环境

android studio 2.2

步骤：创建aidl文件，编写service，activity中绑定service

在项目上点击创建 aidl文件，会自动创建相关目录和文件 app/aidl/jlsky.myaidl/IMaidl.aidl。修改文件如下

package jlsky.myaidl;
interface IMaidl {
    int sum(int num1,int num2);
}
ctrl+F9,或者点击那个锤子的图标，生成java代码。如果不是深入研究，生成的java文件就不用关心了。
创建service文件。

public class SumService extends Service {
    private static final String TAG = "service";

    @Override
    public IBinder onBind(Intent intent) {
        return iBinder;
    }

    private IMaidl.Stub iBinder = new IMaidl.Stub(){
        @Override
        public int sum(int num1,int num2) throws RemoteException{
            return num1 + num2 ;
        }
    };

    @Override
    public void onCreate() {
        super.onCreate();
        Log.i(TAG, " onCreate");
    }
    @Override
    public boolean onUnbind(Intent intent) {
        Log.i(TAG, " onUnbind");
        return super.onUnbind(intent);
    }
    @Override
    public void onDestroy() {
        Log.i(TAG, " onDestroy");
        super.onDestroy();
    }
}
重点是private IMaidl.Stub iBinder = new IMaidl.Stub()中的<IMaidl>要与你的aidl的文件名一致。里面实现的方法就是在aidl中的声明一致。

然后这个<iBinder>在service被绑定时，通过onBind（）返回给activity。

在activity中绑定service。
比如在activity的onCreate中绑定service

Intent intent = new Intent();
intent.setComponent(new ComponentName("jlsky.myaidl","jlsky.myaidl.SumService"));
//intent.setAction("jlsky.myaidl.SumService"); //如此写是错误的!
boolean b = bindService(intent,conn,BIND_AUTO_CREATE);
intent的参数是service的包名和service的全称。
b，不是必要的，但可以判断b的值来了解是否绑定成功。
事先声明一下

private IMaidl maidl;  //与aidl文件名一致。

conn的来历如下,（直接放在activity中即可。）

private ServiceConnection conn = new ServiceConnection(){
//   private class Conn implements ServiceConnection{
       @Override
       public void onServiceConnected(ComponentName name, IBinder iBinder){
           maidl = IMaidl.Stub.asInterface(iBinder);
           Log.d(TAG, "onServiceConnected: aidl");
       }
       @Override
       public void onServiceDisconnected(ComponentName name){
           maidl=null;
           Log.d(TAG, "onServiceDisconnected: aidl");
       }
   };
activity的完整代码如下：

public class MainActivity extends Activity {
    private EditText tv1,tv2;
    private TextView tv3;
    private Button btnSum;
    private IMaidl maidl;  //from ServiceConnection
    private final static String TAG ="MainActivity";
  //  private ServiceConnection conn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bindaidl();
        Log.d(TAG, "onCreate: bindaidl");
        initview();
        Log.d(TAG, "onCreate: initview");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unbindService(conn);
        Log.d(TAG, "onDestroy: unbindService");
    }

    private void initview() {
        tv1=(EditText)findViewById(R.id.tv1);
        tv2=(EditText)findViewById(R.id.tv2);
        tv3=(TextView)findViewById(R.id.tv3);
        btnSum=(Button)findViewById(R.id.btnSum);
        btnSum.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                String str1,str2;
                str1=tv1.getText().toString();
                str2=tv2.getText().toString();
                if(str1.length()>0 && str2.length()>0){
                    int data1,data2,result;
                    try{
                        result = maidl.sum(Integer.parseInt(str1),Integer.parseInt(str2));
                        Log.d(TAG, "onClick: result"+result);
                      //  tv3.setText(""+result);  //int to String
                        tv3.setText(String.valueOf(result));//int to String
                    } catch (RemoteException e) {
                        e.printStackTrace();
                    }
                }else{
                    Toast.makeText(getApplicationContext(),"Pls input",Toast.LENGTH_SHORT).show();
                }
            }
        });
    }

    private void bindaidl(){
        Intent intent = new Intent();
        intent.setComponent(new ComponentName("jlsky.myaidl","jlsky.myaidl.SumService"));
        //intent.setAction("jlsky.myaidl.SumService"); //it is failed for here !
        boolean b = bindService(intent,conn,BIND_AUTO_CREATE);
        if(b){
            Log.d(TAG, "bindaidl: ok");
        }else{
            Log.d(TAG, "bindaidl: fault");
        }
    }

    private ServiceConnection conn = new ServiceConnection(){
 //   private class Conn implements ServiceConnection{
        @Override
        public void onServiceConnected(ComponentName name, IBinder iBinder){
            maidl = IMaidl.Stub.asInterface(iBinder);
            Log.d(TAG, "onServiceConnected: aidl");
        }
        @Override
        public void onServiceDisconnected(ComponentName name){
            maidl=null;
            Log.d(TAG, "onServiceDisconnected: aidl");
        }
    };
}

manifest中的定义如下

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="jlsky.myaidl">
    <application   ...>
        <service
            android:name=".SumService"
            android:enabled="true"
            android:exported="true"
            android:process=":sum">
            <intent-filter>
                <action android:name="jlsky.myaidl"></action>//用来启动服务
            </intent-filter>
        </service>
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>
这个定义是让service单独作为一个进程（不是线程）。省略包名的默认写法。定义为私有线程，这与以点作为分割的公有线程不同。

android:process=":sum"
贴出来的代码都是反复实验的结果。有些测试由于记不住了是怎么回事，以免误导，就不写说明了。

多进程通讯笔记 android aidl