If you have a class that you would like to send from one process to another through an IPC interface, you can do that. However, you must ensure that the code for your class is available to the other side of the IPC channel and your class must support the Parcelable interface.Supporting the Parcelable interface is important because it allows the Android system to decompose objects into primitives that can be marshalled across processes.
翻译：跨进程传递对象
To create a class that supports the Parcelable protocol, you must do the following:
Make your class implement the Parcelable interface.Implement writeToParcel, which takes the current state of the object and writes it to a Parcel.Add a static field called CREATOR to your class which is an object implementing the Parcelable.Creatorinterface.Finally, create an .aidl file that declares your parcelable class (as shown for the Rect.aidl file, below).If you are using a custom build process, do not add the .aidl file to your build. Similar to a header file in the C language, this .aidl file isn't compiled.
翻译：如果你自己build的话，不用把.aidl也给编了，这个类似于c语言的头文件，不参与编译。
AIDL uses these methods and fields in the code it generates to marshall and unmarshall your objects.
For example, here is a Rect.aidl file to create a Rect class that's parcelable:
parcelable举例：
import android.os.Parcel; import android.os.Parcelable; public final class Rect implements Parcelable { public int left; public int top; public int right; public int bottom; public static final Parcelable.Creator<Rect> CREATOR = new Parcelable.Creator<Rect>() { public Rect createFromParcel(Parcel in) { return new Rect(in); } public Rect[] newArray(int size) { return new Rect[size]; } }; public Rect() { } private Rect(Parcel in) { readFromParcel(in); } public void writeToParcel(Parcel out, int flags) { out.writeInt(left); out.writeInt(top); out.writeInt(right); out.writeInt(bottom); } public void readFromParcel(Parcel in) { left = in.readInt(); top = in.readInt(); right = in.readInt(); bottom = in.readInt(); } public int describeContents() { return 0; } }The marshalling in the Rect class is pretty simple. Take a look at the other methods on Parcel to see the other kinds of values you can write to a Parcel.
Warning: Don't forget the security implications of receiving data from other processes. In this case, the Rect reads four numbers from the Parcel, but it is up to you to ensure that these are within the acceptable range of values for whatever the caller is trying to do. See Security and Permissions for more information about how to keep your application secure from malware.
翻译：注意安全问题
if you have an .aidl file:
// IRectInsideBundle.aidl package com.example.android; /** Example service interface */ interface IRectInsideBundle { /** Rect parcelable is stored in the bundle with key "rect" */ void saveRect(in Bundle bundle); } As can be seen from the implementation below, the ClassLoaderis being explicitly set in the Bundle before reading Rect private final IRectInsideBundle.Stub binder = new IRectInsideBundle.Stub() { public void saveRect(Bundle bundle){ bundle.setClassLoader(getClass().getClassLoader()); Rect rect = bundle.getParcelable("rect"); process(rect); // Do more with the parcelable. } };Here are the steps a calling class must take to call a remote interface defined with AIDL:
Include the .aidl file in the project src/ directory.Declare an instance of the IBinder interface (generated based on the AIDL).Implement ServiceConnection.Call Context.bindService(), passing in your ServiceConnection implementation.In your implementation of onServiceConnected(), you will receive an IBinder instance (called service). Call YourInterfaceName.Stub.asInterface((IBinder)service) to cast the returned parameter to YourInterface type.Call the methods that you defined on your interface. You should always trap DeadObjectException exceptions, which are thrown when the connection has broken. You should also trap SecurityException exceptions, which are thrown when the two processes involved in the IPC method call have conflicting AIDL definitions.To disconnect, call Context.unbindService() with the instance of your interface.
A few comments on calling an IPC service:
Objects are reference counted across processes.You can send anonymous objects as method arguments.For more information about binding to a service, read the Bound Services document.
Here is some sample code demonstrating calling an AIDL-created service, taken from the Remote Service sample in the ApiDemos project.
