Android之本地缓存——LruCache（内存缓存）与DiskLruCache（硬...

admin · 发表于 2016-7-6 12:39:46

Android之本地缓存——LruCache（内存缓存）与DiskLruCache（硬盘缓存）统一框架

本文参考郭霖大神的DiskLruCache解析，感兴趣的朋友可以先到http://blog.csdn.net/guolin_blog/article/details/28863651了解。

一、前言

该框架或者说库，主要是用于本地的图片缓存处理。

数据的存入

当你取到图片的元数据，会将数据存入硬盘缓存以及内存缓存中。

数据的获取

取数据的时候，先从内存缓存中取；

如果没有取到，则从硬盘缓存中取（此时如果硬盘缓存有数据，硬盘缓存会重新将数据写入内存缓存中）；

如果硬盘缓存中没有取到，则从网上重新获取元数据；

二、设计

根据以上提到的功能：

首先，我们对LruCache以及DiskLruCache分别做了一个管理类，分别命名为LruCacheManager、DiskLruCacheManager，类中对用户可能用到的方法做封装；

其次，需要一个统一管理来CacheManager，对LruCacheManager、DiskLruCacheManager中的方法做调度；

三、具体实现1、内存缓存管理——LruCacheManager

先贴代码，有个直观认识：

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);
}
//设置自定义大小的LruCache
public LruCacheManager(int maxSize){
lruCache=new LruCache<String, Bitmap>(maxSize*1024){
@Override
protected int sizeOf(String key, Bitmap value) {
return value.getByteCount()/1024;
}
};
}
/**
* 写入索引key对应的缓存
* @param key 索引
* @param bitmap 缓存内容
* @return 写入结果
*/
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;
}
/**
* 获取缓存
* @param key 索引key对应的缓存
* @return 缓存
*/
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;
}
}

复制代码

该类是依赖于Android提供的LruCache类实现的。

在该类中，提供了两个构造方法，默认的构造方法是给内存缓存分配当前Android操作系统分配给该app的内存的1/8。这话比较拗口，意识就是，如果操作系统分配给app的内存是96M，那么默认构造方法就是给内存缓存分配内存96/8M。另一个构造方法是让用户自定义内存缓存大小。

该类中其他的方法就不多做解释，都是对LruCache方法的一次封装。

2、硬盘缓存管理——DiskLruCacheManager

使用硬盘缓存管理前，需要先下载一个开源类：DiskLruCache，如下：

/*
* 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.
*
* 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.
*
* 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.
*
* 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 created 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 edited, 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.
*
* 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.
*
* 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");
}
}
}

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对于该类不了解的可以参考文章首行提到的郭霖的博客链接。

针对这个DIskLruCache，也对它做一层封装，也就是我们的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();
}
}
/**
* 获取文件夹地址，如果不存在，则创建
* @param context 上下文
* @param dirName 文件名
* @return File 文件
*/
private File getDiskCacheFile(Context context,String dirName){
File cacheDir=packDiskCacheFile(context,dirName);
if (!cacheDir.exists()) {
cacheDir.mkdirs();
}
return cacheDir;
}
/**
* 获取文件夹地址
* @param context 上下文
* @param dirName 文件名
* @return File 文件
*/
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);
}
/**
* 获取当前应用程序的版本号。
*/
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算法对传入的key进行加密并返回。
*/
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格式数据写入到outputstream中
* @param bm Bitmap数据
* @param baos outputstream
* @return outputstream
*/
private OutputStream Bitmap2OutputStream(Bitmap bm,OutputStream baos) {
if(bm!=null){
bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
}
return baos;
}
/**
* 将缓存记录同步到journal文件中。
*/
public void fluchCache() {
if (mDiskLruCache != null) {
try {
mDiskLruCache.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* 获取硬盘缓存
* @param key 所有
* @return Bitmap格式缓存
*/
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;
}
/**
* 设置key对应的缓存
* @param key 索引
* @param bitmap Bitmap格式数据
* @return 是否写入
*/
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();
}
}
}
}

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该封装类中包含4个构造函数，主要也是用于用户的自定义，让用户可以使用默认设置，以及自定义硬盘缓存的文件夹名称以及大小。

