Catch 中的语句未执行[重复]

Question

我需要从我的 Web 服务中获取登录详细信息，以在我的应用中验证登录。下面是完成这项工作的代码。

      try {
                //Apache Libraries and namevaluepair has been deprecated since APK 21(?). Using HttpURLConnection instead.
                URL url = new URL(wsURL + authenticate);
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();

                connection.setRequestMethod("POST");
                connection.setDoOutput(true);
                connection.setDoInput(true);
                connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded");

                OutputStream os = connection.getOutputStream();
                os.write(postParam.getBytes());
                os.flush();
                os.close();

                // Fetching the response code for debugging purposes.
                int responseCode = connection.getResponseCode();
                Log.d(TAG, "POST Response Code: " + responseCode);

                if (responseCode == HttpURLConnection.HTTP_OK) {
                    BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                    String inputLine;
                    StringBuilder response = new StringBuilder();

                    //Adding every responseCode in the inputLine.
                    while ((inputLine = in.readLine()) != null) {
                        response.append(inputLine);
                    }
                    in.close();

                    Log.d(TAG, "HTTP Response: " + response.toString());
                    //TODO: Check login logic again
                    //Sets Authentication flag
                    if (!response.toString().contains("Authentication Failed!")) {
                        authFlag = true;
                        Log.i(TAG, "Authentication Completed: Logged in Successfully!");
                        try {
                            JSONObject jsonObject = new JSONObject(response.toString());
                            JSONArray jsonArray = jsonObject.getJSONArray("rows");
                            JSONObject beanObject = jsonArray.getJSONObject(0);

                            userBean = new UserBean(username, beanObject.getString("User_FullName"), beanObject.getInt("UserType_Code"));

                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                } else {
                    Log.e(TAG, "Error!!! Abort!!!");
                }
                connection.disconnect();
            } catch (MalformedURLException e) {
                System.out.println("URLConnection Exception: " + e);
            } catch (IOException e) {
                System.out.println("IOStream Exception: " + e);
            }

            return postParam;
        }

我面临的问题是我在我的 logcat 中看不到任何与之相关的内容，但在调试时我发现控件转到
} catch (MalformedURLException e) {
但是
System.out.println("URLConnection Exception: " + e);
永远不会被执行。
我是 Android 开发的新手，所以可能有些东西我看不到。请帮忙。

编辑 - 我第一次尝试使用Log.e，但它不起作用，所以我输入了System.out.println，它也不起作用。

Answer 1

试试看

Log.e("tag","Exception: " + e);

你可以在安卓监视器中找到它

Answer 2

你不应该使用 System.out， 而是使用 logcat 之类的日志记录函数进行调试。

在这个例子中，考虑到catch捕获了一个错误，你应该使用：

private static final String TAG = "MyActivity";
...
catch (MalformedURLException e) {
Log.e(TAG, "URLConnection Exception: " + e.getMessage());
                } catch (IOException e) {
Log.e(TAG, "IO error: " + e.getMessage());
                }

这里是how to use them properly的解释。

如果看不到 logcat，请转到 there。