DiskLruCache缓存机制
- 关于Android的三级缓存，其中最主要的就是内存缓存和硬盘缓存。这两种缓存机制的实现都应用到了LruCache(Least Recently Used)，采用LRU算法的缓存有两种：LruCache和DisLruCache,分别用于实现内存缓存和硬盘缓存，其核心思想都是LRU算法。
- 一般来说，缓存策略主要包含缓存的添加、获取和删除这三类操作。
- 而LruCache和DisLruCache一般用于缓存图片信息。
/storage/emulated/0/Android/data/package_name/cache 当应用卸载后，存储数据也会被删除。(系统所认定的缓存的路径)
/storage/emulated/0/mDiskCache 这种存储路径，即使应用卸载，存储数据依然会存在。
好了不多说，今天我们讲讲DiskLruCache如何缓存请求数据。我会先贴几个类，第一个类不多说大家都很熟悉：
DiskLruCache.java
public final class DiskLruCache implements Closeable {
static final String JOURNAL_FILE = "journal";
static final String JOURNAL_FILE_TEMP = "journal.tmp";
static final String JOURNAL_FILE_BACKUP = "journal.bkp";
static final String MAGIC = "libcore.io.DiskLruCache";
static final String VERSION_1 = "1";
static final long ANY_SEQUENCE_NUMBER = -1;
static final String STRING_KEY_PATTERN = "[a-z0-9_-]{1,120}";
static final Pattern LEGAL_KEY_PATTERN = Pattern.compile(STRING_KEY_PATTERN);
private static final String CLEAN = "CLEAN";
private static final String DIRTY = "DIRTY";
private static final String REMOVE = "REMOVE";
private static final String READ = "READ";
/*
* 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 File journalFileBackup;
private final int appVersion;
private long maxSize;
private final int valueCount;
private long size = 0;
private Writer journalWriter;
private final LinkedHashMap lruEntries =
new LinkedHashMap(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;
/**
* This cache uses a single background thread to evict entries.
*/
final ThreadPoolExecutor executorService =
new ThreadPoolExecutor(0, 1, 60L, TimeUnit.SECONDS, new LinkedBlockingQueue());
private final Callable cleanupCallable = new Callable() {
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_TEMP);
this.journalFileBackup = new File(directory, JOURNAL_FILE_BACKUP);
this.valueCount = valueCount;
this.maxSize = maxSize;
}/**
* Opens the cache in {@code directory}, creating a cache if none exists
* there.
*
* @param directorya writable directory
* @param appVersion appVersion
* @param valueCount the number of values per cache entry. Must be positive.
* @param maxSizethe maximum number of bytes this cache should use to store
* @return DiskLruCache
* @throws 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");
}System.out.println("......appVersion: " + appVersion + "......");
// If a bkp file exists, use it instead.
File backupFile = new File(directory, JOURNAL_FILE_BACKUP);
if (backupFile.exists()) {
File journalFile = new File(directory, JOURNAL_FILE);
// If journal file also exists just delete backup file.
if (journalFile.exists()) {
backupFile.delete();
} else {
renameTo(backupFile, journalFile, false);
}
}// 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();
return cache;
} catch (IOException journalIsCorrupt) {
System.out
.println("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 {
StrictLineReader reader = new StrictLineReader(new FileInputStream(journalFile), Util.US_ASCII);
try {
String magic = reader.readLine();
String version = reader.readLine();
String appVersionString = reader.readLine();
String valueCountString = reader.readLine();
String blank = reader.readLine();
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 + "]");
}int lineCount = 0;
while (true) {
try {
readJournalLine(reader.readLine());
lineCount++;
} catch (EOFException endOfJournal) {
break;
}
}
redundantOpCount = lineCount - lruEntries.size();
// If we ended on a truncated line, rebuild the journal before appending to it.
