GithubViewModelFactory.java

/*
 * Copyright (C) 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.android.example.github.viewmodel;

import com.android.example.github.di.ViewModelSubComponent;
import com.android.example.github.repository.RepoRepository;
import com.android.example.github.repository.UserRepository;
import com.android.example.github.ui.repo.RepoViewModel;
import com.android.example.github.ui.search.SearchViewModel;
import com.android.example.github.ui.user.UserViewModel;

import android.arch.lifecycle.ViewModel;
import android.arch.lifecycle.ViewModelProvider;
import android.support.v4.util.ArrayMap;

import java.util.Map;
import java.util.concurrent.Callable;

import javax.inject.Inject;
import javax.inject.Singleton;

@Singleton
public class GithubViewModelFactory implements ViewModelProvider.Factory {
    private final ArrayMap<Class, Callable<? extends ViewModel>> creators;

    @Inject
    public GithubViewModelFactory(ViewModelSubComponent viewModelSubComponent) {
        creators = new ArrayMap<>();
        // we cannot inject view models directly because they won't be bound to the owner's
        // view model scope.
        creators.put(SearchViewModel.class, () -> viewModelSubComponent.searchViewModel());
        creators.put(UserViewModel.class, () -> viewModelSubComponent.userViewModel());
        creators.put(RepoViewModel.class, () -> viewModelSubComponent.repoViewModel());
    }

    @Override
    public <T extends ViewModel> T create(Class<T> modelClass) {
        Callable<? extends ViewModel> creator = creators.get(modelClass);
        if (creator == null) {
            for (Map.Entry<Class, Callable<? extends ViewModel>> entry : creators.entrySet()) {
                if (modelClass.isAssignableFrom(entry.getKey())) {
                    creator = entry.getValue();
                    break;
                }
            }
        }
        if (creator == null) {
            throw new IllegalArgumentException("unknown model class " + modelClass);
        }
        try {
            return (T) creator.call();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}