先上流程图
我们先来看看编写的aidl文件编译器为我们自动生成的.java类都有哪些元素分别代表什么意思
DESCRIPTOR
Binder的唯一标识,一般用当前Binder的类名表示,比如本例中的"test.sym.com.myapplication.IBookManager"
asInterface(android.os.IBinder obj)
用于将服务器端的Binder对象转换成客户端所需的AIDL接口类型的对象,这种转换过程是区分进程的,如果客户端和服务端位于同一进程;那么此方法返回的就是服务端的Stub对象本身,否则返回的就是系统封装后的Stub.proxy对象
/**
* Cast an IBinder object into an test.sym.com.myapplication.IBookManager interface,
* generating a proxy if needed.
*/
public static test.sym.com.myapplication.IBookManager asInterface(android.os.IBinder obj) {
if ((obj == null)) {
return null;
}
android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
if (((iin != null) && (iin instanceof test.sym.com.myapplication.IBookManager))) {
return ((test.sym.com.myapplication.IBookManager) iin);
}
return new test.sym.com.myapplication.IBookManager.Stub.Proxy(obj);
}
asBinder
此方法用于返回当前Binder对象
@Override
public android.os.IBinder asBinder() {
return this;
}
onTransact
@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_getBookList: {
data.enforceInterface(DESCRIPTOR);
java.util.List<test.sym.com.myapplication.Book> _result = this.getBookList();
reply.writeNoException();
reply.writeTypedList(_result);
return true;
}
case TRANSACTION_addBook: {
data.enforceInterface(DESCRIPTOR);
test.sym.com.myapplication.Book _arg0;
if ((0 != data.readInt())) {
_arg0 = test.sym.com.myapplication.Book.CREATOR.createFromParcel(data);
} else {
_arg0 = null;
}
this.addBook(_arg0);
reply.writeNoException();
return true;
}
}
return super.onTransact(code, data, reply, flags);
}
- 这个方法运行在服务端中的Binder线程池中
- 当客户端发起跨进程请求时,远程请求会通过系统底层封装后交由此方法来处理。
- 方法原型public boolean onTransact(int code, android.os.Parcel data, android.os.Parcel reply,int flags)
- 服务端通过code可以确定客户端所请求的目标方法是什么
- 接着从data中取出目标方法所需的参数(如果目标方法有参数的话)
- 然后执行目标方法。
- 当目标方法执行完毕后,就向reply中写入返回值(如果目标方法有返回值的话)
- 注意:如果此方法返回false,那么客户端的请求会失败,因此我们可以利用这个特性来做权限验证。
Proxy#getBookList
@Override
public java.util.List<test.sym.com.myapplication.Book> getBookList()
throws android.os.RemoteException {
//创建该方法所需要的输入型Parcel对象_data;
android.os.Parcel _data = android.os.Parcel.obtain();
//输出型Parcel对象_reply
android.os.Parcel _reply = android.os.Parcel.obtain();
//返回值对象List
java.util.List<test.sym.com.myapplication.Book> _result;
try {
_data.writeInterfaceToken(DESCRIPTOR);
//调用transact方法发起RPC(远程过程调用)请求
mRemote.transact(Stub.TRANSACTION_getBookList, _data, _reply, 0);
//同时当前线程挂起
//然后服务端的onTransact方法会被调用,直到RPC过程返回,当前线程继续执行
_reply.readException();
//从_reply中取出RPC过程中返回的结果
_result = _reply.createTypedArrayList(test.sym.com.myapplication.Book.CREATOR);
} finally {
_reply.recycle();
_data.recycle();
}
//返回_reply中的数据
return _result;
}
Proxy#addBook
这个方法运行在客户端,它的执行过程和getBookList是一样的,addBook没有返回值,所以它不需要从_reply中取出返回值
注意:
1. 当客户端发起远程请求时,由于当前线程会被挂起直至服务器端进程返回数据,所以如果一个远程方法是很耗时的,那么不能在UI线程中发起此远程请求
2. 由于服务器端的Binder方法运行在Binder的线程池中,随意Binder方法不管是否耗时都应该采用同步的方法去实现,因为它已经运行在一个线程中了。
源码:
/*
* This file is auto-generated. DO NOT MODIFY.
* Original file: /Users/sym/project/app/src/main/aidl/test/sym/com/myapplication/IBookManager.aidl
*/
package test.sym.com.myapplication;
// Declare any non-default types here with import statements
public interface IBookManager extends android.os.IInterface {
/** Local-side IPC implementation stub class. */
public static abstract class Stub extends android.os.Binder implements
test.sym.com.myapplication.IBookManager {
private static final java.lang.String DESCRIPTOR =
"test.sym.com.myapplication.IBookManager";
/** Construct the stub at attach it to the interface. */
public Stub() {
this.attachInterface(this, DESCRIPTOR);
}
/**
* Cast an IBinder object into an test.sym.com.myapplication.IBookManager interface,
* generating a proxy if needed.
*/
public static test.sym.com.myapplication.IBookManager asInterface(android.os.IBinder obj) {
if ((obj == null)) {
return null;
}
android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
if (((iin != null) && (iin instanceof test.sym.com.myapplication.IBookManager))) {
return ((test.sym.com.myapplication.IBookManager) iin);
}
return new test.sym.com.myapplication.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_getBookList: {
data.enforceInterface(DESCRIPTOR);
java.util.List<test.sym.com.myapplication.Book> _result = this.getBookList();
reply.writeNoException();
reply.writeTypedList(_result);
return true;
}
case TRANSACTION_addBook: {
data.enforceInterface(DESCRIPTOR);
test.sym.com.myapplication.Book _arg0;
if ((0 != data.readInt())) {
_arg0 = test.sym.com.myapplication.Book.CREATOR.createFromParcel(data);
} else {
_arg0 = null;
}
this.addBook(_arg0);
reply.writeNoException();
return true;
}
}
return super.onTransact(code, data, reply, flags);
}
private static class Proxy implements test.sym.com.myapplication.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 java.util.List<test.sym.com.myapplication.Book> getBookList()
throws android.os.RemoteException {
//创建该方法所需要的输入型Parcel对象_data;
android.os.Parcel _data = android.os.Parcel.obtain();
//输出型Parcel对象_reply
android.os.Parcel _reply = android.os.Parcel.obtain();
//返回值对象List
java.util.List<test.sym.com.myapplication.Book> _result;
try {
_data.writeInterfaceToken(DESCRIPTOR);
//调用transact方法发起RPC(远程过程调用)请求
mRemote.transact(Stub.TRANSACTION_getBookList, _data, _reply, 0);
//同时当前线程挂起
//然后服务端的onTransact方法会被调用,直到RPC过程返回,当前线程继续执行
_reply.readException();
//从_reply中取出RPC过程中返回的结果
_result = _reply.createTypedArrayList(test.sym.com.myapplication.Book.CREATOR);
} finally {
_reply.recycle();
_data.recycle();
}
//返回_reply中的数据
return _result;
}
@Override
public void addBook(test.sym.com.myapplication.Book book)
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 ((book != null)) {
_data.writeInt(1);
book.writeToParcel(_data, 0);
} else {
_data.writeInt(0);
}
mRemote.transact(Stub.TRANSACTION_addBook, _data, _reply, 0);
_reply.readException();
} finally {
_reply.recycle();
_data.recycle();
}
}
}
static final int TRANSACTION_getBookList = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
static final int TRANSACTION_addBook = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);
}
public java.util.List<test.sym.com.myapplication.Book> getBookList()
throws android.os.RemoteException;
public void addBook(test.sym.com.myapplication.Book book) throws android.os.RemoteException;
}