content: /*
   * Copyright (C) 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 com.android.launcher3.util;
  
  import static com.android.launcher3.util.Executors.MAIN_EXECUTOR;
  
  import android.content.Context;
  import android.os.Looper;
  
  import androidx.annotation.VisibleForTesting;
  
  import com.android.launcher3.util.ResourceBasedOverride.Overrides;
  
  import java.util.concurrent.ExecutionException;
  
  /**
   * Utility class for defining singletons which are initiated on main thread.
   */
  public class MainThreadInitializedObject<T> {
  
      private final ObjectProvider<T> mProvider;
      private T mValue;
  
      public MainThreadInitializedObject(ObjectProvider<T> provider) {
          mProvider = provider;
      }
  
      public T get(Context context) {
          if (mValue == null) {
              if (Looper.myLooper() == Looper.getMainLooper()) {
                  mValue = mProvider.get(context.getApplicationContext());
              } else {
                  try {
                      return MAIN_EXECUTOR.submit(() -> get(context)).get();
                  } catch (InterruptedException|ExecutionException e) {
                      throw new RuntimeException(e);
                  }
              }
          }
          return mValue;
      }
  
      public T getNoCreate() {
          return mValue;
      }
  
      @VisibleForTesting
      public void initializeForTesting(T value) {
          mValue = value;
      }
  
      /**
       * Initializes a provider based on resource overrides
       */
      public static <T extends ResourceBasedOverride> MainThreadInitializedObject<T> forOverride(
              Class<T> clazz, int resourceId) {
          return new MainThreadInitializedObject<>(c -> Overrides.getObject(clazz, c, resourceId));
      }
  
      public interface ObjectProvider<T> {
  
          T get(Context context);
      }
  }
  