项目地址：https://github.com/ZaBlanc/WebImageView
作者对加载图片，以及图片的内存缓存和磁盘缓存做了封装。
代码量不多，但是能够满足一般的加载图片。
先看下项目结构：
我认为通常情况下自己去实现的话，这点需要仔细看下。
/**
*
* @param urlString 对应图片的网络地址
* @return
*/
private String hashURLString(String urlString) {
try {
// Create MD5 Hash
MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
digest.update(urlString.getBytes());
byte messageDigest[] = digest.digest();
// Create Hex String
StringBuffer hexString = new StringBuffer();
for (int i=0; i<messageDigest.length; i++)
hexString.append(Integer.toHexString(0xFF & messageDigest[i]));
return hexString.toString();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
//fall back to old method
return urlString.replaceAll("[^A-Za-z0-9]", "#");
}
以及这里的文件流操作
@Override
protected Bitmap doInBackground(Void... params) {
// check mem cache first先从内存中查找
Bitmap bitmap = mCache.getBitmapFromMemCache(mURLString);
// check disk cache first然后从磁盘中查找
if (bitmap == null) {
bitmap = mCache.getBitmapFromDiskCache(mContext, mURLString,
mDiskCacheTimeoutInSeconds);
if (bitmap != null) {
//获取到后加入内存中缓存起来
mCache.addBitmapToMemCache(mURLString, bitmap);
}
}
if (bitmap == null) {
InputStream is = null;
FlushedInputStream fis = null;
try {
URL url = new URL(mURLString);
URLConnection conn = url.openConnection();
is = conn.getInputStream();
fis = new FlushedInputStream(is);
bitmap = BitmapFactory.decodeStream(fis);
// cache
if (bitmap != null) {
mCache.addBitmapToCache(mContext, mURLString, bitmap);
}
} catch (Exception ex) {
Log.e(TAG, "Error loading image from URL " + mURLString + ": "
+ ex.toString());
} finally {
try {
is.close();
} catch (Exception ex) {
}
}
}
return bitmap;
}
@Override
protected void onPostExecute(Bitmap bitmap) {
// complete!完成后回调回去
if (null != mListener) {
if (null == bitmap) {
mListener.onWebImageError();
} else {
mListener.onWebImageLoad(mURLString, bitmap);
}
}
}
static class FlushedInputStream extends FilterInputStream {
public FlushedInputStream(InputStream inputStream) {
super(inputStream);
}
@Override
public long skip(long n) throws IOException {
long totalBytesSkipped = 0L;
while (totalBytesSkipped < n) {
long bytesSkipped = in.skip(n - totalBytesSkipped);
if (bytesSkipped == 0L) {
int b = read();
if (b < 0) {
break; // we reached EOF
} else {
bytesSkipped = 1; // we read one byte
}
}
totalBytesSkipped += bytesSkipped;
}
return totalBytesSkipped;
}
}
附上源代码：
WebImageCache
/*
Copyright (c) 2011 Rapture In Venice
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
package com.raptureinvenice.webimageview.cache;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.ref.SoftReference;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
/**
* 处理图片缓存的类
*
*/
public class WebImageCache {
private final static String TAG = WebImageCache.class.getSimpleName();
// cache rules
/**
* 是否允许内存缓存
*/
private static boolean mIsMemoryCachingEnabled = true;
/**
* 是否允许磁盘缓存
*/
private static boolean mIsDiskCachingEnabled = true;
/**
* 缺省的默认超时显示时间
*/
private static int mDefaultDiskCacheTimeoutInSeconds = 60 * 60 * 24; // one day default
/**
* 缓存 软饮用？说好的弱引用呢？？
*/
private Map<String, SoftReference<Bitmap>> mMemCache;
public WebImageCache() {
mMemCache = new HashMap<String, SoftReference<Bitmap>>();
}
// ----------setter and getter
public static void setMemoryCachingEnabled(boolean enabled) {
mIsMemoryCachingEnabled = enabled;
Log.v(TAG, "Memory cache " + (enabled ? "enabled" : "disabled") + ".");
}
public static void setDiskCachingEnabled(boolean enabled) {
mIsDiskCachingEnabled = enabled;
Log.v(TAG, "Disk cache " + (enabled ? "enabled" : "disabled") + ".");
}
public static void setDiskCachingDefaultCacheTimeout(int seconds) {
mDefaultDiskCacheTimeoutInSeconds = seconds;
Log.v(TAG, "Disk cache timeout set to " + seconds + " seconds.");
}
/**
* 从缓存中取出图片
* @param urlString 对应图片的URL,在cache中是键
* @return
*/
public Bitmap getBitmapFromMemCache(String urlString) {
if (mIsMemoryCachingEnabled) {
//同步缓存
synchronized (mMemCache) {
SoftReference<Bitmap> bitmapRef = mMemCache.get(urlString);
if (bitmapRef != null) {
Bitmap bitmap = bitmapRef.get();
if (bitmap == null) {
//键对应的Bitmap为空,则T掉。去掉无效值
mMemCache.remove(urlString);