public static class Binding extends Activity { /** The primary interface we will be calling on the service. */ IRemoteService mService = null; /** Another interface we use on the service. */ ISecondary secondaryService = null; Button killButton; TextView callbackText; private InternalHandler handler; private boolean isBound; /** * Standard initialization of this activity. Set up the UI, then wait * for the user to poke it before doing anything. */ @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.remote_service_binding); // Watch for button clicks. Button button = (Button)findViewById(R.id.bind); button.setOnClickListener(mBindListener); button = (Button)findViewById(R.id.unbind); button.setOnClickListener(unbindListener); killButton = (Button)findViewById(R.id.kill); killButton.setOnClickListener(killListener); killButton.setEnabled(false); callbackText = (TextView)findViewById(R.id.callback); callbackText.setText("Not attached."); handler = new InternalHandler(callbackText); } /** * Class for interacting with the main interface of the service. */ private ServiceConnection mConnection = new ServiceConnection() { public void onServiceConnected(ComponentName className, IBinder service) { // This is called when the connection with the service has been // established, giving us the service object we can use to // interact with the service. We are communicating with our // service through an IDL interface, so get a client-side // representation of that from the raw service object. mService = IRemoteService.Stub.asInterface(service); killButton.setEnabled(true); callbackText.setText("Attached."); // We want to monitor the service for as long as we are // connected to it. try { mService.registerCallback(mCallback); } catch (RemoteException e) { // In this case the service has crashed before we could even // do anything with it; we can count on soon being // disconnected (and then reconnected if it can be restarted) // so there is no need to do anything here. } // As part of the sample, tell the user what happened. Toast.makeText(Binding.this, R.string.remote_service_connected, Toast.LENGTH_SHORT).show(); } public void onServiceDisconnected(ComponentName className) { // This is called when the connection with the service has been // unexpectedly disconnected -- that is, its process crashed. mService = null; killButton.setEnabled(false); callbackText.setText("Disconnected."); // As part of the sample, tell the user what happened. Toast.makeText(Binding.this, R.string.remote_service_disconnected, Toast.LENGTH_SHORT).show(); } }; /** * Class for interacting with the secondary interface of the service. */ private ServiceConnection secondaryConnection = new ServiceConnection() { public void onServiceConnected(ComponentName className, IBinder service) { // Connecting to a secondary interface is the same as any // other interface. secondaryService = ISecondary.Stub.asInterface(service); killButton.setEnabled(true); } public void onServiceDisconnected(ComponentName className) { secondaryService = null; killButton.setEnabled(false); } }; private OnClickListener mBindListener = new OnClickListener() { public void onClick(View v) { // Establish a couple connections with the service, binding // by interface names. This allows other applications to be // installed that replace the remote service by implementing // the same interface. Intent intent = new Intent(Binding.this, RemoteService.class); intent.setAction(IRemoteService.class.getName()); bindService(intent, mConnection, Context.BIND_AUTO_CREATE); intent.setAction(ISecondary.class.getName()); bindService(intent, secondaryConnection, Context.BIND_AUTO_CREATE); isBound = true; callbackText.setText("Binding."); } }; private OnClickListener unbindListener = new OnClickListener() { public void onClick(View v) { if (isBound) { // If we have received the service, and hence registered with // it, then now is the time to unregister. if (mService != null) { try { mService.unregisterCallback(mCallback); } catch (RemoteException e) { // There is nothing special we need to do if the service // has crashed. } } // Detach our existing connection. unbindService(mConnection); unbindService(secondaryConnection); killButton.setEnabled(false); isBound = false; callbackText.setText("Unbinding."); } } }; private OnClickListener killListener = new OnClickListener() { public void onClick(View v) { // To kill the process hosting our service, we need to know its // PID. Conveniently our service has a call that will return // to us that information. if (secondaryService != null) { try { int pid = secondaryService.getPid(); // Note that, though this API allows us to request to // kill any process based on its PID, the kernel will // still impose standard restrictions on which PIDs you // are actually able to kill. Typically this means only // the process running your application and any additional // processes created by that app as shown here; packages // sharing a common UID will also be able to kill each // other's processes. Process.killProcess(pid); callbackText.setText("Killed service process."); } catch (RemoteException ex) { // Recover gracefully from the process hosting the // server dying. // Just for purposes of the sample, put up a notification. Toast.makeText(Binding.this, R.string.remote_call_failed, Toast.LENGTH_SHORT).show(); } } } }; // ---------------------------------------------------------------------- // Code showing how to deal with callbacks. // ---------------------------------------------------------------------- /** * This implementation is used to receive callbacks from the remote * service. */ private IRemoteServiceCallback mCallback = new IRemoteServiceCallback.Stub() { /** * This is called by the remote service regularly to tell us about * new values. Note that IPC calls are dispatched through a thread * pool running in each process, so the code executing here will * NOT be running in our main thread like most other things -- so, * to update the UI, we need to use a Handler to hop over there. */ public void valueChanged(int value) { handler.sendMessage(handler.obtainMessage(BUMP_MSG, value, 0)); } }; private static final int BUMP_MSG = 1; private static class InternalHandler extends Handler { private final WeakReference<TextView> weakTextView; InternalHandler(TextView textView) { weakTextView = new WeakReference<>(textView); } @Override public void handleMessage(Message msg) { switch (msg.what) { case BUMP_MSG: TextView textView = weakTextView.get(); if (textView != null) { textView.setText("Received from service: " + msg.arg1); } break; default: super.handleMessage(msg); } } } }
