HostDispatcher.java
/*
* Copyright 2020 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.car.app;
import static androidx.annotation.RestrictTo.Scope.LIBRARY;
import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP;
import static java.util.Objects.requireNonNull;
import android.os.IInterface;
import android.os.RemoteException;
import android.util.Log;
import androidx.annotation.MainThread;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RestrictTo;
import androidx.car.app.CarContext.CarServiceType;
import androidx.car.app.navigation.INavigationHost;
import androidx.car.app.utils.LogTags;
import androidx.car.app.utils.RemoteUtils;
import androidx.car.app.utils.ThreadUtils;
import java.security.InvalidParameterException;
/**
* Dispatches calls to the host and manages possible exceptions.
*
* @hide
*/
@RestrictTo(LIBRARY_GROUP) // Restrict to testing library
public final class HostDispatcher {
@Nullable
private ICarHost mCarHost;
@Nullable
private IAppHost mAppHost;
@Nullable
private INavigationHost mNavigationHost;
/**
* Dispatches the {@code call} to the host for the given {@code hostType}.
*
* @param hostType the service to dispatch to
* @param callName the name of the call for logging purposes
* @param call the request to dispatch
*
* @throws RemoteException if the host is unresponsive
* @throws SecurityException if the host has thrown it
* @throws HostException if the host throws any exception other than
* {@link SecurityException}
*/
@Nullable
@SuppressWarnings({"unchecked", "cast.unsafe"}) // Cannot check if instanceof ServiceT
public <ServiceT, ReturnT> ReturnT dispatchForResult(
@CarServiceType @NonNull String hostType, @NonNull String callName,
@NonNull HostCall<ServiceT, ReturnT> call) throws RemoteException {
return RemoteUtils.dispatchCallToHostForResult(callName, () -> {
IInterface service = getHost(hostType);
if (service == null) {
Log.e(LogTags.TAG_DISPATCH,
"Could not retrieve host while dispatching call " + callName);
return null;
}
return call.dispatch((ServiceT) service);
});
}
/**
* Dispatches the {@code call} to the host for the given {@code hostType}.
*
* @param hostType the service to dispatch to
* @param callName the name of the call for logging purposes
* @param call the request to dispatch
*
* @throws SecurityException if the host has thrown it
* @throws HostException if the host throws any exception other than
* {@link SecurityException}
*/
@SuppressWarnings({"unchecked", "cast.unsafe"}) // Cannot check if instanceof ServiceT
public <ServiceT, ReturnT> void dispatch(
@CarServiceType @NonNull String hostType, @NonNull String callName,
@NonNull HostCall<ServiceT, ReturnT> call) {
RemoteUtils.dispatchCallToHost(callName, () -> {
IInterface service = getHost(hostType);
if (service == null) {
Log.e(LogTags.TAG_DISPATCH,
"Could not retrieve host while dispatching call " + callName);
return null;
}
call.dispatch((ServiceT) service);
return null;
});
}
@MainThread
public void setCarHost(@NonNull ICarHost carHost) {
ThreadUtils.checkMainThread();
resetHosts();
mCarHost = carHost;
}
/** Removes references to remote services which are no longer valid. */
@MainThread
void resetHosts() {
ThreadUtils.checkMainThread();
mCarHost = null;
mAppHost = null;
mNavigationHost = null;
}
/**
* Retrieves the {@link IInterface} for the given {@code hostType}.
*
* @throws RemoteException if the host is unresponsive
* @hide
*/
@RestrictTo(LIBRARY)
@Nullable
IInterface getHost(@CarServiceType String hostType) throws RemoteException {
if (mCarHost == null) {
Log.e(LogTags.TAG_DISPATCH, "Host is not bound when attempting to retrieve host "
+ "service");
return null;
}
IInterface host = null;
switch (hostType) {
case CarContext.APP_SERVICE:
if (mAppHost == null) {
mAppHost =
RemoteUtils.dispatchCallToHostForResult("getHost(App)", () ->
IAppHost.Stub.asInterface(requireNonNull(mCarHost).getHost(
CarContext.APP_SERVICE)));
}
host = mAppHost;
break;
case CarContext.NAVIGATION_SERVICE:
if (mNavigationHost == null) {
mNavigationHost =
RemoteUtils.dispatchCallToHostForResult(
"getHost(Navigation)", () ->
INavigationHost.Stub.asInterface(
requireNonNull(mCarHost).getHost(
CarContext.NAVIGATION_SERVICE))
);
}
host = mNavigationHost;
break;
case CarContext.CAR_SERVICE:
host = mCarHost;
break;
default:
throw new InvalidParameterException("Invalid host type: " + hostType);
}
return host;
}
}