在后台下载图像，同时显示列表视图 [英] Downloading images in background while showing the listview

问题描述

我有我的列表我展示这些图像的所有URI的数组。
现在我想在后台运行一个线程从网上得到这个图像并存储在SD卡上。
所以，当我点击列表中的，而不是从网络获取特定的元素，应该在新的活动SD卡读取。

I have an array of all the URIs of the images which I am showing in a List. Now I want to run a thread in background which gets this images from web and store them on the SD card. So when I click a particular element in the list instead of fetching from web it should fetch from the SD card in the new activity.

我如何做到这一点？

推荐答案

您的可能的尝试使用我的懒惰，可绘制框架（GPL V3行货）：

You could try using my lazy-drawables framework (GPL v3 licensed):

https://github.com/rtyley/lazy-drawables

-unfortunately它不是完全准备好生产还没有，但其中的东西它试图处理：

-unfortunately it's not quite ready for production yet, but among the things it attempts to handle:

• 图像资源的背景（非UI线程）加载


• 缩放位图的高效的缓存 - 对于您正在下载一个大的上下的形象，要显示它几百次在ListView什么
小图标格式用例

• 使用的透明度，我的意思是...

• background (non-UI-thread) loading of image resources
• efficient caching of scaled bitmaps - for the use-case where you're downloading a single big-ish image, and want to show it hundreds of times in a smaller icon format in a listview or something
• transparency of use, by which I mean...

...一旦你有一个懒惰的抽拉会话建立，填充图像的看法是一样容易：

...once you have a lazy-drawable session set up, populating an image view is as easy as:

Drawable avatarDrawable = imageSession.get(someUserIdentifier); // doesn't block
imageView.setImageDrawable(avatarDrawable);

您不要的保养的，它可能会立即返回你一个正常的bitmapdrawable，或者可能催生一个异步任务，并返回一个占位符绘制 - 提拉会自动更新，它的主机的ImageView当异步任务已经完成了。

You don't care that it may have immediately returned you a normal bitmapdrawable, or possibly spawned an async task and returned a placeholder drawable - the drawable will update itself and it's host ImageView when the async task has completed.

这是理论呢。这似乎八九不离十，有点工作至今，但有时自发UI更新不会发生......不知道为什么： - }

That's the theory anyway. It seems to sorta-kinda work so far, but sometimes that spontaneous UI update doesn't happen... not sure why :-}

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