[Android]从一个简单的AIDL实现看binder原理（一）简单的AIDL实现

参考链接：

从一个简单的AIDL实现看binder原理（一）简单的AIDL实现
 从一个简单的AIDL实现看binder原理（二）bindService的调用过程
 从一个简单的AIDL实现看binder原理（三）bindService调用过程中Binder的传递
 从一个简单的AIDL实现看binder原理（四）bindService调用过程中Binder的写入
 从一个简单的AIDL实现看binder原理（五）bindService调用过程中Binder的转换
 从一个简单的AIDL实现看binder原理（六）Android系统中Binder的运行
 从一个简单的AIDL实现看binder原理（七）Binder的一次拷贝和内存限制

首先在main目录下新建aidl文件夹，如下图所示：

aild1.png

然后在java文件夹中创建Model类,需实现Parcelable接口：

package org.hrcy.ipctest;

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

public class Student implements Parcelable {
    private int code;
    private String name;

    public Student(int code, String name) {
        this.code = code;
        this.name = name;
    }

    protected Student(Parcel in) {
        code = in.readInt();
        name = in.readString();
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getName() {
        return name;
    }

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

    public static final Creator<Student> CREATOR = new Creator<Student>() {
        @Override
        public Student createFromParcel(Parcel in) {
            return new Student(in);
        }

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

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

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInt(code);
        dest.writeString(name);
    }
}

接下来在aidl文件夹中创建aidl文件,名字随意，创建后长这样：

// IAIDLInterface.aidl
package org.hrcy.ipctest;

// Declare any non-default types here with import statements

interface IAIDLInterface {
    /**
     * 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);
}

其中basicTypes方法表明了AIDL过程支持的基本数据类型，用不到删除即可

需要注意的是，如果在AIDL文件中使用了自定义的Parcelable类型，则需要在aidl文件夹中定义一个和这个类型同名的aidl文件，并表明该类型为parcelable,代码如下：

//Student.aild
package org.hrcy.ipctest;

parcelable Student;

需要注意，package 需要与自定义类型的package一致

接下来，在IAIDLInterface文件中手动导入Student类型并定义我们在跨进程通信时所需要的方法：

// IAIDLInterface.aidl
package org.hrcy.ipctest;

// Declare any non-default types here with import statements
import org.hrcy.ipctest.Student;

interface IAIDLInterface {
    List<Student> getStudent();
    void setStudent(in Student student);
}

除了基本类型数据，其它类型的参数必须标上方向：in、out、inout。in 表示输入；out 表示输出；inout 表示输入输出型的参数，注意按需使用，因为 out 以及 inout 在底层实现是需要一定开销的。

完成之后点击菜单中Build -> Make Project 选项

image.png

在Make过程完成之后，会根据定义的aidl文件自动生成所需的java类，路径如下：

image.png

我们看一下IAIDLInterface的代码：

/*
 * This file is auto-generated.  DO NOT MODIFY.
 */
package org.hrcy.ipctest;

public interface IAIDLInterface extends android.os.IInterface {
    /**
     * Local-side IPC implementation stub class.
     */
    public static abstract class Stub extends android.os.Binder implements org.hrcy.ipctest.IAIDLInterface {
        private static final java.lang.String DESCRIPTOR = "org.hrcy.ipctest.IAIDLInterface";

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

        /**
         * Cast an IBinder object into an org.hrcy.ipctest.IAIDLInterface interface,
         * generating a proxy if needed.
         */
        public static org.hrcy.ipctest.IAIDLInterface asInterface(android.os.IBinder obj) {
            if ((obj == null)) {
                return null;
            }
            android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
            if (((iin != null) && (iin instanceof org.hrcy.ipctest.IAIDLInterface))) {
                return ((org.hrcy.ipctest.IAIDLInterface) iin);
            }
            return new org.hrcy.ipctest.IAIDLInterface.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 {
            java.lang.String descriptor = DESCRIPTOR;
            switch (code) {
                case INTERFACE_TRANSACTION: {
                    reply.writeString(descriptor);
                    return true;
                }
                case TRANSACTION_getStudent: {
                    data.enforceInterface(descriptor);
                    java.util.List<org.hrcy.ipctest.Student> _result = this.getStudent();
                    reply.writeNoException();
                    reply.writeTypedList(_result);
                    return true;
                }
                case TRANSACTION_setStudent: {
                    data.enforceInterface(descriptor);
                    org.hrcy.ipctest.Student _arg0;
                    if ((0 != data.readInt())) {
                        _arg0 = org.hrcy.ipctest.Student.CREATOR.createFromParcel(data);
                    } else {
                        _arg0 = null;
                    }
                    this.setStudent(_arg0);
                    reply.writeNoException();
                    return true;
                }
                default: {
                    return super.onTransact(code, data, reply, flags);
                }
            }
        }

