java - jsoup 代码适用于 Java 但不适用于 Android-Nullpointerexception

Question

我正在尝试使用 jsoup 编写一个天气抓取 Android 应用程序。我有使用 Java 的代码，但即使是我可以在 android 中编写的最简单的形式也会引发错误。这是我的代码的一部分：

private class Retrieve_Weather extends AsyncTask<Void, Void, String> {
    private final String TAG = "Retrieve_Weather";

    protected String doInBackground(Void... params) {

        String weatherline= "oTHErly";
        Log.i(TAG, weatherline);
        Document doc = null;
        try {
            Log.i(TAG, "trying document...");
            doc = Jsoup.connect("http://m.wund.com/cgi-bin/findweather/getForecast?brand=mobile&query=02139").get();
            Log.i(TAG, "after document");
            weatherline = "newline";
            }
        catch (IOException except) {
            Log.i(TAG, "Cannot Connect", except);   
            except.printStackTrace();
            weatherline = "Can't Connect";
            Log.i(TAG, "End stacktrace");

        }

        Log.i(TAG, weatherline);
        return weatherline;
    }

    @Override
    protected void onPreExecute() {
        Log.i(TAG, "onPreExecute");
    }

    @Override
    protected void onProgressUpdate(Void... values) {
        Log.i(TAG, "onProgressUpdate");
    }
    @Override
    protected void onPostExecute(String result){
        //super.onPostExecute(result);
        Log.i(TAG, "onPostExecute");
    }


