {
      switch (code)
      {
      case INTERFACE_TRANSACTION:
      {
        reply.writeString(DESCRIPTOR);
        return true;
      }
      case TRANSACTION_getStudentById:
      {
        data.enforceInterface(DESCRIPTOR);
        int _arg0;
        _arg0 = data.readInt();
        com.example.service.Student _result = this
            .getStudentById(_arg0);
        reply.writeNoException();
        if ((_result != null))
        {
          reply.writeInt(1);
          _result.writeToParcel(reply,
              android.os.Parcelable.PARCELABLE_WRITE_RETURN_VALUE);
        } else
        {
          reply.writeInt(0);
        }
        return true;
      }
      }
      return super.onTransact(code, data, reply, flags);
    }

    private static class Proxy implements
        com.example.service.IStudentService
    {
      private android.os.IBinder mRemote;

      Proxy(android.os.IBinder remote)
      {
        mRemote = remote;
      }

      @Override
      public android.os.IBinder asBinder()
      {
        return mRemote;
      }

      public java.lang.String getInterfaceDescriptor()
      {
        return DESCRIPTOR;
      }

      @Override
      public com.example.service.Student getStudentById(int id)
          throws android.os.RemoteException
      {
        android.os.Parcel _data = android.os.Parcel.obtain();
        android.os.Parcel _reply = android.os.Parcel.obtain();
        com.example.service.Student _result;
        try
        {
          _data.writeInterfaceToken(DESCRIPTOR);
          _data.writeInt(id);
          mRemote.transact(Stub.TRANSACTION_getStudentById, _data,
              _reply, 0);
          _reply.readException();
          if ((0 != _reply.readInt()))
          {
            _result = com.example.service.Student.CREATOR
                .createFromParcel(_reply);
          } else
          {
            _result = null;
          }
        } finally
        {
          _reply.recycle();
          _data.recycle();
        }
        return _result;
      }
    }

    static final int TRANSACTION_getStudentById = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
  }

  public com.example.service.Student getStudentById(int id)
      throws android.os.RemoteException;
}

下一步是:
  在Service類中使用生成的類實作業務方法
  
package com.example.service;

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

public class MyRemoteService extends Service
{

  @Override
  public IBinder onBind(Intent intent)
  {
    Log.e("TAG", "onBind()");
    return new StudentService();
  }

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

  // 處理Student相關的業務邏輯類
  class StudentService extends IStudentService.Stub
  {
    @Override
    public Student getStudentById(int id) throws RemoteException
    {
      Log.e("TAG", "Service getStudentById() " + id);
      return new Student(id, "jane", 10000000);
    }
  }

}

然後再到用戶端進行編碼的了
首先複制服務端AIDL的相關定義
自動生成一個通信接口類
在Activity中bind遠端Service，并調用業務方法

  public void bindRemoteService(View v)
  {

    Intent intent = new Intent("com.example.service.MyRemoteService.Action");
    if (conn == null)
    {
      conn = new ServiceConnection()
      {
        @Override
        public void onServiceDisconnected(ComponentName name)
        {

        }

        @Override
        public void onServiceConnected(ComponentName name,IBinder service)
        {
          Log.e("TAG", "onServiceConnected()");
          studentService = IStudentService.Stub.asInterface(service);
        }
      };
      bindService(intent, conn, Context.BIND_AUTO_CREATE);
      Toast.makeText(this, "綁定Service", 0).show();
    } else
    {
      Toast.makeText(this, "已經綁定Service", 0).show();
    }
  }

到這裡是終于結束了

總的代碼

服務端

package com.example.service;

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

public class MyRemoteService extends Service
{

  @Override
  public IBinder onBind(Intent intent)
  {
    Log.e("TAG", "onBind()");
    return new StudentService();
  }

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

  // 處理Student相關的業務邏輯類
  class StudentService extends IStudentService.Stub
  {
    @Override
    public Student getStudentById(int id) throws RemoteException
    {
      Log.e("TAG", "Service getStudentById() " + id);
      return new Student(id, "jane", 10000000);
    }
  }

}

package com.example.service;

import android.os.Parcel;
import android.os.Parcelable;
import android.util.Log;

public class Student implements Parcelable
{

  private int id;
  private String name;
  private double price;