后续的封装类，是对硬盘缓存的读写、大小、移除等功能的封装。

3、统一的缓存管理类——CacheManager

这个类是对整个缓存的调度类。使用者也只需要接触这个类即可。CacheManager简化了内存缓存与硬盘缓存同时使用时的代码操作。如下：

package com.utils.cache;
import android.content.Context;
import android.graphics.Bitmap;
import android.text.TextUtils;
public class CacheManager {
/**
* 只使用内存缓存(LruCache)
*/
public static final int ONLY_LRU=1;
/**
* 只使用硬盘缓存(DiskLruCache)
*/
public static final int ONLY_DISKLRU=2;
/**
* 同时使用内存缓存(LruCache)与硬盘缓存(DiskLruCache)
*/
public static final int ALL_ALLOW=0;
/**
* 设置类型为硬盘缓存——用于取硬盘缓存大小
*/
public static final int DISKSIZE=0;
/**
* 设置类型为内存缓存——用于取内存缓存大小
*/
public static final int MEMORYSIZE=1;
//设置硬盘缓存的最大值，单位为M
private static int maxSizeForDiskLruCache=0;
//设置内存缓存的最大值，单位为M
private static int maxMemoryForLruCache=0;
//设置自定义的硬盘缓存文件夹名称
private static String dirNameForDiskLruCache="";
//记录硬盘缓存与内存缓存起效标志
private static int model=0;
//硬盘缓存管理类
private static DiskLruCacheManager diskLruCacheManager;
//内存缓存管理类
private static LruCacheManager lruCacheManager;
private static Context ct;
/**
* 初始化缓存管理
* @param context 上下文
*/
public static void init(Context context){
ct=context;
init_();
}
//根据传入的标志，初始化内存缓存以及硬盘缓存，默认开启是同时使用
private static void init_(){
switch (model) {
case ALL_ALLOW:
initDiskLruCacheManager();
initLruCacheManager();
break;
case ONLY_LRU:
initLruCacheManager();
break;
case ONLY_DISKLRU:
initDiskLruCacheManager();
break;
default:
break;
}
}
//初始化内存缓存管理
private static void initLruCacheManager(){
if(maxMemoryForLruCache>0){
lruCacheManager=new LruCacheManager(maxMemoryForLruCache);
}else {
lruCacheManager=new LruCacheManager();
}
}
//初始化硬盘缓存管理
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);
}
}
/**
* 设置硬盘缓存的最大值，单位为兆（M）.
* @param maxSizeForDisk 硬盘缓存最大值，单位为兆（M）
*/
public static void setMaxSize(int maxSizeForDisk){
maxSizeForDiskLruCache=maxSizeForDisk;
}
/**
* 设置内存缓存的最大值，单位为兆（M）.
* @param maxMemory 内存缓存最大值，单位为兆（M）
*/
public static void setMaxMemory(int maxMemory){
maxMemoryForLruCache=maxMemory;
}
/**
* 设置硬盘缓存自定义的文件名
* @param dirName 自定义文件名
*/
public static void setDirName(String dirName){
dirNameForDiskLruCache=dirName;
}
/**
* 索引key对应的bitmap写入缓存
* @param key 缓存索引
* @param bitmap bitmap格式数据
*/
public static void put(String key,Bitmap bitmap){
switch (model) {
case ALL_ALLOW:
if(lruCacheManager!=null&&diskLruCacheManager!=null){
//设置硬盘缓存成功后，再设置内存缓存
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;
}
}
/**
* 获取索引key对应的缓存内容
* @param key 缓存索引key
* @return key索引对应的Bitmap数据
*/
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){
//如果硬盘缓存内容存在，内存缓存不存在。则在获取硬盘缓存后，将内容写入内存缓存
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;
}
/**
* 删除所有缓存
*/
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;
}
}
/**
* 移除一条索引key对应的缓存
* @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;
}
}
/**
* 缓存数据同步
*/
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;
}
}
/**
* 设置缓存模式
* @param modelSet ONLY_LRU、ONLY_DISK、ALL_ALLOW
*/
public static void setCacheModel(int modelSet){
model=modelSet;
}
/**
* 删除特定文件名的缓存文件
* @param dirName 文件名
*/
public static void deleteFile(String dirName){
if(diskLruCacheManager!=null){
diskLruCacheManager.deleteFile(ct, dirName);
}
}
/**
* 获取缓存大小——内存缓存+硬盘缓存
* @return
*/
public static int size(){
int size=0;
if(diskLruCacheManager!=null){
size+=diskLruCacheManager.size();
}
if(lruCacheManager!=null){
size+=lruCacheManager.size();
}
return size;
}
/**
* 获取缓存大小
* @param type 硬盘缓存类型：DISKSIZE、内存缓存类型：MEMORYSIZE
* @return 对应类型的缓存大小
*/
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;
}
/**
* 关闭缓存
*/
public static void close(){
if(diskLruCacheManager!=null){
diskLruCacheManager.close();
}
}
}

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各方法在代码中都有详细注释。

简单的说，在使用时，如果使用默认的设置（默认情况下，内存缓存与硬盘缓存同时开启），只需要以下几句简单代码即可实现：

你首先需要初始化：CacheManager.init(Context context);

当你需要设置缓存的时候：CacheManager.put(String key,Bitmap bitmap)；

当你需要获取缓存的时候：CacheManager.get(String key)；

最后：你可以在这个基础上，添加一些其他你需要的方法，如果缓存文本、字符串等。

四、源码

github上eclipse版本：https://github.com/yangzhaomuma/CacheManager

csdn上android studio版本：http://download.csdn.net/detail/yangzhaomuma/9565578

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