| /* |
| * Copyright 2017, 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 com.example.android.persistence.viewmodel; |
| |
| import android.app.Application; |
| import android.arch.core.util.Function; |
| import android.arch.lifecycle.AndroidViewModel; |
| import android.arch.lifecycle.LiveData; |
| import android.arch.lifecycle.MutableLiveData; |
| import android.arch.lifecycle.Transformations; |
| |
| import com.example.android.persistence.db.DatabaseCreator; |
| import com.example.android.persistence.db.entity.ProductEntity; |
| |
| import java.util.List; |
| |
| public class ProductListViewModel extends AndroidViewModel { |
| |
| private static final MutableLiveData ABSENT = new MutableLiveData(); |
| { |
| //noinspection unchecked |
| ABSENT.setValue(null); |
| } |
| |
| private final LiveData<List<ProductEntity>> mObservableProducts; |
| |
| public ProductListViewModel(Application application) { |
| super(application); |
| |
| final DatabaseCreator databaseCreator = DatabaseCreator.getInstance(this.getApplication()); |
| |
| LiveData<Boolean> databaseCreated = databaseCreator.isDatabaseCreated(); |
| mObservableProducts = Transformations.switchMap(databaseCreated, |
| new Function<Boolean, LiveData<List<ProductEntity>>>() { |
| @Override |
| public LiveData<List<ProductEntity>> apply(Boolean isDbCreated) { |
| if (!Boolean.TRUE.equals(isDbCreated)) { // Not needed here, but watch out for null |
| //noinspection unchecked |
| return ABSENT; |
| } else { |
| //noinspection ConstantConditions |
| return databaseCreator.getDatabase().productDao().loadAllProducts(); |
| } |
| } |
| }); |
| |
| databaseCreator.createDb(this.getApplication()); |
| } |
| |
| /** |
| * Expose the LiveData Products query so the UI can observe it. |
| */ |
| public LiveData<List<ProductEntity>> getProducts() { |
| return mObservableProducts; |
| } |
| } |