本文介绍了android 教程中的 DiskLruCache 缺少很多方法.的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
这是我正在关注的磁盘缓存教程.我已将源代码下载到 DiskLruCache，但源代码中不存在此示例中使用的任何方法.
Here is the disk cache tutorial I'm following. I've downloaded the source code to DiskLruCache but none of the methods used in this example exist in the source code.
http://developer.android.com/训练/显示位图/缓存位图.html#disk-cache
我是否需要自己实现这些方法，或者是否有我在某处丢失的 DiskLruCache 版本?
Do I need to implement these methods myself or is there a version of DiskLruCache that I'm missing somewhere?
推荐答案
这里是DiskLruCache的完整实现.
首先下载DiskLruCache.java 来自 AOSP.
First download DiskLruCache.java from AOSP.
这是我的 DiskCache.java 一个用于基本缓存操作的辅助类.
Here is my DiskCache.java a helper class for basic cache operations.
/**
* Created by Babar on 12-Aug-15.
*/
public class DiskCache
{
private Context context;
private static DiskCache diskCache;
public DiskLruCache mDiskLruCache;
private final Object mDiskCacheLock = new Object();
private BitmapProcessor bitmapProcessor;
private static final int DISK_CACHE_INDEX = 0;
public static boolean mDiskCacheStarting = true;
private static final String DISK_CACHE_SUBDIR = "ooredoo_thumbnails";
private static final int DISK_CACHE_SIZE = 1024 * 1024 * 100; // 100MB
public static DiskCache getInstance()
{
if(diskCache == null)
{
diskCache = new DiskCache();
}
return diskCache;
}
private DiskCache() {}
public void requestInit(Context context)
{
this.context = context;
bitmapProcessor = new BitmapProcessor();
new DiskCacheTask(this).execute(DiskCacheTask.INIT);
}
public void init() throws IOException {
synchronized (mDiskCacheLock)
{
if(mDiskLruCache == null || mDiskLruCache.isClosed())
{
File cacheDir = FileUtils.getDiskCacheDir(context, DISK_CACHE_SUBDIR);
if(!cacheDir.exists())
{
cacheDir.mkdir();
}
if(FileUtils.getUsableSpace(cacheDir) > DISK_CACHE_SIZE)
{
mDiskLruCache = DiskLruCache.open(cacheDir, 1, 1, DISK_CACHE_SIZE);
}
else
{
Logger.print("InitDiskCache failed: NOT enough space on disk");
}
}
mDiskCacheStarting = false; // Finished initialization
mDiskCacheLock.notifyAll(); // Wake any waiting threads
}
}
public void addBitmapToDiskCache(final String key, final Bitmap value) {
if (key == null || value == null) {
return;
}
synchronized (mDiskCacheLock)
{
if (mDiskLruCache != null) {
OutputStream out = null;
String encryptedKey = CryptoUtils.encryptToMD5(key);
Logger.print("addBitmapToDiskCache encryptToMD5: " + encryptedKey);
try {
DiskLruCache.Snapshot snapshot = mDiskLruCache.get(encryptedKey);
if (snapshot == null) {
final DiskLruCache.Editor editor = mDiskLruCache.edit(encryptedKey);
if (editor != null) {
out = editor.newOutputStream(DISK_CACHE_INDEX);
value.compress(Bitmap.CompressFormat.JPEG, 100, out);
editor.commit();
out.close();
}
} else {
snapshot.getInputStream(DISK_CACHE_INDEX).close();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (out != null) {
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
}
/**
* Get from disk cache.
*
* @param key Unique identifier for which item to get
* @return The bitmap if found in cache, null otherwise
*/
public Bitmap getBitmapFromDiskCache(final String key)
{
Bitmap bitmap = null;
String encryptedKey = CryptoUtils.encryptToMD5(key);
Logger.print("getBitmapFromDiskCache encryptToMD5: " + encryptedKey);
synchronized (mDiskCacheLock)
{
Logger.print("mDiskcachestarting: "+mDiskCacheStarting);
// Wait while disk cache is started from background thread
while (mDiskCacheStarting)
{
try
{
mDiskCacheLock.wait();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
if(mDiskLruCache != null)
{
InputStream inputStream = null;
try
{
final DiskLruCache.Snapshot snapshot = mDiskLruCache.get(encryptedKey);
if(snapshot != null)
{
Logger.print("Disk cache hit");
inputStream = snapshot.getInputStream(DISK_CACHE_INDEX);
if(inputStream != null)
{
FileDescriptor fd = ((FileInputStream) inputStream).getFD();
// Decode bitmap, but we don't want to sample so give
// MAX_VALUE as the target dimensions
bitmap = bitmapProcessor.decodeSampledBitmapFromDescriptor(fd);
}
}
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
if(inputStream != null)
{
try
{
inputStream.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
Logger.print("dCache getBitmapFromDiskCache synchronized completed");
}
Logger.print("dCache getBitmapFromDiskCache returning Bitmap");
return bitmap;
}
public void requestFlush()
{
new DiskCacheTask(this).execute(DiskCacheTask.FLUSH);
}
/**
* Flushes the disk cache associated with this ImageCache object. Note that this includes
* disk access so this should not be executed on the main/UI thread.
