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 org.mrchen.commlib.bitmapfun; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import org.mrchen.commlib.BuildConfig; import android.annotation.TargetApi; import android.app.Activity; 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 android.util.AttributeSet; import android.util.Log; /** * 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;// ? 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 * @param uniqueName * A unique name that will be appended to the cache directory */ public ImageCache(Context context, String uniqueName) { init(new ImageCacheParams(context, 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 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) { if (BuildConfig.DEBUG) { Log.d(TAG, "Memory cache created (size = " + mCacheParams.memCacheSize + ")"); } mMemoryCache = new LruCache<String, Bitmap>(mCacheParams.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 getBitmapSize(bitmap); } }; } // 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); if (BuildConfig.DEBUG) { Log.d(TAG, "Disk cache initialized"); } } catch (final IOException e) { mCacheParams.diskCacheDir = null; Log.e(TAG, "initDiskCache - " + 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) { Log.e(TAG, "addBitmapToCache - " + e); } catch (Exception e) { Log.e(TAG, "addBitmapToCache - " + 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) { 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) { final String key = hashKeyForDisk(data); synchronized (mDiskCacheLock) { while (mDiskCacheStarting) { try { // ??mDiskCacheStartingfalsemDiskCacheLock.notifyAll()? mDiskCacheLock.wait(); } catch (InterruptedException e) { } } if (mDiskLruCache != null) { InputStream inputStream = null; try { final DiskLruCache.Snapshot snapshot = mDiskLruCache.get(key); if (snapshot != null) { if (BuildConfig.DEBUG) { Log.d(TAG, "Disk cache hit"); } inputStream = snapshot.getInputStream(DISK_CACHE_INDEX); if (inputStream != null) { final Bitmap bitmap = BitmapFactory.decodeStream(inputStream); return bitmap; } } } catch (final IOException e) { Log.e(TAG, "getBitmapFromDiskCache - " + e); } finally { try { if (inputStream != null) { inputStream.close(); } } catch (IOException 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. * (ImageCache?????UI????) */ public void clearCache() { if (mMemoryCache != null) { mMemoryCache.evictAll(); if (BuildConfig.DEBUG) { Log.d(TAG, "Memory cache cleared"); } } synchronized (mDiskCacheLock) { mDiskCacheStarting = true; if (mDiskLruCache != null && !mDiskLruCache.isClosed()) { try { mDiskLruCache.delete(); if (BuildConfig.DEBUG) { Log.d(TAG, "Disk cache cleared"); } } catch (IOException e) { Log.e(TAG, "clearCache - " + 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(); if (BuildConfig.DEBUG) { Log.d(TAG, "Disk cache flushed"); } } catch (IOException e) { Log.e(TAG, "flush - " + 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()) { mDiskLruCache.close(); mDiskLruCache = null; if (BuildConfig.DEBUG) { Log.d(TAG, "Disk cache closed"); } } } catch (IOException e) { Log.e(TAG, "close - " + e); } } } } /** * A holder class that contains cache parameters. */ public static class ImageCacheParams { public int memCacheSize = DEFAULT_MEM_CACHE_SIZE; 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, String uniqueName) { diskCacheDir = getDiskCacheDir(context, uniqueName); } public ImageCacheParams(File diskCacheDir) { this.diskCacheDir = diskCacheDir; } /** * Sets the memory cache size based on a percentage of the device memory * class. Eg. setting percent to 0.2 would set the memory cache to one * fifth of the device memory class. Throws * {@link IllegalArgumentException} if percent is < 0.05 or > .8. * * 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 context * Context to use to fetch memory class * @param percent * Percent of memory class to use to size memory cache */ public void setMemCacheSizePercent(Context context, 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 * getMemoryClass(context) * 1024 * 1024); } 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 (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. */ @TargetApi(9) 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 */ @TargetApi(8) 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); } /** * Check how much usable space is available at a given path. * * @param path * The path to check * @return The space available in bytes */ @TargetApi(9) public static long getUsableSpace(File path) { if (Utils.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(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; } /** * 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<br> * ??Fragment??? */ public RetainFragment() { } // onAttach?setContentViewxmlView<fragment> // ??onSaveInstanceState()????Bundle??? // onInflate()?onInflate()onAttach()?Activity??? // onInflate()?onCreateView()?BundlesetArguments() // AndroidFragmentonInflate()??AndroidonInflate() @Override public void onInflate(Activity activity, AttributeSet attrs, Bundle savedInstanceState) { super.onInflate(activity, attrs, savedInstanceState); } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Fragment??Activity????Fragment // Fragment???onCreate()setRetainInstance(true/false)? // onCreate()setRetainInstance(true)?Fragment?? // onCreate()onDestroy()?onCreate()?? // 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; } } }