Log.v(TAG, "Expiring memory cache for URL " + urlString + ".");
} else {
Log.v(TAG, "Retrieved " + urlString + " from memory cache.");
return bitmap;
}
}
}
}
return null;
}
/**
* 从磁盘中获取缓存图片
* @param context
* @param urlString
* @param diskCacheTimeoutInSeconds
* @return
*/
public Bitmap getBitmapFromDiskCache(Context context, String urlString, int diskCacheTimeoutInSeconds) {
if (mIsDiskCachingEnabled) {
Bitmap bitmap = null;
File path = context.getCacheDir();
InputStream is = null;
String hashedURLString = hashURLString(urlString);
// correct timeout保证正确的超时设置
if (diskCacheTimeoutInSeconds < 0) {
diskCacheTimeoutInSeconds = mDefaultDiskCacheTimeoutInSeconds;
}
File file = new File(path, hashedURLString);
if (file.exists() && file.canRead()) {
// check for timeout
if ((file.lastModified() + (diskCacheTimeoutInSeconds * 1000L)) < new Date().getTime()) {
Log.v(TAG, "Expiring disk cache (TO: " + diskCacheTimeoutInSeconds + "s) for URL " + urlString);
// expire
file.delete();
} else {
try {
is = new FileInputStream(file);
bitmap = BitmapFactory.decodeStream(is);
Log.v(TAG, "Retrieved " + urlString + " from disk cache (TO: " + diskCacheTimeoutInSeconds + "s).");
} catch (Exception ex) {
Log.e(TAG, "Could not retrieve " + urlString + " from disk cache: " + ex.toString());
} finally {
try {
is.close();
} catch (Exception ex) {}
}
}
}
return bitmap;
}
return null;
}
/**
* 将图片加入缓存中
* @param urlString 对应的http网络地址
* @param bitmap 对应的Bitmap对象
*/
public void addBitmapToMemCache(String urlString, Bitmap bitmap) {
if (mIsMemoryCachingEnabled) {
synchronized (mMemCache) {
mMemCache.put(urlString, new SoftReference<Bitmap>(bitmap));
}
}
}
/**
* 将图片加入磁盘缓存中
* @param context
* @param urlString
* @param bitmap
*/
public void addBitmapToCache(Context context, String urlString, Bitmap bitmap) {
// mem cache
addBitmapToMemCache(urlString, bitmap);
// disk cache
// TODO: manual cache cleanup
if (mIsDiskCachingEnabled) {
File path = context.getCacheDir();
OutputStream os = null;
String hashedURLString = hashURLString(urlString);
try {
// NOWORKY File tmpFile = File.createTempFile("wic.", null);
File file = new File(path, hashedURLString);
os = new FileOutputStream(file.getAbsolutePath());
//对图片进行压缩处理
bitmap.compress(Bitmap.CompressFormat.PNG, 100, os);
os.flush();
os.close();
// NOWORKY tmpFile.renameTo(file);
} catch (Exception ex) {
Log.e(TAG, "Could not store " + urlString + " to disk cache: " + ex.toString());
} finally {
try {
os.close();
} catch (Exception ex) {}
}
}
}
/**
*
* @param urlString 对应图片的网络地址
* @return
*/
private String hashURLString(String urlString) {
try {
// Create MD5 Hash
MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
digest.update(urlString.getBytes());
byte messageDigest[] = digest.digest();
// Create Hex String
StringBuffer hexString = new StringBuffer();
for (int i=0; i<messageDigest.length; i++)
hexString.append(Integer.toHexString(0xFF & messageDigest[i]));
return hexString.toString();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
//fall back to old method
return urlString.replaceAll("[^A-Za-z0-9]", "#");
}
}
WebImageManagerRetriever
/*
Copyright (c) 2011 Rapture In Venice
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
package com.raptureinvenice.webimageview.download;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.Log;
import com.raptureinvenice.webimageview.cache.WebImageCache;
/**
*
* 异步获取图片
*/
public class WebImageManagerRetriever extends AsyncTask<Void, Void, Bitmap> {
private final static String TAG = WebImageManagerRetriever.class
.getSimpleName();
// cache
private static WebImageCache mCache;
// what we're looking for
private Context mContext;
private String mURLString;
private int mDiskCacheTimeoutInSeconds;
/**
* 回调
*/
private OnWebImageLoadListener mListener;
static {
mCache = new WebImageCache();
}
public WebImageManagerRetriever(Context context, String urlString,
int diskCacheTimeoutInSeconds, OnWebImageLoadListener listener) {
mContext = context;
mURLString = urlString;
mDiskCacheTimeoutInSeconds = diskCacheTimeoutInSeconds;
mListener = listener;
}
@Override
protected Bitmap doInBackground(Void... params) {
// check mem cache first先从内存中查找
