AIDL源码解析in、out和inout

为什么会想写这篇文章，只因为一个error idl.exe E 4928 5836 type_namespace.cpp:130] 'Book' can be an out type, so you must declare it as in, out or inout. 看过上一篇文章Android：IPC之AIDL的学习和总结的同学都知道这是因为在AIDL文件中使用非常规类型作为参数传递的时候没有标记指向tag。

介绍

官网介绍AIDL的时候上有这么一段话

All non-primitive parameters require a directional tag indicating which way the data goes. Either in, out, or inout (see the example below).

Primitives are in by default, and cannot be otherwise.

Caution: You should limit the direction to what is truly needed, because marshalling parameters is expensive.

大概意思是非默认类型的参数都需要添加指向标签in，out或inout。根据自己的需求去添加，因为实现是有代价的。

已知结论

看过Android：IPC之AIDL的学习和总结的同学都知道：

in表示输入型参数（Server可以获取到Client传递过去的数据，但是不能对Client端的数据进行修改）

out表示输出型参数（Server获取不到Client传递过去的数据，但是能对Client端的数据进行修改）

inout表示输入输出型参数（Server可以获取到Client传递过去的数据，但是能对Client端的数据进行修改）。

提出问题

下边我们就研究一个in，out或inout为什么能代表不同的传输方式，为什么实现的代价不一样。

过程验证

创建Book.aidl文件

package com.tzx.aidldemo.aidl;parcelable Book;

创建Book.java文件

package com.tzx.aidldemo.aidl;public class Book implements Parcelable {    public int bookId;    public String bookName;    public Book() {    }    public Book(int bookId, String bookName) {        this.bookId = bookId;        this.bookName = bookName;    }    //从序列化后的对象中创建原始对象    protected Book(Parcel in) {        bookId = in.readInt();        bookName = in.readString();    }    public static final Creator CREATOR = new Creator() {        //从序列化后的对象中创建原始对象        @Override        public Book createFromParcel(Parcel in) {            return new Book(in);        }        //指定长度的原始对象数组        @Override        public Book[] newArray(int size) {            return new Book[size];        }    };    //返回当前对象的内容描述。如果含有文件描述符，返回1，否则返回0，几乎所有情况都返回0    @Override    public int describeContents() {        return 0;    }    //将当前对象写入序列化结构中，其flags标识有两种（1|0）。    //为1时标识当前对象需要作为返回值返回，不能立即释放资源，几乎所有情况下都为0.    @Override    public void writeToParcel(Parcel dest, int flags) {        dest.writeInt(bookId);        dest.writeString(bookName);    }    @Override    public String toString() {        return "[bookId=" + bookId + ",bookName='" + bookName + "']";    }}

创建aidl接口文件IBookManager.aidl文件

package com.tzx.aidlinout.aidl;import com.tzx.aidlinout.aidl.Book;interface IBookManager {    Book addInBook(in Book book);    Book addOutBook(out Book book);    Book addInoutBook(inout Book book);}

创建远程服务

//将bookId都改为-1，在bookName后面都添加参数的tag标记public class BookManagerService extends Service {    private CopyOnWriteArrayList list = new CopyOnWriteArrayList();    private IBinder mBinder = new IBookManager.Stub(){        @Override        public Book addInBook(Book book) throws RemoteException {            book.bookId = -1;            book.bookName = book.bookName + "-in";            list.add(book);            return book;        }        @Override        public Book addOutBook(Book book) throws RemoteException {            book.bookId = -1;            book.bookName = book.bookName + "-out";            list.add(book);            return book;        }        @Override        public Book addInoutBook(Book book) throws RemoteException {            book.bookId = -1;            book.bookName = book.bookName + "-inout";            list.add(book);            return book;        }        @Override        public List getBookList() throws RemoteException {            return list;        }    };    @Nullable    @Override    public IBinder onBind(Intent intent) {        return mBinder;    }}

