Android之本地快取——LruCache(記憶體快取)與DiskLruCache(硬碟快取)統一框架
本文參考郭霖大神的DiskLruCache解析,感興趣的朋友可以先到http://blog.csdn.net/guolin_blog/article/details/28863651瞭解。
一、前言
該框架或者說庫,主要是用於本地的圖片快取處理。
資料的存入
當你取到圖片的元資料,會將資料存入硬碟快取以及記憶體快取中。
資料的獲取
取資料的時候,先從記憶體快取中取;
如果沒有取到,則從硬碟快取中取(此時如果硬碟快取有資料,硬碟快取會重新將資料寫入記憶體快取中);
如果硬碟快取中沒有取到,則從網上重新獲取元資料;
二、設計
根據以上提到的功能:
首先,我們對LruCache以及DiskLruCache分別做了一個管理類,分別命名為LruCacheManager、DiskLruCacheManager,類中對使用者可能用到的方法做封裝;
其次,需要一個統一管理來CacheManager,對LruCacheManager、DiskLruCacheManager中的方法做排程;
三、具體實現
1、記憶體快取管理——LruCacheManager
先貼程式碼,有個直觀認識:
該類是依賴於Android提供的LruCache類實現的。package com.utils.cache; import android.graphics.Bitmap; import android.support.v4.util.LruCache; public class LruCacheManager { private LruCache<String, Bitmap> lruCache; public LruCacheManager(){ this((int)Runtime.getRuntime().maxMemory()/1024/8); } //設定自定義大小的LruCache public LruCacheManager(int maxSize){ lruCache=new LruCache<String, Bitmap>(maxSize*1024){ @Override protected int sizeOf(String key, Bitmap value) { return value.getByteCount()/1024; } }; } /** * 寫入索引key對應的快取 * @param key 索引 * @param bitmap 快取內容 * @return 寫入結果 */ public Bitmap putCache(String key,Bitmap bitmap){ Bitmap bitmapValue=getCache(key); if(bitmapValue==null){ if(lruCache!=null&&bitmap!=null) bitmapValue= lruCache.put(key, bitmap); } return bitmapValue; } /** * 獲取快取 * @param key 索引key對應的快取 * @return 快取 */ public Bitmap getCache(String key){ if(lruCache!=null){ return lruCache.get(key); } return null; } public void deleteCache(){ if(lruCache!=null) lruCache.evictAll(); } public void removeCache(String key){ if(lruCache!=null) lruCache.remove(key); } public int size(){ int size=0; if(lruCache!=null) size+=lruCache.size(); return size; } }
在該類中,提供了兩個構造方法,預設的構造方法是給記憶體快取分配當前android作業系統分配給該app的記憶體的1/8。這話比較拗口,意識就是,如果作業系統分配給app的記憶體是96M,那麼預設構造方法就是給記憶體快取分配記憶體96/8M。另一個構造方法是讓使用者自定義記憶體快取大小。
該類中其他的方法就不多做解釋,都是對LruCache方法的一次封裝。
2、硬碟快取管理——DiskLruCacheManager
使用硬碟快取管理前,需要先下載一個開源類:DiskLruCache,如下:
對於該類不瞭解的可以參考文章首行提到的郭霖的部落格連結。/* * Copyright (C) 2011 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.utils.cache; import java.io.BufferedInputStream; import java.io.BufferedWriter; import java.io.Closeable; import java.io.EOFException; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.FileWriter; import java.io.FilterOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.OutputStreamWriter; import java.io.Reader; import java.io.StringWriter; import java.io.Writer; import java.lang.reflect.Array; import java.nio.charset.Charset; import java.util.ArrayList; import java.util.Arrays; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.Map; import java.util.concurrent.Callable; import java.util.concurrent.ExecutorService; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; /** ****************************************************************************** * Taken from the JB source code, can be found in: * libcore/luni/src/main/java/libcore/io/DiskLruCache.java * or direct link: * https://android.googlesource.com/platform/libcore/+/android-4.1.1_r1/luni/src/main/java/libcore/io/DiskLruCache.java ****************************************************************************** * * A cache that uses a bounded amount of space on a filesystem. Each cache * entry has a string key and a fixed number of values. Values are byte * sequences, accessible as streams or files. Each value must be between {@code * 0} and {@code Integer.MAX_VALUE} bytes in length. * * <p>The cache stores its data in a directory on the filesystem. This * directory must be exclusive to the cache; the cache may delete or overwrite * files from its directory. It is an error for multiple processes to use the * same cache directory at the same time. * * <p>This cache limits the number of bytes that it will store on the * filesystem. When the number of stored bytes exceeds the limit, the cache will * remove entries in the background until the limit is satisfied. The limit is * not strict: the cache may temporarily exceed it while waiting for files to be * deleted. The limit does not include filesystem overhead or the cache * journal so space-sensitive applications should set a conservative limit. * * <p>Clients call {@link #edit} to create or update the values of an entry. An * entry may have only one editor at one time; if a value is not available to be * edited then {@link #edit} will return null. * <ul> * <li>When an entry is being <strong>created</strong> it is necessary to * supply a full set of values; the empty value should be used as a * placeholder if necessary. * <li>When an entry is being <strong>edited</strong>, it is not necessary * to supply data for every value; values default to their previous * value. * </ul> * Every {@link #edit} call must be matched by a call to {@link Editor#commit} * or {@link Editor#abort}. Committing is atomic: a read observes the full set * of values as they were before or after the commit, but never a mix of