Android的HttpURLConnection类的getInputStream引发NullPoi

我想从这个网址下载图片：

https://hme_player_pictures.s3.amazonaws.com/test-512813ed3b83286c72f376c7-thumb100.jpg

这里是堆栈跟踪：

03-21 12:58:04.040: W/System.err(7084): java.lang.NullPointerException
03-21 12:58:04.040: W/System.err(7084):     at libcore.net.http.HttpConnection$Address.hashCode(HttpConnection.java:343)
03-21 12:58:04.045: W/System.err(7084):     at java.util.HashMap.get(HashMap.java:298)
03-21 12:58:04.050: W/System.err(7084):     at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:67)
03-21 12:58:04.050: W/System.err(7084):     at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
03-21 12:58:04.050: W/System.err(7084):     at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:308)
03-21 12:58:04.055: W/System.err(7084):     at libcore.net.http.HttpsURLConnectionImpl$HttpsEngine.makeSslConnection(HttpsURLConnectionImpl.java:460)
03-21 12:58:04.055: W/System.err(7084):     at libcore.net.http.HttpsURLConnectionImpl$HttpsEngine.connect(HttpsURLConnectionImpl.java:432)
03-21 12:58:04.055: W/System.err(7084):     at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:282)
03-21 12:58:04.060: W/System.err(7084):     at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:232)
03-21 12:58:04.065: W/System.err(7084):     at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:273)
03-21 12:58:04.065: W/System.err(7084):     at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:168)
03-21 12:58:04.070: W/System.err(7084):     at libcore.net.http.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:270)
03-21 12:58:04.070: W/System.err(7084): ...

码：

URL imageUrl = new URL(url);
HttpURLConnection c = (HttpURLConnection)imageUrl.openConnection();
InputStream in = c.getInputStream(); // Nullpointer exception on this line, c is definitely not null, I debugged

想不通为什么它被抛出NullPointerException异常。上面的网址并在浏览器中运行。

Answer 1:

对于它的价值，我看到了很多的错误从Android HTTP库中。从条码扫描器我得到跨越约3500万人堆栈跟踪而来，所以我觉得我什么都见过之一。这里的一切奇怪的东西，我们正好赶上和吞咽的应用程序，以下。我建议你解决它作为一个平台的错误和失败的优雅。

https://code.google.com/p/zxing/source/browse/trunk/android/src/com/google/zxing/client/android/HttpHelper.java

  private static int safelyConnect(String uri, HttpURLConnection connection) throws IOException {
    try {
      connection.connect();
    } catch (NullPointerException npe) {
      // this is an Android bug: http://code.google.com/p/android/issues/detail?id=16895
      Log.w(TAG, "Bad URI? " + uri);
      throw new IOException(npe.toString());
    } catch (IllegalArgumentException iae) {
      // Also seen this in the wild, not sure what to make of it. Probably a bad URL
      Log.w(TAG, "Bad URI? " + uri);
      throw new IOException(iae.toString());
    } catch (SecurityException se) {
      // due to bad VPN settings?
      Log.w(TAG, "Restricted URI? " + uri);
      throw new IOException(se.toString());
    } catch (IndexOutOfBoundsException ioobe) {
      // Another Android problem? https://groups.google.com/forum/?fromgroups#!topic/google-admob-ads-sdk/U-WfmYa9or0
      Log.w(TAG, "Bad URI? " + uri);
      throw new IOException(ioobe.toString());
    }
    try {
      return connection.getResponseCode();
    } catch (NullPointerException npe) {
      // this is maybe this Android bug: http://code.google.com/p/android/issues/detail?id=15554
      Log.w(TAG, "Bad URI? " + uri);
      throw new IOException(npe.toString());
    } catch (NumberFormatException nfe) {
      // Again seen this in the wild for bad header fields in the server response!
      Log.w(TAG, "Bad server status? " + uri);
      throw new IOException(nfe.toString());
    }
  }