        private static class Proxy implements org.hrcy.ipctest.IAIDLInterface {
            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 java.util.List<org.hrcy.ipctest.Student> getStudent() throws android.os.RemoteException {
                android.os.Parcel _data = android.os.Parcel.obtain();
                android.os.Parcel _reply = android.os.Parcel.obtain();
                java.util.List<org.hrcy.ipctest.Student> _result;
                try {
                    _data.writeInterfaceToken(DESCRIPTOR);
                    mRemote.transact(Stub.TRANSACTION_getStudent, _data, _reply, 0);
                    _reply.readException();
                    _result = _reply.createTypedArrayList(org.hrcy.ipctest.Student.CREATOR);
                } finally {
                    _reply.recycle();
                    _data.recycle();
                }
                return _result;
            }

            @Override
            public void setStudent(org.hrcy.ipctest.Student student) throws android.os.RemoteException {
                android.os.Parcel _data = android.os.Parcel.obtain();
                android.os.Parcel _reply = android.os.Parcel.obtain();
                try {
                    _data.writeInterfaceToken(DESCRIPTOR);
                    if ((student != null)) {
                        _data.writeInt(1);
                        student.writeToParcel(_data, 0);
                    } else {
                        _data.writeInt(0);
                    }
                    mRemote.transact(Stub.TRANSACTION_setStudent, _data, _reply, 0);
                    _reply.readException();
                } finally {
                    _reply.recycle();
                    _data.recycle();
                }
            }
        }

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

    public java.util.List<org.hrcy.ipctest.Student> getStudent() throws android.os.RemoteException;

    public void setStudent(org.hrcy.ipctest.Student student) throws android.os.RemoteException;
}

接下来创建一个Service，注意要在AndroidManifest文件中标明Service的进程为不同进程：

<service android:name=".RemoteService"
            android:process=":remote"/>

process的值随意。

Service的代码如下：

package org.hrcy.ipctest;

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

import java.util.ArrayList;
import java.util.List;

import androidx.annotation.Nullable;

public class RemoteService extends Service {

    private List<Student> studentList = new ArrayList<>();

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

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

    IAIDLInterface.Stub stub = new IAIDLInterface.Stub() {
        @Override
        public List<Student> getStudent() throws RemoteException {
            return studentList;
        }

        @Override
        public void setStudent(Student student) throws RemoteException {
            studentList.add(student);
        }
    };
}

再看一下Activity的代码：

package org.hrcy.ipctest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.os.RemoteException;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.util.List;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private Button startBtn;
    private EditText codeEt;
    private EditText nameEt;
    private Button addBtn;
    private Button getBtn;
    private TextView studentListText;
    private IAIDLInterface proxy;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        startBtn = findViewById(R.id.btn_start);
        codeEt = findViewById(R.id.et_code);
        nameEt = findViewById(R.id.et_name);
        addBtn = findViewById(R.id.btn_add);
        getBtn = findViewById(R.id.btn_get);
        studentListText = findViewById(R.id.text_student_list);
        initListener();
    }

    private void initListener() {
        startBtn.setOnClickListener(this);
        addBtn.setOnClickListener(this);
        getBtn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btn_start:
                bindService(new Intent(this, RemoteService.class), connection, BIND_AUTO_CREATE);
                break;

            case R.id.btn_add:
                int code = Integer.valueOf(codeEt.getText().toString().trim());
                String name = nameEt.getText().toString().trim();
                try {
                    proxy.setStudent(new Student(code, name));
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
                break;

            case R.id.btn_get:
                try {
                    List<Student> students = proxy.getStudent();
                    if (students != null && students.size() > 0) {
                        StringBuilder sb = new StringBuilder();
                        for (Student student : students) {
                            sb.append(student.toString());
                            sb.append("\n");
                        }
                        studentListText.setText(sb.toString());
                    }
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
                break;

            default:
                break;
        }
    }

    ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            proxy = IAIDLInterface.Stub.asInterface(service);
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };
}

至此，一个简单的AIDL实现过程就完成了

运行效果：

效果

代码地址
AIDL demo
https://github.com/zylsdut/IpcTest