EnumWrapper.java
/*
* Copyright 2018 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.cluster.navigation;
import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP_PREFIX;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RestrictTo;
import androidx.core.util.Preconditions;
import androidx.versionedparcelable.ParcelField;
import androidx.versionedparcelable.VersionedParcelable;
import androidx.versionedparcelable.VersionedParcelize;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
/**
* An {@link Enum} wrapper that implements {@link VersionedParcelable} and provides backwards and
* forward compatibility by allowing the data producer to provide an optional set of "fallback"
* values. If a value provided by the producer is not known by the data consumer (e.g.: a new value
* was introduced, but the consumer still is using a older version of the API), then this
* class would return the first "fallback" value that is known to the consumer.
* @param <T> Enum type to be wrapped.
* @hide
*/
@RestrictTo(LIBRARY_GROUP_PREFIX)
@VersionedParcelize
final class EnumWrapper<T extends Enum<T>> implements VersionedParcelable {
@ParcelField(1)
List<String> mValues = new ArrayList<>();
/**
* Used by {@link VersionedParcelable}
*/
EnumWrapper() {
}
@SafeVarargs
EnumWrapper(@NonNull T value, @NonNull T ... fallbacks) {
mValues.add(Preconditions.checkNotNull(value).name());
for (T fallback : fallbacks) {
mValues.add(fallback.name());
}
}
/**
* Returns the first value wrapped by the given {@link VersionedParcelable}, that is known to
* this consumer, or a default value if none of the fallback alternatives is known, or the
* provided wrapper is null.
*
* @param defaultValue Value to return if none of the reported values is known to the consumer.
*/
@NonNull
public static <T extends Enum<T>> T getValue(@Nullable EnumWrapper<T> wrapper,
@NonNull T defaultValue) {
if (wrapper != null) {
for (String value : wrapper.mValues) {
T result = getEnumByName(defaultValue.getDeclaringClass(), value);
if (result != null) {
return result;
}
}
}
return defaultValue;
}
@Nullable
private static <T extends Enum<T>> T getEnumByName(@NonNull Class<T> clazz,
@NonNull String name) {
try {
return Enum.valueOf(clazz, name);
} catch (IllegalArgumentException ex) {
return null;
}
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
EnumWrapper<?> that = (EnumWrapper<?>) o;
return Objects.equals(mValues, that.mValues);
}
@Override
public int hashCode() {
return Objects.hash(mValues);
}
@Override
public String toString() {
return String.format("{values: %s}", mValues);
}
/**
* Wraps the given value and an optional list of fallback values.
*
* @param value Value to be wrapped.
* @param fallbacks An optional list of fallback values, in order of preference, to be used in
* case the consumer of this API doesn't know the value provided. This will be
* used only if {@code value} is not null.
*/
@SafeVarargs
@NonNull
public static <T extends Enum<T>> EnumWrapper<T> of(@NonNull T value,
@NonNull T ... fallbacks) {
return new EnumWrapper<>(Preconditions.checkNotNull(value), fallbacks);
}
}