0

相关代码片段：

BasicHttpParams params = new BasicHttpParams();
Object dateFormats = "E, dd-MMM-yyyy HH:mm:ss zzz";
List<Object> dateFormatList = new ArrayList<Object>();

dateFormatList.add(dateFormats);

params.setParameter(CookieSpecPNames.DATE_PATTERNS, dateFormatList);

HttpClient client = new DefaultHttpClient(params);
HttpGet httpGet = new HttpGet("http://twitter.com/statuses/user_timeline/sample_user.json");

try {
    HttpResponse response = client.execute(httpGet);

我试图用字符串转换列表，一个数组，在字符串数组上使用 Arrays.asList，我能想到的一切。但是每次我得到一个 ClassCastException 如下所示。我浏览了源代码，在发生异常的那一行，BestMatchSpecFactory 使用 getParameter() 来检索在 CookieSpecPNames.DATE_PATTERNS（应该是我的 List<>）中设置的参数并将其保存到集合中。

这是来自第 49 行 org.apache.http.impl.cookie 中 BestMatchSpecFactory.java 的代码：

Collection<?> param = (Collection<?>) params.getParameter(CookieSpecPNames.DATE_PATTERNS);

ArrayList 实现了 List 实现了 Collection，那么这里的强制转换到底有什么问题呢？

02-28 10:09:29.117: W/System.err(1222): java.lang.ClassCastException: java.util.ArrayList
02-28 10:09:29.137: W/System.err(1222):     at org.apache.http.impl.cookie.BestMatchSpecFactory.newInstance(BestMatchSpecFactory.java:49)
02-28 10:09:29.137: W/System.err(1222):     at org.apache.http.cookie.CookieSpecRegistry.getCookieSpec(CookieSpecRegistry.java:113)
02-28 10:09:29.137: W/System.err(1222):     at org.apache.http.client.protocol.RequestAddCookies.process(RequestAddCookies.java:147)
02-28 10:09:29.147: W/System.err(1222):     at org.apache.http.protocol.BasicHttpProcessor.process(BasicHttpProcessor.java:290)
02-28 10:09:29.147: W/System.err(1222):     at org.apache.http.protocol.HttpRequestExecutor.preProcess(HttpRequestExecutor.java:160)
02-28 10:09:29.167: W/System.err(1222):     at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:401)
02-28 10:09:29.167: W/System.err(1222):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
02-28 10:09:29.181: W/System.err(1222):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
02-28 10:09:29.181: W/System.err(1222):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
02-28 10:09:29.181: W/System.err(1222):     at com.duderlabs.candr.MainActivity.readTwitterFeed(MainActivity.java:80)
02-28 10:09:29.181: W/System.err(1222):     at com.duderlabs.candr.MainActivity.onCreate(MainActivity.java:39)
02-28 10:09:29.189: W/System.err(1222):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
02-28 10:09:29.217: W/System.err(1222):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
02-28 10:09:29.217: W/System.err(1222):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
02-28 10:09:29.217: W/System.err(1222):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
02-28 10:09:29.217: W/System.err(1222):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
02-28 10:09:29.238: W/System.err(1222):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-28 10:09:29.238: W/System.err(1222):     at android.os.Looper.loop(Looper.java:123)
02-28 10:09:29.258: W/System.err(1222):     at android.app.ActivityThread.main(ActivityThread.java:3683)
02-28 10:09:29.258: W/System.err(1222):     at java.lang.reflect.Method.invokeNative(Native Method)
02-28 10:09:29.258: W/System.err(1222):     at java.lang.reflect.Method.invoke(Method.java:507)
02-28 10:09:29.258: W/System.err(1222):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
02-28 10:09:29.258: W/System.err(1222):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-28 10:09:29.258: W/System.err(1222):     at dalvik.system.NativeStart.main(Native Method)

更新

我已根据以下答案更新了代码：

BasicHttpParams params = new BasicHttpParams();
String dateFormat = "E, dd-MMM-yyyy HH:mm:ss zzz";
Collection<String> dateFormatList = new ArrayList<String>();

dateFormatList.add(dateFormat);

params.setParameter(CookieSpecPNames.DATE_PATTERNS, dateFormatList);

HttpClient client = new DefaultHttpClient(params);
HttpGet httpGet = new HttpGet("http://twitter.com/statuses/user_timeline/sample_user.json");

try {
    HttpResponse response = client.execute(httpGet);

但仍然得到同样的例外。

4

2 回答 2

1

根据Spec，这是您应该注册的方式CookieSpecPNames.DATE_PATTERNS（尽管您的代码是正确的）：

BasicHttpParams params = new BasicHttpParams();
String dateFormats = "E, dd-MMM-yyyy HH:mm:ss zzz";
java.util.Collection<String> dateFormatList = new ArrayList<String>();

dateFormatList.add(dateFormats);

params.setParameter(CookieSpecPNames.DATE_PATTERNS, dateFormatList);

对于调试，我也会尝试看看是否

client.getParams().setParameter(CookieSpecPNames.DATE_PATTERNS, dateFormatList);

导致ClassCastException. 如果不是，那么您的params.

于 2013-02-28T20:12:10.733 回答
0

实际上，它应该是

client.getParams().setParameter(CookieSpecPNames.DATE_PATTERNS, new String[] { ... });
于 2015-01-06T23:42:03.877 回答