NavHost.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.navigation;
import android.os.Bundle;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.lifecycle.LifecycleOwner;
import androidx.lifecycle.ViewModelStore;
/**
* A host is a single context or container for navigation via a {@link NavController}.
* <p>
* It is strongly recommended to construct the nav controller by instantiating a
* {@link NavHostController}, which offers additional APIs specifically for a NavHost.
* The NavHostController should still only be externally accessible as a {@link NavController},
* rather than directly exposing it as a {@link NavHostController}.
* <p>
* Navigation hosts must:
* <ul>
* <li>Handle {@link NavController#saveState() saving} and
* {@link NavController#restoreState(Bundle) restoring} their controller's state</li>
* <li>Call {@link Navigation#setViewNavController(View, NavController)} on their root view</li>
* <li>Route system Back button events to the NavController either by manually calling
* {@link NavController#popBackStack()} or by calling
* {@link NavHostController#setOnBackPressedDispatcher(androidx.activity.OnBackPressedDispatcher)}
* when constructing the NavController.</li>
* </ul>
* Optionally, a navigation host should consider calling:
* <ul>
* <li>Call {@link NavHostController#setLifecycleOwner(LifecycleOwner)} to associate the
* NavController with a specific Lifecycle.</li>
* <li>Call {@link NavHostController#setViewModelStore(ViewModelStore)} to enable usage of
* {@link NavController#getViewModelStoreOwner(int)} and navigation graph scoped ViewModels.</li>
* </ul>
*/
public interface NavHost {
/**
* Returns the {@link NavController navigation controller} for this navigation host.
*
* @return this host's navigation controller
*/
@NonNull
NavController getNavController();
}