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.xpple.jahoqy.util; import java.io.File; import java.lang.ref.SoftReference; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.util.Collections; import java.util.HashSet; import java.util.Iterator; import java.util.Set; import android.content.Context; import android.graphics.Bitmap; import android.graphics.Bitmap.Config; import android.graphics.BitmapFactory; import android.graphics.drawable.BitmapDrawable; import android.os.Build.VERSION_CODES; import android.os.Bundle; import android.os.Environment; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentManager; import android.support.v4.util.LruCache; import android.util.Log; import com.xpple.jahoqy.config.BuildConfig; /** * This class memory caching of bitmaps in conjunction with the * {@link ImageWorker} class and its subclasses. Use * {@link videoImageCache#getInstance(FragmentManager, ImageCacheParams)} * to get an instance of this class, although usually a cache should be added * directly to an {@link ImageWorker} by calling * {@link ImageWorker#addImageCache(FragmentManager, ImageCacheParams)} * . */ public class videoImageCache { private static final String TAG = "ImageCache"; // Default memory cache size in kilobytes private static final int DEFAULT_MEM_CACHE_SIZE = 1024 * 5; // 5MB 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_INIT_DISK_CACHE_ON_CREATE = false; private LruCache<String, BitmapDrawable> mMemoryCache; private ImageCacheParams mCacheParams; private Set<SoftReference<Bitmap>> mReusableBitmaps; /** * Create a new ImageCache object using the specified parameters. This * should not be called directly by other classes, instead use * {@link videoImageCache#getInstance(FragmentManager, ImageCacheParams)} * to fetch an ImageCache instance. * * @param cacheParams * The cache parameters to use to initialize the cache */ private videoImageCache(ImageCacheParams cacheParams) { init(cacheParams); } /** * Return an {@link videoImageCache} instance. A {@link RetainFragment} is used * to retain the ImageCache object across configuration changes such as a * change in device orientation. * * @param fragmentManager * The fragment manager to use when dealing with the retained * fragment. * @param cacheParams * The cache parameters to use if the ImageCache needs * instantiation. * @return An existing retained ImageCache object or a new one if one did * not exist */ public static videoImageCache getInstance(FragmentManager fragmentManager, ImageCacheParams cacheParams) { // Search for, or create an instance of the non-UI RetainFragment final RetainFragment mRetainFragment = findOrCreateRetainFragment(fragmentManager); // See if we already have an ImageCache stored in RetainFragment videoImageCache imageCache = (videoImageCache) mRetainFragment.getObject(); // No existing ImageCache, create one and store it in RetainFragment if (imageCache == null) { imageCache = new videoImageCache(cacheParams); mRetainFragment.setObject(imageCache); } return imageCache; } /** * Initialize the cache, providing all parameters. * * @param cacheParams * The cache parameters to initialize the cache */ private void init(ImageCacheParams cacheParams) { mCacheParams = cacheParams; // BEGIN_INCLUDE(init_memory_cache) // Set up memory cache if (mCacheParams.memoryCacheEnabled) { if (BuildConfig.DEBUG) { Log.d(TAG, "Memory cache created (size = " + mCacheParams.memCacheSize + ")"); } // If we're running on Honeycomb or newer, create a set of reusable // bitmaps that can be // populated into the inBitmap field of BitmapFactory.Options. Note // that the set is // of SoftReferences which will actually not be very effective due // to the garbage // collector being aggressive clearing Soft/WeakReferences. A better // approach // would be to use a strongly references bitmaps, however this would // require some // balancing of memory usage between this set and the bitmap // LruCache. It would also // require knowledge of the expected size of the bitmaps. From // Honeycomb to JellyBean // the size would need to be precise, from KitKat onward the size // would just need to // be the upper bound (due to changes in how inBitmap can re-use // bitmaps). if (Utils.hasHoneycomb()) { mReusableBitmaps = Collections.synchronizedSet(new HashSet<SoftReference<Bitmap>>()); } mMemoryCache = new LruCache<String, BitmapDrawable>(mCacheParams.memCacheSize) { /** * Notify the removed entry that is no longer being cached */ @Override protected void entryRemoved(boolean evicted, String key, BitmapDrawable oldValue, BitmapDrawable newValue) { if (RecyclingBitmapDrawable.class.isInstance(oldValue)) { // The removed entry is a recycling drawable, so notify // it // that it has been removed from the memory cache ((RecyclingBitmapDrawable) oldValue).setIsCached(false); } else { // The removed entry is a standard BitmapDrawable if (Utils.hasHoneycomb()) { // We're running on Honeycomb or later, so add the // bitmap // to a SoftReference set for possible use with // inBitmap later mReusableBitmaps.add(new SoftReference<Bitmap>(oldValue.getBitmap())); } } } /** * Measure item size in kilobytes rather than units which is * more practical for a bitmap cache */ @Override protected int sizeOf(String key, BitmapDrawable value) { final int bitmapSize = getBitmapSize(value) / 1024; return bitmapSize == 0 ? 