values. * * <p>Clients call {@link #get} to read a snapshot of an entry. The read will * observe the value at the time that {@link #get} was called. Updates and * removals after the call do not impact ongoing reads. * * <p>This class is tolerant of some I/O errors. If files are missing from the * filesystem, the corresponding entries will be dropped from the cache. If * an error occurs while writing a cache value, the edit will fail silently. * Callers should handle other problems by catching {@code IOException} and * responding appropriately. */ public final class DiskLruCache implements Closeable { static final String JOURNAL_FILE = "journal"; static final String JOURNAL_FILE_TMP = "journal.tmp"; static final String MAGIC = "libcore.io.DiskLruCache"; static final String VERSION_1 = "1"; static final long ANY_SEQUENCE_NUMBER = -1; private static final String CLEAN = "CLEAN"; private static final String DIRTY = "DIRTY"; private static final String REMOVE = "REMOVE"; private static final String READ = "READ"; private static final Charset UTF_8 = Charset.forName("UTF-8"); private static final int IO_BUFFER_SIZE = 8 * 1024; /* * This cache uses a journal file named "journal". A typical journal file * looks like this: * libcore.io.DiskLruCache * 1 * 100 * 2 * * CLEAN 3400330d1dfc7f3f7f4b8d4d803dfcf6 832 21054 * DIRTY 335c4c6028171cfddfbaae1a9c313c52 * CLEAN 335c4c6028171cfddfbaae1a9c313c52 3934 2342 * REMOVE 335c4c6028171cfddfbaae1a9c313c52 * DIRTY 1ab96a171faeeee38496d8b330771a7a * CLEAN 1ab96a171faeeee38496d8b330771a7a 1600 234 * READ 335c4c6028171cfddfbaae1a9c313c52 * READ 3400330d1dfc7f3f7f4b8d4d803dfcf6 * * The first five lines of the journal form its header. They are the * constant string "libcore.io.DiskLruCache", the disk cache's version, * the application's version, the value count, and a blank line. * * Each of the subsequent lines in the file is a record of the state of a * cache entry. Each line contains space-separated values: a state, a key, * and optional state-specific values. * o DIRTY lines track that an entry is actively being created or updated. * Every successful DIRTY action should be followed by a CLEAN or REMOVE * action. DIRTY lines without a matching CLEAN or REMOVE indicate that * temporary files may need to be deleted. * o CLEAN lines track a cache entry that has been successfully published * and may be read. A publish line is followed by the lengths of each of * its values. * o READ lines track accesses for LRU. * o REMOVE lines track entries that have been deleted. * * The journal file is appended to as cache operations occur. The journal may * occasionally be compacted by dropping redundant lines. A temporary file named * "journal.tmp" will be used during compaction; that file should be deleted if * it exists when the cache is opened. */ private final File directory; private final File journalFile; private final File journalFileTmp; private final int appVersion; private final long maxSize; private final int valueCount; private long size = 0; private Writer journalWriter; private final LinkedHashMap<String, Entry> lruEntries = new LinkedHashMap<String, Entry>(0, 0.75f, true); private int redundantOpCount; /** * To differentiate between old and current snapshots, each entry is given * a sequence number each time an edit is committed. A snapshot is stale if * its sequence number is not equal to its entry's sequence number. */ private long nextSequenceNumber = 0; /* From java.util.Arrays */ @SuppressWarnings("unchecked") private static <T> T[] copyOfRange(T[] original, int start, int end) { final int originalLength = original.length; // For exception priority compatibility. if (start > end) { throw new IllegalArgumentException(); } if (start < 0 || start > originalLength) { throw new ArrayIndexOutOfBoundsException(); } final int resultLength = end - start; final int copyLength = Math.min(resultLength, originalLength - start); final T[] result = (T[]) Array .newInstance(original.getClass().getComponentType(), resultLength); System.arraycopy(original, start, result, 0, copyLength); return result; } /** * Returns the remainder of 'reader' as a string, closing it when done. */ public static String readFully(Reader reader) throws IOException { try { StringWriter writer = new StringWriter(); char[] buffer = new char[1024]; int count; while ((count = reader.read(buffer)) != -1) { writer.write(buffer, 0, count); } return writer.toString(); } finally { reader.close(); } } /** * Returns the ASCII characters up to but not including the next "\r\n", or * "\n". * * @throws java.io.EOFException if the stream is exhausted before the next newline * character. */ public static String readAsciiLine(InputStream in) throws IOException { // TODO: support UTF-8 here instead StringBuilder result = new StringBuilder(80); while (true) { int c = in.read(); if (c == -1) { throw new EOFException(); } else if (c == '\n') { break; } result.append((char) c); } int length = result.length(); if (length > 0 && result.charAt(length - 1) == '\r') { result.setLength(length - 1); } return result.toString(); } /** * Closes 'closeable', ignoring any checked exceptions. Does nothing if 'closeable' is null. */ public static void closeQuietly(Closeable closeable) { if (closeable != null) { try { closeable.close(); } catch (RuntimeException rethrown) { throw rethrown; } catch (Exception ignored) { } } } /** * Recursively delete everything in {@code dir}. */ // TODO: this should specify paths as Strings rather than as Files public static void deleteContents(File dir) throws IOException { File[] files = dir.listFiles(); if (files == null) { throw new IllegalArgumentException("not a directory: " + dir); } for (File file : files) { if (file.isDirectory()) { deleteContents(file); } if (!file.delete()) { throw new IOException("failed to delete file: " + file); } } } /** This cache uses a single background thread to evict entries. */ private final ExecutorService executorService = new ThreadPoolExecutor(0, 1, 60L, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>()); private final Callable<Void> cleanupCallable = new Callable<Void>() { @Override public Void call() throws Exception { synchronized (DiskLruCache.this) { if (journalWriter == null) { return null; // closed } trimToSize(); if (journalRebuildRequired()) { rebuildJournal(); redundantOpCount = 0; } } return null; } }; private DiskLruCache(File directory, int appVersion, int valueCount, long maxSize) { this.directory = directory; this.appVersion = appVersion; this.journalFile = new File(directory, JOURNAL_FILE); this.journalFileTmp = new File(directory, JOURNAL_FILE_TMP); this.valueCount = valueCount; this.maxSize = maxSize; } /** * Opens the cache in {@code directory}, creating a cache if none exists * there. * * @param directory a writable directory * @param appVersion * @param valueCount the number of values per cache entry. Must be positive. * @param maxSize the maximum number of bytes this cache should use to store * @throws java.io.IOException if reading or writing the cache directory fails */ public static DiskLruCache open(File directory, int appVersion, int valueCount, long maxSize) throws IOException { if (maxSize <= 0) { throw new IllegalArgumentException("maxSize <= 0"); } if (valueCount <= 0) { throw new IllegalArgumentException("valueCount <= 0"); } // prefer to pick up where we left off DiskLruCache cache = new DiskLruCache(directory, appVersion, valueCount, maxSize); if (cache.journalFile.exists()) { try { cache.readJournal(); cache.processJournal(); cache.journalWriter = new BufferedWriter(new FileWriter(cache.journalFile, true), IO_BUFFER_SIZE); return cache; } catch (IOException journalIsCorrupt) { // System.logW("DiskLruCache " + directory + " is corrupt: " // + journalIsCorrupt.getMessage() + ", removing"); cache.delete(); } } // create a new empty cache directory.mkdirs(); cache = new DiskLruCache(directory, appVersion, valueCount, maxSize); cache.rebuildJournal(); return cache; } private void readJournal() throws IOException { InputStream in = new BufferedInputStream(new FileInputStream(journalFile), IO_BUFFER_SIZE); try { String magic = readAsciiLine(in); String version = readAsciiLine(in); String appVersionString = readAsciiLine(in); String valueCountString = readAsciiLine(in); String blank = readAsciiLine(in); if (!MAGIC.equals(magic) || !VERSION_1.equals(version) || !Integer.toString(appVersion).equals(appVersionString) || !Integer.toString(valueCount).equals(valueCountString) || !"".equals(blank)) { throw new IOException("unexpected journal header: [" + magic + ", " + version + ", " + valueCountString + ", " + blank + "]"); } while (true) { try { readJournalLine(readAsciiLine(in)); } catch (EOFException endOfJournal) { break; } } } finally { closeQuietly(in); } } private void readJournalLine(String line) throws IOException { String[] parts = line.split(" "); if (parts.length < 2) { throw new IOException("unexpected journal line: " + line); } String key = parts[1]; if (parts[0].equals(REMOVE) && parts.length == 2) { lruEntries.remove(key); return; } Entry entry = lruEntries.get(key); if (entry == null) { entry = new Entry(key); lruEntries.put(key, entry); } if (parts[0].equals(CLEAN) && parts.length == 2 + valueCount) { entry.readable = true; entry.currentEditor = null; entry.setLengths(copyOfRange(parts, 2, parts.length)); } else if (parts[0].equals(DIRTY) && parts.length == 2) { entry.currentEditor = new Editor(entry); } else if (parts[0].equals(READ) && parts.length == 2) { // this work was already done by calling lruEntries.get() } else { throw new IOException("unexpected journal line: " + line); } } /** * Computes the initial size and collects garbage as a part of opening the * cache. Dirty entries are assumed to be inconsistent and will be deleted. */ private void