java - java.lang.String 类型的值数据库无法转换为 JSONObject

Question

使用下面的代码给出的数据插入到数据库中，但不显示是否成功的对话框。

我的目标 API 是 23。

我应该使用gson吗？

请帮忙。

public class BackgroundTask extends AsyncTask<String, Void, String> {

String register_url = "http://192.168.1.101/loginapp/register.php";

    Context ctx;

    Activity activity;

    ProgressDialog progressDialog;

    AlertDialog.Builder builder;

    public BackgroundTask(Context ctx)
    {
        this.ctx = ctx;
        activity = (Activity)ctx;
    }

    @Override
    protected void onPreExecute() {
        builder = new AlertDialog.Builder(activity);
        progressDialog = new ProgressDialog(ctx);
        progressDialog.setTitle("Please wait...");
        progressDialog.setMessage("Connecting to server...");
        progressDialog.setIndeterminate(true);
        progressDialog.setCancelable(false);
        progressDialog.show();

        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params) {
        String method = params[0];
        if(method.equals("register"))
        {
            try {
                URL url = new URL(register_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);
                OutputStream outputStream = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream,"UTF-8"));
                String name = params[1];
                String email = params[2];
                String password = params[3];
                String data = URLEncoder.encode("name", "UTF-8")+"="+URLEncoder.encode(name,"UTF-8")+"&"+
                        URLEncoder.encode("email","UTF-8")+"="+URLEncoder.encode(email,"UTF-8")+"&"+
                        URLEncoder.encode("password","UTF-8")+"="+URLEncoder.encode(password,"UTF-8");
                bufferedWriter.write(data);
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();
                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                StringBuilder stringBuilder = new StringBuilder();
                String line = "";
                while((line=bufferedReader.readLine()) != null)
                {
                    stringBuilder.append(line+"\n");
                }
                httpURLConnection.disconnect();
                Thread.sleep(5000);
                // return string builder as normal string.
                return  stringBuilder.toString();

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
    }

    @Override
    protected void onPostExecute(String json) {
        try {
            progressDialog.dismiss();
            JSONObject jsonObject = new JSONObject(json);
            //need to get json array from json object.
            JSONArray jsonArray = jsonObject.getJSONArray("server_response");
            //now we can get each of the json data from json array.
            JSONObject jo = jsonArray.getJSONObject(0);
            //now we can read each data from json object;
            String code = jo.getString("code");
            String message = jo.getString("message");
            if(code.equals("reg_true"))
            {
                showDialog("Registration Success..",message,code);
            }
            else if(code.equals("reg_false"))
            {
                showDialog("Registration failed..",message,code);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }


    }

    public void showDialog(String title, String message, String code)
    {
            builder.setTitle(title);
           if(code.equals("reg_true")||code.equals("reg_false"))
           {
               builder.setMessage(message);
               builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                   @Override
                   public void onClick(DialogInterface dialog, int which) {
                       dialog.dismiss();
                       activity.finish();
                   }
               });
               AlertDialog alertDialog = builder.create();
               alertDialog.show();

           }
    }
}

Answer 1

doInBackground()方法的返回值被传递给onPostExecute()。在这个方法里面:

    @Override
    protected String doInBackground(String... params) {
        String method = params[0];
        if(method.equals("register"))
        {
            try {
                URL url = new URL(register_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
                //....
                // return string builder as normal string.
                return  stringBuilder.toString();

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        return null;            //YOU ARE RETURNING NULL. CHECK WHETHER params[0] is "register"
    }
    //....
    @Override
    protected void onPostExecute(String json) { //json might be null. Try to print it using log.debug()
        try {
            progressDialog.dismiss();
            JSONObject jsonObject = new JSONObject(json);   //This might throw exception
            //...
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

将日志粘贴到pastebin中并在此处附加链接。另请参阅:String cannot be converted to JSONObject exception