com.wowcow.chat10.imagecache.ImageCache.java Source code

Java tutorial

Introduction

Here is the source code for com.wowcow.chat10.imagecache.ImageCache.java

Source

/*
 * Copyright 2012 Google Inc.
 *
 * 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.wowcow.chat10.imagecache;

import android.annotation.TargetApi;
import android.app.ActivityManager;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Environment;
import android.os.StatFs;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.util.LruCache;

import com.wowcow.chat10.Utils.Logger;
import com.wowcow.chat10.Utils.VersionUtil;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * This class holds our bitmap caches (memory and disk).
 */
public class ImageCache {
    private static final Logger logger = Logger.getInstance(ImageCache.class);

    // Default memory cache size as a percent of device memory class
    private static final float DEFAULT_MEM_CACHE_PERCENT = 0.15f;

    // Default disk cache size
    private static final int DEFAULT_DISK_CACHE_SIZE = 1024 * 1024 * 10; // 10MB

    // Default disk cache directory name
    private static final String DEFAULT_DISK_CACHE_DIR = "images";

    // Compression settings when writing images to disk cache
    private static final CompressFormat DEFAULT_COMPRESS_FORMAT = CompressFormat.PNG;
    private static final int DEFAULT_COMPRESS_QUALITY = 100;
    private static final int DISK_CACHE_INDEX = 0;

    // 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 static final boolean DEFAULT_INIT_DISK_CACHE_ON_CREATE = false;

    private DiskLruCache mDiskLruCache;
    private LruCache<String, Bitmap> mMemoryCache;
    private ImageCacheParams mCacheParams;
    private final Object mDiskCacheLock = new Object();
    private boolean mDiskCacheStarting = true;

    /**
     * Creating a new ImageCache object using the specified parameters.
     * 
     * @param cacheParams
     *          The cache parameters to use to initialize the cache
     */
    public ImageCache(ImageCacheParams cacheParams) {
        init(cacheParams);
    }

    /**
     * Creating a new ImageCache object using the default parameters.
     * 
     * @param context
     *          The context to use
     */
    public ImageCache(Context context) {
        init(new ImageCacheParams(context));
    }

    /**
     * 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 fragmentManager
     *          The fragment manager to use when dealing with the retained
     *          fragment.
     * @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(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
        ImageCache imageCache = (ImageCache) mRetainFragment.getObject();

        // No existing ImageCache, create one and store it in RetainFragment
        if (imageCache == null) {
            imageCache = new ImageCache(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;

        // Set up memory cache
        if (mCacheParams.memoryCacheEnabled) {
            logger.d("Memory cache created (size = " + mCacheParams.memCacheSize + ")");
            mMemoryCache = new LruCache<String, Bitmap>(mCacheParams.memCacheSize) {
                /**
                 * Measure item size in kilobytes rather than units which is more
                 * practical for a bitmap cache
                 */
                @Override
                protected int sizeOf(String key, Bitmap bitmap) {
                    final int bitmapSize = getBitmapSize(bitmap) / 1024;
                    return bitmapSize == 0 ? 1 : bitmapSize;
                }
            };
        }

        // By default the disk cache is not initialized here as it should be
        // initialized
        // on a separate thread due to disk access.
        if (cacheParams.initDiskCacheOnCreate) {
            // Set up disk cache
            initDiskCache();
        }
    }

    /**
     * Initializes the disk cache. Note that this includes disk access so this
     * should not be executed on the main/UI thread. By default an ImageCache does
     * not initialize the disk cache when it is created, instead you should call
     * initDiskCache() to initialize it on a background thread.
     */
    public void initDiskCache() {
        // Set up disk cache
        synchronized (mDiskCacheLock) {
            if (mDiskLruCache == null || mDiskLruCache.isClosed()) {
                File diskCacheDir = mCacheParams.diskCacheDir;
                if (mCacheParams.diskCacheEnabled && diskCacheDir != null) {
                    if (!diskCacheDir.exists()) {
                        diskCacheDir.mkdirs();
                    }
                    if (getUsableSpace(diskCacheDir) > mCacheParams.diskCacheSize) {
                        try {
                            mDiskLruCache = DiskLruCache.open(diskCacheDir, 1, 1, mCacheParams.diskCacheSize);
                            logger.d("Disk cache initialized");
                        } catch (final IOException e) {
                            mCacheParams.diskCacheDir = null;
                            logger.e("initDiskCache - " + e.getMessage(), e);
                        }
                    }
                }
            }
            mDiskCacheStarting = false;
            mDiskCacheLock.notifyAll();
        }
    }

    /**
     * Adds a bitmap to both memory and disk cache.
     * 
     * @param data
     *          Unique identifier for the bitmap to store
     * @param bitmap
     *          The bitmap to store
     */
    public void addBitmapToCache(String data, Bitmap bitmap) {
        if (data == null || bitmap == null) {
            return;
        }

        // Add to memory cache
        if (mMemoryCache != null && mMemoryCache.get(data) == null) {
            mMemoryCache.put(data, bitmap);
        }

        synchronized (mDiskCacheLock) {
            // Add to disk cache
            if (mDiskLruCache != null) {
                final String key = hashKeyForDisk(data);
                OutputStream out = null;
                try {
                    DiskLruCache.Snapshot snapshot = mDiskLruCache.get(key);
                    if (snapshot == null) {
                        final DiskLruCache.Editor editor = mDiskLruCache.edit(key);
                        if (editor != null) {
                            out = editor.newOutputStream(DISK_CACHE_INDEX);
                            bitmap.compress(mCacheParams.compressFormat, mCacheParams.compressQuality, out);
                            editor.commit();
                            out.close();
                        }
                    } else {
                        snapshot.getInputStream(DISK_CACHE_INDEX).close();
                    }
                } catch (final IOException e) {
                    logger.e("addBitmapToCache - " + e.getMessage(), e);
                } catch (Exception e) {
                    logger.e("addBitmapToCache - " + e.getMessage(), e);
                } finally {
                    try {
                        if (out != null) {
                            out.close();
                        }
                    } catch (IOException e) {
                    }
                }
            }
        }
    }

