java - HttpURLConnection.getResponse 代码错误

Question

在我的 android 应用程序中，我正在尝试检查是否可以访问互联网以及是否需要下载一些数据。但是，当我运行下面的代码来验证连接时，即使存在有效连接，.getResponseCode() 方法也会返回 -1 而不是 200。该设备通过 4G 或 WIFI 连接到互联网，但它不工作。设备上安装的其他应用程序可以访问互联网。

protected Boolean doInBackground(String... args) {
        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        if (netInfo != null && netInfo.isConnected()) {
            try {
                URL url = new URL("http://www.google.com");
                HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
                urlc.setConnectTimeout(3000);
                urlc.connect();
                if (urlc.getResponseCode() == 200) {
                    return true;
                }
            } catch (MalformedURLException e1) {
                e1.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return false;
    }

AndroidManifests.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.sg.help">

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

更新 添加了调试的以下输出。如您所见，responseCode 为 -1。

urlc = {HttpURLConnectionImpl@19895} "com.android.okhttp.internal.http.HttpURLConnectionImpl:http://www.google.com"
 client = {OkHttpClient@19909} 
 handshake = null
 httpEngine = {HttpEngine@19910} 
 httpEngineFailure = null
 requestHeaders = {Headers$Builder@19911} 
 route = {Route@19912} 
 fixedContentLength = -1
 redirectionCount = 0
 method = {String@19913} "GET"
 responseMessage = null
 fixedContentLengthLong = -1
 chunkLength = -1
 fixedContentLength = -1
 instanceFollowRedirects = true
 responseCode = -1
 contentType = null
 defaultHandler = {URLConnection$DefaultContentHandler@19914} 
 url = {URL@19883} "http://www.google.com"
 allowUserInteraction = false
 ifModifiedSince = 0
 lastModified = -1
 connectTimeout = 0
 connected = true
 doInput = true
 doOutput = false
 readTimeout = 0
 useCaches = true
 shadow$_klass_ = {Class@17437} "class com.android.okhttp.internal.http.HttpURLConnectionImpl"
 shadow$_monitor_ = -1761921262

Answer 1

尝试更改您的网址，例如https://www.android.com/ .此外，之后尝试断开您的 http 连接，看看是否有帮助。

Disconnect. Once the response body has been read, the HttpURLConnection should be closed by calling disconnect(). Disconnecting releases the resources held by a connection so they may be closed or reused.

http://developer.android.com/reference/java/net/HttpURLConnection.html

尝试以下操作。

URL url = new URL("https://www.android.com");
                HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
                urlc.setConnectTimeout(5000);
                urlc.connect();
                if (urlc.getResponseCode() == 200) {
                    urlc.disconnect();
                    return true;
                }