package android.os;

/**
 * Base class for Binder interfaces.  When defining a new interface,
 * you must derive it from IInterface.
 */
public interface IInterface
{
    /**
     * Retrieve the Binder object associated with this interface.
     * You must use this instead of a plain cast, so that proxy objects
     * can return the correct result.
     */
    public IBinder asBinder();
}

public interface IBinder {
    /**
     * The first transaction code available for user commands.
     */
    int FIRST_CALL_TRANSACTION = 0x00000001;
    /**
     * The last transaction code available for user commands.
     */
    int LAST_CALL_TRANSACTION = 0x00ffffff;
    //...

    /**
     * Get the canonical name of the interface supported by this binder.
     */
    public @Nullable
    String getInterfaceDescriptor() throws RemoteException;

    public @Nullable
    IInterface queryLocalInterface(@NonNull String descriptor);
    //...
    public boolean transact(int code, @NonNull Parcel data, @Nullable Parcel reply, int flags)
            throws RemoteException;

    public interface DeathRecipient {
        public void binderDied();

        default void binderDied(IBinder who) {
            binderDied();
        }
    }
}

/*
 * This file is auto-generated.  DO NOT MODIFY.
 */
public interface IMyService extends android.os.IInterface
{
  /** Default implementation for IMyService. */
  public static class Default implements IMyService
  {
    @Override public void sayHello() throws android.os.RemoteException
    {
    }
    @Override
    public android.os.IBinder asBinder() {
      return null;
    }
  }
  /** Local-side IPC implementation stub class. */
  public static abstract class Stub extends android.os.Binder implements IMyService
  {
    private static final java.lang.String DESCRIPTOR = "IMyService";
    /** Construct the stub at attach it to the interface. */
    public Stub()
    {
      this.attachInterface(this, DESCRIPTOR);
    }
    /**
     * Cast an IBinder object into an IMyService interface,
     * generating a proxy if needed.
     */
    public static IMyService asInterface(android.os.IBinder obj)
    {
      if ((obj==null)) {
        return null;
      }
      android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
      if (((iin!=null)&&(iin instanceof IMyService))) {
        return ((IMyService)iin);
      }
      return new IMyService.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_sayHello:
        {
          data.enforceInterface(descriptor);
          this.sayHello();
          reply.writeNoException();
          return true;
        }
        default:
        {
          return super.onTransact(code, data, reply, flags);
        }
      }
    }
    private static class Proxy implements IMyService
    {
      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 void sayHello() throws android.os.RemoteException
      {
        android.os.Parcel _data = android.os.Parcel.obtain();
        android.os.Parcel _reply = android.os.Parcel.obtain();
        try {
          _data.writeInterfaceToken(DESCRIPTOR);
          boolean _status = mRemote.transact(Stub.TRANSACTION_sayHello, _data, _reply, 0);
          if (!_status && getDefaultImpl() != null) {
            getDefaultImpl().sayHello();
            return;
          }
          _reply.readException();
        }
        finally {
          _reply.recycle();
          _data.recycle();
        }
      }
      public static IMyService sDefaultImpl;
    }
    static final int TRANSACTION_sayHello = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
    public static boolean setDefaultImpl(IMyService impl) {
      // Only one user of this interface can use this function
      // at a time. This is a heuristic to detect if two different
      // users in the same process use this function.
      if (Stub.Proxy.sDefaultImpl != null) {
        throw new IllegalStateException("setDefaultImpl() called twice");
      }
      if (impl != null) {
        Stub.Proxy.sDefaultImpl = impl;
        return true;
      }
      return false;
    }
    public static IMyService getDefaultImpl() {
      return Stub.Proxy.sDefaultImpl;
    }
  }
  public void sayHello() throws android.os.RemoteException;
}

package android.os;

/**
 * Base class for Binder interfaces.  When defining a new interface,
 * you must derive it from IInterface.
 */
public interface IInterface
{
    /**
     * Retrieve the Binder object associated with this interface.
     * You must use this instead of a plain cast, so that proxy objects
     * can return the correct result.
     */
    public IBinder asBinder();
}

IBinder也是一个接口类，其定义及关键方法如下：
package android.os;

import android.annotation.NonNull;
import android.annotation.Nullable;
import android.compat.annotation.UnsupportedAppUsage;
import java.io.FileDescriptor;

public interface IBinder {
	
	//..........（属性）
	
	//..........（接口方法）
	
    /**
     * Get the canonical name of the interface supported by this binder.
     */
    public @Nullable String getInterfaceDescriptor() throws RemoteException;

	//........

    /**
     * Perform a generic operation with the object.
     *
     * @param code The action to perform.  This should
     * be a number between {@link #FIRST_CALL_TRANSACTION} and
     * {@link #LAST_CALL_TRANSACTION}.
     * @param data Marshalled data to send to the target.  Must not be null.
     * If you are not sending any data, you must create an empty Parcel
     * that is given here.
     * @param reply Marshalled data to be received from the target.  May be
     * null if you are not interested in the return value.
     * @param flags Additional operation flags.  Either 0 for a normal
     * RPC, or {@link #FLAG_ONEWAY} for a one-way RPC.
     *
     * @return Returns the result from {@link Binder#onTransact}.  A successful call
     * generally returns true; false generally means the transaction code was not
     * understood.
     */
    public boolean transact(int code, @NonNull Parcel data, @Nullable Parcel reply, int flags)
        throws RemoteException;
}

public void sayHello() throws android.os.RemoteException;

public Stub()
{
    this.attachInterface(this, DESCRIPTOR);
}

//attachInterface()的定义在Binder类中：
private IInterface mOwner;
private String mDescriptor;
public void attachInterface(IInterface owner, String descriptor) {
    mOwner = owner;
    mDescriptor = descriptor;
}

public static IMyService asInterface(android.os.IBinder obj)
{
    if ((obj==null)) {
        return null;
    }
    android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
    if (((iin!=null)&&(iin instanceof IMyService))) {
        return ((IMyService)iin);
    }
    return new IMyService.Stub.Proxy(obj);
}

// 通过服务名获取服务的引用
IBinder binder = ServiceManager.getService("server.myservice");
//通过引用获取代理对象
IMyService myService = IMyService.Stub.asInterface(binder);
//通过代理对象调用接口的方法
myService.sayHello();

在asInterface()调用客户端的IBinder对象的queryLocalInterface(DESCRIPTOR)方法：
    private IInterface mOwner;
private String mDescriptor;
public IInterface queryLocalInterface(String descriptor) {
    if (mDescriptor != null && mDescriptor.equals(descriptor)) {
        return mOwner;
    }
    return null;
}

@Override public android.os.IBinder asBinder()
{
  return this;
}