}

我已经玩弄了我的代码和 logcat，足以发现我的错误是运行 .get() 时引发的空指针异常。我只是不知道为什么或如何解决它。这是我的堆栈跟踪：

07-09 03:18:13.901: I/Retrieve_Weather(1754): trying document...
07-09 03:18:15.900: D/dalvikvm(1754): GC_CONCURRENT freed 80K, 7% free 2711K/2912K, paused 83ms+20ms, total 244ms
07-09 03:18:15.910: D/dalvikvm(1754): WAIT_FOR_CONCURRENT_GC blocked 157ms
07-09 03:18:16.351: D/dalvikvm(1754): GC_CONCURRENT freed 297K, 15% free 2841K/3340K, paused 81ms+124ms, total 329ms
07-09 03:18:16.740: W/dalvikvm(1754): Exception Ljava/lang/NullPointerException; thrown while initializing Lorg/jsoup/nodes/Entities;
07-09 03:18:16.740: W/dalvikvm(1754): Exception Ljava/lang/ExceptionInInitializerError; thrown while initializing Lorg/jsoup/nodes/Entities$EscapeMode;
07-09 03:18:16.810: W/System.err(1754): java.util.concurrent.ExecutionException: java.lang.ExceptionInInitializerError
07-09 03:18:16.830: W/System.err(1754):     at java.util.concurrent.FutureTask.report(FutureTask.java:94)
07-09 03:18:16.830: W/System.err(1754):     at java.util.concurrent.FutureTask.get(FutureTask.java:160)
07-09 03:18:16.860: W/System.err(1754):     at android.os.AsyncTask.get(AsyncTask.java:482)
07-09 03:18:16.880: W/System.err(1754):     at com.example.weatherresponse.Weather.onCreate(Weather.java:35)
07-09 03:18:16.880: W/System.err(1754):     at android.app.Activity.performCreate(Activity.java:5104)
07-09 03:18:16.911: W/System.err(1754):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-09 03:18:16.911: W/System.err(1754):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-09 03:18:16.960: W/System.err(1754):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-09 03:18:16.970: W/System.err(1754):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-09 03:18:16.970: W/System.err(1754):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-09 03:18:16.980: W/System.err(1754):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-09 03:18:16.990: W/System.err(1754):     at android.os.Looper.loop(Looper.java:137)
07-09 03:18:16.990: W/System.err(1754):     at android.app.ActivityThread.main(ActivityThread.java:5041)
07-09 03:18:16.990: W/System.err(1754):     at java.lang.reflect.Method.invokeNative(Native Method)
07-09 03:18:17.010: W/System.err(1754):     at java.lang.reflect.Method.invoke(Method.java:511)
07-09 03:18:17.061: W/System.err(1754):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-09 03:18:17.061: W/System.err(1754):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-09 03:18:17.061: W/System.err(1754):     at dalvik.system.NativeStart.main(Native Method)
07-09 03:18:17.090: W/System.err(1754): Caused by: java.lang.ExceptionInInitializerError
07-09 03:18:17.090: W/System.err(1754):     at org.jsoup.nodes.Document$OutputSettings.<init>(Document.java:210)
07-09 03:18:17.150: W/dalvikvm(1754): threadid=11: thread exiting with uncaught exception (group=0x40a71930)
07-09 03:18:17.150: W/System.err(1754):     at org.jsoup.nodes.Document.<init>(Document.java:18)
07-09 03:18:17.160: W/System.err(1754):     at org.jsoup.parser.TreeBuilder.initialiseParse(TreeBuilder.java:27)
07-09 03:18:17.160: W/System.err(1754):     at org.jsoup.parser.TreeBuilder.parse(TreeBuilder.java:40)
07-09 03:18:17.160: W/System.err(1754):     at org.jsoup.parser.HtmlTreeBuilder.parse(HtmlTreeBuilder.java:37)
07-09 03:18:17.170: W/System.err(1754):     at org.jsoup.parser.Parser.parseInput(Parser.java:30)
07-09 03:18:17.170: W/System.err(1754):     at org.jsoup.helper.DataUtil.parseByteData(DataUtil.java:102)
07-09 03:18:17.170: W/System.err(1754):     at org.jsoup.helper.HttpConnection$Response.parse(HttpConnection.java:498)
07-09 03:18:17.215: W/System.err(1754):     at org.jsoup.helper.HttpConnection.get(HttpConnection.java:154)
07-09 03:18:17.215: W/System.err(1754):     at com.example.weatherresponse.Weather$Retrieve_Weather.doInBackground(Weather.java:85)
07-09 03:18:17.220: W/System.err(1754):     at com.example.weatherresponse.Weather$Retrieve_Weather.doInBackground(Weather.java:1)
07-09 03:18:17.220: W/System.err(1754):     at android.os.AsyncTask$2.call(AsyncTask.java:287)
07-09 03:18:17.230: W/System.err(1754):     at java.util.concurrent.FutureTask.run(FutureTask.java:234)
07-09 03:18:17.230: W/System.err(1754):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
07-09 03:18:17.240: W/System.err(1754):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
07-09 03:18:17.240: W/System.err(1754):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
07-09 03:18:17.240: W/System.err(1754):     at java.lang.Thread.run(Thread.java:856)
07-09 03:18:17.260: W/System.err(1754): Caused by: java.lang.ExceptionInInitializerError
07-09 03:18:17.290: W/System.err(1754):     at org.jsoup.nodes.Entities$EscapeMode.<clinit>(Entities.java:20)
07-09 03:18:17.290: W/System.err(1754):     ... 17 more
07-09 03:18:17.290: W/System.err(1754): Caused by: java.lang.NullPointerException: in == null
07-09 03:18:17.290: W/System.err(1754):     at java.util.Properties.load(Properties.java:246)
07-09 03:18:17.290: W/System.err(1754):     at org.jsoup.nodes.Entities.loadEntities(Entities.java:151)
07-09 03:18:17.290: W/System.err(1754):     at org.jsoup.nodes.Entities.<clinit>(Entities.java:135)
07-09 03:18:17.290: W/System.err(1754):     ... 18 more
07-09 03:18:17.383: I/System.out(1754): ExecExceptjava.lang.ExceptionInInitializerError
07-09 03:18:19.570: E/AndroidRuntime(1754): FATAL EXCEPTION: AsyncTask #1
07-09 03:18:19.570: E/AndroidRuntime(1754): java.lang.RuntimeException: An error occured while executing doInBackground()
07-09 03:18:19.570: E/AndroidRuntime(1754):     at android.os.AsyncTask$3.done(AsyncTask.java:299)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at java.util.concurrent.FutureTask.run(FutureTask.java:239)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at java.lang.Thread.run(Thread.java:856)
07-09 03:18:19.570: E/AndroidRuntime(1754): Caused by: java.lang.ExceptionInInitializerError
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.nodes.Document$OutputSettings.<init>(Document.java:210)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.nodes.Document.<init>(Document.java:18)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.parser.TreeBuilder.initialiseParse(TreeBuilder.java:27)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.parser.TreeBuilder.parse(TreeBuilder.java:40)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.parser.HtmlTreeBuilder.parse(HtmlTreeBuilder.java:37)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.parser.Parser.parseInput(Parser.java:30)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.helper.DataUtil.parseByteData(DataUtil.java:102)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.helper.HttpConnection$Response.parse(HttpConnection.java:498)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.helper.HttpConnection.get(HttpConnection.java:154)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at com.example.weatherresponse.Weather$Retrieve_Weather.doInBackground(Weather.java:85)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at com.example.weatherresponse.Weather$Retrieve_Weather.doInBackground(Weather.java:1)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at android.os.AsyncTask$2.call(AsyncTask.java:287)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at java.util.concurrent.FutureTask.run(FutureTask.java:234)
07-09 03:18:19.570: E/AndroidRuntime(1754):     ... 4 more
07-09 03:18:19.570: E/AndroidRuntime(1754): Caused by: java.lang.ExceptionInInitializerError
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.nodes.Entities$EscapeMode.<clinit>(Entities.java:20)
07-09 03:18:19.570: E/AndroidRuntime(1754):     ... 17 more
07-09 03:18:19.570: E/AndroidRuntime(1754): Caused by: java.lang.NullPointerException: in == null
07-09 03:18:19.570: E/AndroidRuntime(1754):     at java.util.Properties.load(Properties.java:246)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.nodes.Entities.loadEntities(Entities.java:151)
07-09 03:18:19.570: E/AndroidRuntime(1754):     at org.jsoup.nodes.Entities.<clinit>(Entities.java:135)
07-09 03:18:19.570: E/AndroidRuntime(1754):     ... 18 more

