（原创）使用AsyncTask（带修改线程池方式）+自定义ImageLoader+LRU算法对图片三级缓存及其显示优化

package com.example.lainanzhou.imagecachedemo.utils; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.AsyncTask; import android.os.Environment; import android.os.Message; import android.os.StatFs; import android.util.Log; import android.util.LruCache; import android.widget.ImageView; import android.widget.ListView; import com.example.lainanzhou.imagecachedemo.R; import com.example.lainanzhou.imagecachedemo.adapter.NewsAdapter; import java.io.BufferedInputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.HttpURLConnection; import java.net.URL; import java.util.concurrent.BlockingQueue; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.RejectedExecutionHandler; import java.util.concurrent.ThreadFactory; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; /** * TODO: * 通过AsyncTask和LRU算法实现图片三级缓存的图片操作类 * 存： * 1.先网络获取 * 2.存到运行内存中和写到sd卡上 * 取： * 1.先取运行内存中的图片缓存 * 2.再取sd卡图片缓存资源 * 3.最后取网络上的图片资源 * 还有避免图片出现显示错乱情况（ListView的缓存机制复用convertView导致） * 设置View的Tag即可避免 * * @author Joker * @createDate 2016/7/15. */ public class ImageLoader { private static ImageLoader mImageLoader; private ImageView iv; private String mUrl; public static LruCache<String, Bitmap> mLruCache; private static final int FREE_SD_SPACE_NEEDED_TO_CACHE = 10; private android.os.Handler mHandler = new android.os.Handler() { @Override public void handleMessage(Message msg) { super.handleMessage(msg); if (iv.getTag() == mUrl) {//获取ImageView的tag区别设置图片避免图片显示错乱 Bitmap bitmap = (Bitmap) msg.obj; iv.setImageBitmap(bitmap); } } }; private int mCorePoolSize = 10; private int mMaximumPoolSize = 20; private int mKeepAliveTime ; private TimeUnit unit = TimeUnit.MILLISECONDS; // BlockingQueue<Runnable> workQueue = new // ArrayBlockingQueue<Runnable>(10);// 阻塞队列 private BlockingQueue<Runnable> workQueue = new LinkedBlockingQueue<Runnable>();// 阻塞队列 private ThreadFactory threadFactory = Executors.defaultThreadFactory(); // RejectedExecutionHandler handler = new // ThreadPoolExecutor.AbortPolicy();//如果出现错误，则直接抛出异常 // RejectedExecutionHandler handler = new // ThreadPoolExecutor.CallerRunsPolicy();// 如果出现错误，直接执行加入的任务 // RejectedExecutionHandler handler = new // ThreadPoolExecutor.DiscardOldestPolicy();// // 如果出现错误,移除第一个任务,执行加入的任务 private RejectedExecutionHandler handler = new ThreadPoolExecutor.DiscardPolicy();// 如果出现错误，不做处理 //第一种设置AsyncTask线程池方式 private ThreadPoolExecutor mExecutor = new ThreadPoolExecutor(mCorePoolSize,// 核心线程数 : 10 mMaximumPoolSize,// 最大线程数 : 20 mKeepAliveTime,// 保持的时间长度 unit,// keepAliveTime单位 workQueue,// 任务队列 threadFactory,// 线程工厂 handler);// 错误捕获器 //第二种修改AsyncTask线程池方式 private ExecutorService mExecutorService = Executors.newFixedThreadPool(10); public synchronized static ImageLoader instance() { if (mImageLoader == null) { mImageLoader = new ImageLoader(); //获取程序运行时最大内存空间 long maxMemory = Runtime.getRuntime().maxMemory(); int cacheSize = (int) (maxMemory / 4); mLruCache = new LruCache<String, Bitmap>(cacheSize) { //获取每次加载对象缓存的内存大小；默认返回的是元素的个数而非内存大小 @Override protected int sizeOf(String key, Bitmap value) { //每次存对象都会走的方法 return value.getByteCount(); } }; } return mImageLoader; } private ImageLoader() { } /** * 直接开启线程处理方式显示图片 * 加锁避免疯狂滑动开启多余线程处理同个url * * @param imageView * @param url */ public void showImageFromThread(final ImageView imageView, final String url) { //取缓存 Bitmap bitmap = getBitmapFromCache(url); //缓存存在就直接显示 if (bitmap != null) { imageView.setImageBitmap(bitmap); Log.d(getClass().getSimpleName(), "取内存缓存" + url); } else { synchronized (url) { new Thread() { @Override public void run() { super.run(); iv = imageView; mUrl = url; Bitmap bitmap = getBitmapFromUrl(url); //缓存图片 addBitmap2Cache(url, bitmap); Message mes = Message.obtain(); mes.obj = bitmap; mHandler.sendMessage(mes); } }.start(); } } } /** * 从Url获取bitmap对象 * * @param urlString * @return */ private Bitmap getBitmapFromUrl(String urlString) { Bitmap bitmap = null; InputStream is = null; try { URL url = new URL(urlString); HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); is = new BufferedInputStream(urlConnection.getInputStream()); bitmap = BitmapFactory.decodeStream(is);//将流对象转成bitmap对象 urlConnection.disconnect();//释放资源 } catch (IOException e) { e.printStackTrace(); } finally { try { if (is != null) is.close(); } catch (IOException e) { e.printStackTrace(); } } return bitmap; } public void showImageFromAsyncTask(ImageView imageView, String urlString, boolean isLoader) { //取缓存 Bitmap bitmap = getBitmapFromCache(urlString); if (bitmap == null) { if (isLoader) { bitmap = getBitmapFromSdCard(urlString); if (bitmap == null && isLoader) // new ImageAsyncTask(imageView).execute(urlString);//缓存没有就网络加载 new ImageAsyncTask(imageView,urlString);//缓存没有就网络加载 else if (imageView.getTag().equals(urlString)) { addBitmap2Cache(urlString, bitmap);//缓存到内存 imageView.setImageBitmap(bitmap);//有缓存就直接显示 Log.d(getClass().getSimpleName(), "取Sd卡缓存" + urlString); } } else if (imageView.getTag().equals(urlString)) { imageView.setImageResource(R.mipmap.ic_launcher);//设置默认图片 } } else if (imageView.getTag().equals(urlString)) { imageView.setImageBitmap(bitmap);//有缓存就直接显示 Log.d(getClass().getSimpleName(), "取内存缓存" + urlString); }