Bitmap bitmap = mCache.getBitmapFromMemCache(mURLString);
// check disk cache first然后从磁盘中查找
if (bitmap == null) {
bitmap = mCache.getBitmapFromDiskCache(mContext, mURLString,
mDiskCacheTimeoutInSeconds);
if (bitmap != null) {
//获取到后加入内存中缓存起来
mCache.addBitmapToMemCache(mURLString, bitmap);
}
}
if (bitmap == null) {
InputStream is = null;
FlushedInputStream fis = null;
try {
URL url = new URL(mURLString);
URLConnection conn = url.openConnection();
is = conn.getInputStream();
fis = new FlushedInputStream(is);
bitmap = BitmapFactory.decodeStream(fis);
// cache
if (bitmap != null) {
mCache.addBitmapToCache(mContext, mURLString, bitmap);
}
} catch (Exception ex) {
Log.e(TAG, "Error loading image from URL " + mURLString + ": "
+ ex.toString());
} finally {
try {
is.close();
} catch (Exception ex) {
}
}
}
return bitmap;
}
@Override
protected void onPostExecute(Bitmap bitmap) {
// complete!完成后回调回去
if (null != mListener) {
if (null == bitmap) {
mListener.onWebImageError();
} else {
mListener.onWebImageLoad(mURLString, bitmap);
}
}
}
static class FlushedInputStream extends FilterInputStream {
public FlushedInputStream(InputStream inputStream) {
super(inputStream);
}
@Override
public long skip(long n) throws IOException {
long totalBytesSkipped = 0L;
while (totalBytesSkipped < n) {
long bytesSkipped = in.skip(n - totalBytesSkipped);
if (bytesSkipped == 0L) {
int b = read();
if (b < 0) {
break; // we reached EOF
} else {
bytesSkipped = 1; // we read one byte
}
}
totalBytesSkipped += bytesSkipped;
}
return totalBytesSkipped;
}
}
public interface OnWebImageLoadListener {
public void onWebImageLoad(String url, Bitmap bitmap);
public void onWebImageError();
}
}
WebImageManager
/*
Copyright (c) 2011 Rapture In Venice
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
package com.raptureinvenice.webimageview.download;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import android.content.Context;
import android.graphics.Bitmap;
import com.raptureinvenice.webimageview.download.WebImageManagerRetriever.OnWebImageLoadListener;
import com.raptureinvenice.webimageview.image.WebImageView;
public class WebImageManager implements OnWebImageLoadListener {
private static WebImageManager mInstance = null;
// TODO: pool retrievers
// views waiting for an image to load in
private Map<String, WebImageManagerRetriever> mRetrievers;
private Map<WebImageManagerRetriever, Set<WebImageView>> mRetrieverWaiters;
private Set<WebImageView> mWaiters;
public static WebImageManager getInstance() {
if (mInstance == null) {
mInstance = new WebImageManager();
}
return mInstance;
}
private WebImageManager() {
mRetrievers = new HashMap<String, WebImageManagerRetriever>();
mRetrieverWaiters = new HashMap<WebImageManagerRetriever, Set<WebImageView>>();
mWaiters = new HashSet<WebImageView>();
}
/**
* 处理多个同时加载图片
* @param context
* @param urlString
* @param view
* @param diskCacheTimeoutInSeconds
*/
public void downloadURL(Context context, String urlString, final WebImageView view, int diskCacheTimeoutInSeconds) {
WebImageManagerRetriever retriever = mRetrievers.get(urlString);
if (mRetrievers.get(urlString) == null) {
retriever = new WebImageManagerRetriever(context, urlString, diskCacheTimeoutInSeconds, this);
mRetrievers.put(urlString, retriever);
mWaiters.add(view);
Set<WebImageView> views = new HashSet<WebImageView>();
views.add(view);
mRetrieverWaiters.put(retriever, views);
// start!
retriever.execute();
} else {
mRetrieverWaiters.get(retriever).add(view);
mWaiters.add(view);
}
}
public void reportImageLoad(String urlString, Bitmap bitmap) {
WebImageManagerRetriever retriever = mRetrievers.get(urlString);
for (WebImageView iWebImageView : mRetrieverWaiters.get(retriever)) {
if (mWaiters.contains(iWebImageView)) {
iWebImageView.setImageBitmap(bitmap);
mWaiters.remove(iWebImageView);
}
}
mRetrievers.remove(urlString);
mRetrieverWaiters.remove(retriever);
}
public void cancelForWebImageView(WebImageView view) {
// TODO: cancel connection in progress, too
mWaiters.remove(view);
}
@Override
public void onWebImageLoad(String url, Bitmap bitmap) {
reportImageLoad(url, bitmap);
}
@Override
public void onWebImageError() {
}
}