Aidl和Binder解析
先上实例代码：
service:
public class AidlService extends Service{
@Override
public IBinder onBind(Intent arg0) {
/*return new AIDLTest.Stub() {
@Override
public String hello(String name) throws RemoteException {
// TODO Auto-generated method stub
return "hello"+name;
}
};*/
return mBinder;
}
//一个类，继承了Binder，那么它的对象就可以被远程的进程使用了(前提是远程进程获取了这个类的对象【对象的引用】
private final AIDLTest.Stub mBinder = new AIDLTest.Stub() {
@Override
public String hello(String name) throws RemoteException {
// TODO Auto-generated method stub
return "hello"+name;
}
};
@Override
public IBinder onBind(Intent arg0) {
/*return new AIDLTest.Stub() {
@Override
public String hello(String name) throws RemoteException {
// TODO Auto-generated method stub
return "hello"+name;
}
};*/
return mBinder;
}
//一个类，继承了Binder，那么它的对象就可以被远程的进程使用了(前提是远程进程获取了这个类的对象【对象的引用】
private final AIDLTest.Stub mBinder = new AIDLTest.Stub() {
@Override
public String hello(String name) throws RemoteException {
// TODO Auto-generated method stub
return "hello"+name;
}
};
client:
Intent intent = new Intent();
intent.setPackage("包名");
context.bindService(intent, serviceConnection,Context.BIND_AUTO_CREATE);
private ServiceConnection serviceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Log.d(TAG, "++++++ onServiceConnected: success ++++++");
AIDLTest vasInterface = AIDLTest.Stub.asInterface(service);
}
@Override
public void onServiceDisconnected(ComponentName name) {
vasInterface = null;
}
};
vasInterface.hello("aaaaaaaa");
解析：
最主要的部分是AS自动生成的AIDLTest文件：
/* * This file is auto-generated. DO NOT MODIFY. * Original file: F:\\Project\\Practice\\FrameworkDemo\\app\\src\\main\\aidl\\com\\example\\admin\\frameworkdemo\\AIDLTest.aidl */ package com.example.admin.frameworkdemo; public interface AIDLTest extends android.os.IInterface { /** * Local-side IPC implementation stub class. */ public static abstract class Stub extends android.os.Binder implements com.example.admin.frameworkdemo.AIDLTest { private static final java.lang.String DESCRIPTOR = "com.example.admin.frameworkdemo.AIDLTest"; /** * Construct the stub at attach it to the interface. */ public Stub() { this.attachInterface(this, DESCRIPTOR); } /** * Cast an IBinder object into an com.example.admin.frameworkdemo.AIDLTest interface, * generating a proxy if needed. */ public static com.example.admin.frameworkdemo.AIDLTest asInterface(android.os.IBinder obj) { if ((obj == null)) { return null; } android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR); if (((iin != null) && (iin instanceof com.example.admin.frameworkdemo.AIDLTest))) { return ((com.example.admin.frameworkdemo.AIDLTest) iin); } return new com.example.admin.frameworkdemo.AIDLTest.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_hello: { data.enforceInterface(DESCRIPTOR); java.lang.String _arg0; _arg0 = data.readString(); java.lang.String _result = this.hello(_arg0); reply.writeNoException(); reply.writeString(_result); return true; } } return super.onTransact(code, data, reply, flags); } private static class Proxy implements com.example.admin.frameworkdemo.AIDLTest { 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.lang.String hello(java.lang.String name) throws android.os.RemoteException { android.os.Parcel _data = android.os.Parcel.obtain(); android.os.Parcel _reply = android.os.Parcel.obtain(); java.lang.String _result; try { _data.writeInterfaceToken(DESCRIPTOR); _data.writeString(name); mRemote.transact(Stub.TRANSACTION_hello, _data, _reply, 0); _reply.readException(); _result = _reply.readString(); } finally { _reply.recycle(); _data.recycle(); } return _result; } } static final int TRANSACTION_hello = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0); } public java.lang.String hello(java.lang.String name) throws android.os.RemoteException; }