if (reader.hasUnterminatedLine()) {
rebuildJournal();
} else {
journalWriter = new BufferedWriter(new OutputStreamWriter(
new FileOutputStream(journalFile, true), Util.US_ASCII));
}
} finally {
Util.closeQuietly(reader);
}
}private void readJournalLine(String line) throws IOException {
int firstSpace = line.indexOf(' ');
if (firstSpace == -1) {
throw new IOException("unexpected journal line: " + line);
}int keyBegin = firstSpace + 1;
int secondSpace = line.indexOf(' ', keyBegin);
final String key;
if (secondSpace == -1) {
key = line.substring(keyBegin);
if (firstSpace == REMOVE.length() && line.startsWith(REMOVE)) {
lruEntries.remove(key);
return;
}
} else {
key = line.substring(keyBegin, secondSpace);
}Entry entry = lruEntries.get(key);
if (entry == null) {
entry = new Entry(key);
lruEntries.put(key, entry);
}if (secondSpace != -1 && firstSpace == CLEAN.length() && line.startsWith(CLEAN)) {
String[] parts = line.substring(secondSpace + 1).split(" ");
entry.readable = true;
entry.currentEditor = null;
entry.setLengths(parts);
} else if (secondSpace == -1 && firstSpace == DIRTY.length() && line.startsWith(DIRTY)) {
entry.currentEditor = new Editor(entry);
} else if (secondSpace == -1 && firstSpace == READ.length() && line.startsWith(READ)) {
// 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 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 OutputStreamWriter(new FileOutputStream(journalFileTmp), Util.US_ASCII));
try {
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');
}
}
} finally {
writer.close();
}if (journalFile.exists()) {
renameTo(journalFile, journalFileBackup, true);
}
renameTo(journalFileTmp, journalFile, false);
journalFileBackup.delete();
journalWriter = new BufferedWriter(
new OutputStreamWriter(new FileOutputStream(journalFile, true), Util.US_ASCII));
}private static void deleteIfExists(File file) throws IOException {
if (file.exists() && !file.delete()) {
throw new IOException();
}
}private static void renameTo(File from, File to, boolean deleteDestination) throws IOException {
if (deleteDestination) {
deleteIfExists(to);
}
if (!from.renameTo(to)) {
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.
*
* @param key key
* @return Snapshot
* @throws IOException e
*/
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!
for (int i = 0;
i < valueCount;
i++) {
if (ins[i] != null) {
Util.closeQuietly(ins[i]);
} else {
break;
}
}
return null;
}redundantOpCount++;
journalWriter.append(READ + ' ' + key + '\n');
if (journalRebuildRequired()) {
executorService.submit(cleanupCallable);
}return new Snapshot(key, entry.sequenceNumber, ins, entry.lengths);
}/**
* Returns an editor for the entry named {@code key}, or null if another
* edit is in progress.
*
* @param key key
* @return Editor
* @throws IOException e
*/
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.
*
* @return File
*/
public File getDirectory() {
return directory;
}/**
* Returns the maximum number of bytes that this cache should use to store
* its data.
*
* @return long
*/
public synchronized long getMaxSize() {
return maxSize;
}public synchronized void setMaxSize(long maxSize) {
this.maxSize = maxSize;
executorService.submit(cleanupCallable);
}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 (!editor.written[i]) {
editor.abort();
throw new IllegalStateException("Newly created entry didn't create value for index " + i);
}
if (!entry.getDirtyFile(i).exists()) {
editor.abort();
return;
}
}
}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');
}
journalWriter.flush();
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 redundantOpCompactThreshold = 2000;
return redundantOpCount >= redundantOpCompactThreshold //
&& redundantOpCount >= lruEntries.size();
}/**
* Drops the entry for {@code key} if it exists and can be removed. Entries
* actively being edited cannot be removed.
*
* @param key key
* @return true if an entry was removed.
* @throws IOException e
*/
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.exists() && !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.
*
* @return true
*/
public synchronized boolean isClosed() {
return journalWriter == null;
}private void checkNotClosed() {
if (journalWriter == null) {
throw new IllegalStateException("cache is closed");
}
}/**
* Force buffered operations to the filesystem.
*
* @throws IOException e
*/
public synchronized void flush() throws IOException {
checkNotClosed();
trimToSize();
journalWriter.flush();
}/**
* Closes this cache. Stored values will remain on the filesystem.
*
* @throws IOException e
*/
public synchronized void close() throws IOException {
if (journalWriter == null) {
return;
// Already closed.
