Android图片管理组件（双缓存+异步加载）

Android程序常常会内存溢出，网上也有很多解决方案，如软引用，手动调用recycle等等。但经过我们实践发现这些方案，都没能起到很好的效果，我们的应用依然会出现很多oom，尤其我们的应用包含大量的图片。android3.0之后软引用基本已经失效，因为虚拟机只要碰到软引用就回收，所以带不来任何性能的提升。

我这里的解决方案是HandlerThread(异步加载)+LruCache(内存缓存)+DiskLruCache(硬盘缓存)。

作为程序员，我也不多说，直接和大家共享我的代码，用代码交流更方便些。

源码demo地址：https://github.com/yueyueniao2012/multiimagechooser

package com.example.util;

import java.io.File;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.util.EntityUtils;

import android.app.ActivityManager;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.TransitionDrawable;
import android.media.ThumbnailUtils;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;
import android.os.Message;
import android.support.v4.util.LruCache;
import android.widget.ImageView;

import com.example.MyApplication;

/**
* 图片加载类
*
* @author 月月鸟
*/
public class ImageManager2 {

private static ImageManager2 imageManager;
public LruCache<String, Bitmap> mMemoryCache;
private static final int DISK_CACHE_SIZE = 1024 * 1024 * 20; // 10MB
private static final String DISK_CACHE_SUBDIR = "thumbnails";
public DiskLruCache mDiskCache;
private static MyApplication myapp;

/** 图片加载队列，后进先出 */
private Stack<ImageRef> mImageQueue = new Stack<ImageRef>();

/** 图片请求队列，先进先出，用于存放已发送的请求。 */
private Queue<ImageRef> mRequestQueue = new LinkedList<ImageRef>();

/** 图片加载线程消息处理器 */
private Handler mImageLoaderHandler;

/** 图片加载线程是否就绪 */
private boolean mImageLoaderIdle = true;

/** 请求图片 */
private static final int MSG_REQUEST = 1;
/** 图片加载完成 */
private static final int MSG_REPLY = 2;
/** 中止图片加载线程 */
private static final int MSG_STOP = 3;
/** 如果图片是从网络加载，则应用渐显动画，如果从缓存读出则不应用动画 */
private boolean isFromNet = true;

/**
* 获取单例，只能在UI线程中使用。
*
* @param context
* @return
*/
public static ImageManager2 from(Context context) {

// 如果不在ui线程中，则抛出异常
if (Looper.myLooper() != Looper.getMainLooper()) {
throw new RuntimeException("Cannot instantiate outside UI thread.");
}

if (myapp == null) {
myapp = (MyApplication) context.getApplicationContext();
}

if (imageManager == null) {
imageManager = new ImageManager2(myapp);
}

return imageManager;
}

/**
* 私有构造函数，保证单例模式
*
* @param context
*/
private ImageManager2(Context context) {
int memClass = ((ActivityManager) context
.getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass();
memClass = memClass > 32 ? 32 : memClass;
// 使用可用内存的1/8作为图片缓存
final int cacheSize = 1024 * 1024 * memClass / 8;

mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {

protected int sizeOf(String key, Bitmap bitmap) {
return bitmap.getRowBytes() * bitmap.getHeight();
}

};

File cacheDir = DiskLruCache
.getDiskCacheDir(context, DISK_CACHE_SUBDIR);
mDiskCache = DiskLruCache.openCache(context, cacheDir, DISK_CACHE_SIZE);

}

/**
* 存放图片信息
*/
class ImageRef {

/** 图片对应ImageView控件 */
ImageView imageView;
/** 图片URL地址 */
String url;
/** 图片缓存路径 */
String filePath;
/** 默认图资源ID */
int resId;
int width = 0;
int height = 0;

/**
* 构造函数
*
* @param imageView
* @param url
* @param resId
* @param filePath
*/
ImageRef(ImageView imageView, String url, String filePath, int resId) {
this.imageView = imageView;
this.url = url;
this.filePath = filePath;
this.resId = resId;
}

ImageRef(ImageView imageView, String url, String filePath, int resId,
int width, int height) {
this.imageView = imageView;
this.url = url;
this.filePath = filePath;
this.resId = resId;
this.width = width;
this.height = height;
}

}

/**
* 显示图片
*
* @param imageView
* @param url
* @param resId
*/
public void displayImage(ImageView imageView, String url, int resId) {
if (imageView == null) {
return;
}
if (imageView.getTag() != null
&& imageView.getTag().toString().equals(url)) {
return;
}
if (resId >= 0) {
if (imageView.getBackground() == null) {
imageView.setBackgroundResource(resId);
}
imageView.setImageDrawable(null);