*/
public void flush()
{
synchronized (mDiskCacheLock)
{
if(mDiskLruCache != null)
{
try
{
mDiskLruCache.flush();
Logger.print("flush: disk cache flushed");
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
public void requestClose()
{
new DiskCacheTask(this).execute(DiskCacheTask.CLOSE);
}
/**
* Closes the disk cache associated with this ImageCache object. Note that this includes
* disk access so this should not be executed on the main/UI thread.
*/
public void close()
{
synchronized (mDiskCacheLock)
{
if(mDiskLruCache != null)
{
if(!mDiskLruCache.isClosed())
{
try
{
mDiskLruCache.close();
mDiskLruCache = null;
Logger.print("disk cache closed");
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
}
/**
* Do not call this method unless you need to explicitly clear disk cache
*/
public void requestTearDown()
{
new DiskCacheTask(this).execute(DiskCacheTask.TEAR_DOWN);
}
public final void tearDown()
{
synchronized (mDiskCacheLock)
{
mDiskCacheStarting = true;
if(mDiskLruCache != null && !mDiskLruCache.isClosed())
{
try
{
mDiskLruCache.delete();
Logger.print("disk cache cleared");
}
catch (IOException e)
{
e.printStackTrace();
}
mDiskLruCache = null;
}
}
}
}
这里是BitmapProcesser.java
/**
* @author Babar
* @since 15-Jun-15.
*/
public class BitmapProcessor
{
public Bitmap decodeSampledBitmapFromStream(InputStream inputStream, URL url,
int reqWidth, int reqHeight) throws IOException {
Bitmap bitmap;
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeStream(inputStream, null, options);
int width = options.outWidth;
int height = options.outHeight;
Logger.print("@Req Width: "+reqWidth);
Logger.print("@Req Height: " + reqHeight);
Logger.print("@Actual Width: "+width);
Logger.print("@Actual Height: " + height);
int sampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
options.inJustDecodeBounds = false;
options.inSampleSize = sampleSize;
inputStream = url.openStream();
bitmap = BitmapFactory.decodeStream(inputStream, null, options);
if(bitmap != null)
{
width = bitmap.getWidth();
height = bitmap.getHeight();
Logger.print("@inSample:"+sampleSize);
Logger.print("@Modified Width: "+width);
Logger.print("@Modified Height: " + height);
}
return bitmap;
}
public Bitmap decodeSampledBitmapFromDescriptor(FileDescriptor fd)
{
/*final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFileDescriptor(fd, null, options);
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
options.inJustDecodeBounds = false;*/
return BitmapFactory.decodeFileDescriptor(fd);
}
public Bitmap decodeSampledBitmapFromFile(String pathName, int reqWidth, int reqHeight) throws IOException {
Bitmap bitmap;
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(pathName, options);
int width = options.outWidth;
int height = options.outHeight;
Logger.print("@Req Width: "+reqWidth);
Logger.print("@Req Height: " + reqHeight);
Logger.print("@Actual Width: "+width);
Logger.print("@Actual Height: " + height);
int sampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
options.inJustDecodeBounds = false;
options.inSampleSize = sampleSize;
bitmap = BitmapFactory.decodeFile(pathName, options);
if(bitmap != null)
{
width = bitmap.getWidth();
height = bitmap.getHeight();
Logger.print("@inSample:"+sampleSize);
Logger.print("@Modified Width: "+width);
Logger.print("@Modified Height: " + height);
}
return bitmap != null ? rotateBitmapIfNeeded(pathName, bitmap) : null;
}
public int calculateInSampleSize(BitmapFactory.Options options,
int requiredWidth, int requiredHeight)
{
final int width = options.outWidth;
final int height = options.outHeight;
int inSampleSize = 1;
if(width > requiredWidth || height > requiredHeight)
{
final int halfWidth = width / 2;
final int halfHeight = height / 2;
// Calculate the largest inSampleSize value that is a power of 2 and keeps both
// height and width larger than the requested height and width.