在创建上面的文件的过程中，遇到不太清楚的或者编译出现Error的，可以参考Android：IPC之AIDL的学习和总结。

具体方法调用的Activity就不写全部代码了，我们看看三种方法的调用

@Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.book_in:                try {                    int bookId = Integer.parseInt(bookIdET.getText().toString());                    String bookName = bookNameET.getText().toString();                    if (bookId <= 0 || TextUtils.isEmpty(bookName)) return;                    StringBuilder builder = new StringBuilder();                    //LogUtils.d("-----------book_in-----------------");                    Book book0 = new Book(bookId, bookName);                    String source = "source:" + book0.toString();                    //LogUtils.d(source);                    builder.append(source);                    builder.append('\n');                    String result = "result:" + bookManager.addInBook(book0).toString();                    //LogUtils.d(result);                    builder.append(result);                    builder.append('\n');                    source = "source" + book0.toString();                    //LogUtils.d(source);                    builder.append(source);                    //LogUtils.d("**************book_in****************");                    bookinfoTV.setText(builder.toString());                } catch (Exception e) {                    e.printStackTrace();                }                break;            case R.id.book_out:                try {                    int bookId = Integer.parseInt(bookIdET.getText().toString());                    String bookName = bookNameET.getText().toString();                    if (bookId <= 0 || TextUtils.isEmpty(bookName)) return;                    StringBuilder builder = new StringBuilder();                    //LogUtils.d("-----------book_out-----------------");                    Book book0 = new Book(bookId, bookName);                    String source = "source:" + book0.toString();                    //LogUtils.d(source);                    builder.append(source);                    builder.append('\n');                    String result = "result:" + bookManager.addOutBook(book0).toString();                    //LogUtils.d(result);                    builder.append(result);                    builder.append('\n');                    source = "source" + book0.toString();                    //LogUtils.d(source);                    builder.append(source);                    //LogUtils.d("**************book_out****************");                    bookinfoTV.setText(builder.toString());                } catch (Exception e) {                    e.printStackTrace();                }                break;            case R.id.book_inout:                try {                    int bookId = Integer.parseInt(bookIdET.getText().toString());                    String bookName = bookNameET.getText().toString();                    if (bookId <= 0 || TextUtils.isEmpty(bookName)) return;                    StringBuilder builder = new StringBuilder();                    //LogUtils.d("-----------book_inout-----------------");                    Book book0 = new Book(bookId, bookName);                    String source = "source:" + book0.toString();                    //LogUtils.d(source);                    builder.append(source);                    builder.append('\n');                    String result = "result:" + bookManager.addInoutBook(book0).toString();                    //LogUtils.d(result);                    builder.append(result);                    builder.append('\n');                    source = "source" + book0.toString();                    //LogUtils.d(source);                    builder.append(source);                    //LogUtils.d("**************book_inout****************");                    bookinfoTV.setText(builder.toString());                } catch (Exception e) {                    e.printStackTrace();                }                break;        }    }

创建好上面三个文件后，我们编译整个项目工程（PS：生成aidl接口实现类）。

运行结果

下边是与结果相对应的Log输出

14962-14962/com.tzx.aidlinout D/xxx: -----------book_in-----------------14962-14962/com.tzx.aidlinout D/xxx: source:[bookId=1212,bookName=C++]14962-14962/com.tzx.aidlinout D/xxx: result:[bookId=-1,bookName=C++-in]14962-14962/com.tzx.aidlinout D/xxx: source[bookId=1212,bookName=C++]14962-14962/com.tzx.aidlinout D/xxx: **************book_in****************14962-14962/com.tzx.aidlinout D/xxx: -----------book_out-----------------14962-14962/com.tzx.aidlinout D/xxx: source:[bookId=1212,bookName=C++]14962-14962/com.tzx.aidlinout D/xxx: result:[bookId=-1,bookName=null-out]14962-14962/com.tzx.aidlinout D/xxx: source[bookId=-1,bookName=null-out]14962-14962/com.tzx.aidlinout D/xxx: **************book_out****************14962-14962/com.tzx.aidlinout D/xxx: -----------book_inout-----------------14962-14962/com.tzx.aidlinout D/xxx: source:[bookId=1212,bookName=C++]14962-14962/com.tzx.aidlinout D/xxx: result:[bookId=-1,bookName=C++-inout]14962-14962/com.tzx.aidlinout D/xxx: source[bookId=-1,bookName=C++-inout]14962-14962/com.tzx.aidlinout D/xxx: **************book_inout****************

