ContextAware.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.activity.contextaware;
import android.content.Context;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
/**
* A <code>ContextAware</code> class is associated with a {@link Context} sometime after
* the class is instantiated. By adding a {@link OnContextAvailableListener}, you can
* receive a callback for that event.
* <p>
* Classes implementing {@link ContextAware} are strongly recommended to also implement
* {@link androidx.lifecycle.LifecycleOwner} for providing a more general purpose API for
* listening for creation and destruction events.
*
* @see ContextAwareHelper
*/
public interface ContextAware {
/**
* Get the {@link Context} if it is currently available. If this returns
* <code>null</code>, you can use
* {@link #addOnContextAvailableListener(OnContextAvailableListener)} to receive
* a callback for when it available.
*
* @return the Context if it is currently available.
*/
@Nullable
Context peekAvailableContext();
/**
* Add a new {@link OnContextAvailableListener} for receiving a callback for when
* this class is associated with a {@link android.content.Context}.
* <p>
* Listeners are triggered in the order they are added when added before the Context is
* available. Listeners added after the context has been made available will have the Context
* synchronously delivered to them as part of this call.
*
* @param listener The listener that should be added.
* @see #removeOnContextAvailableListener(OnContextAvailableListener)
*/
void addOnContextAvailableListener(@NonNull OnContextAvailableListener listener);
/**
* Remove a {@link OnContextAvailableListener} previously added via
* {@link #addOnContextAvailableListener(OnContextAvailableListener)}.
*
* @param listener The listener that should be removed.
* @see #addOnContextAvailableListener(OnContextAvailableListener)
*/
void removeOnContextAvailableListener(@NonNull OnContextAvailableListener listener);
}