Android中获取网络图片的方法(如果手机缓存里面有就从缓存获取)

// 如果缓存里面有就从缓存获取，否则网络获取图片，返回Drawable对象
  public static Drawable loadImageFromNetwork(Context context, String imageUrl)
  {
    Drawable drawable = null;
    if(imageUrl == null )
      return null;
    String imagePath = "";
    String   fileName   = "";
      
    // 获取url中图片的文件名与后缀
    if(imageUrl!=null&&imageUrl.length()!=0){ 
            fileName  = imageUrl.substring(imageUrl.lastIndexOf("/")+1);
    }
    
    // 图片在手机本地的存放路径,注意：fileName为空的情况
    imagePath = context.getCacheDir() + "/" + fileName;

    Log.i("test","imagePath = " + imagePath);
    File file = new File(context.getCacheDir(),fileName);// 保存文件
    Log.i("test","file.toString()=" + file.toString());
    if(!file.exists()&&!file.isDirectory())
    {
      try {
        // 可以在这里通过文件名来判断，是否本地有此图片
        
        FileOutputStream   fos=new   FileOutputStream( file );
        InputStream is = new URL(imageUrl).openStream();
        int   data = is.read(); 
        while(data!=-1){ 
                fos.write(data); 
                data=is.read();; 
        } 
        fos.close();
        is.close();
//        drawable = Drawable.createFromStream(
//            new URL(imageUrl).openStream(), file.toString() ); // (InputStream) new URL(imageUrl).getContent();
        drawable = Drawable.createFromPath(file.toString());
        Log.i("test", "file.exists()不文件存在，网上下载:" + drawable.toString());
      } catch (IOException e) {
        Log.d("test", e.getMessage());
      }
    }else
    {
      drawable = Drawable.createFromPath(file.toString());
      Log.i("test", "file.exists()文件存在，本地获取");
    }
    
    if (drawable == null) {
      Log.d("test", "null drawable");
    } else {
      Log.d("test", "not null drawable");
    }
    
    return drawable ;
  }