Batch Sending RPCs

There are two ways to send multiple requests to the head unit: concurrently and sequentially. Which method you should use depends on the type of RPCs being sent. Concurrently sent requests might finish in a random order and should only be used when none of the requests in the group depend on the response of another, such as when subscribing to several hard buttons. Sequentially sent requests only send the next request in the group when a response has been received for the previously sent RPC. Requests should be sent sequentially when you need to know the result of a previous request before sending the next, like when sending the several different requests needed to create a menu.

Both methods have optional listener that is specific to them, the OnMultipleRequestListener. This listener will provide more information than the normal OnRPCResponseListener.

Sending Concurrent Requests

When you send multiple RPCs concurrently, it will not wait for the response of the previous RPC before sending the next one. Therefore, there is no guarantee that responses will be returned in order, and you will not be able to use information sent in a previous RPC for a later RPC.

SubscribeButton subscribeButtonLeft = new SubscribeButton(ButtonName.SEEKLEFT);
SubscribeButton subscribeButtonRight = new SubscribeButton(ButtonName.SEEKRIGHT);
sdlManager.sendRPCs(Arrays.asList(subscribeButtonLeft, subscribeButtonRight), new OnMultipleRequestListener() {
    @Override
    public void onUpdate(int remainingRequests) {

    }

    @Override
    public void onFinished() {

    }

    @Override
    public void onResponse(int correlationId, RPCResponse response) {

    }
});

Sending Sequential Requests

Requests sent sequentially are sent in a set order. The next request is only sent when a response has been received for the previously sent request.

The code example below shows how to create a perform interaction choice set. When creating a perform interaction choice set, the PerformInteraction RPC can only be sent after the CreateInteractionChoiceSet RPC has been registered by Core, which is why the requests must be sent sequentially.

int choiceId = 111, choiceSetId = 222;
Choice choice = new Choice(choiceId, "Choice title");
CreateInteractionChoiceSet createInteractionChoiceSet = new CreateInteractionChoiceSet(choiceSetId, Collections.singletonList(choice));
PerformInteraction performInteraction = new PerformInteraction("Initial Text", InteractionMode.MANUAL_ONLY, Collections.singletonList(choiceSetId));
sdlManager.sendSequentialRPCs(Arrays.asList(createInteractionChoiceSet, performInteraction), new OnMultipleRequestListener() {
    @Override
    public void onUpdate(int i) {

    }

    @Override
    public void onFinished() {

    }

    @Override
    public void onResponse(int i, RPCResponse rpcResponse) {

    }
});