Cloud Chou's Tech Blog

Binder service入门—应用层binder service

2014/04/21 次浏览

本文原创作者:Cloud Chou. 欢迎转载，请注明出处和本文链接

1.前言

上一篇介绍了Framework Binder Service，本篇将介绍如何创建应用层的binder service。 实际上在应用层使用binder service时，并没有直接与ServiceManager交互(应用层不能直接使用ServiceManager 类)，一般是在Service子类里覆盖onBind方法，返回新创建的Binder实体对象。应用层使用Activity作为binder service的客户端，在Activity里创建ServiceConnecttion对象，并调用bindService方法绑定service，在ServiceConnection的onServiceConnected方法将接收到的IBinder对象转化为接口对象，然后再通过这个接口对象调用binder service的接口方法。

Binder service入门系列：

2.程序构成

程序在应用开发环境下编译。

整个工程可以在github上下载： https://github.com/cloudchou/AndroidBinderTest

本示例使用remote service，声明service时，使用了android:process属性。

3.程序源码构成

源代码结构如下所示：

app_f

AndroidManifeset.xml：声明用到的activity，service组件

ICloudManager.aidl： binder service接口

CloudService: 创建binder service，并返回给客户端

TestAc: 测试binder service的客户端

实现应用层 binder service的步骤

1) 使用aidl定义binder service接口ICloudManager

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package com.cloud.test;
interface ICloudManager{
    void print(String str) ;
    int add(int a, int b);
}

aidl全称是android interface definition language，用于定义binder service接口，语法与Java的接口非常类似，详情可参考：http://developer.android.com/guide/components/aidl.html

使用eclipse开发时，它会被自动编译成ICloudManager.java，放在gen目录下。生成的ICloudManager.java源码如下所示：

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//声明接口ICloudManager 继承自IInterface，这里和在Framework使用binder service类似
public interface ICloudManager extends android.os.IInterface {
    /**binder service实体类和framework的binder service实体类类似 */
    public static abstract class Stub extends android.os.Binder implements com.cloud.test.ICloudManager {
        private static final java.lang.String DESCRIPTOR = "com.cloud.test.ICloudManager";

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

        /**
         * Cast an IBinder object into an com.cloud.test.ICloudManager interface, generating a proxy if needed.
         */
        public static com.cloud.test.ICloudManager asInterface(android.os.IBinder obj) {
            if ((obj == null)) {
                return null;
            }
            android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
            if (((iin != null) && (iin instanceof com.cloud.test.ICloudManager))) {
                return ((com.cloud.test.ICloudManager) iin);
            }
            return new com.cloud.test.ICloudManager.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_print: {
                data.enforceInterface(DESCRIPTOR);
                java.lang.String _arg0;
                _arg0 = data.readString();
                this.print(_arg0);
                reply.writeNoException();
                return true;
            }
            case TRANSACTION_add: {
                data.enforceInterface(DESCRIPTOR);
                int _arg0;
                _arg0 = data.readInt();
                int _arg1;
                _arg1 = data.readInt();
                int _result = this.add(_arg0, _arg1);
                reply.writeNoException();
                reply.writeInt(_result);
                return true;
            }
            }
            return super.onTransact(code, data, reply, flags);
        }

        //binder service的引用类，或者说是代理，和framework使用binder service类似
        private static class Proxy implements com.cloud.test.ICloudManager {
            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 void print(java.lang.String str) throws android.os.RemoteException {
                android.os.Parcel _data = android.os.Parcel.obtain();
                android.os.Parcel _reply = android.os.Parcel.obtain();
                try {
                    _data.writeInterfaceToken(DESCRIPTOR);
                    _data.writeString(str);
                    mRemote.transact(Stub.TRANSACTION_print, _data, _reply, 0);
                    _reply.readException();
                } finally {
                    _reply.recycle();
                    _data.recycle();
                }
            }