实际结果与我们已知结论一致~！~！

但问题我们还没有解决，我们继续看代码，其实所有的实现都是在改接口实现类中IBookManager.java

package com.tzx.aidlinout.aidl;public interface IBookManager extends android.os.IInterface {    public com.tzx.aidlinout.aidl.Book addInBook(        com.tzx.aidlinout.aidl.Book book) throws android.os.RemoteException;    public com.tzx.aidlinout.aidl.Book addOutBook(        com.tzx.aidlinout.aidl.Book book) throws android.os.RemoteException;    public com.tzx.aidlinout.aidl.Book addInoutBook(        com.tzx.aidlinout.aidl.Book book) throws android.os.RemoteException;    public java.util.List getBookList()        throws android.os.RemoteException;    /** Local-side IPC implementation stub class. */    public static abstract class Stub extends android.os.Binder implements com.tzx.aidlinout.aidl.IBookManager {        private static final java.lang.String DESCRIPTOR = "com.tzx.aidlinout.aidl.IBookManager";        static final int TRANSACTION_addInBook = (android.os.IBinder.FIRST_CALL_TRANSACTION +            0);        static final int TRANSACTION_addOutBook = (android.os.IBinder.FIRST_CALL_TRANSACTION +            1);        static final int TRANSACTION_addInoutBook = (android.os.IBinder.FIRST_CALL_TRANSACTION +            2);        static final int TRANSACTION_getBookList = (android.os.IBinder.FIRST_CALL_TRANSACTION +            3);        /** Construct the stub at attach it to the interface. */        public Stub() {            this.attachInterface(this, DESCRIPTOR);        }        /**         * Cast an IBinder object into an com.tzx.aidlinout.aidl.IBookManager interface,         * generating a proxy if needed.         */        public static com.tzx.aidlinout.aidl.IBookManager asInterface(            android.os.IBinder obj) {            if ((obj == null)) {                return null;            }            android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);            if (((iin != null) &&                    (iin instanceof com.tzx.aidlinout.aidl.IBookManager))) {                return ((com.tzx.aidlinout.aidl.IBookManager) iin);            }            return new com.tzx.aidlinout.aidl.IBookManager.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_addInBook: {                data.enforceInterface(DESCRIPTOR);                //声明输入的参数_arg0的引用                com.tzx.aidlinout.aidl.Book _arg0;                //并根据输入的数据为其创建对象                if ((0 != data.readInt())) {                    _arg0 = com.tzx.aidlinout.aidl.Book.CREATOR.createFromParcel(data);                } else {                    _arg0 = null;                }                //获取调用this.addInBook方法返回的_result                com.tzx.aidlinout.aidl.Book _result = this.addInBook(_arg0);                reply.writeNoException();                //并向reply中写入返回值_result                if ((_result != null)) {                    reply.writeInt(1);                    _result.writeToParcel(reply,                        android.os.Parcelable.PARCELABLE_WRITE_RETURN_VALUE);                } else {                    reply.writeInt(0);                }                return true;            }            case TRANSACTION_addOutBook: {                data.enforceInterface(DESCRIPTOR);                //声明输入的参数_arg0的引用                com.tzx.aidlinout.aidl.Book _arg0;                //并为其创建新的对象                _arg0 = new com.tzx.aidlinout.aidl.Book();                //获取调用this.addOutBook方法返回的_result                com.tzx.aidlinout.aidl.Book _result = this.addOutBook(_arg0);                reply.writeNoException();                //并向reply中写入返回值_result                if ((_result != null)) {                    reply.writeInt(1);                    _result.writeToParcel(reply,                        android.os.Parcelable.PARCELABLE_WRITE_RETURN_VALUE);                } else {                    reply.writeInt(0);                }                //再将参数_arg0写入reply中，至于为什么写入，我们看看客户端Proxy中的读取                if ((_arg0 != null)) {                    reply.writeInt(1);                    _arg0.writeToParcel(reply,                        android.os.Parcelable.PARCELABLE_WRITE_RETURN_VALUE);                } else {                    reply.writeInt(0);                }                return true;            }            case TRANSACTION_addInoutBook: {                data.enforceInterface(DESCRIPTOR);                //声明输入的参数_arg0的引用                com.tzx.aidlinout.aidl.Book _arg0;                //并根据输入的数据为其创建对象                if ((0 != data.readInt())) {                    _arg0 = com.tzx.aidlinout.aidl.Book.CREATOR.createFromParcel(data);                } else {                    _arg0 = null;                }                //获取调用this.addInoutBook方法返回的_result                com.tzx.aidlinout.aidl.Book _result = this.addInoutBook(_arg0);                reply.writeNoException();                //并向reply中写入返回值_result                if ((_result != null)) {                    reply.writeInt(1);                    _result.writeToParcel(reply,                        android.os.Parcelable.PARCELABLE_WRITE_RETURN_VALUE);                } else {                    reply.writeInt(0);                }                //再将参数_arg0写入reply中，至于为什么写入，我们看看客户端Proxy中的读取                if ((_arg0 != null)) {                    reply.writeInt(1);                    _arg0.writeToParcel(reply,                        android.os.Parcelable.PARCELABLE_WRITE_RETURN_VALUE);                } else {                    reply.writeInt(0);                }                return true;            }            case TRANSACTION_getBookList: {                data.enforceInterface(DESCRIPTOR);                java.util.List _result = this.getBookList();                reply.writeNoException();                reply.writeTypedList(_result);                return true;            }            }            return super.onTransact(code, data, reply, flags);        }        private static class Proxy implements com.tzx.aidlinout.aidl.IBookManager {            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.tzx.aidlinout.aidl.Book addInBook(                com.tzx.aidlinout.aidl.Book book)                throws android.os.RemoteException {                android.os.Parcel _data = android.os.Parcel.obtain();                android.os.Parcel _reply = android.os.Parcel.obtain();                com.tzx.aidlinout.aidl.Book _result;                try {                    _data.writeInterfaceToken(DESCRIPTOR);                    //将客户端调用时传入的参数写入_data中                    if ((book != null)) {                        _data.writeInt(1);                        book.writeToParcel(_data, 0);                    } else {                        _data.writeInt(0);                    }                    //将_data、_reply序列化对象和Stub.TRANSACTION_addInBook指令传递到Server端                    mRemote.transact(Stub.TRANSACTION_addInBook, _data, _reply,                        0);                    _reply.readException();                    //读取Server端返回的序列化_reply中的对象                    if ((0 != _reply.readInt())) {                        _result = com.tzx.aidlinout.aidl.Book.CREATOR.createFromParcel(_reply);                    } else {                        _result = null;                    }                    //然后直接将_result返回                    //我们发现整个方法调用期间传入的对象book只是将数据写入到Server，它的值进行并没有任何修改。                    //总结：in类型的参数，它向服务端传入数据，但是却不接受Server返回的值。                } finally {                    _reply.recycle();                    _data.recycle();                }                return _result;            }            @Override            public com.tzx.aidlinout.aidl.Book addOutBook(                com.tzx.aidlinout.aidl.Book book)                throws android.os.RemoteException {                android.os.Parcel _data = android.os.Parcel.obtain();                android.os.Parcel _reply = android.os.Parcel.obtain();                com.tzx.aidlinout.aidl.Book _result;                try {                    _data.writeInterfaceToken(DESCRIPTOR);                    //将_data、_reply序列化对象和Stub.TRANSACTION_addInBook指令传递到Server端                    //_data和_reply序列化对象并没有进行写入                    mRemote.transact(Stub.TRANSACTION_addOutBook, _data,                        _reply, 0);                    _reply.readException();                    //读取Server端返回的序列化_reply中的对象，写入到_result                    if ((0 != _reply.readInt())) {                        _result = com.tzx.aidlinout.aidl.Book.CREATOR.createFromParcel(_reply);                    } else {                        _result = null;                    }                    //读取Server端返回的序列化_reply中的对象，写入到传入的book对象中                    if ((0 != _reply.readInt())) {                        book.readFromParcel(_reply);                    }                    //然后直接将_result返回                    //我们发现整个方法调用期间传入的对象book并没有将数据写入到Server，它的值确实是Server返回的。                    //总结：out类型的参数，它并不向服务端传入数据，但是却接受Server返回的值。                } finally {                    _reply.recycle();                    _data.recycle();                }                return _result;            }            @Override            public com.tzx.aidlinout.aidl.Book addInoutBook(                com.tzx.aidlinout.aidl.Book book)                throws android.os.RemoteException {                android.os.Parcel _data = android.os.Parcel.obtain();                android.os.Parcel _reply = android.os.Parcel.obtain();                com.tzx.aidlinout.aidl.Book _result;                try {                    _data.writeInterfaceToken(DESCRIPTOR);                    //将客户端调用时传入的参数写入_data中                    if ((book != null)) {                        _data.writeInt(1);                        book.writeToParcel(_data, 0);                    } else {                        _data.writeInt(0);                    }                    //将_data、_reply序列化对象和Stub.TRANSACTION_addInoutBook指令传递到Server端                    mRemote.transact(Stub.TRANSACTION_addInoutBook, _data,                        _reply, 0);                    _reply.readException();                    //读取Server端返回的序列化_reply中的对象，写入到_result                    if ((0 != _reply.readInt())) {                        _result = com.tzx.aidlinout.aidl.Book.CREATOR.createFromParcel(_reply);                    } else {                        _result = null;                    }                    //读取Server端返回的序列化_reply中的对象，写入到传入的book对象中                    if ((0 != _reply.readInt())) {                        book.readFromParcel(_reply);                    }                    //然后直接将_result返回                    //我们发现整个方法调用期间传入的对象book将其数据写入到Server，并且它的值被Server返回的数据修改。                    //总结：inout类型的参数，它既向服务端传入数据，也却接受Server返回的值。                } finally {                    _reply.recycle();                    _data.recycle();                }                return _result;            }            @Override            public java.util.List getBookList()                throws android.os.RemoteException {                android.os.Parcel _data = android.os.Parcel.obtain();                android.os.Parcel _reply = android.os.Parcel.obtain();                java.util.List _result;                try {                    _data.writeInterfaceToken(DESCRIPTOR);                    mRemote.transact(Stub.TRANSACTION_getBookList, _data,                        _reply, 0);                    _reply.readException();                    _result = _reply.createTypedArrayList(com.tzx.aidlinout.aidl.Book.CREATOR);                } finally {                    _reply.recycle();                    _data.recycle();                }                return _result;            }        }    }}

看了这么多代码是不是感觉脑袋大了，没事接下来一张图帮你理的清清楚楚的：

经过两篇文章对aidl的讲解，我想你已经把它理解的透透的了，如果还有什么问题可以给我留言哦~！

GitHubDemo地址

更多文章–>我的个人博客下雨天要逛街

介绍

已知结论

提出问题

过程验证

更多相关文章

随机推荐