客户端进程（在带有 aidl 的 android IPC 中）如何知道远程服务器类？

Question

In Android official Aidl document, the IPC client example declares an intent explicitly with the target "RemoteService.class". However, when server and client are not in the same package, client should not be aware of what is "RemoteService" if no dependency set. How does the example works?

ref: https://developer.android.com/guide/components/aidl.html

I searched for several working examples, and the intent is set with Action instead of the remote service class object.

In Android docs,

Intent intent = new Intent(Binding.this, RemoteService.class);
intent.setAction(IRemoteService.class.getName());
bindService(intent, mConnection, Context.BIND_AUTO_CREATE);

Currently, I expect this should be modified to:

Intent intent = new Intent("<remote-service-intent-filter-in-androidmanifest>");
bindService(intent, mConnection, Context.BIND_AUTO_CREATE);

Answer 1

You are on the right path, but if you add the intent action at the manifest, then you should also mention the package name while binding the service.

intent.setPackage("<remote service package name>");

Caution: To ensure that your app is secure, always use an explicit intent when starting a Service and don't declare intent filters for your services. Using an implicit intent to start a service is a security hazard because you cannot be certain of the service that responds to the intent, and the user cannot see which service starts. Beginning with Android 5.0 (API level 21), the system throws an exception if you call bindService() with an implicit intent. https://developer.android.com/guide/components/services

Snipplet: Here is how I connect to a remote service on a different application with the setClassName API.

Note : This approach does not need the intent action at the manifest file.

At Client activity.

/**
 * Init Service
 */
private void initService() {
    if (mSampleService == null) {
        Intent i = new Intent();

        // set intent action
        i.setAction("com.hardian.sample.aidl.ISampleService");
        // mention package name with service's canaonical name
        i.setClassName("com.hardian.sample", "com.hardian.sample.aidl.SampleAidlService");

        // binding to a remote service
        bindService(i, mSampleServiceConnection, Service.BIND_AUTO_CREATE);
    } 
}

At Service

 /**
 * {@inheritDoc}
 */
@Override
public IBinder onBind(Intent intent) {
    Log.d(TAG, "onBind called");
    if (ISampleService.class.getName().equals(intent.getAction())) {
        return mSampleServiceBinder;
    }
    return null;
}