}
for (Entry entry : new ArrayList(lruEntries.values())) {
if (entry.currentEditor != null) {
entry.currentEditor.abort();
}
}
trimToSize();
journalWriter.close();
journalWriter = null;
}private void trimToSize() throws IOException {
while (size > maxSize) {
Map.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.
*
* @throws IOException e
*/
public void delete() throws IOException {
close();
Util.deleteContents(directory);
}private void validateKey(String key) {
Matcher matcher = LEGAL_KEY_PATTERN.matcher(key);
if (!matcher.matches()) {
throw new IllegalArgumentException("keys must match regex "
+ STRING_KEY_PATTERN + ": \"" + key + "\"");
}
}private static String inputStreamToString(InputStream in) throws IOException {
return Util.readFully(new InputStreamReader(in, Util.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 final long[] lengths;
private Snapshot(String key, long sequenceNumber, InputStream[] ins, long[] lengths) {
this.key = key;
this.sequenceNumber = sequenceNumber;
this.ins = ins;
this.lengths = lengths;
}/**
* 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.
*
* @return di
* @throws IOException e
*/
public Editor edit() throws IOException {
return DiskLruCache.this.edit(key, sequenceNumber);
}/**
* Returns the unbuffered stream with the value for {@code index}.
*
* @param index index
* @return InputStream
*/
public InputStream getInputStream(int index) {
return ins[index];
}/**
* Returns the string value for {@code index}.
*
* @param index index
* @return String
* @throws IOException e
*/
public String getString(int index) throws IOException {
return inputStreamToString(getInputStream(index));
}/**
* Returns the byte length of the value for {@code index}.
*
* @param index index
* @return long
*/
public long getLength(int index) {
return lengths[index];
}public void close() {
for (InputStream in : ins) {
Util.closeQuietly(in);
}
}
}private static final OutputStream NULL_OUTPUT_STREAM = new OutputStream() {
@Override
public void write(int b) throws IOException {
// Eat all writes silently. Nom nom.
}
};
/**
* Edits the values for an entry.
*/
public final class Editor {
private final Entry entry;
private final boolean[] written;
private boolean hasErrors;
private boolean committed;
private Editor(Entry entry) {
this.entry = entry;
this.written = (entry.readable) ? null : new boolean[valueCount];
}/**
* Returns an unbuffered input stream to read the last committed value,
* or null if no value has been committed.
*
* @param index in
* @return InputStream
* @throws IOException e
*/
public InputStream newInputStream(int index) throws IOException {
synchronized (DiskLruCache.this) {
if (entry.currentEditor != this) {
throw new IllegalStateException();
}
if (!entry.readable) {
return null;
}
try {
return new FileInputStream(entry.getCleanFile(index));
} catch (FileNotFoundException e) {
return null;
}
}
}/**
* Returns the last committed value as a string, or null if no value
* has been committed.
*
* @param index in
* @return string
* @throws IOException e
*/
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.
*
* @param index in
* @return out
* @throws IOException e
*/
public OutputStream newOutputStream(int index) throws IOException {
if (index < 0 || index >= valueCount) {
throw new IllegalArgumentException("Expected index " + index + " to "
+ "be greater than 0 and less than the maximum value count "
+ "of " + valueCount);
}
synchronized (DiskLruCache.this) {
if (entry.currentEditor != this) {
throw new IllegalStateException();
}
if (!entry.readable) {
written[index] = true;
}
File dirtyFile = entry.getDirtyFile(index);
FileOutputStream outputStream;
try {
outputStream = new FileOutputStream(dirtyFile);
} catch (FileNotFoundException e) {
// Attempt to recreate the cache directory.
directory.mkdirs();
try {
outputStream = new FileOutputStream(dirtyFile);
} catch (FileNotFoundException e2) {
// We are unable to recover. Silently eat the writes.
return NULL_OUTPUT_STREAM;
}
}
return new FaultHidingOutputStream(outputStream);
}
}/**
* Sets the value at {@code index} to {@code value}.
*
* @param index in
* @param value v
* @throws IOException e
*/
public void set(int index, String value) throws IOException {
Writer writer = null;
try {
writer = new OutputStreamWriter(newOutputStream(index), Util.UTF_8);
writer.write(value);
} finally {
Util.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.
*
* @throws IOException e
*/
public void commit() throws IOException {
if (hasErrors) {
completeEdit(this, false);
remove(entry.key);
// The previous entry is stale.