步骤：
如以下代码，在服务端，AidlService在被client端的bindservice启动之后，会执行onBind，返回一个继承于IBinder的类mBinder，
IBinder是底层的一个借口，实现该接口的类也具有了远程调用的能力，并重写了方法hello,这个后面再说。
private final AIDLTest.Stub mBinder = new AIDLTest.Stub() {
@Override
public String hello(String name) throws RemoteException {
// TODO Auto-generated method stub
return "hello"+name;
}
};
client端绑定成功之后，得到IBinder的继承类的应用，其实就是service端的mBinder的引用
private ServiceConnection serviceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Log.d(TAG, "++++++ onServiceConnected: success ++++++");
vasInterface = AIDLTest.Stub.asInterface(service);
}
@Override
public void onServiceDisconnected(ComponentName name) {
vasInterface = null;
}
};
client端紧接着执行
AIDLTest.Stub.asInterface(service);
进入asInterface：
public static com.example.admin.frameworkdemo.AIDLTest asInterface(android.os.IBinder obj) {
if ((obj == null)) {
return null;
}
android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
if (((iin != null) && (iin instanceof com.example.admin.frameworkdemo.AIDLTest))) {
return ((com.example.admin.frameworkdemo.AIDLTest) iin);
}
return new com.example.admin.frameworkdemo.AIDLTest.Stub.Proxy(obj);
}
这里queryLocalInterface判断是跨进程调用，如果是跨进程调用，执行
return new com.example.admin.frameworkdemo.AIDLTest.Stub.Proxy(obj);
此时得到了一个Proxy类，传进去的obj是远程服务端的mBinder引用，即Proxy类持有远程服务端mBinder的引用。
此时回到client调用接口：
vasInterface.hello("aaaaaaaa");
此时我们知道vasInterface是一个AIDLTest.Stub.Proxy，执行里面的方法hello，
@Override public java.lang.String hello(java.lang.String name) throws android.os.RemoteException { android.os.Parcel _data = android.os.Parcel.obtain(); android.os.Parcel _reply = android.os.Parcel.obtain(); java.lang.String _result; try { _data.writeInterfaceToken(DESCRIPTOR); _data.writeString(name); mRemote.transact(Stub.TRANSACTION_hello, _data, _reply, 0); _reply.readException(); _result = _reply.readString(); } finally { _reply.recycle(); _data.recycle(); } return _result; }
可以看到hello里面执行了可以看到里面执行了mRemote.transact(Stub.TRANSACTION_hello, _data, _reply, 0);
data代表了客户端传进去的数据，reply代表了服务端将要返回来的数据。
mRemote.transact(Stub.TRANSACTION_hello, _data, _reply, 0);
该方法实际上是通过底层的Binder驱动调用到C/C++层的JavaBBinder对象的tansact方法，而该方法通过JNI来调用JAVA 层上Binder对象的execTransact()方法，
并进而调用开发者自己可以覆盖的onTransact()方法从而达到了通信的目标
@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_hello: {
data.enforceInterface(DESCRIPTOR);
java.lang.String _arg0;
_arg0 = data.readString();
java.lang.String _result = this.hello(_arg0);
reply.writeNoException();
reply.writeString(_result);
return true;
}
}
return super.onTransact(code, data, reply, flags); }
这里面执行了：this.hello(_arg0)，而这个函数执行的应该就是子类mBinder在应用层定义的匿名类的里面的方法：
rivate final AIDLTest.Stub mBinder = new AIDLTest.Stub() {
@Override
public String hello(String name) throws RemoteException {
// TODO Auto-generated method stub
return "hello"+name;
}
};
然后通过reply.writeString(_result);将执行结果写到replay里面。
为什么AS自动生成的AIDLTest文件里面，Stub要定义为AIDLTest的内部类：
自动生成的aidl文件可能不止一个，Stub定义成内部类，使用的时候容易区分，比如：AIDLTest.Stub，AIDLTest2.Stub...