processJournal() throws IOException { deleteIfExists(journalFileTmp); for (Iterator<Entry> i = lruEntries.values().iterator(); i.hasNext(); ) { Entry entry = i.next(); if (entry.currentEditor == null) { for (int t = 0; t < valueCount; t++) { size += entry.lengths[t]; } } else { entry.currentEditor = null; for (int t = 0; t < valueCount; t++) { deleteIfExists(entry.getCleanFile(t)); deleteIfExists(entry.getDirtyFile(t)); } i.remove(); } } } /** * Creates a new journal that omits redundant information. This replaces the * current journal if it exists. */ private synchronized void rebuildJournal() throws IOException { if (journalWriter != null) { journalWriter.close(); } Writer writer = new BufferedWriter(new FileWriter(journalFileTmp), IO_BUFFER_SIZE); writer.write(MAGIC); writer.write("\n"); writer.write(VERSION_1); writer.write("\n"); writer.write(Integer.toString(appVersion)); writer.write("\n"); writer.write(Integer.toString(valueCount)); writer.write("\n"); writer.write("\n"); for (Entry entry : lruEntries.values()) { if (entry.currentEditor != null) { writer.write(DIRTY + ' ' + entry.key + '\n'); } else { writer.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n'); } } writer.close(); journalFileTmp.renameTo(journalFile); journalWriter = new BufferedWriter(new FileWriter(journalFile, true), IO_BUFFER_SIZE); } private static void deleteIfExists(File file) throws IOException { // try { // Libcore.os.remove(file.getPath()); // } catch (ErrnoException errnoException) { // if (errnoException.errno != OsConstants.ENOENT) { // throw errnoException.rethrowAsIOException(); // } // } if (file.exists() && !file.delete()) { throw new IOException(); } } /** * Returns a snapshot of the entry named {@code key}, or null if it doesn't * exist is not currently readable. If a value is returned, it is moved to * the head of the LRU queue. */ public synchronized Snapshot get(String key) throws IOException { checkNotClosed(); validateKey(key); Entry entry = lruEntries.get(key); if (entry == null) { return null; } if (!entry.readable) { return null; } /* * Open all streams eagerly to guarantee that we see a single published * snapshot. If we opened streams lazily then the streams could come * from different edits. */ InputStream[] ins = new InputStream[valueCount]; try { for (int i = 0; i < valueCount; i++) { ins[i] = new FileInputStream(entry.getCleanFile(i)); } } catch (FileNotFoundException e) { // a file must have been deleted manually! return null; } redundantOpCount++; journalWriter.append(READ + ' ' + key + '\n'); if (journalRebuildRequired()) { executorService.submit(cleanupCallable); } return new Snapshot(key, entry.sequenceNumber, ins); } /** * Returns an editor for the entry named {@code key}, or null if another * edit is in progress. */ public Editor edit(String key) throws IOException { return edit(key, ANY_SEQUENCE_NUMBER); } private synchronized Editor edit(String key, long expectedSequenceNumber) throws IOException { checkNotClosed(); validateKey(key); Entry entry = lruEntries.get(key); if (expectedSequenceNumber != ANY_SEQUENCE_NUMBER && (entry == null || entry.sequenceNumber != expectedSequenceNumber)) { return null; // snapshot is stale } if (entry == null) { entry = new Entry(key); lruEntries.put(key, entry); } else if (entry.currentEditor != null) { return null; // another edit is in progress } Editor editor = new Editor(entry); entry.currentEditor = editor; // flush the journal before creating files to prevent file leaks journalWriter.write(DIRTY + ' ' + key + '\n'); journalWriter.flush(); return editor; } /** * Returns the directory where this cache stores its data. */ public File getDirectory() { return directory; } /** * Returns the maximum number of bytes that this cache should use to store * its data. */ public long maxSize() { return maxSize; } /** * Returns the number of bytes currently being used to store the values in * this cache. This may be greater than the max size if a background * deletion is pending. */ public synchronized long size() { return size; } private synchronized void completeEdit(Editor editor, boolean success) throws IOException { Entry entry = editor.entry; if (entry.currentEditor != editor) { throw new IllegalStateException(); } // if this edit is creating the entry for the first time, every index must have a value if (success && !entry.readable) { for (int i = 0; i < valueCount; i++) { if (!entry.getDirtyFile(i).exists()) { editor.abort(); throw new IllegalStateException("edit didn't create file " + i); } } } for (int i = 0; i < valueCount; i++) { File dirty = entry.getDirtyFile(i); if (success) { if (dirty.exists()) { File clean = entry.getCleanFile(i); dirty.renameTo(clean); long oldLength = entry.lengths[i]; long newLength = clean.length(); entry.lengths[i] = newLength; size = size - oldLength + newLength; } } else { deleteIfExists(dirty); } } redundantOpCount++; entry.currentEditor = null; if (entry.readable | success) { entry.readable = true; journalWriter.