首先回顾下AIDL的使用。
1.新建aidl文件，MyAidlServer.aidl .
interface MyAidlServer {
/**
* 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);
int addTwoNums(int a,int b);
}
同步下工程，就会生成对应aidl文件的接口类。
public interface MyAidlServer extends android.os.IInterface {
/**
* Local-side IPC implementation stub class.
*/
public static abstract class Stub extends android.os.Binder implements com.example.dengxuan.learnproject.MyAidlServer {
private static final java.lang.String DESCRIPTOR = "com.example.dengxuan.learnproject.MyAidlServer";
/**
* Construct the stub at attach it to the interface.
*/
public Stub() {
this.attachInterface(this, DESCRIPTOR);
}
/**
* Cast an IBinder object into an com.example.dengxuan.learnproject.MyAidlServer interface,
* generating a proxy if needed.
*/
public static com.example.dengxuan.learnproject.MyAidlServer asInterface(android.os.IBinder obj) {
if ((obj == null)) {
return null;
}
android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
if (((iin != null) && (iin instanceof com.example.dengxuan.learnproject.MyAidlServer))) {
return ((com.example.dengxuan.learnproject.MyAidlServer) iin);
}
return new com.example.dengxuan.learnproject.MyAidlServer.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_basicTypes: {
data.enforceInterface(DESCRIPTOR);
int _arg0;
_arg0 = data.readInt();
long _arg1;
_arg1 = data.readLong();
boolean _arg2;
_arg2 = (0 != data.readInt());
float _arg3;
_arg3 = data.readFloat();
double _arg4;
_arg4 = data.readDouble();
java.lang.String _arg5;
_arg5 = data.readString();
this.basicTypes(_arg0, _arg1, _arg2, _arg3, _arg4, _arg5);
reply.writeNoException();
return true;
}
case TRANSACTION_addTwoNums: {
data.enforceInterface(DESCRIPTOR);
int _arg0;
_arg0 = data.readInt();
int _arg1;
_arg1 = data.readInt();
int _result = this.addTwoNums(_arg0, _arg1);
reply.writeNoException();
reply.writeInt(_result);
return true;
}
}
return super.onTransact(code, data, reply, flags);
}
private static class Proxy implements com.example.dengxuan.learnproject.MyAidlServer {
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;
}
/**
* Demonstrates some basic types that you can use as parameters
* and return values in AIDL.
*/
@Override
public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, java.lang.String aString) throws android.os.RemoteException {
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
try {
_data.writeInterfaceToken(DESCRIPTOR);
_data.writeInt(anInt);
_data.writeLong(aLong);
_data.writeInt(((aBoolean) ? (1) : (0)));
_data.writeFloat(aFloat);
_data.writeDouble(aDouble);
_data.writeString(aString);
mRemote.transact(Stub.TRANSACTION_basicTypes, _data, _reply, 0);
_reply.readException();
} finally {
_reply.recycle();
_data.recycle();
}
}
@Override
public int addTwoNums(int a, int b) throws android.os.RemoteException {
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
int _result;
try {
_data.writeInterfaceToken(DESCRIPTOR);
_data.writeInt(a);
_data.writeInt(b);
mRemote.transact(Stub.TRANSACTION_addTwoNums, _data, _reply, 0);
_reply.readException();
_result = _reply.readInt();
} finally {
_reply.recycle();
_data.recycle();
}
return _result;
}
}
static final int TRANSACTION_basicTypes = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
static final int TRANSACTION_addTwoNums = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);
}
/**
* Demonstrates some basic types that you can use as parameters
* and return values in AIDL.
*/
public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, java.lang.String aString) throws android.os.RemoteException;
public int addTwoNums(int a, int b) throws android.os.RemoteException;
}
2.新建service类，MyAidlService
public class MyAidlService extends Service {
MyAidlServer.Stub myBinder = new MyAidlServer.Stub() {
@Override
public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, String aString) throws RemoteException {
}
@Override
public int addTwoNums(int a, int b) throws RemoteException {
return a+b;
}
};
@Override
public void onCreate() {
super.onCreate();
}
@Nullable
@Override
public IBinder onBind(Intent intent) {
Log.i("dx","onBind");
return myBinder;
}
}
3.绑定Service。
private void bindMsgService(){
Intent intent = new Intent();
intent.setClass(MainActivity.this, MyAidlService.class);
bindService(intent,mConn,Context.BIND_AUTO_CREATE);
}
MyAidlServer server;
private ServiceConnection mConn = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
server = MyAidlServer.Stub.asInterface(service);
if(server != null){
try {
int i = server.addTwoNums(5, 6);
Log.i("dx result",String.valueOf(i));
} catch (RemoteException e) {
e.printStackTrace();
}
}
}
@Override
public void onServiceDisconnected(ComponentName name) {
Log.i("dx add","onServiceDisconnected");
server = null;
}
};
至此，一个简单的AIDL使用的例子就完成了。 下面我们根据这个例子来分析AIDL的工作原理。
客户端通过bindService来绑定服务端的服务。当服务绑定成功后，ServiceConnection 中 有一个onServiceConnected的回调，第一个参数ComponentName对应服务组件(包含Service的包名和类的全名)
第二个参数返回一个iBinder对象。通过 MyAidlServer.Stub.asInterface 实例化出具体的对象。再来看asInterface的代码
image.png
如果在同进程中(即MainActivity 与 MyAidlService在同一进程)，代码将会走到
return ((com.example.dengxuan.learnproject.MyAidlServer) iin);
中，这里返回来的实际上是之前我们在MyAidlService 的 onBind方法中返回的对象。 也就是 MyAidlServer.Stub 对象。
如果是跨进程调用，service定义
image.png
在另一个app中使用如下方式调用当前app的service：
Intent intent = new Intent();
intent.setAction("com.dx.aidl");
intent.setPackage("com.example.dengxuan.learnproject");
bindService(intent,mConn, Context.BIND_AUTO_CREATE);
或者在定义service的时候 指定了 属性android:process=":remote"
那么asInterface中将会走到
return new com.example.dengxuan.learnproject.MyAidlServer.Stub.Proxy(obj);
此时返回回来的是 一个代理对象。
image.png
然后在通过代理对象去调用不同进程的方法 涉及到进程间的数据传输， android系统中的binder进程间通信(IPC)就使用了Parcel类来进行客户端与服务端数据的交互。在代理类里的方法实现首先把需要传输的数据包装成Parcel对象。
image.png
然后通过调用 transact 方法 指定调用的方法名(Stub.TRANSACTION_addTwoNums)，以及参数（_data），以及方法的返回结果(_reply) 这是一个同步方法，执行完成后的结果保存在_reply 对象中。代理对象调用transact会映射到远端服务的onTransact方法中，在这里具体完成调用过程。
image.png