}
if (url == null || url.equals("")) {
return;
}

// 添加url tag
imageView.setTag(url);

// 读取map缓存
Bitmap bitmap = mMemoryCache.get(url);
if (bitmap != null) {
setImageBitmap(imageView, bitmap, false);
return;
}

// 生成文件名
String filePath = urlToFilePath(url);
if (filePath == null) {
return;
}

queueImage(new ImageRef(imageView, url, filePath, resId));
}

/**
* 显示图片固定大小图片的缩略图，一般用于显示列表的图片，可以大大减小内存使用
*
* @param imageView 加载图片的控件
* @param url 加载地址
* @param resId 默认图片
* @param width 指定宽度
* @param height 指定高度
*/
public void displayImage(ImageView imageView, String url, int resId,
int width, int height) {
if (imageView == null) {
return;
}
if (resId >= 0) {

if (imageView.getBackground() == null) {
imageView.setBackgroundResource(resId);
}
imageView.setImageDrawable(null);

}
if (url == null || url.equals("")) {
return;
}

// 添加url tag
imageView.setTag(url);
// 读取map缓存
Bitmap bitmap = mMemoryCache.get(url + width + height);
if (bitmap != null) {
setImageBitmap(imageView, bitmap, false);
return;
}

// 生成文件名
String filePath = urlToFilePath(url);
if (filePath == null) {
return;
}

queueImage(new ImageRef(imageView, url, filePath, resId, width, height));
}

/**
* 入队，后进先出
*
* @param imageRef
*/
public void queueImage(ImageRef imageRef) {

// 删除已有ImageView
Iterator<ImageRef> iterator = mImageQueue.iterator();
while (iterator.hasNext()) {
if (iterator.next().imageView == imageRef.imageView) {
iterator.remove();
}
}

// 添加请求
mImageQueue.push(imageRef);
sendRequest();
}

/**
* 发送请求
*/
private void sendRequest() {

// 开启图片加载线程
if (mImageLoaderHandler == null) {
HandlerThread imageLoader = new HandlerThread("image_loader");
imageLoader.start();
mImageLoaderHandler = new ImageLoaderHandler(
imageLoader.getLooper());
}

// 发送请求
if (mImageLoaderIdle && mImageQueue.size() > 0) {
ImageRef imageRef = mImageQueue.pop();
Message message = mImageLoaderHandler.obtainMessage(MSG_REQUEST,
imageRef);
mImageLoaderHandler.sendMessage(message);
mImageLoaderIdle = false;
mRequestQueue.add(imageRef);
}
}

/**
* 图片加载线程
*/
class ImageLoaderHandler extends Handler {

public ImageLoaderHandler(Looper looper) {
super(looper);
}

public void handleMessage(Message msg) {
if (msg == null)
return;

switch (msg.what) {

case MSG_REQUEST: // 收到请求
Bitmap bitmap = null;
Bitmap tBitmap = null;
if (msg.obj != null && msg.obj instanceof ImageRef) {

ImageRef imageRef = (ImageRef) msg.obj;
String url = imageRef.url;
if (url == null)
return;
// 如果本地url即读取sd相册图片，则直接读取，不用经过DiskCache
if (url.toLowerCase().contains("dcim")) {

tBitmap = null;
BitmapFactory.Options opt = new BitmapFactory.Options();
opt.inSampleSize = 1;
opt.inJustDecodeBounds = true;
BitmapFactory.decodeFile(url, opt);
int bitmapSize = opt.outHeight * opt.outWidth * 4;
opt.inSampleSize = bitmapSize / (1000 * 2000);
opt.inJustDecodeBounds = false;
tBitmap = BitmapFactory.decodeFile(url, opt);
if (imageRef.width != 0 && imageRef.height != 0) {
bitmap = ThumbnailUtils.extractThumbnail(tBitmap,
imageRef.width, imageRef.height,
ThumbnailUtils.OPTIONS_RECYCLE_INPUT);
isFromNet = true;
} else {
bitmap = tBitmap;
tBitmap = null;
}

} else
bitmap = mDiskCache.get(url);

if (bitmap != null) {
// ToolUtil.log("从disk缓存读取");
// 写入map缓存
if (imageRef.width != 0 && imageRef.height != 0) {
if (mMemoryCache.get(url + imageRef.width
+ imageRef.height) == null)
mMemoryCache.put(url + imageRef.width
+ imageRef.height, bitmap);
} else {
if (mMemoryCache.get(url) == null)
mMemoryCache.put(url, bitmap);
}