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n'); if (success) { entry.sequenceNumber = nextSequenceNumber++; } } else { lruEntries.remove(entry.key); journalWriter.write(REMOVE + ' ' + entry.key + '\n'); } if (size > maxSize || journalRebuildRequired()) { executorService.submit(cleanupCallable); } } /** * We only rebuild the journal when it will halve the size of the journal * and eliminate at least 2000 ops. */ private boolean journalRebuildRequired() { final int REDUNDANT_OP_COMPACT_THRESHOLD = 2000; return redundantOpCount >= REDUNDANT_OP_COMPACT_THRESHOLD && redundantOpCount >= lruEntries.size(); } /** * Drops the entry for {@code key} if it exists and can be removed. Entries * actively being edited cannot be removed. * * @return true if an entry was removed. */ public synchronized boolean remove(String key) throws IOException { checkNotClosed(); validateKey(key); Entry entry = lruEntries.get(key); if (entry == null || entry.currentEditor != null) { return false; } for (int i = 0; i < valueCount; i++) { File file = entry.getCleanFile(i); if (!file.delete()) { throw new IOException("failed to delete " + file); } size -= entry.lengths[i]; entry.lengths[i] = 0; } redundantOpCount++; journalWriter.append(REMOVE + ' ' + key + '\n'); lruEntries.remove(key); if (journalRebuildRequired()) { executorService.submit(cleanupCallable); } return true; } /** * Returns true if this cache has been closed. */ public boolean isClosed() { return journalWriter == null; } private void checkNotClosed() { if (journalWriter == null) { throw new IllegalStateException("cache is closed"); } } /** * Force buffered operations to the filesystem. */ public synchronized void flush() throws IOException { checkNotClosed(); trimToSize(); journalWriter.flush(); } /** * Closes this cache. Stored values will remain on the filesystem. */ public synchronized void close() throws IOException { if (journalWriter == null) { return; // already closed } for (Entry entry : new ArrayList<Entry>(lruEntries.values())) { if (entry.currentEditor != null) { entry.currentEditor.abort(); } } trimToSize(); journalWriter.close(); journalWriter = null; } private void trimToSize() throws IOException { while (size > maxSize) { // Map.Entry<String, Entry> toEvict = lruEntries.eldest(); final Map.Entry<String, Entry> toEvict = lruEntries.entrySet().iterator().next(); remove(toEvict.getKey()); } } /** * Closes the cache and deletes all of its stored values. This will delete * all files in the cache directory including files that weren't created by * the cache. */ public void delete() throws IOException { close(); deleteContents(directory); } private void validateKey(String key) { if (key.contains(" ") || key.contains("\n") || key.contains("\r")) { throw new IllegalArgumentException( "keys must not contain spaces or newlines: \"" + key + "\""); } } private static String inputStreamToString(InputStream in) throws IOException { return readFully(new InputStreamReader(in, UTF_8)); } /** * A snapshot of the values for an entry. */ public final class Snapshot implements Closeable { private final String key; private final long sequenceNumber; private final InputStream[] ins; private Snapshot(String key, long sequenceNumber, InputStream[] ins) { this.key = key; this.sequenceNumber = sequenceNumber; this.ins = ins; } /** * Returns an editor for this snapshot's entry, or null if either the * entry has changed since this snapshot was created or if another edit * is in progress. */ public Editor edit() throws IOException { return DiskLruCache.this.edit(key, sequenceNumber); } /** * Returns the unbuffered stream with the value for {@code index}. */ public InputStream getInputStream(int index) { return ins[index]; } /** * Returns the string value for {@code index}. */ public String getString(int index) throws IOException { return inputStreamToString(getInputStream(index)); } @Override public void close() { for (InputStream in : ins) { closeQuietly(in); } } } /** * Edits the values for an entry. */ public final class Editor { private final Entry entry; private boolean hasErrors; private Editor(Entry entry) { this.entry = entry; } /** * Returns an unbuffered input stream to read the last committed value, * or null if no value has been committed. */ public InputStream newInputStream(int index) throws IOException { synchronized (DiskLruCache.this) { if (entry.currentEditor != this) { throw new IllegalStateException(); } if (!entry.readable) { return null; } return new FileInputStream(entry.getCleanFile(index)); } } /** * Returns the last committed value as a string, or null if no value * has been committed. */ public String getString(int index) throws IOException { InputStream in = newInputStream(index); return in != null ? inputStreamToString(in) : null; } /** * Returns a new unbuffered output stream to write the value at * {@code index}. If the underlying output stream encounters errors * when writing to the filesystem, this edit will be aborted when * {@link #commit} is called. The returned output stream does not throw * IOExceptions. */ public OutputStream newOutputStream(int index) throws IOException { synchronized (DiskLruCache.this) { if (entry.currentEditor != this) { throw new IllegalStateException(); } return new FaultHidingOutputStream(new FileOutputStream(entry.getDirtyFile(index))); } } /** * Sets the value at {@code index} to {@code value}. */ public void set(int index, String value) throws IOException { Writer writer = null; try { writer = new OutputStreamWriter(newOutputStream(index), UTF_8); writer.write(value); } finally { closeQuietly(writer); } } /** * Commits this edit so it is visible to readers. This releases the * edit lock so another edit may be started on the same key. */ public void commit() throws IOException { if (hasErrors) { completeEdit(this, false); remove(entry.key); // the previous entry is stale } else { completeEdit(this, true); } } /** * Aborts this edit. This releases the edit lock so another edit may be * started on the same key. */ public void abort() throws IOException { completeEdit(this, false); } private class FaultHidingOutputStream extends FilterOutputStream { private FaultHidingOutputStream(OutputStream out) { super(out); } @Override public void write(int oneByte) { try { out.write(oneByte); } catch (IOException e) { hasErrors = true; } } @Override public void write(byte[] buffer, int offset, int length) { try { out.write(buffer, offset, length); } catch (IOException e) { hasErrors = true; } } @Override public void close() { try { out.close(); } catch (IOException e) { hasErrors = true; } } @Override public void flush() { try { out.flush(); } catch (IOException e) { hasErrors = true; } } } } private final class Entry { private final String key; /** Lengths of this entry's files. */ private final long[] lengths; /** True if this entry has ever been published */ private boolean readable; /** The ongoing edit or null if this entry is not being edited. */ private Editor currentEditor; /** The sequence number of the most recently committed edit to this entry. */ private long sequenceNumber; private Entry(String key) { this.key = key; this.lengths = new long[valueCount]; } public String getLengths() throws IOException { StringBuilder result = new StringBuilder(); for (long size : lengths) { result.append(' ').append(size); } return result.toString(); } /** * Set lengths using decimal numbers like "10123". */ private void setLengths(String[] strings) throws IOException { if (strings.length != valueCount) { throw invalidLengths(strings); } try { for (int i = 0; i < strings.length; i++) { lengths[i] = Long.parseLong(strings[i]); } } catch (NumberFormatException e) { throw invalidLengths(strings); } } private IOException invalidLengths(String[] strings) throws IOException { throw new IOException("unexpected journal line: " + Arrays.toString(strings)); } public File getCleanFile(int i) { return new File(directory, key + "." + i); } public File getDirtyFile(int i) { return new File(directory, key + "." + i + ".tmp"); } } }
針對這個DIskLruCache,也對它做一層封裝,也就是我們的DiskLruCacheManager:
package com.utils.cache;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import com.utils.cache.DiskLruCache.Snapshot;
import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager.NameNotFoundException;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;
public class DiskLruCacheManager {
private static int maxSize=20*1024*1024;
private DiskLruCache mDiskLruCache;
private final static String defaultName="default";
public DiskLruCacheManager(Context context){
this(context, defaultName, maxSize);
}
public DiskLruCacheManager(Context context,int maxDiskLruCacheSize){
this(context, defaultName, maxDiskLruCacheSize);
}
public DiskLruCacheManager(Context context,String dirName){
this(context, dirName, maxSize);
}
public DiskLruCacheManager(Context context,String dirName,int maxDiskLruCacheSize){
try {
mDiskLruCache=DiskLruCache.open(getDiskCacheFile(context,dirName), getAppVersion(context), 1, maxDiskLruCacheSize);
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 獲取資料夾地址,如果不存在,則建立
* @param context 上下文
* @param dirName 檔名
* @return File 檔案
*/
private File getDiskCacheFile(Context context,String dirName){
File cacheDir=packDiskCacheFile(context,dirName);
if (!cacheDir.exists()) {
cacheDir.mkdirs();
}
return cacheDir;
}
/**
* 獲取資料夾地址
* @param context 上下文
* @param dirName 檔名
* @return File 檔案
*/
private File packDiskCacheFile(Context context,String dirName){
String cachePath;
if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())
|| !Environment.isExternalStorageRemovable()) {
cachePath = context.getExternalCacheDir().getPath();
} else {
cachePath = context.getCacheDir().getPath();
}
return new File(cachePath + File.separator + dirName);
