Advanced Error Handling

Hi,

in my app it's not always guaranteed, that the URL for streaming is still available. Therefore I somehow need to know when AndroidVideoCache fails to open the URL. It would be cool, if you didn't catch the exceptions, but throw them, so we can try/catch them ourselves. So for example `proxy.getProxyUrl(url);` throws `ProxyCacheException`. Or is there another way you suggest? I don't want to `HEAD` request the resource first, just to check if it's available.

Any ideas? Thanks!

从入口点 proxy.getProxyUrl(url) 开始，跟踪无法打开流式 URL 时如何处理 ProxyCacheException。确定当前可观察到的失败行为，并定义调用方应该能够捕获或检查的内容；无需预先发出 HEAD 请求即可使所请求的失败处理保持一致，即为完成。

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