NavControllerViewModel.java
/*
* Copyright 2019 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 androidx.annotation.NonNull;
import androidx.lifecycle.ViewModel;
import androidx.lifecycle.ViewModelProvider;
import androidx.lifecycle.ViewModelStore;
import java.util.HashMap;
import java.util.Iterator;
import java.util.UUID;
/**
* NavControllerViewModel is the always up to date view of the NavController's
* non configuration state
*/
class NavControllerViewModel extends ViewModel {
private static final ViewModelProvider.Factory FACTORY = new ViewModelProvider.Factory() {
@NonNull
@Override
@SuppressWarnings("unchecked")
public <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
NavControllerViewModel viewModel = new NavControllerViewModel();
return (T) viewModel;
}
};
@NonNull
static NavControllerViewModel getInstance(ViewModelStore viewModelStore) {
ViewModelProvider viewModelProvider = new ViewModelProvider(viewModelStore, FACTORY);
return viewModelProvider.get(NavControllerViewModel.class);
}
private final HashMap<UUID, ViewModelStore> mViewModelStores = new HashMap<>();
void clear(@NonNull UUID backStackEntryUUID) {
// Clear and remove the NavGraph's ViewModelStore
ViewModelStore viewModelStore = mViewModelStores.remove(backStackEntryUUID);
if (viewModelStore != null) {
viewModelStore.clear();
}
}
@Override
protected void onCleared() {
for (ViewModelStore store: mViewModelStores.values()) {
store.clear();
}
mViewModelStores.clear();
}
@NonNull
ViewModelStore getViewModelStore(@NonNull UUID backStackEntryUUID) {
ViewModelStore viewModelStore = mViewModelStores.get(backStackEntryUUID);
if (viewModelStore == null) {
viewModelStore = new ViewModelStore();
mViewModelStores.put(backStackEntryUUID, viewModelStore);
}
return viewModelStore;
}
@NonNull
@Override
public String toString() {
StringBuilder sb = new StringBuilder("NavControllerViewModel{");
sb.append(Integer.toHexString(System.identityHashCode(this)));
sb.append("} ViewModelStores (");
Iterator<UUID> viewModelStoreIterator = mViewModelStores.keySet().iterator();
while (viewModelStoreIterator.hasNext()) {
sb.append(viewModelStoreIterator.next());
if (viewModelStoreIterator.hasNext()) {
sb.append(", ");
}
}
sb.append(')');
return sb.toString();
}
}