title: cache a array list of bitmap in android
body: <p>i have a ArrayList that contains more than 15 bitmaps. this bitmaps have to be read from sdcard. my array is in the loop .so i dont want to read bitmaps from storage each time and i want to save this bitmaps as cache. my arraylist of bitmap is less than 2 Mb.
  i wanna display it with canvas in my Custom View.so i think it's good to save it as cache or something else because of the number of bitmaps. i think it doesn't make sense to read more than 15 bitmap from sdcard even if they are very light(about 15kb) pleas help me how to do this.
  in additional each bitmap is 256*256 pixel.</p>
  
  <pre><code>Bitmap bmp;
  String zoom = String.valueOf(ZoomLevel);
  File file = new File(Environment.getExternalStorageDirectory()+"/GreatMap/"+zoom);
  File image = FolderExist(ZoomLevel);
  if (file.exists())
  {   
      if(image.exists())
      {
          for(int a = 1; a &lt; 20 ;a++)
          {
              bmp = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory()+"/GreatMap/"+zoom+"/"+a+".jpg");
              Images.add(a,bmp);                          
  
          }
          postInvalidate();
  
          }
  }
  </code></pre>