Jsoup空指针异常

-1

04-16 23:05:29.133: W/dalvikvm(7474): threadid=1: thread exiting with uncaught exception (group=0x41550930) 
04-16 23:05:29.133: E/AndroidRuntime(7474): FATAL EXCEPTION: main 
04-16 23:05:29.133: E/AndroidRuntime(7474): java.lang.NullPointerException 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at com.example.yo.MainActivity$jsoupexample.onPostExecute(MainActivity.java:74) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at com.example.yo.MainActivity$jsoupexample.onPostExecute(MainActivity.java:1) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at android.os.AsyncTask.finish(AsyncTask.java:631) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at android.os.AsyncTask.access$600(AsyncTask.java:177) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at android.os.Handler.dispatchMessage(Handler.java:99) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at android.os.Looper.loop(Looper.java:137) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at android.app.ActivityThread.main(ActivityThread.java:5041) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at java.lang.reflect.Method.invokeNative(Native Method) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at java.lang.reflect.Method.invoke(Method.java:511) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
04-16 23:05:29.133: E/AndroidRuntime(7474):  at dalvik.system.NativeStart.main(Native Method) 
04-16 23:05:29.163: D/dalvikvm(7474): GC_CONCURRENT freed 557K, 9% free 8027K/8736K, paused 2ms+4ms, total 28ms

代码

@TargetApi(Build.VERSION_CODES.GINGERBREAD) 
public class MainActivity extends Activity { 

    Document doc; 
    TextView tv; 
    String res=""; 
    String BLOG_URL = "http://www.google.co.in/"; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     // set layout view 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     new jsoupexample().execute(BLOG_URL); 
    } 
    public class jsoupexample extends AsyncTask<String,Integer,String> 
    { 
     @Override 
     protected String doInBackground(String... BLOG_URL) { 
      try { 
       doc= Jsoup.connect(BLOG_URL[0]).userAgent("Mozilla/5.0").timeout(20000).get(); 
      } catch (IOException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 
      Elements links = doc.select("a[href]"); 
      for(Element element: links) 
      { 
       res = element.attr("href"); 
      } 
      return res; 
     } 
     @Override 
     protected void onPostExecute(String result) { 
      // TODO Auto-generated method stub 
      super.onPostExecute(result); 

      if(result!=null && !result.isEmpty()) 
      tv.setText(result); 
      else 
      tv.setText("no value returned"); 
     } 
    } 
}

来源

2013-04-16 Gunjit Dhawan

问题在哪里？ –

我在这段代码中得到了NullPointerException –

@GunjitDhawan如果你的代码实际上的格式与你在IDE中发布它的方式相同，你需要返回并正确格式化（如果你使用的是eclipse，请尝试ctrl-shift-F ）。不正确缩进的代码将使它更难找到一些错误 – FoamyGuy

tv为空。在onCreate初始化：

tv = (TextView)findViewById(R.id.<the-id>);

来源

2013-04-16 17:55:45 eightx2

Thnxx很多！：D –

在你onPstExecute()方法你有这样一行： tv.setText（结果）;

你从未实例化过tv，因此它是空的。当你试图在null上调用一个方法时，你会得到一个NullPointerException。

来源

2013-04-16 17:56:16 FoamyGuy

Thnxx很多！：d –

Jsoup空指针异常

回答

相关问题