            @Override
            public int add(int a, int b) throws android.os.RemoteException {
                android.os.Parcel _data = android.os.Parcel.obtain();
                android.os.Parcel _reply = android.os.Parcel.obtain();
                int _result;
                try {
                    _data.writeInterfaceToken(DESCRIPTOR);
                    _data.writeInt(a);
                    _data.writeInt(b);
                    mRemote.transact(Stub.TRANSACTION_add, _data, _reply, 0);
                    _reply.readException();
                    _result = _reply.readInt();
                } finally {
                    _reply.recycle();
                    _data.recycle();
                }
                return _result;
            }
        }

        static final int TRANSACTION_print = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
        static final int TRANSACTION_add = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);
    }

    public void print(java.lang.String str) throws android.os.RemoteException;

    public int add(int a, int b) throws android.os.RemoteException;
}

由此可见应用层使用binder service实际上和framework使用binder service是非常类似的，只是在应用层使用binder service时，只需编写aidl，开发工具可帮我们自动编译生成java源码文件，该源文件里包含接口，binder service实体类(抽象类，接口方法还未实现)，binder service引用类的源码。

2) 实现Service

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public class CloudService extends Service {
  private final static String TAG = CloudService.class.getSimpleName();
  
  //实现binder service实体类
  class CloudMananger extends ICloudManager.Stub {

      @Override
      public void print(String str) throws RemoteException {
          Log.d(TAG, "[ThreadId " + Thread.currentThread().getId() 
                     + "] [ProcessId" + Process.myPid()
                     + "]CloudService receive client print msg request: " 
                     + str);
      }

      @Override
      public int add(int a, int b) throws RemoteException {
          Log.d(TAG, "[ThreadId " + Thread.currentThread().getId() 
                      + "] [ProcessId" + Process.myPid()
                      + "[CloudService receive client add request : ");
          return a + b;
      }
  }

  @Override
  public void onCreate() {
      super.onCreate();
      Log.d(TAG, "[ThreadId " + Thread.currentThread().getId() 
                 + "] [ProcessId" + Process.myPid() + "]  onCreate");
  }

 //定义binder service实体类对象
  private CloudMananger manager = new CloudMananger();
  
 //覆盖onBind方法，返回binder service实体类对象
  @Override
  public IBinder onBind(Intent intent) {
      Log.d(TAG, "[ThreadId " + Thread.currentThread().getId() 
                 + "] [ProcessId" + Process.myPid() + "]  onBind");
      return manager;
  }

}

3) 实现Client

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public class TestAc extends Activity {
    private static final String TAG = TestAc.class.getSimpleName();
    private ICloudManager manager = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Log.d(TAG, "[ThreadId " + Thread.currentThread().getId() 
                    + "] [ProcessId" + Process.myPid() + "]  onCreate");
        findViewById(R.id.btn_print).setOnClickListener(
           new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    Log.d(TAG, "=========== Client call "
                               +"CloudService print function");
                    //调用print方法
                    manager.print("Hello world");
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
            }
        });
        findViewById(R.id.btn_add).setOnClickListener(
            new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    Log.d(TAG, "======Client call "
                               +"CloudService add function");
                    int a = manager.add(3, 2);
                    Log.d(TAG, "======Client add function reuslt : " + a);
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
            }
        });
    }

    @Override
    protected void onStart() {
        super.onStart();
        //绑定 remote service
        Intent intent = new Intent(this, CloudService.class);
        bindService(intent, connection, BIND_AUTO_CREATE);
    }

    @Override
    protected void onStop() {
        super.onStop();
        unbindService(connection);
    }
    
    //和remote service绑定时用的ServiceConnection对象
    private ServiceConnection connection = new ServiceConnection() {

        @Override
        public void onServiceDisconnected(ComponentName name) {
            Log.d(TAG, "[ThreadId " + Thread.currentThread().getId() 
                       + "] [ProcessId" + Process.myPid()
                       + "]  onServiceDisconnected");
        }

        @Override
        public void onServiceConnected(ComponentName name, IBinder service)
        {
            Log.d(TAG, "[ThreadId " + Thread.currentThread().getId() 
                       + "] [ProcessId" + Process.myPid()
                       + "]  onServiceConnected");
            //将IBinder对象转为ICloudManager接口对象，实际上是创建了一个代理对象
            manager = ICloudManager.Stub.asInterface(service);
            findViewById(R.id.btn_print).setEnabled(true);
            findViewById(R.id.btn_add).setEnabled(true);
        }
    };

}

4) AndroidManifest.xml，声明程序组件Activity和Service

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<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.cloud.test"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="15"
        android:targetSdkVersion="15" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity android:name=".TestAc" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        <!—remote service-->
        <service
            android:name=".CloudService"
            android:enabled="true"
            android:process=":remote" />
    </application>

</manifest>

4.测试

运行apk程序： app_test

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