while ((halfWidth / inSampleSize) > requiredWidth
&&
(halfHeight / inSampleSize) > requiredHeight)
{
inSampleSize *= 2;
}
}
return inSampleSize;
}
public static Bitmap rotateBitmapIfNeeded(String pathName, Bitmap bitmap) throws IOException {
ExifInterface exifInterface = new ExifInterface(pathName);
int orientation = exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION,
ExifInterface.ORIENTATION_NORMAL);
Logger.logI("BITMAP_ORIENTATION: " + orientation, pathName);
switch (orientation)
{
case ExifInterface.ORIENTATION_ROTATE_90:
return rotateBitmap(bitmap, 90);
case ExifInterface.ORIENTATION_ROTATE_180:
return rotateBitmap(bitmap, 180);
case ExifInterface.ORIENTATION_ROTATE_270:
return rotateBitmap(bitmap, 270);
}
return bitmap;
}
public Bitmap makeBitmapRound(Bitmap src)
{
int width = src.getWidth();
int height = src.getHeight();
Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
// Canvas canvas = new Canvas(bitmap);
BitmapShader shader = new BitmapShader(src, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setShader(shader);
RectF rectF = new RectF(0.0f, 0.0f, width, height);
// rect contains the bounds of the shape
// radius is the radius in pixels of the rounded corners
// paint contains the shader that will texture the shape
Canvas canvas = new Canvas(src);
canvas.drawRoundRect(rectF, 30, 30, paint);
return src;
}
public static Bitmap rotateBitmap(Bitmap bitmap, int degree) {
Matrix matrix = new Matrix();
matrix.postRotate(degree);
return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
}
}
这里是CryptoUtils.java
/**
* @author Babar
* @since 29-Jun-15.
*/
public class CryptoUtils
{
private static final String MD5_ALGO = "MD5";
public static String encryptToMD5(String text)
{
try
{
java.security.MessageDigest md = java.security.MessageDigest.getInstance(MD5_ALGO);
md.update(text.getBytes());
byte[] bytes = md.digest();
String hex = bytesToHexString(bytes);
return hex;
}
catch (NoSuchAlgorithmException e)
{
e.printStackTrace();
return String.valueOf(text.hashCode());
}
}
private static String bytesToHexString(byte[] bytes)
{
StringBuffer sb = new StringBuffer();
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();
}
public static String encodeToBase64(String str) {
String tmp = "";
if(isNotNullOrEmpty(str)) {
try {
tmp = new String(Base64.encode(str.getBytes(), Base64.DEFAULT)).trim();
} catch(Throwable e) {
e.printStackTrace();
}
}
return tmp;
}
}
这里是DiskCacheTask.java
/**
* Created by Babar on 12-Aug-15.
*/
public class DiskCacheTask extends BaseAsyncTask<Integer, Void, Void>
{
private DiskCache diskCache;
public static final int INIT = 1;
public static final int FLUSH = 2;
public static final int CLOSE = 3;
public static final int TEAR_DOWN = 4;
public static final int REMOVE = 5;
public DiskCacheTask(DiskCache diskCache)
{
this.diskCache = diskCache;
}
@Override
protected Void doInBackground(Integer... params)
{
switch (params[0])
{
case INIT:
try
{
diskCache.init();
}
catch (IOException e)
{
e.printStackTrace();
}
break;
case FLUSH:
diskCache.flush();
break;
case CLOSE:
diskCache.close();
break;
case TEAR_DOWN:
diskCache.tearDown();
break;
case REMOVE:
diskCache.remove();
break;
}
return null;
}
}
要初始化缓存，只需从 MainActivity 的 onCreate() 理想情况下调用 new DiskCache().getInstance().requestInit();.还要注意磁盘操作应该在单独的线程中完成，例如 Handler ，AsyncTask.因此，当您想向/从磁盘缓存添加/获取位图时，请从工作线程执行此操作.
To initialize the cache simply call new DiskCache().getInstance().requestInit(); ideally from your MainActivity's onCreate(). Also note Disk operation should be done in separate thread for example Handler , AsyncTask. So when ever you want to add/get bitmap to/from disk cache do this from a worker thread.
这篇关于android 教程中的 DiskLruCache 缺少很多方法.的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！