ImageRequester.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 io.material.demo.codelab.buildingbeautifulapps;

import android.content.Context;
import android.graphics.Bitmap;
import android.util.DisplayMetrics;
import android.util.LruCache;

import com.android.volley.RequestQueue;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.NetworkImageView;
import com.android.volley.toolbox.Volley;

/**
 * Singleton class that handles image requests using Volley.
 */
public class ImageRequester {
    private static volatile ImageRequester instance;
    private final RequestQueue requestQueue;
    private final ImageLoader imageLoader;
    private final int maxByteSize;

    private ImageRequester(Context context) {
        this.requestQueue = Volley.newRequestQueue(context.getApplicationContext());
        this.requestQueue.start();
        this.maxByteSize = calculateMaxByteSize(context);
        this.imageLoader =
                new ImageLoader(
                        requestQueue,
                        new ImageLoader.ImageCache() {
                            private final LruCache<String, Bitmap> lruCache =
                                    new LruCache<String, Bitmap>(maxByteSize) {
                                        @Override
                                        protected int sizeOf(String url, Bitmap bitmap) {
                                            return bitmap.getByteCount();
                                        }
                                    };

                            @Override
                            public synchronized Bitmap getBitmap(String url) {
                                return lruCache.get(url);
                            }

                            @Override
                            public synchronized void putBitmap(String url, Bitmap bitmap) {
                                lruCache.put(url, bitmap);
                            }
                        });
    }

    private static int calculateMaxByteSize(Context context) {
        DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();
        final int screenBytes = displayMetrics.widthPixels * displayMetrics.heightPixels * 4;
        return screenBytes * 3;
    }

    /**
     * Returns the {@link ImageRequester} that is associated with the specified context,
     * instantiating one if it has not been created yet.
     *
     * @param context the activity that will use the ImageRequester
     */
    public static ImageRequester getInstance(Context context) {
        ImageRequester result = instance;
        if (result == null) {
            synchronized (ImageRequester.class) {
                result = instance;
                if (result == null) {
                    result = instance = new ImageRequester(context);
                }
            }
        }

        return result;
    }

    public void setImageFromUrl(NetworkImageView networkImageView, String url) {
        networkImageView.setImageUrl(url, imageLoader);
    }
}