} else {
completeEdit(this, true);
}
committed = true;
}/**
* Aborts this edit. This releases the edit lock so another edit may be
* started on the same key.
*
* @throws IOException e
*/
public void abort() throws IOException {
completeEdit(this, false);
}public void abortUnlessCommitted() {
if (!committed) {
try {
abort();
} catch (IOException ignored) {
}
}
}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: " + java.util.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");
}
}
}
StreamUtil.java
public class StreamUtil {/**
*
* @param inputStream inputStream
* @param cls cls
* @param T
* @return D
*/
public static List readListStream(InputStream inputStream, Class cls) {System.out.println("...... className : " + cls.getSimpleName() + " ......");
List resultList = new ArrayList<>();
ObjectInputStream ois = null;
try {
ois = new ObjectInputStream(inputStream);
ArrayList list_ext = (ArrayList) ois.readObject();
for (D obj : list_ext) {
if (obj != null) {
resultList.add(obj);
}
}
return resultList;
} catch (Exception e) {
e.printStackTrace();
} finally {if (ois != null) {
try {
ois.close();
} catch (IOException e2) {
e2.printStackTrace();
}
}
}
return resultList;
}public static D readStream(InputStream inputStream, Class cls) {System.out.println("...... className : " + cls.getSimpleName() + " ......");
ObjectInputStream ois = null;
try {
ois = new ObjectInputStream(inputStream);
D object = (D) ois.readObject();
return object;
} catch (Exception e) {
e.printStackTrace();
} finally {
if (ois != null) {
try {
ois.close();
} catch (IOException e2) {
e2.printStackTrace();
}
}
}return null;
}public static boolean writeToStream(OutputStream fos, Object object) {ObjectOutputStream oos = null;
try {
oos = new ObjectOutputStream(fos);
oos.writeObject(object);
oos.flush();
return true;
} catch (Exception e) {
e.printStackTrace();
} finally {
if (oos != null) {
try {
oos.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
return false;
}/**
* url to diskStream
*
* @param imageUrlimageUrl
* @param outputStream outputStream
* @return is
*/
public static boolean writeUrlToStream(String imageUrl, OutputStream outputStream) {
HttpURLConnection urlConnection = null;
BufferedOutputStream out = null;
BufferedInputStream in = null;
try {
final URL url = new URL(imageUrl);
urlConnection = (HttpURLConnection) url.openConnection();
in = new BufferedInputStream(urlConnection.getInputStream(), 8 * 1024);
out = new BufferedOutputStream(outputStream, 8 * 1024);
int b;
while ((b = in.read()) != -1) {
out.write(b);
}
return true;
} catch (final IOException e) {
e.printStackTrace();
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
try {
if (out != null) {
out.close();
}
if (in != null) {
in.close();
}
} catch (final IOException e) {
e.printStackTrace();
}
}
return false;
}
} StrictLineReader.java
public class StrictLineReader implements Closeable {
private static final byte CR = (byte) '\r';
private static final byte LF = (byte) '\n';
private final InputStream in;
private final Charset charset;
/*
* Buffered data is stored in {@code buf}. As long as no exception occurs, 0 <= pos <= end
* and the data in the range [pos, end) is buffered for reading. At end of input, if there is
* an unterminated line, we set end == -1, otherwise end == pos. If the underlying
* {@code InputStream} throws an {@code IOException}, end may remain as either pos or -1.
*/
private byte[] buf;
private int pos;
private int end;
/**
* Constructs a new {@code LineReader} with the specified charset and the default capacity.
*
* @param in the {@code InputStream} to read data from.
* @param charset the charset used to decode data. Only US-ASCII, UTF-8 and ISO-8859-1 are
* supported.
* @throws NullPointerException if {@code in} or {@code charset} is null.
* @throws IllegalArgumentException if the specified charset is not supported.
*/
public StrictLineReader(InputStream in, Charset charset) {
this(in, 8192, charset);
}/**
* Constructs a new {@code LineReader} with the specified capacity and charset.
*
* @param in the {@code InputStream} to read data from.
* @param capacity the capacity of the buffer.
* @param charset the charset used to decode data. Only US-ASCII, UTF-8 and ISO-8859-1 are
* supported.