} else {
try {
byte[] data = loadByteArrayFromNetwork(url);

if (data != null) {

BitmapFactory.Options opt = new BitmapFactory.Options();
opt.inSampleSize = 1;

opt.inJustDecodeBounds = true;
BitmapFactory.decodeByteArray(data, 0,
data.length, opt);
int bitmapSize = opt.outHeight * opt.outWidth
* 4;// pixels*3 if it's RGB and pixels*4
// if it's ARGB
if (bitmapSize > 1000 * 1200)
opt.inSampleSize = 2;
opt.inJustDecodeBounds = false;
tBitmap = BitmapFactory.decodeByteArray(data,
0, data.length, opt);
if (imageRef.width != 0 && imageRef.height != 0) {
bitmap = ThumbnailUtils
.extractThumbnail(
tBitmap,
imageRef.width,
imageRef.height,
ThumbnailUtils.OPTIONS_RECYCLE_INPUT);
} else {
bitmap = tBitmap;
tBitmap = null;
}

if (bitmap != null && url != null) {
// 写入SD卡
if (imageRef.width != 0
&& imageRef.height != 0) {
mDiskCache.put(url + imageRef.width
+ imageRef.height, bitmap);
mMemoryCache.put(url + imageRef.width
+ imageRef.height, bitmap);
} else {
mDiskCache.put(url, bitmap);
mMemoryCache.put(url, bitmap);
}
isFromNet = true;
}
}
} catch (OutOfMemoryError e) {
}

}

}

if (mImageManagerHandler != null) {
Message message = mImageManagerHandler.obtainMessage(
MSG_REPLY, bitmap);
mImageManagerHandler.sendMessage(message);
}
break;

case MSG_STOP: // 收到终止指令
Looper.myLooper().quit();
break;

}
}
}

/** UI线程消息处理器 */
private Handler mImageManagerHandler = new Handler() {

@Override
public void handleMessage(Message msg) {
if (msg != null) {
switch (msg.what) {

case MSG_REPLY: // 收到应答

do {
ImageRef imageRef = mRequestQueue.remove();

if (imageRef == null)
break;

if (imageRef.imageView == null
|| imageRef.imageView.getTag() == null
|| imageRef.url == null)
break;

if (!(msg.obj instanceof Bitmap) || msg.obj == null) {
break;
}
Bitmap bitmap = (Bitmap) msg.obj;

// 非同一ImageView
if (!(imageRef.url).equals((String) imageRef.imageView
.getTag())) {
break;
}

setImageBitmap(imageRef.imageView, bitmap, isFromNet);
isFromNet = false;

} while (false);

break;
}
}
// 设置闲置标志
mImageLoaderIdle = true;

// 若服务未关闭，则发送下一个请求。
if (mImageLoaderHandler != null) {
sendRequest();
}
}
};

/**
* 添加图片显示渐现动画
*
*/
private void setImageBitmap(ImageView imageView, Bitmap bitmap,
boolean isTran) {
if (isTran) {
final TransitionDrawable td = new TransitionDrawable(
new Drawable[] {
new ColorDrawable(android.R.color.transparent),
new BitmapDrawable(bitmap) });
td.setCrossFadeEnabled(true);
imageView.setImageDrawable(td);
td.startTransition(300);
} else {
imageView.setImageBitmap(bitmap);
}
}

/**
* 从网络获取图片字节数组
*
* @param url
* @return
*/
private byte[] loadByteArrayFromNetwork(String url) {

try {

HttpGet method = new HttpGet(url);
HttpResponse response = myapp.getHttpClient().execute(method);
HttpEntity entity = response.getEntity();
return EntityUtils.toByteArray(entity);

} catch (Exception e) {
return null;
}

}

/**
* 根据url生成缓存文件完整路径名
*
* @param url
* @return
*/
public String urlToFilePath(String url) {

// 扩展名位置
int index = url.lastIndexOf('.');
if (index == -1) {
return null;
}

StringBuilder filePath = new StringBuilder();

// 图片存取路径
filePath.append(myapp.getCacheDir().toString()).append('/');

// 图片文件名
filePath.append(MD5.Md5(url)).append(url.substring(index));

return filePath.toString();
}

/**
* Activity#onStop后，ListView不会有残余请求。
*/
public void stop() {

// 清空请求队列
mImageQueue.clear();

}

}