基于LruCache listView缓存图片工具类

package com.yitian.activity.utils; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.AsyncTask; import android.util.Log; import android.util.LruCache; import android.widget.ImageView; import java.io.BufferedInputStream; import java.net.HttpURLConnection; import java.net.URL; /** * Created by Huang hai-sen on 2015/12/10. */ public class ImageLoaders { //创建Cache private LruCache<String, Bitmap> mCaches; public ImageLoaders() { //获取最大可用内存 int maxMemory = (int) Runtime.getRuntime().maxMemory(); int cacheSize = maxMemory / 4; mCaches = new LruCache<String, Bitmap>(cacheSize) { @Override protected int sizeOf(String key, Bitmap bitmap) { //每次存入缓存时使用 return bitmap.getByteCount(); } }; } /** * 将Bitnap对象存入缓存中 * * @param url //缓存图片的路径 * @param bitmap //缓存图片的对象 */ public void addBitmapToCache(String url, Bitmap bitmap) { if (getBitmapForCache(url) == null&&bitmap !=null) { mCaches.put(url, bitmap); } } /** * 通过URL获取缓存图片，返回Bitmap对象或者返回null值 * * @param url * @return */ public Bitmap getBitmapForCache(String url) { return mCaches.get(url);//底层linkHasMap } /** * 通过url用get方法获取Bitmap对象图片 * * @param url * @return */ public Bitmap getBitmapForUrl(String url) { try { URL u = new URL(url); HttpURLConnection conn = (HttpURLConnection) u.openConnection(); BufferedInputStream bis = new BufferedInputStream(conn.getInputStream()); Bitmap bitmap = BitmapFactory.decodeStream(bis); bis.close(); conn.disconnect(); return bitmap; } catch (Exception e) { e.printStackTrace(); } return null; } /** * 通过ImageView和url显示图片方法 * * @param imageView * @param url * * 调用方法： * （1）在自定义的adapter中设置一个标记imageView.setTag（url）（注：在显示图片是先拿标记中的url和获取图片的url对比，一致时再显示图片） * （2）调用new ImageLoader().showImageViewByAsyncTask(imageView,url); */ public void showImageViewByAsyncTask(ImageView imageView, String url) { //先从缓存中获取图片 Bitmap bitmap = getBitmapForCache(url); if (bitmap == null) {//不存在缓存中，直接开启异步任务下载 new MyAsnyTask(imageView, url).execute(url); } else {//存在缓存中，直接显示 imageView.setImageBitmap(bitmap); } } class MyAsnyTask extends AsyncTask<String, Void, Bitmap> { private ImageView imageView; private String url; public MyAsnyTask(ImageView imageView, String url) { this.imageView = imageView; this.url = url; } @Override protected Bitmap doInBackground(String... strings) { String urlStr = strings[0]; Bitmap bitmap = getBitmapForUrl(urlStr); //将不在缓存的图片加入缓存 addBitmapToCache(urlStr, bitmap); return bitmap; } @Override protected void onPostExecute(Bitmap bitmap) { super.onPostExecute(bitmap); //在向主线程提交时先检查Tag避免图片错位 if (imageView.getTag().equals(url)) imageView.setImageBitmap(bitmap); } } /* private Handler handler = new Handler() { @Override public void handleMessage(Message msg) { super.handleMessage(msg); if (imageView.getTag().equals(url)) imageView.setImageBitmap((Bitmap) msg.obj); } }; public void showImageView(ImageView imageView, final String url) { this.imageView = imageView; this.url = url; new Thread(new Runnable() { @Override public void run() { Bitmap bitmap = getBitmapForUrl(url); Message message = Message.obtain(); message.obj = bitmap; handler.sendMessage(message); } }).start(); } */ }