* @throws NullPointerException if {@code in} or {@code charset} is null.
* @throws IllegalArgumentException if {@code capacity} is negative or zero
* or the specified charset is not supported.
*/
public StrictLineReader(InputStream in, int capacity, Charset charset) {
if (in == null || charset == null) {
throw new NullPointerException();
}
if (capacity < 0) {
throw new IllegalArgumentException("capacity <= 0");
}
if (!(charset.equals(Util.US_ASCII))) {
throw new IllegalArgumentException("Unsupported encoding");
}this.in = in;
this.charset = charset;
buf = new byte[capacity];
}/**
* Closes the reader by closing the underlying {@code InputStream} and
* marking this reader as closed.
*
* @throws IOException for errors when closing the underlying {@code InputStream}.
*/
public void close() throws IOException {
synchronized (in) {
if (buf != null) {
buf = null;
in.close();
}
}
}/**
* Reads the next line. A line ends with {@code "\n"} or {@code "\r\n"},
* this end of line marker is not included in the result.
*
* @return the next line from the input.
* @throws IOException for underlying {@code InputStream} errors.
* @throws EOFException for the end of source stream.
*/
public String readLine() throws IOException {
synchronized (in) {
if (buf == null) {
throw new IOException("LineReader is closed");
}// Read more data if we are at the end of the buffered data.
// Though it's an error to read after an exception, we will let {@code fillBuf()}
// throw again if that happens;
thus we need to handle end == -1 as well as end == pos.
if (pos >= end) {
fillBuf();
}
// Try to find LF in the buffered data and return the line if successful.
for (int i = pos;
i != end;
++i) {
if (buf[i] == LF) {
int lineEnd = (i != pos && buf[i - 1] == CR) ? i - 1 : i;
String res = new String(buf, pos, lineEnd - pos, charset.name());
pos = i + 1;
return res;
}
}// Let's anticipate up to 80 characters on top of those already read.
ByteArrayOutputStream out = new ByteArrayOutputStream(end - pos + 80) {
@Override
public String toString() {
int length = (count > 0 && buf[count - 1] == CR) ? count - 1 : count;
try {
return new String(buf, 0, length, charset.name());
} catch (UnsupportedEncodingException e) {
throw new AssertionError(e);
// Since we control the charset this will never happen.
}
}
};
while (true) {
out.write(buf, pos, end - pos);
// Mark unterminated line in case fillBuf throws EOFException or IOException.
end = -1;
fillBuf();
// Try to find LF in the buffered data and return the line if successful.
for (int i = pos;
i != end;
++i) {
if (buf[i] == LF) {
if (i != pos) {
out.write(buf, pos, i - pos);
}
pos = i + 1;
return out.toString();
}
}
}
}
}public boolean hasUnterminatedLine() {
return end == -1;
}/**
* Reads new input data into the buffer. Call only with pos == end or end == -1,
* depending on the desired outcome if the function throws.
*/
private void fillBuf() throws IOException {
int result = in.read(buf, 0, buf.length);
if (result == -1) {
throw new EOFException();
}
pos = 0;
end = result;
}
}Util.java
public final class Util {
public static final Charset US_ASCII = Charset.forName("US-ASCII");
public static final Charset UTF_8 = Charset.forName("UTF-8");
private Util() {
}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();
}
}/**
* Deletes the contents of {@code dir}. Throws an IOException if any file
* could not be deleted, or if {@code dir} is not a readable directory.