我的代码运行正常，除了这个单一的基本行。我已经在模拟器和安卓手机上测试了我的代码，并且都可以访问互联网。我尝试了多个网站以及这些网站的移动版本，但都没有奏效。我的清单和我的库文件在正确的位置有互联网权限。我在这个网站和其他网站上环顾四周，寻找解决我问题的方法。由于我在相关帖子中找到的内容，我已经修改了我的代码和权限，但我还没有找到适合我的已回答帖子。但是，我发现一些未回答的帖子提出了完全相同的问题。我发现我没有尝试过的唯一答案是这个问题Error when release APK with AsyncTask and Jsoup：我不知道要更改哪个文件来测试它是否解决了我的问题。我对编程相当陌生 - 任何帮助将不胜感激。谢谢！

Answer 1

将这些行添加到 proguard-project.txt

-keep public enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

Answer 2

我的代码现在可以工作了！我最终将我的 .jar 文件移动到 lib 中，而不是按照Android-SDK r17 破坏工作项目中的建议将其用作引用的外部 jar 。我还添加了一个用户代理并重新设计了我的 AsyncTask，以便 Jsoup.connect( url ) 在 onPreExecute 中，而 .get() 在 doInBackground 中。

    private class Retrieve_Weather extends AsyncTask<Void, Void, String> {
    private final String TAG = "Retrieve_Weather";
    Connection con = null;

    protected Void doInBackground(String... params) {

        //Log.i(TAG, weatherline);
        Document doc = null;
        if (con !=null){
            try {
                Log.i(TAG, "trying document...");
                doc = con.get();
                Log.i(TAG, "after document");
                Element currentWeather = doc.getElementById("curCond");
                currentweather = currentWeather.text();
                Log.i(TAG, currentWeather.text());
                }
            catch (IOException except) {
                Log.i(TAG, "Cannot Connect", except);   
                except.printStackTrace();
                currentweather = "Can't Connect";
                Log.i(TAG, "End stacktrace");

            }

        }
        else{
            currentweather = "Connection returned null";
        }

        //Log.i(TAG, weatherline);
        return currentweather;

    }

    @Override
    protected void onPreExecute() {
        //Log.i(TAG, "onPreExecute");
        Log.i(TAG, "trying to connect...");
        con = Jsoup.connect("http://www.wunderground.com/cgi-bin/findweather/getForecast?query=zmw:02142.1.99999").userAgent("Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0");
        Log.i(TAG, "CONNECTED!!!");

        }




    @Override
    protected void onProgressUpdate(Void... values) {
        Log.i(TAG, "onProgressUpdate");
    }

    @Override
    protected void onPostExecute(Void result){
        Log.i(TAG, "onPostExecute");

    }


}

Answer 3

查看 org.jsoup.nodes.Entties 的源代码https://github.com/jhy/jsoup/blob/master/src/main/java/org/jsoup/nodes/Entities.java

看起来它试图从类路径加载“entities-base.properties”并且无法找到它。您能否确保这些文件在类路径中是可用的“entities-full.properties”。

只是对未来调试的提示总是寻找最深的异常，在你的情况下

07-09 03:18:17.290: W/System.err(1754): Caused by: java.lang.NullPointerException: in == null
07-09 03:18:17.290: W/System.err(1754):     at java.util.Properties.load(Properties.java:246)
07-09 03:18:17.290: W/System.err(1754):     at org.jsoup.nodes.Entities.loadEntities(Entities.java:151)
07-09 03:18:17.290: W/System.err(1754):     at org.jsoup.nodes.Entities.<clinit>(Entities.java:135)

最后一行向我指出了在哪里寻找。希望这可以帮助

Answer 4

经过一番研究，我相信这实际上是一个Android错误。似乎Android缓存了META-INF/MANIFEST.MF文件，但在重新安装应用程序时并没有使缓存失效。结果，系统看不到新.property文件，从而导致getResourceAsStream返回null.

解决方法：重启设备。