Question

我的onDestroy函数中有这个函数，导致崩溃：

@Override
protected void onDestroy() {
    Server.setPresence(false, CONSTANTS.USER.userId);
    super.onDestroy();
}

<小时/> 的 Server.Java

private static final String TAG = "Cove Server";
private static final String PATH = "http://10.0.0.2:8001/data_connection";
private static HttpResponse response = null;
private static StringEntity se = null;
private static final int TIMEOUT = 30000;
private static HttpParams hParams = new BasicHttpParams();
private static HttpClient client;
private static HttpPost post = null;
public static String actionKey = null;

private static JSONObject sendRequest(JSONObject req) {
    try {
        HttpConnectionParams.setConnectionTimeout(hParams, TIMEOUT);
        client = new DefaultHttpClient(hParams);
        actionKey = req.getString("actionKey");
        se = new StringEntity(req.toString());
        se.setContentEncoding(new BasicHeader(HTTP.CONTENT_ENCODING,
                "application/json"));
        se.setContentType(new BasicHeader(HTTP.CONTENT_TYPE,
                "application/json"));
        post = new HttpPost(PATH);
        post.setEntity(se);

        Log.d(TAG, "http request is being sent");
        response = client.execute(post);
        Log.d(TAG, "http request was sent");

        if (response != null
                && response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
            InputStream in = response.getEntity().getContent();
            String a = convertFromInputStream(in); // CALLS A FUNCTION THAT PARSES THE RESPONSE TO String
            in.close();
            return new JSONObject(a);
        }

    } catch (UnsupportedEncodingException e) {
        Log.d(TAG, "encoding request to String entity faild!");
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        Log.d(TAG, "executing the http POST didn't work");
        e.printStackTrace();
    } catch (IOException e) {
        Log.d(TAG, "executing the http POST didn't work");
        e.printStackTrace();
    } catch (JSONException e) {
        Log.d(TAG, "no ActionKey");
        e.printStackTrace();
    }
    return null;
}

public static JSONObject setPresence(boolean isActive, String userId) {
    JSONObject request = new JSONObject();
    try {
        request.put("actionKey", (isActive) ? "UserPresenceActive"
                : "UserPresenceInactive");
        request.put("userId", userId);
        return sendRequest(request);
    } catch (JSONException e) {
        e.printStackTrace();
    }
    return null;
}

logcat的

06-28 12:59:11.970: E/AndroidRuntime(19806): FATAL EXCEPTION: main
06-28 12:59:11.970: E/AndroidRuntime(19806): java.lang.RuntimeException: Unable to destroy activity {com.yishai/com.thepoosh.MyActivity}: java.lang.NullPointerException
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3124)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3142)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.app.ActivityThread.access$1200(ActivityThread.java:127)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1192)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.os.Handler.dispatchMessage(Handler.java:99)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.os.Looper.loop(Looper.java:137)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.app.ActivityThread.main(ActivityThread.java:4507)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at java.lang.reflect.Method.invokeNative(Native Method)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at java.lang.reflect.Method.invoke(Method.java:511)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at dalvik.system.NativeStart.main(Native Method)
06-28 12:59:11.970: E/AndroidRuntime(19806): Caused by: java.lang.NullPointerException
06-28 12:59:11.970: E/AndroidRuntime(19806):    at com.thepoosh.MyActivity.onDestroy(MyActivity.java:340)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.app.Activity.performDestroy(Activity.java:4629)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.app.Instrumentation.callActivityOnDestroy(Instrumentation.java:1082)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3111)
06-28 12:59:11.970: E/AndroidRuntime(19806):    ... 11 more

我怀疑由于服务器没有发回回复而且Server.setPresence()没有返回，因此应用程序进入ANR。

这是对的吗？我该怎么做才能解决这个问题？坠机原因有什么不同吗？

Answer 1

06-28 12:59:11.970: E/AndroidRuntime(19806): Caused by: java.lang.NullPointerException
06-28 12:59:11.970: E/AndroidRuntime(19806):    at com.thepoosh.MyActivity.onDestroy(MyActivity.java:340)
06-28 12:59:11.970: E/AndroidRuntime(19806):    at android.app.Activity.performDestroy(Activity.java:4629)

在onDestroy is last function is stacktrace上查看，因此调用尚未转到Server.setPresence ..因此USER中的CONSTANTS.USER.userId看起来可能只在该行处为空。所以请检查一下。

@Override
protected void onDestroy() {
    if(null==CONSTANTS.USER){
    Server.setPresence(false, CONSTANTS.USER.userId);
    }else{
         Toast.makeText(this,"is null",Toast.LENGHT_LONG).show();
      }
    super.onDestroy();
}

onDestroy中的NullPointer异常

1 个答案: