7

可能重复：
异常始终为 NULL

我对 IOException 对象有一个奇怪的问题，找不到答案。

代码如下所示：

try { // This isn't very important part, but maybe it has something to do with a problem
  HttpResponse response = client.execute(httpGet);
  StatusLine statusLine = response.getStatusLine();
  int statusCode = statusLine.getStatusCode();
  if (statusCode == 200) {
    HttpEntity entity = response.getEntity();
    InputStream content = entity.getContent();
    BufferedReader reader = new BufferedReader(new InputStreamReader(content));
    String line;
    while ((line = reader.readLine()) != null) {
      builder.append(line);
    }
  } else {
    Log.e(ParseJSON.class.toString(), "Failed to download file");
  }
} catch (IOException e) {
        System.out.println("I'm here in the IOException catch clause");
        e.printStackTrace(); // e is null (line 126)
} catch (Exception e) {
        e.printStackTrace();
}

程序捕获IOException，但其对象 (e) 是null。这怎么可能？

编辑：堆栈跟踪：

09-25 19:35:59.438: I/System.out(31732): I'm here in the IOException catch clause
09-25 19:36:04.377: W/dalvikvm(31732): threadid=1: thread exiting with uncaught exception (group=0x40020ac0)
09-25 19:36:04.447: E/AndroidRuntime(31732): FATAL EXCEPTION: main
09-25 19:36:04.447: E/AndroidRuntime(31732): java.lang.RuntimeException: Unable to start activity ComponentInfo{uniwersytet.ekiosk/uniwersytet.ekiosk.EkioskActivity}: java.lang.NullPointerException
09-25 19:36:04.447: E/AndroidRuntime(31732):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at android.app.ActivityThread.access$2300(ActivityThread.java:125)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at android.os.Handler.dispatchMessage(Handler.java:99)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at android.os.Looper.loop(Looper.java:123)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at android.app.ActivityThread.main(ActivityThread.java:4627)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at java.lang.reflect.Method.invokeNative(Native Method)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at java.lang.reflect.Method.invoke(Method.java:521)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at dalvik.system.NativeStart.main(Native Method)
09-25 19:36:04.447: E/AndroidRuntime(31732): Caused by: java.lang.NullPointerException
09-25 19:36:04.447: E/AndroidRuntime(31732):    at uniwersytet.ekiosk.EkioskActivity.onCreate(EkioskActivity.java:126)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
09-25 19:36:04.447: E/AndroidRuntime(31732):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
09-25 19:36:04.447: E/AndroidRuntime(31732):    ... 11 more
4

1 回答 1

1

-请检查response您从服务器获取的信息。

-还请注意...UI work should be on UI thread and Non-UI work on the Non-UI thread从 HoneyComb 版本的 Android 开始，它已成为规则。

-对于这种耗时较长的任务，请使用thread with handler或。AsyncTask

于 2012-09-25T16:32:57.693 回答