异步 Html.ImageGetter 用于在 TextView 中设置多个图像
我正在编写一个应用程序，它获取 HTML 页面并解析它们以在屏幕上显示。具体来说，该应用程序从留言板中提取 HTML 并列出用户发布的帖子。
问题是帖子中的很多内容都是 Html.ImageGetter 来处理图片的下载。
我的 textView.setText() 方法将如下所示：
myTextView.setText(Html.fromHtml(myText, new ImageGetter() {
@Override
public Drawable getDrawable(String source) {
Drawable d;
// Need to async download image here
return d;
}
}, null));
同步执行此操作很简单，但是是否有建议的方法来异步执行此操作，以便它不会锁定我的 UI 线程？我还想最终构建这些图像的缓存，但我想一旦异步下载出现，这将非常简单。
I'm writing an application that takes HTML pages and parses them to display on the screen. Specifically, this application pulls HTML from a message board and lists posts made by users.
The problem is that a lot of the content in posts are pictures in <img> tags, so I need to write a Html.ImageGetter to handle the downloading of the images.
My textView.setText() method will look like this:
myTextView.setText(Html.fromHtml(myText, new ImageGetter() {
@Override
public Drawable getDrawable(String source) {
Drawable d;
// Need to async download image here
return d;
}
}, null));
Doing this synchronously is trivial, but is there a suggested way to do this asynchronously so that it doesn't lock up my UI thread? I would also like to eventually build in caching of these images, but I imagine that would be pretty simple once the async downloading was there.
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评论（4）
这将是困难的，也许是不可能的。您必须立即归还一些东西。即使这是一个占位符，您也会面临下载完成后如何替换占位符的挑战。由于您无法访问渲染图像的
ImageView（如果有ImageView），我不知道您将如何安排替换占位符。That will be difficult, perhaps impossible. You have to return something immediately. Even if that is a placeholder, you then have the challenge of how to replace the placeholder once the download is complete. Since you lack access to the
ImageViewrendering the image (if there is anImageView), I don't know how you would arrange to replace the placeholder.我会使用
AsyncTask或Thread/Handler组合。I'd use either an
AsyncTaskor aThread/Handlercombination.如何在显示 html 之前使用不可见的 Html.fromHtml 提取所有 url，将这些 url 放入列表中，异步下载所有图像，将它们存储在内存缓存中，然后实现 ImageGetter 以使用以下命令进行缓存查找： url 作为键，drawable 作为值。
How about extract all the urls before displaying the html by using an invisible Html.fromHtml, putting those urls in a list, asynchronously downloading all images, storing them in an in memory cache, then implementing the ImageGetter to just do a cache lookup using the url as a key and the drawable as the value.
为了异步下载图像并将它们存储在内存缓存中，这里有一个迷你库:)
https://github.com/koush/UrlImageViewHelper
for downloading asynchronously the images and storing them in memory cache there is a mini-library here :)
https://github.com/koush/UrlImageViewHelper