}
/**
* 獲取當前應用程式的版本號。
*/
private int getAppVersion(Context context) {
try {
PackageInfo info = context.getPackageManager().getPackageInfo(context.getPackageName(),0);
return info.versionCode;
} catch (NameNotFoundException e) {
e.printStackTrace();
}
return 1;
}
/**
* 使用MD5演算法對傳入的key進行加密並返回。
*/
private String Md5(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 String bytesToHexString(byte[] bytes) {
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();
}
/**
* Bitmap格式資料寫入到outputstream中
* @param bm Bitmap資料
* @param baos outputstream
* @return outputstream
*/
private OutputStream Bitmap2OutputStream(Bitmap bm,OutputStream baos) {
if(bm!=null){
bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
}
return baos;
}
/**
* 將快取記錄同步到journal檔案中。
*/
public void fluchCache() {
if (mDiskLruCache != null) {
try {
mDiskLruCache.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* 獲取硬碟快取
* @param key 所有
* @return Bitmap格式快取
*/
public Bitmap getDiskCache(String key){
String md5Key=Md5(key);
Bitmap bitmap=null;
try {
if(mDiskLruCache!=null){
Snapshot snapshot = mDiskLruCache.get(md5Key);
if(snapshot!=null){
bitmap=BitmapFactory.decodeStream(snapshot.getInputStream(0)) ;
}
}
}
catch (IOException e) {
e.printStackTrace();
}
return bitmap;
}
/**
* 設定key對應的快取
* @param key 索引
* @param bitmap Bitmap格式資料
* @return 是否寫入
*/
public boolean putDiskCache(String key,Bitmap bitmap){
String md5Key=Md5(key);
try {
if(mDiskLruCache!=null){
if(mDiskLruCache.get(md5Key)!=null){
return true;
}
DiskLruCache.Editor editor=mDiskLruCache.edit(md5Key);
if(editor!=null){
OutputStream outputStream= editor.newOutputStream(0);
Bitmap2OutputStream(bitmap,outputStream);
if(outputStream!=null){
editor.commit();
return true;
}
else {
editor.abort();
return false;
}
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return false;
}
public void deleteDiskCache(){
try {
if(mDiskLruCache!=null){
mDiskLruCache.delete();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void removeDiskCache(String key){
if(mDiskLruCache!=null){
try {
mDiskLruCache.remove(key);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public void deleteFile(Context context,String dirName){
try {
DiskLruCache.deleteContents(packDiskCacheFile(context,dirName));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public int size(){
int size=0;
if(mDiskLruCache!=null){
size=(int) mDiskLruCache.size();
}
return size;
}
public void close(){
if(mDiskLruCache!=null){
try {
mDiskLruCache.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
該封裝類中包含4個建構函式,主要也是用於使用者的自定義,讓使用者可以使用預設設定,以及自定義硬碟快取的資料夾名稱以及大小。
後續的封裝類,是對硬碟快取的讀寫、大小、移除等功能的封裝。
3、統一的快取管理類——CacheManager
這個類是對整個快取的排程類。使用者也只需要接觸這個類即可。CacheManager簡化了記憶體快取與硬碟快取同時使用時的程式碼操作。如下:
package com.utils.cache;
import android.content.Context;
import android.graphics.Bitmap;
import android.text.TextUtils;
public class CacheManager {
/**
* 只使用記憶體快取(LruCache)
*/
public static final int ONLY_LRU=1;
/**
* 只使用硬碟快取(DiskLruCache)
*/
public static final int ONLY_DISKLRU=2;
/**
* 同時使用記憶體快取(LruCache)與硬碟快取(DiskLruCache)
*/
public static final int ALL_ALLOW=0;
/**
* 設定型別為硬碟快取——用於取硬碟快取大小
*/
public static final int DISKSIZE=0;
/**
* 設定型別為記憶體快取——用於取記憶體快取大小
*/
public static final int MEMORYSIZE=1;
//設定硬碟快取的最大值,單位為M
private static int maxSizeForDiskLruCache=0;
//設定記憶體快取的最大值,單位為M
private static int maxMemoryForLruCache=0;
//設定自定義的硬碟快取資料夾名稱
private static String dirNameForDiskLruCache="";
//記錄硬碟快取與記憶體快取起效標誌
private static int model=0;
//硬碟快取管理類
private static DiskLruCacheManager diskLruCacheManager;
//記憶體快取管理類
private static LruCacheManager lruCacheManager;
private static Context ct;
/**
* 初始化快取管理
* @param context 上下文
*/
public static void init(Context context){
ct=context;
init_();
}
//根據傳入的標誌,初始化記憶體快取以及硬碟快取,預設開啟是同時使用
private static void init_(){
switch (model) {
case ALL_ALLOW:
initDiskLruCacheManager();
initLruCacheManager();
break;
case ONLY_LRU:
initLruCacheManager();
break;
case ONLY_DISKLRU:
initDiskLruCacheManager();
break;
default:
break;
}
}
//初始化記憶體快取管理
private static void initLruCacheManager(){
if(maxMemoryForLruCache>0){
lruCacheManager=new LruCacheManager(maxMemoryForLruCache);
}else {
lruCacheManager=new LruCacheManager();
}
}
//初始化硬碟快取管理
private static void initDiskLruCacheManager(){
if(maxSizeForDiskLruCache>0&&!TextUtils.isEmpty(dirNameForDiskLruCache)){
diskLruCacheManager=new DiskLruCacheManager(ct,dirNameForDiskLruCache,maxSizeForDiskLruCache*1024*1024);
}else if(maxSizeForDiskLruCache>0){
diskLruCacheManager=new DiskLruCacheManager(ct, maxSizeForDiskLruCache*1024*1024);
}else if(!TextUtils.isEmpty(dirNameForDiskLruCache)){
diskLruCacheManager=new DiskLruCacheManager(ct, dirNameForDiskLruCache);
}else {
diskLruCacheManager=new DiskLruCacheManager(ct);
}
}
/**
* 設定硬碟快取的最大值,單位為兆(M).
* @param maxSizeForDisk 硬碟快取最大值,單位為兆(M)
*/
public static void setMaxSize(int maxSizeForDisk){
maxSizeForDiskLruCache=maxSizeForDisk;
}
/**
* 設定記憶體快取的最大值,單位為兆(M).
