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android图片异步加载到本地
package com.example.health.util;
import java.lang.ref.SoftReference;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import android.content.Context;
import android.graphics.Bitmap;
import android.os.Handler;
import android.util.Log;
public class AsyncImageLoader {
//保存正在下载的图片URL集合，避免重复下载用
private static HashSet<String> sDownloadingSet;
//软引用内存缓存
private static Map<String,SoftReference<Bitmap>> sImageCache;
//图片三种获取方式管理者，网络URL获取、内存缓存获取、外部文件缓存获取
private static LoaderImpl impl;
//线程池相关
private static ExecutorService sExecutorService;
//通知UI线程图片获取ok时使用
private Handler handler;
/**
* 异步加载图片完毕的回调接口
*/
public interface ImageCallback{
/**
* 回调函数
* @param bitmap: may be null!
* @param imageUrl
*/
public void onImageLoaded(Bitmap bitmap, String imageUrl);
}
static{
sDownloadingSet = new HashSet<String>();
sImageCache = new HashMap<String,SoftReference<Bitmap>>();
impl = new LoaderImpl(sImageCache);
}
public AsyncImageLoader(Context context){
handler = new Handler();
startThreadPoolIfNecessary();
String defaultDir = context.getCacheDir().getAbsolutePath();
setCachedDir(defaultDir);
}
/**
* 是否缓存图片至/data/data/package/cache/目录
* 默认不缓存
*/
public void setCache2File(boolean flag){
impl.setCache2File(flag);
}
/**
* 设置缓存路径，setCache2File(true)时有效
*/
public void setCachedDir(String dir){
impl.setCachedDir(dir);
}
/**开启线程池*/
public static void startThreadPoolIfNecessary(){
if(sExecutorService == null || sExecutorService.isShutdown() || sExecutorService.isTerminated()){
sExecutorService = Executors.newFixedThreadPool(3);
//sExecutorService = Executors.newSingleThreadExecutor();
}
}
/**
* 异步下载图片，并缓存到memory中
* @param url
* @param callback see ImageCallback interface
*/
public void downloadImage(final String url, final ImageCallback callback){
downloadImage(url, true, callback);
}
/**
*
* @param url
* @param cache2Memory 是否缓存至memory中
* @param callback
*/
public void downloadImage(final String url, final boolean cache2Memory, final ImageCallback callback){
if(sDownloadingSet.contains(url)){
Log.i("AsyncImageLoader", "###该图片正在下载，不能重复下载！");
return;
}
Bitmap bitmap = impl.getBitmapFromMemory(url);
if(bitmap != null){
if(callback != null){
callback.onImageLoaded(bitmap, url);
}
}else{
//从网络端下载图片
sDownloadingSet.add(url);
sExecutorService.submit(new Runnable(){
@Override
public void run() {
final Bitmap bitmap = impl.getBitmapFromUrl(url, cache2Memory);
handler.post(new Runnable(){
@Override
public void run(){
if(callback != null)
callback.onImageLoaded(bitmap, url);
sDownloadingSet.remove(url);
}
});
}
});
}
}
/**
* 预加载下一张图片，缓存至memory中
* @param url
*/
public void preLoadNextImage(final String url){
//将callback置为空，只将bitmap缓存到memory即可。
downloadImage(url, null);
}
}
private void showImage(String imgUrl) {
if(null==LoadingActivity.userList) {
image.setImageResource(images[2]);
} else {
//for test
AsyncImageLoader loader = new AsyncImageLoader(getApplicationContext());
//将图片缓存至外部文件中
loader.setCache2File(false); //false
//设置外部缓存文件夹
loader.setCachedDir(this.getCacheDir().getAbsolutePath());
//下载图片，第二个参数是否缓存至内存中
loader.downloadImage(imgUrl, true/*false*/, new AsyncImageLoader.ImageCallback() {
@Override
public void onImageLoaded(Bitmap bitmap, String imageUrl) {
if(bitmap != null){
image.setImageBitmap(bitmap);
}else{
//下载失败，设置默认图片
image.setImageResource(images[2]);
}
}
});
}
}
最后更新：2017-04-03 16:49:00