    /**
     * 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) {
                logger.d("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) {
        final String key = hashKeyForDisk(data);
        synchronized (mDiskCacheLock) {
            while (mDiskCacheStarting) {
                try {
                    mDiskCacheLock.wait();
                } catch (InterruptedException e) {
                }
            }
            if (mDiskLruCache != null) {
                InputStream inputStream = null;
                try {
                    final DiskLruCache.Snapshot snapshot = mDiskLruCache.get(key);
                    if (snapshot != null) {
                        logger.d("Disk cache hit");
                        inputStream = snapshot.getInputStream(DISK_CACHE_INDEX);
                        if (inputStream != null) {
                            final Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                            return bitmap;
                        }
                    }
                } catch (final IOException e) {
                    logger.e("getBitmapFromDiskCache - " + e, e);
                } finally {
                    try {
                        if (inputStream != null) {
                            inputStream.close();
                        }
                    } catch (IOException e) {
                        logger.e(e.getMessage(), e);
                    }
                }
            }
            return null;
        }
    }

    /**
     * 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();
            logger.d("Memory cache cleared");
        }

        synchronized (mDiskCacheLock) {
            mDiskCacheStarting = true;
            if (mDiskLruCache != null && !mDiskLruCache.isClosed()) {
                try {
                    mDiskLruCache.delete();
                    logger.d("Disk cache cleared");
                } catch (IOException e) {
                    logger.e("clearCache - " + e.getMessage(), e);
                }
                mDiskLruCache = null;
                initDiskCache();
            }
        }
    }

    /**
     * Flushes the 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 flush() {
        synchronized (mDiskCacheLock) {
            if (mDiskLruCache != null) {
                try {
                    mDiskLruCache.flush();
                    logger.d("Disk cache flushed");
                } catch (IOException e) {
                    logger.e("flush - " + e.getMessage(), e);
                }
            }
        }
    }

    /**
     * Closes the 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 close() {
        synchronized (mDiskCacheLock) {
            if (mDiskLruCache != null) {
                try {
                    if (mDiskLruCache.isClosed() == false) {
                        mDiskLruCache.close();
                        mDiskLruCache = null;
                        logger.d("Disk cache closed");
                    }
                } catch (IOException e) {
                    logger.e(e.getMessage(), e);
                }
            }
        }
    }

    /**
     * A holder class that contains cache parameters.
     */
    public static class ImageCacheParams {
        public int memCacheSize;
        public int diskCacheSize = DEFAULT_DISK_CACHE_SIZE;
        public File diskCacheDir;
        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 boolean initDiskCacheOnCreate = DEFAULT_INIT_DISK_CACHE_ON_CREATE;

        public ImageCacheParams(Context context) {
            init(getDiskCacheDir(context, DEFAULT_DISK_CACHE_DIR));
        }

        public ImageCacheParams(Context context, String uniqueName) {
            init(getDiskCacheDir(context, uniqueName));
        }

        public ImageCacheParams(File diskCacheDir) {
            init(diskCacheDir);
        }

        private void init(File diskCacheDir) {
            setMemCacheSizePercent(DEFAULT_MEM_CACHE_PERCENT);
            this.diskCacheDir = diskCacheDir;
        }

        /**
         * 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 avilable memory. Throws {@link IllegalArgumentException} if
         * percent is < 0.05 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 memory class to use to size memory cache
         */
        public void setMemCacheSizePercent(float percent) {
            if (percent < 0.05f || percent > 0.8f) {
                throw new IllegalArgumentException(
                        "setMemCacheSizePercent - percent must be " + "between 0.05 and 0.8 (inclusive)");
            }
            memCacheSize = Math.round(percent * Runtime.getRuntime().maxMemory() / 1024);
        }

        @SuppressWarnings("unused")
        private static int getMemoryClass(Context context) {
            return ((ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass();
        }
    }

    /**
     * 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.
     * 
     * @param bitmap
     * @return size in bytes
     */
    @TargetApi(12)
    public static int getBitmapSize(Bitmap bitmap) {
        if (VersionUtil.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.
     */
    @TargetApi(9)
    public static boolean isExternalStorageRemovable() {
        if (VersionUtil.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 (context.getExternalCacheDir() == null) {
            return context.getCacheDir();
        } else {
            return context.getExternalCacheDir();
        }
    }

    /**
     * Check how much usable space is available at a given path.
     * 
     * @param path
     *          The path to check
     * @return The space available in bytes
     */
    @SuppressWarnings("deprecation")
    @TargetApi(9)
    public static long getUsableSpace(File path) {
        if (VersionUtil.hasGingerbread()) {
            return path.getUsableSpace();
        }
        final StatFs stats = new StatFs(path.getPath());
        return (long) stats.getBlockSize() * (long) stats.getAvailableBlocks();
    }

    /**
     * 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.
     */
    public static RetainFragment findOrCreateRetainFragment(FragmentManager fm) {
        // Check to see if we have retained the worker fragment.
        RetainFragment mRetainFragment = (RetainFragment) fm.findFragmentByTag(logger.getTag());

        // If not retained (or first time running), we need to create and add it.
        if (mRetainFragment == null) {
            mRetainFragment = new RetainFragment();
            fm.beginTransaction().add(mRetainFragment, logger.getTag()).commitAllowingStateLoss();
        }

        return mRetainFragment;
    }

    /**
     * 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;
        }
    }
}