连接MySQL触发JSONException且应用崩溃，插入成功如何修复？

Hey there, let's break down your problem and work through fixes step by step: you're hitting a JSONException at jObj = new JSONObject(json);, and updating the progress dialog with pDialog.setMessage("7777"); causes a crash—even though your data successfully makes it into MySQL. Here's how to resolve both issues:

1. Root Cause of the JSONException #

The exception happens because the string you’re trying to parse as JSON (json variable) isn’t valid JSON. Since the insert works, your server is likely returning a non-JSON response (like plain text "Insert successful") or malformed JSON with extra characters (debug logs, HTML snippets, or invisible whitespace).

Fix Steps: #

• Log the raw response first: In your JSONParser.java, right before creating the JSONObject, add a log to see exactly what your server sends back:

  Log.d("RAW_SERVER_RESPONSE", json);
  

  Check logcat to confirm if the response is properly formatted JSON (e.g., {"success":1,"message":"Data inserted"} instead of just "success").
• Fix the server-side output: Ensure your backend returns valid JSON every time, even on success. For example, in PHP:

  // Return clean JSON after insert
  echo json_encode(array("success" => 1, "message" => "Insert completed"));
  exit; // Stop any extra output after JSON
  

  Avoid echoing debug messages, HTML errors, or whitespace before/after the JSON—this breaks the structure.
• Add a fallback for invalid JSON: If you can’t fix the server immediately, add a safety check in parsing code:

  try {
      jObj = new JSONObject(json);
  } catch (JSONException e) {
      Log.e("JSON_ERROR", "Invalid JSON: " + json, e);
      // Create a dummy object to prevent further crashes
      jObj = new JSONObject();
      jObj.put("success", 1); // Match your app's success flag logic
  }
  

2. Fix the Progress Dialog Crash #

The crash when calling pDialog.setMessage("7777"); almost always means the dialog is already dismissed, uninitialized, or you’re modifying it from a non-UI thread.

Fix Steps: #

• Check dialog state before updating: Verify the dialog exists and is still showing before changing its message:

  if (pDialog != null && pDialog.isShowing()) {
      pDialog.setMessage("7777");
  }
  

• Update the dialog on the UI thread: Network operations run on background threads, so post the dialog update to the main thread:

  runOnUiThread(new Runnable() {
      @Override
      public void run() {
          if (pDialog != null && pDialog.isShowing()) {
              pDialog.setMessage("7777");
          }
      }
  });
  

• Manage dialog lifecycle correctly: Don’t dismiss the dialog until you’ve fully handled the response (success and error cases). If you have pDialog.dismiss(); right after triggering the network request, move it to after parsing the response.

3. Extra Debug Tips #

• Clean the response string: Sometimes server responses have invisible UTF-8 BOM characters. Clean the string before parsing:

  json = json.trim().replaceFirst("^\\uFEFF", "");
  

• Validate JSON online: Copy the raw response from logcat into a JSON validator tool to confirm if it’s properly formatted.

内容的提问来源于stack exchange，提问作者GNassro