1 : bitmapSize; } }; } } /** * Adds a bitmap to both memory and disk cache. * * @param data * Unique identifier for the bitmap to store * @param value * The bitmap drawable to store */ public void addBitmapToCache(String data, BitmapDrawable value) { // BEGIN_INCLUDE(add_bitmap_to_cache) if (data == null || value == null) { return; } // Add to memory cache if (mMemoryCache != null) { if (RecyclingBitmapDrawable.class.isInstance(value)) { // The removed entry is a recycling drawable, so notify it // that it has been added into the memory cache ((RecyclingBitmapDrawable) value).setIsCached(true); } mMemoryCache.put(data, value); } } /** * Get from memory cache. * * @param data * Unique identifier for which item to get * @return The bitmap drawable if found in cache, null otherwise */ public BitmapDrawable getBitmapFromMemCache(String data) { // BEGIN_INCLUDE(get_bitmap_from_mem_cache) BitmapDrawable memValue = null; if (mMemoryCache != null) { memValue = mMemoryCache.get(data); } if (BuildConfig.DEBUG && memValue != null) { Log.d(TAG, "Memory cache hit"); } return memValue; // END_INCLUDE(get_bitmap_from_mem_cache) } /** * @param options * - BitmapFactory.Options with out* options populated * @return Bitmap that case be used for inBitmap */ protected Bitmap getBitmapFromReusableSet(BitmapFactory.Options options) { // BEGIN_INCLUDE(get_bitmap_from_reusable_set) Bitmap bitmap = null; if (mReusableBitmaps != null && !mReusableBitmaps.isEmpty()) { synchronized (mReusableBitmaps) { final Iterator<SoftReference<Bitmap>> iterator = mReusableBitmaps.iterator(); Bitmap item; while (iterator.hasNext()) { item = iterator.next().get(); if (null != item && item.isMutable()) { // Check to see it the item can be used for inBitmap if (canUseForInBitmap(item, options)) { bitmap = item; // Remove from reusable set so it can't be used // again iterator.remove(); break; } } else { // Remove from the set if the reference has been // cleared. iterator.remove(); } } } } return bitmap; // END_INCLUDE(get_bitmap_from_reusable_set) } /** * Clears both the memory and disk cache associated with this ImageCache * object. Note that this includes disk access so this should not be * executed on the main/UI thread. */ public void clearCache() { if (mMemoryCache != null) { mMemoryCache.evictAll(); if (BuildConfig.DEBUG) { Log.d(TAG, "Memory cache cleared"); } } } /** * A holder class that contains cache parameters. */ public static class ImageCacheParams { public int memCacheSize = DEFAULT_MEM_CACHE_SIZE; public int compressQuality = DEFAULT_COMPRESS_QUALITY; public boolean memoryCacheEnabled = DEFAULT_MEM_CACHE_ENABLED; public boolean initDiskCacheOnCreate = DEFAULT_INIT_DISK_CACHE_ON_CREATE; /** * Sets the memory cache size based on a percentage of the max available * VM memory. Eg. setting percent to 0.2 would set the memory cache to * one fifth of the available memory. Throws * {@link IllegalArgumentException} if percent is < 0.01 or > .8. * memCacheSize is stored in kilobytes instead of bytes as this will * eventually be passed to construct a LruCache which takes an int in * its constructor. * * This value should be chosen carefully based on a number of factors * Refer to the corresponding Android Training class for more * discussion: http://developer.android.com/training/displaying-bitmaps/ * * @param percent * Percent of available app memory to use to size memory * cache */ public void setMemCacheSizePercent(float percent) { if (percent < 0.01f || percent > 0.8f) { throw new IllegalArgumentException( "setMemCacheSizePercent - percent must be " + "between 0.01 and 0.8 (inclusive)"); } memCacheSize = Math.round(percent * Runtime.getRuntime().maxMemory() / 1024); } } /** * @param candidate * - Bitmap to check * @param targetOptions * - Options that have the out* value populated * @return true if <code>candidate</code> can be used for inBitmap re-use * with <code>targetOptions</code> */ private static boolean canUseForInBitmap(Bitmap candidate, BitmapFactory.Options targetOptions) { // BEGIN_INCLUDE(can_use_for_inbitmap) if (!Utils.hasKitKat()) { // On earlier versions, the dimensions must match exactly and the // inSampleSize must be 1 return candidate.getWidth() == targetOptions.outWidth && candidate.getHeight() == targetOptions.outHeight && targetOptions.inSampleSize == 1; } // From Android 4.4 (KitKat) onward we can re-use if the byte size of // the new bitmap // is smaller than the reusable bitmap candidate allocation byte count. int width = targetOptions.outWidth / targetOptions.inSampleSize; int height = targetOptions.outHeight / targetOptions.inSampleSize; int byteCount = width * height * getBytesPerPixel(candidate.getConfig()); return byteCount <= candidate.getByteCount(); // END_INCLUDE(can_use_for_inbitmap) } /** * Return the byte usage per pixel of a bitmap based on its configuration. * * @param config * The bitmap configuration. * @return The byte usage per pixel. */ private static int getBytesPerPixel(Config config) { if (config == Config.ARGB_8888) { return 4; } else if (config == Config.RGB_565) { return 2; } else if (config == Config.ARGB_4444) { return 2; } else if (config == Config.ALPHA_8) { return 1; } return 1; } /** * Get a usable cache directory (external if available, internal otherwise). * * @param context * The context to use * @param uniqueName * A unique directory name to append to the cache dir * @return The cache dir */ public static File getDiskCacheDir(Context context, String uniqueName) { // Check if media is mounted or storage is built-in, if so, try and use // external cache dir // otherwise use internal cache dir final String cachePath = Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()) || !isExternalStorageRemovable() ? getExternalCacheDir(context).getPath() : context.getCacheDir().getPath(); return new File(cachePath + File.separator + uniqueName); } /** * A hashing method that changes a string (like a URL) into a hash suitable * for using as a disk filename. */ public static String hashKeyForDisk(String key) { String cacheKey; try { final MessageDigest mDigest = MessageDigest.getInstance("MD5"); mDigest.update(key.getBytes()); cacheKey = bytesToHexString(mDigest.digest()); } catch (NoSuchAlgorithmException e) { cacheKey = String.valueOf(key.hashCode()); } return cacheKey; } private static String bytesToHexString(byte[] bytes) { // http://stackoverflow.com/questions/332079 StringBuilder sb = new StringBuilder(); for (int i = 0; i < bytes.length; i++) { String hex = Integer.toHexString(0xFF & bytes[i]); if (hex.length() == 1) { sb.append('0'); } sb.append(hex); } return sb.toString(); } /** * Get the size in bytes of a bitmap in a BitmapDrawable. Note that from * Android 4.4 (KitKat) onward this returns the allocated memory size of the * bitmap which can be larger than the actual bitmap data byte count (in the * case it was re-used). * * @param value * @return size in bytes */ public static int getBitmapSize(BitmapDrawable value) { Bitmap bitmap = value.getBitmap(); // From KitKat onward use getAllocationByteCount() as allocated bytes // can potentially be // larger than bitmap byte count. // if (Utils.hasKitKat()) { // return bitmap.getAllocationByteCount(); // } if (Utils.hasHoneycombMR1()) { return bitmap.getByteCount(); } // Pre HC-MR1 return bitmap.getRowBytes() * bitmap.getHeight(); } /** * Check if external storage is built-in or removable. * * @return True if external storage is removable (like an SD card), false * otherwise. */ public static boolean isExternalStorageRemovable() { if (Utils.hasGingerbread()) { return Environment.isExternalStorageRemovable(); } return true; } /** * Get the external app cache directory. * * @param context * The context to use * @return The external cache dir */ public static File getExternalCacheDir(Context context) { if (Utils.hasFroyo()) { return context.getExternalCacheDir(); } // Before Froyo we need to construct the external cache dir ourselves final String cacheDir = "/Android/data/" + context.getPackageName() + "/cache/"; return new File(Environment.getExternalStorageDirectory().getPath() + cacheDir); } /** * Locate an existing instance of this Fragment or if not found, create and * add it using FragmentManager. * * @param fm * The FragmentManager manager to use. * @return The existing instance of the Fragment or the new instance if just * created. */ private static RetainFragment findOrCreateRetainFragment(FragmentManager fm) { // BEGIN_INCLUDE(find_create_retain_fragment) // Check to see if we have retained the worker fragment. RetainFragment mRetainFragment = (RetainFragment) fm.findFragmentByTag(TAG); // If not retained (or first time running), we need to create and add // it. if (mRetainFragment == null) { mRetainFragment = new RetainFragment(); fm.beginTransaction().add(mRetainFragment, TAG).commitAllowingStateLoss(); } return mRetainFragment; // END_INCLUDE(find_create_retain_fragment) } /** * A simple non-UI Fragment that stores a single Object and is retained over * configuration changes. It will be used to retain the ImageCache object. */ public static class RetainFragment extends Fragment { private Object mObject; /** * Empty constructor as per the Fragment documentation */ public RetainFragment() { } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Make sure this Fragment is retained over a configuration change setRetainInstance(true); } /** * Store a single object in this Fragment. * * @param object * The object to store */ public void setObject(Object object) { mObject = object; } /** * Get the stored object. * * @return The stored object */ public Object getObject() { return mObject; } } }