Android AIDL跨进程通信

AIDL其实是一个IPC通信机制， 即进程之间也可以相互通信，传递有效数据，那么怎么创建使用呢？第一次创建一整套AIDL还是有点懵逼，而且我们平时不经常使用AIDL，今天记录下创建的整个过程，以备不时之需。

我们知道AIDL是跨进程通信，那么肯定是在两个进程中，我们这里创建两个工程，分别作为server端和client端，整个项目的目录结构如图：

server端：                                                                      client端：

                    

1.AIDL server端的创建：

1.1 Person的创建，实现Parcelable接口，以符合AIDL的传输数据的要求

import android.os.Parcel;
import android.os.Parcelable;

public class Person implements Parcelable{

    private String mUserName;
    private String mUserAge;

    public Person(String userName, String userAge) {
        mUserName = userName;
        mUserAge = userAge;
    }

    public String getmUserName() {
        return mUserName;
    }

    public void setmUserName(String mUserName) {
        this.mUserName = mUserName;
    }

    public String getmUserAge() {
        return mUserAge;
    }

    public void setmUserAge(String mUserAge) {
        this.mUserAge = mUserAge;
    }

    @Override
    public String toString() {
        return super.toString();
    }

    // 这里的读的顺序必须与writeToParcel(Parcel dest, int flags)方法中写的顺序一致
    // 否则数据会有差错
    public Person(Parcel in) {
        mUserName = in.readString();
        mUserAge = in.readString();
    }

    public static final Creator CREATOR = new Creator() {
        // 从Parcel中读取数据
        @Override
        public Person createFromParcel(Parcel in) {
            return new Person(in);
        }

        @Override
        public Person[] newArray(int size) {
            return new Person[size];
        }
    };

    @Override
    public int describeContents() {
        return 0;
    }

    //作用：把值写入Parcel中
    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(mUserAge);
        dest.writeString(mUserAge);
    }
}

1.2 Person对应的AIDL文件 IPersonAidlInterface.aidl

// IPersonAidlInterface.aidl
package com.example.server;

parcelable Person;

1.3 远程通信service的AIDL文件IRomteAidlInterface.aidl

// IRomteAidlInterface.aidl
package com.example.server;
// Declare any non-default types here with import statements
//此处的导包是按需导入

interface IRomteAidlInterface {
    /**
     * Demonstrates some basic types that you can use as parameters
     * and return values in AIDL.
     */
    void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat,
            double aDouble, String aString);

    String getPersonUserName();
    String getPersonUserAge();
}

 创建或修改过AIDL文件后需要clean下工程，使系统及时生成我们需要的文件。注意如果这个AIDL需要使用Person类的话，则需要明确导包，将Person类给import进来，同理，客户端同样需要把Person类给拷贝过去然后进行导包。本例中我们没有使用AIDL不支持的外来类，因此这里就不需要导包操作了。

1.4 远程通信的service创建 RmoteService.java

 接下来需要来创建一个 Service 供客户端远程绑定，这里实现的两个方法就是AIDL接口中的那两个方法的具体实现。

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.RemoteException;
import android.support.annotation.Nullable;

public class RmoteService extends Service{

    private Person mPerson;
    private String mUserName;
    private String mUserAge;

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        mPerson = new Person("buder_mm", "18");
        return new RomteBinder();
    }

    private class RomteBinder extends IRomteAidlInterface.Stub {
        @Override
        public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, String aString) throws RemoteException {

        }

        @Override
        public String getPersonUserName() throws RemoteException {
            mUserName = mPerson.getmUserName();
            return mUserName;
        }

        @Override
        public String getPersonUserAge() throws RemoteException {
            mUserAge = mPerson.getmUserAge();
            return mUserAge;
        }
    }

    @Override
    public boolean onUnbind(Intent intent) {
        return super.onUnbind(intent);
    }
}

