android - 检查url是否为有扩展名限制的图片

Question

如何检查 URL 是否为必须为 PNG、GIF、JPG 格式的图像 URL

我看到可以用这段代码来完成:

URLConnection connection = new URL("http://foo.bar/w23afv").openConnection();
String contentType = connection.getHeaderField("Content-Type");
boolean image = contentType.startsWith("image/");

但是，我需要使用 Glide 或 OKHttpClient 进行检查。

如何使用上述两种技术实现这一点？

Answer 1

如果您只想检查 URL 的 Content-Type，而不实际下载内容，则 HTTP HEAD request将是合适的。

The HEAD method is identical to GET except that the server MUST NOT return a message-body in the response. The metainformation contained in the HTTP headers in response to a HEAD request SHOULD be identical to the information sent in response to a GET request. This method can be used for obtaining metainformation about the entity implied by the request without transferring the entity-body itself. This method is often used for testing hypertext links for validity, accessibility, and recent modification.

您可以使用 OkHttp 执行此操作，如下所示:

OkHttpClient client = new OkHttpClient();

Request request = new Request.Builder()
        .url("http://foo.bar/w23afv")
        .head()
        .build();

try {
    Response response = client.newCall(request).execute();
    String contentType = response.header("Content-Type");
    boolean image = false;
    if (contentType != null) {
        image = contentType.startsWith("image/");
    }

} catch (IOException e) {
    // handle error
}