Java tutorial
/* * Copyright (C) 2012 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.ustc.dystu.dandelion.utils.image; import java.io.File; import com.ustc.dystu.dandelion.BuildConfig; import android.content.Context; import android.graphics.Bitmap; import android.graphics.Bitmap.CompressFormat; import android.support.v4.app.FragmentActivity; import android.support.v4.util.LruCache; /** * This class holds our bitmap caches (memory and disk). */ public class ImageCache { private static final String TAG = "ImageCache"; // Default memory cache size private static final int DEFAULT_MEM_CACHE_SIZE = 1024 * 1024 * 5; // 5MB // Default disk cache size private static final int DEFAULT_DISK_CACHE_SIZE = 1024 * 1024 * 10; // 10MB // Compression settings when writing images to disk cache private static final CompressFormat DEFAULT_COMPRESS_FORMAT = CompressFormat.JPEG; private static final int DEFAULT_COMPRESS_QUALITY = 70; // Constants to easily toggle various caches private static final boolean DEFAULT_MEM_CACHE_ENABLED = true; private static final boolean DEFAULT_DISK_CACHE_ENABLED = true; private static final boolean DEFAULT_CLEAR_DISK_CACHE_ON_START = false; private DiskLruCache mDiskCache; private LruCache<String, Bitmap> mMemoryCache; /** * Creating a new ImageCache object using the specified parameters. * * @param context The context to use * @param cacheParams The cache parameters to use to initialize the cache */ public ImageCache(Context context, ImageCacheParams cacheParams) { init(context, cacheParams); } /** * Creating a new ImageCache object using the default parameters. * * @param context The context to use * @param uniqueName A unique name that will be appended to the cache directory */ public ImageCache(Context context, String uniqueName) { init(context, new ImageCacheParams(uniqueName)); } /** * Find and return an existing ImageCache stored in a {@link RetainFragment}, if not found a new * one is created with defaults and saved to a {@link RetainFragment}. * * @param activity The calling {@link FragmentActivity} * @param uniqueName A unique name to append to the cache directory * @return An existing retained ImageCache object or a new one if one did not exist. */ public static ImageCache findOrCreateCache(final FragmentActivity activity, final String uniqueName) { return findOrCreateCache(activity, new ImageCacheParams(uniqueName)); } /** * Find and return an existing ImageCache stored in a {@link RetainFragment}, if not found a new * one is created using the supplied params and saved to a {@link RetainFragment}. * * @param activity The calling {@link FragmentActivity} * @param cacheParams The cache parameters to use if creating the ImageCache * @return An existing retained ImageCache object or a new one if one did not exist */ public static ImageCache findOrCreateCache(final FragmentActivity activity, ImageCacheParams cacheParams) { // Search for, or create an instance of the non-UI RetainFragment final RetainFragment mRetainFragment = RetainFragment .findOrCreateRetainFragment(activity.getSupportFragmentManager()); // See if we already have an ImageCache stored in RetainFragment ImageCache imageCache = (ImageCache) mRetainFragment.getObject(); // No existing ImageCache, create one and store it in RetainFragment if (imageCache == null) { imageCache = new ImageCache(activity, cacheParams); mRetainFragment.setObject(imageCache); } return imageCache; } /** * Initialize the cache, providing all parameters. * * @param context The context to use * @param cacheParams The cache parameters to initialize the cache */ private void init(Context context, ImageCacheParams cacheParams) { final File diskCacheDir = DiskLruCache.getDiskCacheDir(context, cacheParams.uniqueName); // Set up disk cache if (cacheParams.diskCacheEnabled) { mDiskCache = DiskLruCache.openCache(context, diskCacheDir, cacheParams.diskCacheSize); if (mDiskCache == null) { return; } mDiskCache.setCompressParams(cacheParams.compressFormat, cacheParams.compressQuality); if (cacheParams.clearDiskCacheOnStart) { mDiskCache.clearCache(); } } // Set up memory cache if (cacheParams.memoryCacheEnabled) { mMemoryCache = new LruCache<String, Bitmap>(cacheParams.memCacheSize) { /** * Measure item size in bytes rather than units which is more practical for a bitmap * cache */ @Override protected int sizeOf(String key, Bitmap bitmap) { return Utils.getBitmapSize(bitmap); } }; } } public void addBitmapToCache(String data, Bitmap bitmap, boolean needDiskCache) { if (data == null || bitmap == null) { return; } // Add to memory cache if (mMemoryCache != null && mMemoryCache.get(data) == null) { mMemoryCache.put(data, bitmap); } // Add to disk cache if (needDiskCache && mDiskCache != null && !mDiskCache.containsKey(data)) { mDiskCache.put(data, bitmap); } } /** * Get from memory cache. * * @param data Unique identifier for which item to get * @return The bitmap if found in cache, null otherwise */ public Bitmap getBitmapFromMemCache(String data) { if (mMemoryCache != null) { final Bitmap memBitmap = mMemoryCache.get(data); if (memBitmap != null) { if (BuildConfig.DEBUG) { // Log.d(TAG, "Memory cache hit"); } return memBitmap; } } return null; } /** * Get from disk cache. * * @param data Unique identifier for which item to get * @return The bitmap if found in cache, null otherwise */ public Bitmap getBitmapFromDiskCache(String data) { if (mDiskCache != null) { return mDiskCache.get(data); } return null; } public void clearCaches() { if (mDiskCache != null) { mDiskCache.clearCache(); } if (mMemoryCache != null) { mMemoryCache.evictAll(); } } public LruCache<String, Bitmap> getMemCache() { return mMemoryCache; } /** * A holder class that contains cache parameters. */ public static class ImageCacheParams { public String uniqueName; public int memCacheSize = DEFAULT_MEM_CACHE_SIZE; public int diskCacheSize = DEFAULT_DISK_CACHE_SIZE; public CompressFormat compressFormat = DEFAULT_COMPRESS_FORMAT; public int compressQuality = DEFAULT_COMPRESS_QUALITY; public boolean memoryCacheEnabled = DEFAULT_MEM_CACHE_ENABLED; public boolean diskCacheEnabled = DEFAULT_DISK_CACHE_ENABLED; public boolean clearDiskCacheOnStart = DEFAULT_CLEAR_DISK_CACHE_ON_START; public ImageCacheParams(String uniqueName) { this.uniqueName = uniqueName; } } }