  @Override
  public int describeContents()
  {
    return 0;
  }
  
  // 将目前對象的屬性資料打成包: 寫到包對象中
  @Override
  public void writeToParcel(Parcel dest, int flags)
  {
    Log.e("TAG", "打包 writeToParcel()");
    // id
    dest.writeInt(id);
    // name
    dest.writeString(name);
    // price
    dest.writeDouble(price);
  }
  
  // 添加一個靜态成員,名為CREATOR,該對象實作了Parcelable.Creator接口
  public static final Parcelable.Creator<Student> CREATOR = new Parcelable.Creator<Student>()
  {
    
    // 解包: 讀取包中的資料并封裝成對象
    @Override
    public Student createFromParcel(Parcel source)
    {
      Log.e("TAG", "解包 createFromParcel()");
      // id
      int id = source.readInt();
      // name
      String name = source.readString();
      // price
      double price = source.readDouble();
      
      return new Student(id, name, price);
    }
    
    // 傳回一個指定大小的對象容器
    @Override
    public Student[] newArray(int size)
    {
      return new Student[size];
    }
  };
  
  public Student(int id, String name, double price)
  {
    super();
    this.id = id;
    this.name = name;
    this.price = price;
  }

  public Student()
  {
    super();
  }

  public int getId()
  {
    return id;
  }

  public void setId(int id)
  {
    this.id = id;
  }

  public String getName()
  {
    return name;
  }

  public void setName(String name)
  {
    this.name = name;
  }

  public double getPrice()
  {
    return price;
  }

  public void setPrice(double price)
  {
    this.price = price;
  }

  @Override
  public String toString()
  {
    return "Student [id=" + id + ", name=" + name + ", price=" + price+ "]";
  }
}

package com.example.service;
import com.example.service.Student;
interface IStudentService 
{
  Student getStudentById(int id);
}

package com.example.service;
parcelable Student;

對應下面四個檔案

用戶端

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="bindRemoteService"
        android:text="bind remote Service" />

    <EditText
        android:id="@+id/et_aidl_id"
        android:layout_width="fill_parent"
        android:layout_height="50dip"
        android:hint="學員ID"
        android:text="3" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="invokeRemote"
        android:text="調用遠端服務端的方法" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="unbindRemoteService"
        android:text="unbind remote Service" />

</LinearLayout>

package com.example.client;

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.os.RemoteException;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import com.example.service.IStudentService;
import com.example.service.Student;

public class MainActivity extends Activity
{
  private EditText et_aidl_id;

  @Override
  protected void onCreate(Bundle savedInstanceState)
  {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    et_aidl_id = (EditText) findViewById(R.id.et_aidl_id);
  }

  private ServiceConnection conn;
  private IStudentService studentService;

  public void bindRemoteService(View v)
  {

    Intent intent = new Intent("com.example.service.MyRemoteService.Action");
    if (conn == null)
    {
      conn = new ServiceConnection()
      {
        @Override
        public void onServiceDisconnected(ComponentName name)
        {

        }

        @Override
        public void onServiceConnected(ComponentName name,IBinder service)
        {
          Log.e("TAG", "onServiceConnected()");
          studentService = IStudentService.Stub.asInterface(service);
        }
      };
      bindService(intent, conn, Context.BIND_AUTO_CREATE);
      Toast.makeText(this, "綁定Service", 0).show();
    } else
    {
      Toast.makeText(this, "已經綁定Service", 0).show();
    }
  }

  public void invokeRemote(View v) throws RemoteException
  {
    if (studentService != null)
    {
      int id = Integer.parseInt(et_aidl_id.getText().toString());
      Student student = studentService.getStudentById(id);
      Toast.makeText(this, student.toString(), 0).show();
    }
  }

  public void unbindRemoteService(View v)
  {
    if (conn != null)
    {
      unbindService(conn);
      conn = null;
      studentService = null;
      Toast.makeText(this, "解綁Service", 0).show();
    } else
    {
      Toast.makeText(this, "還未綁定Service", 0).show();
    }
  }
}

還需要導入服務端AIDL的相關定義
比如
  Student.java
  IStudentService.aidl
  Student.aidl

Android四大元件之Service:遠端service

遠端service

AIDL

練習例子

總的代碼

服務端

用戶端

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