public final class

HostDispatcher

extends java.lang.Object

 java.lang.Object

↳androidx.car.app.HostDispatcher

Gradle dependencies

compile group: 'androidx.car.app', name: 'app', version: '1.2.0-rc01'

  • groupId: androidx.car.app
  • artifactId: app
  • version: 1.2.0-rc01

Artifact androidx.car.app:app:1.2.0-rc01 it located at Google repository (https://maven.google.com/)

Overview

Dispatches calls to the host and manages possible exceptions.

Summary

Constructors
publicHostDispatcher()

Methods
public voiddispatch(java.lang.String hostType, java.lang.String callName, HostCall<java.lang.Object, java.lang.Object> call)

Dispatches the call to the host for the given hostType.

public java.lang.ObjectdispatchForResult(java.lang.String hostType, java.lang.String callName, HostCall<java.lang.Object, java.lang.Object> call)

Dispatches the call to the host for the given hostType.

public voidsetCarHost(ICarHost carHost)

from java.lang.Objectclone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructors

public HostDispatcher()

Methods

public java.lang.Object dispatchForResult(java.lang.String hostType, java.lang.String callName, HostCall<java.lang.Object, java.lang.Object> call)

Dispatches the call to the host for the given hostType.

Parameters:

hostType: the service to dispatch to
callName: the name of the call for logging purposes
call: the request to dispatch

public void dispatch(java.lang.String hostType, java.lang.String callName, HostCall<java.lang.Object, java.lang.Object> call)

Dispatches the call to the host for the given hostType.

Parameters:

hostType: the service to dispatch to
callName: the name of the call for logging purposes
call: the request to dispatch

public void setCarHost(ICarHost carHost)

Source

/*
 * 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.constraints.IConstraintHost;
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 IConstraintHost mConstraintHost;
    @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 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.CONSTRAINT_SERVICE:
                if (mConstraintHost == null) {
                    mConstraintHost =
                            RemoteUtils.dispatchCallToHostForResult("getHost(Constraints)", () ->
                                    IConstraintHost.Stub.asInterface(
                                            requireNonNull(mCarHost).getHost(
                                                    CarContext.CONSTRAINT_SERVICE)));
                }
                host = mConstraintHost;
                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;
    }
}