1.5 该service对应的AndroidManifest配置文件

2.AIDL client端的创建：

2.1 将server端创建的两个AIDL文件连同文件夹一起拷贝到client端

把服务端的AIDL文件以及Person类复制过来，将 aidl 文件夹整个复制到和Java文件夹同个层级下，需要创建和服务端Person类所在的相同包名来存放 Person类，不需要改动任何代码。创建或修改过AIDL文件后需要clean下工程，使系统及时生成我们需要的文件。 这里我们不需要将Person类复制过来，因为客户端的AIDL没有使用到Person类，如果使用到的话就需要一并粘贴过来。

2.2 client端对服务的连接和请求MainActivity.java

import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.os.IBinder;
import android.os.RemoteException;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.example.server.IRomteAidlInterface;

import java.util.List;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    private static final String BIND_SERVICE_ACTION = "android.intent.action.RESPOND_AIDL_MESSAGE";

    private IRomteAidlInterface iRomteAidlInterface;

    private Button mConnectButton;
    private Button mAcquireButton;

    private String mUsername;
    private String mUserage;

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

    private void initView() {
        mConnectButton = findViewById(R.id.connect);
        mAcquireButton = findViewById(R.id.acquire_info);

        mConnectButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                bindService();
            }
        });

        mAcquireButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (null != iRomteAidlInterface) {
                    try {
                        mUsername = iRomteAidlInterface.getPersonUserName();
                        mUserage = iRomteAidlInterface.getPersonUserAge();
                        Toast.makeText(getApplicationContext(), "mUsername = " + mUsername + ",mUserage = " + mUserage, Toast.LENGTH_SHORT).show();
                    } catch (RemoteException e) {
                        e.printStackTrace();
                    }
                }
            }
        });
    }

    ServiceConnection serviceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            iRomteAidlInterface = IRomteAidlInterface.Stub.asInterface(service);
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            iRomteAidlInterface = null;
        }
    };

    private void bindService() {
        Intent intent = new Intent();
        intent.setAction(BIND_SERVICE_ACTION);
        final Intent newIntent = new Intent(achieveExplicitFromImplicitIntent(this, intent));
        bindService(newIntent, serviceConnection, Context.BIND_AUTO_CREATE);
    }

    private Intent achieveExplicitFromImplicitIntent(Context context, Intent implicitIntent) {
        // Retrieve all services that can match the given intent
        PackageManager pm = context.getPackageManager();
        List resolveInfo = pm.queryIntentServices(implicitIntent, 0);

        // Make sure only one match was found
        if (resolveInfo == null || resolveInfo.size() != 1) {
            return null;
        }

        // Get component info and create ComponentName
        ResolveInfo serviceInfo = resolveInfo.get(0);
        String packageName = serviceInfo.serviceInfo.packageName;
        String className = serviceInfo.serviceInfo.name;
        ComponentName component = new ComponentName(packageName, className);

        Intent explicitIntent = new Intent(implicitIntent);

        explicitIntent.setComponent(component);
        return explicitIntent;
    }

    private void unBindService() {
        unbindService(serviceConnection);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unBindService();
    }
}

 客户端绑定service的方法里面需要注意， 这个方法achieveExplicitFromImplicitIntent是为了显示跨进程启动service，这里需要设置远程service的包名和service名，如果不设置的话，将无法启动远程service，将会报 Service Intent must be explicit: Intent { act=android.intent.action.RESPOND_AIDL_MESSAGE } 详见 https://blog.csdn.net/cpcpcp123/article/details/90205693

2.3 server端没有界面，client端对应的界面 activity_main.xml

demo参考：https://www.jianshu.com/p/83bdeac67ee7

上面两个项目已上传到git上，可以对比查看：

server端：https://github.com/buder-cp/base_component_learn/tree/master/server

client端：https://github.com/buder-cp/base_component_learn/tree/master/client

更多的例子可以参考：https://github.com/buder-cp/IPCSamples