*/
public static void deleteContents(File dir) throws IOException {
File[] files = dir.listFiles();
if (files == null) {
throw new IOException("not a readable directory: " + dir);
}
for (File file : files) {
if (file.isDirectory()) {
deleteContents(file);
}
if (!file.delete()) {
throw new IOException("failed to delete file: " + file);
}
}
}public static void closeQuietly(/*Auto*/Closeable closeable) {
if (closeable != null) {
try {
closeable.close();
} catch (RuntimeException rethrown) {
throw rethrown;
} catch (Exception ignored) {
}
}
}public static String getCacheDir(Context context) {
String cachePath;
if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())
|| !Environment.isExternalStorageRemovable()) {
cachePath = context.getExternalCacheDir().getPath();
} else {
cachePath = context.getCacheDir().getPath();
}
return cachePath;
}public static int getAppVersion(Context context) {
try {
PackageInfo info = context.getPackageManager().getPackageInfo(context.getPackageName(), 0);
return info.versionCode;
} catch (PackageManager.NameNotFoundException e) {
e.printStackTrace();
}
return 1;
}public static T requireNonNull(T object, String message) {
if (object == null) {
throw new NullPointerException(message);
}
return object;
}//获取Cache 存储目录
public static File getCacheFile(Context context,String uniqueName){String cachePath = null;
if((Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())||
!Environment.isExternalStorageRemovable()
&& context.getExternalCacheDir().getPath()!=null)){
cachePath = context.getExternalCacheDir().getPath();
}else{
cachePath = context.getCacheDir().getPath();
}
return new File(cachePath + File.separator +uniqueName);
}
}
MD5.java
/**
* Created by SerryWang
* on 2018/8/29
*/
public class MD5 {
/**
* 主要是将key进行MD5编码
*/
public static String encodeKey(String key){
String cacheKey;
try {
final MessageDigest mDigest = MessageDigest.getInstance("MD5");
mDigest.update(key.getBytes());
cacheKey = bytesToHexString(mDigest.digest());
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
cacheKey = String.valueOf(key.hashCode());
}
return cacheKey;
}private static String bytesToHexString(byte[] bytes){StringBuilder sb = new StringBuilder();
for(int i = 0;
i以上几个就是配合使用DiskLruCache的工具类。
那么具体该如何使用呢？
- 初始化DiskLruCache
//初始化DiskLruCache
public DiskLruCache.Editor initDiskLruCaches(){
File cacheFile = getCacheFile(getApplicationContext(),"testCache");
//获取文件路径
try {
mDiskLruCache =DiskLruCache.open(cacheFile,getVersionCode(getApplicationContext()),1,10*1024*1024);
String myCache = MD5.encodeKey("DiskCache");
editor = mDiskLruCache.edit(myCache);
if(editor != null){
return editor;
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
- 写入缓存
//写入缓存
public boolean writeToDisk(Listdata){
try {
if(initDiskLruCaches()!=null){
OutputStream outputStream = initDiskLruCaches().newOutputStream(0);
//零为索引
if(StreamUtil.writeToStream(outputStream,data)){
return true;
}
}
} catch (IOException e) {
e.printStackTrace();
}
return false;
}
- 得到缓存
//得到缓存
public List getCacheFromDisk(){
String myCache = MD5.encodeKey("DiskCache");
try {
DiskLruCache.Snapshot snapshot =mDiskLruCache.get(myCache);
//Snapshot为空
if(snapshot!=null){
InputStream inputStream = snapshot.getInputStream(0);
//所引与写入流保持一致
return StreamUtil.readListStream(inputStream,ListItem.class);
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
- Demo使用
写入缓存
@Override
public void showData(BaseResponse> data) {
//更新界面
ListlistData = https://www.it610.com/article/data.getResults();
//添加进内存缓存
//MyCachedata.put("cache",listData);
//添加进磁盘缓存
if(writeToDisk(listData)){
try {
editor.commit();
Toast.makeText(MainActivity.this,"添加磁盘缓存成功!",Toast.LENGTH_SHORT).show();
} catch (IOException e) {
e.printStackTrace();
}}else{
try {
editor.abort();
Toast.makeText(MainActivity.this,"添加磁盘缓存失败!",Toast.LENGTH_SHORT).show();
} catch (IOException e) {
e.printStackTrace();
}
}myadapter.setData(listData);
myadapter.notifyDataSetChanged();
}
读取缓存
private void initAdapter() {
//设置排列格式
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
//读磁盘缓存
if(getCacheFromDisk()!=null){
data = https://www.it610.com/article/getCacheFromDisk();
}
myadapter = new Myadapter(this,data);
myadapter.notifyDataSetChanged();
mRecyclerView.setAdapter(myadapter);
mRecyclerView.setLayoutManager(linearLayoutManager);
}
最后来一个断网，读取缓存并加载的Demo图片
文章图片
cache.PNG 需要注意得是 【DiskLruCache缓存机制】我们得ListItem数据模型需要实现Serializable这个接口。
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