android 同步多线程下载

【实例简介】

android 同步多线程下载
【实例截图】
【核心代码】

package com.sx.aysnc.img;

import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.SoftReference;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import com.sx.aysnc.img.util.FileOperator;
import com.sx.aysnc.img.util.NewOperator;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.os.Handler;
import android.os.Message;

public class LoadImageAysnc {

 //图片缓存软引用
 private HashMap<String, SoftReference<Drawable>> imageCache;
 //线程池
 private BlockingQueue<Runnable> queue;
 private ThreadPoolExecutor executor;
 private FileOperator fileOperator;
 private NewOperator newOperator;
 
 public LoadImageAysnc(Context context) {
  
  imageCache = new HashMap<String, SoftReference<Drawable>>();
  fileOperator = new FileOperator();
  newOperator = new NewOperator(context);
  queue = new LinkedBlockingQueue<Runnable>();
  executor = new ThreadPoolExecutor(1, 5, 180, TimeUnit.SECONDS, queue);
  
 }

 //异步加载图片的方法（其实可以以任何形式得到图片）
 public Drawable loadImage(final String id, final String iconSrc, final String localSrc,
   final String localFlg, final ImageCallBack imageCallBack)
 {
 
  //如果有缓存则使用缓存中的图片
  if(imageCache.containsKey(id)){
   SoftReference<Drawable> softReference = imageCache.get(id);
   Drawable drawable = softReference.get();
   if(drawable != null) {
    return drawable;
   }
  }
  
  //图片加载完成
  final Handler handler = new Handler()
  {
   @Override
   public void handleMessage(Message msg) {
    Drawable drawable = (Drawable) msg.obj;
    //图片加载完成的回调函数，用于更新imageview
    imageCallBack.imageLoaded(drawable, iconSrc);
   }
  };
  
  //异步图片下载方法
  executor.execute(
    new Runnable() {
     
     @Override
     public void run() {
      
      Drawable drawable = null;
      if("0".equals(localFlg)) { //如果本地不存在图片则去网上下载，并写入本地文件
       fileOperator.write2SDFromInput("news/", "img" id ".jpg", getInputStream(iconSrc));
       String svaeLocalSrc = "img" id ".jpg";
       //更新数据库
       newOperator.update(id, svaeLocalSrc , "1");
       drawable = loadImageFromLocalStorage(svaeLocalSrc); //本地读取图片
      } else {
       drawable = loadImageFromLocalStorage(localSrc); //如果本地有图片则直接读取
      }
      
      imageCache.put(id, new SoftReference<Drawable>(drawable));
      Message msg = handler.obtainMessage(0, drawable);
      msg.sendToTarget();
      
     }
    });
  return null;
 }
 
 //网络图片下载方法
 public Drawable loadImageFromUrl(String url) {
  Drawable d = Drawable.createFromStream(getInputStream(url), "src");
  return d;
 }
 //本地图片加载方法
 public Drawable loadImageFromLocalStorage(String fileName) {
  Drawable d = fileOperator.readFromSD2Output(fileName);
  return d;
 }
 
 //得到网上下载的图片数据流
 public InputStream getInputStream(String url)
 {
  URL m;
  InputStream i = null;
  try {
   m = new URL(url);
   i = (InputStream) m.getContent();
  } catch (MalformedURLException e1) {
   e1.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
  return i;
 }
 
 //回调接口
 public interface ImageCallBack
 {
  public void imageLoaded(Drawable drawable, String iconSrc);
 }
}