* @param maxMemory 記憶體快取最大值,單位為兆(M)
*/
public static void setMaxMemory(int maxMemory){
maxMemoryForLruCache=maxMemory;
}
/**
* 設定硬碟快取自定義的檔名
* @param dirName 自定義檔名
*/
public static void setDirName(String dirName){
dirNameForDiskLruCache=dirName;
}
/**
* 索引key對應的bitmap寫入快取
* @param key 快取索引
* @param bitmap bitmap格式資料
*/
public static void put(String key,Bitmap bitmap){
switch (model) {
case ALL_ALLOW:
if(lruCacheManager!=null&&diskLruCacheManager!=null){
//設定硬碟快取成功後,再設定記憶體快取
if(diskLruCacheManager.putDiskCache(key,bitmap)){
lruCacheManager.putCache(key, bitmap);
}
}
break;
case ONLY_LRU:
if(lruCacheManager!=null){
lruCacheManager.putCache(key, bitmap);
}
break;
case ONLY_DISKLRU:
if(diskLruCacheManager!=null){
diskLruCacheManager.putDiskCache(key,bitmap);
}
break;
default:
break;
}
}
/**
* 獲取索引key對應的快取內容
* @param key 快取索引key
* @return key索引對應的Bitmap資料
*/
public static Bitmap get(String key){
Bitmap bitmap=null;
switch (model) {
case ALL_ALLOW:
if(lruCacheManager!=null&&diskLruCacheManager!=null){
bitmap=lruCacheManager.getCache(key);
if(bitmap==null){
//如果硬碟快取內容存在,記憶體快取不存在。則在獲取硬碟快取後,將內容寫入記憶體快取
bitmap=diskLruCacheManager.getDiskCache(key);
lruCacheManager.putCache(key, bitmap);
}
}
break;
case ONLY_LRU:
if(lruCacheManager!=null){
bitmap=lruCacheManager.getCache(key);
}
break;
case ONLY_DISKLRU:
if(diskLruCacheManager!=null){
bitmap=diskLruCacheManager.getDiskCache(key);
}
break;
default:
break;
}
return bitmap;
}
/**
* 刪除所有快取
*/
public static void delete(){
switch (model) {
case ALL_ALLOW:
if(lruCacheManager!=null&&diskLruCacheManager!=null){
lruCacheManager.deleteCache();
diskLruCacheManager.deleteDiskCache();
}
break;
case ONLY_LRU:
if(lruCacheManager!=null){
lruCacheManager.deleteCache();
}
break;
case ONLY_DISKLRU:
if(diskLruCacheManager!=null){
diskLruCacheManager.deleteDiskCache();
}
break;
default:
break;
}
}
/**
* 移除一條索引key對應的快取
* @param key 索引
*/
public static void remove(String key){
switch (model) {
case ALL_ALLOW:
if(lruCacheManager!=null&&diskLruCacheManager!=null){
lruCacheManager.removeCache(key);
diskLruCacheManager.removeDiskCache(key);
}
break;
case ONLY_LRU:
if(lruCacheManager!=null){
lruCacheManager.removeCache(key);
}
break;
case ONLY_DISKLRU:
if(diskLruCacheManager!=null){
diskLruCacheManager.removeDiskCache(key);
}
break;
default:
break;
}
}
/**
* 快取資料同步
*/
public static void flush(){
switch (model) {
case ALL_ALLOW:
if(lruCacheManager!=null&&diskLruCacheManager!=null){
diskLruCacheManager.fluchCache();
}
break;
case ONLY_LRU:
break;
case ONLY_DISKLRU:
if(diskLruCacheManager!=null){
diskLruCacheManager.fluchCache();
}
break;
default:
break;
}
}
/**
* 設定快取模式
* @param modelSet ONLY_LRU、ONLY_DISK、ALL_ALLOW
*/
public static void setCacheModel(int modelSet){
model=modelSet;
}
/**
* 刪除特定檔名的快取檔案
* @param dirName 檔名
*/
public static void deleteFile(String dirName){
if(diskLruCacheManager!=null){
diskLruCacheManager.deleteFile(ct, dirName);
}
}
/**
* 獲取快取大小——記憶體快取+硬碟快取
* @return
*/
public static int size(){
int size=0;
if(diskLruCacheManager!=null){
size+=diskLruCacheManager.size();
}
if(lruCacheManager!=null){
size+=lruCacheManager.size();
}
return size;
}
/**
* 獲取快取大小
* @param type 硬碟快取型別:DISKSIZE、記憶體快取型別:MEMORYSIZE
* @return 對應型別的快取大小
*/
public static int size(int type){
int size=0;
switch (type) {
case DISKSIZE:
if(diskLruCacheManager!=null){
size+=diskLruCacheManager.size();
}
break;
case MEMORYSIZE:
if(lruCacheManager!=null){
size+=lruCacheManager.size();
}
break;
default:
break;
}
return size;
}
/**
* 關閉快取
*/
public static void close(){
if(diskLruCacheManager!=null){
diskLruCacheManager.close();
}
}
}
各方法在程式碼中都有詳細註釋。
簡單的說,在使用時,如果使用預設的設定(預設情況下,記憶體快取與硬碟快取同時開啟),只需要以下幾句簡單程式碼即可實現:
你首先需要初始化:CacheManager.init(Context context);
當你需要設定快取的時候:CacheManager.put(String
key,Bitmap bitmap);
當你需要獲取快取的時候:CacheManager.get(String key);
最後:你可以在這個基礎上,新增一些其他你需要的方法,如果快取文字、字串等。