php - 从mysql/php获取数据出错

Question

我试图从我的数据库获取数据，但我的应用程序崩溃了。我已经尝试一步步调试，发现这条线会崩溃

jArray = new JSONArray(result);

这是我的整个代码:

   public class get_data extends AsyncTask<Void, Void, Boolean>
    {

        @Override
        protected Boolean doInBackground(Void... params) {

            String result = null;
            InputStream is = null;
            StringBuilder sb = null;
            // http post
            try {
                HttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost("http://example.com/output.php");
                // httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
                HttpResponse response = httpclient.execute(httppost);
                HttpEntity entity = response.getEntity();
                is = entity.getContent();
            } catch (Exception e) {
                Log.e("log_tag", "Error in http connection" + e.toString());
            }
            // convert response to string
            try {
                BufferedReader reader = new BufferedReader(new InputStreamReader(
                        is, "iso-8859-1"), 8);
                sb = new StringBuilder();
                sb.append(reader.readLine() + "\n");
                String line = "0";
                while ((line = reader.readLine()) != null) {
                    sb.append(line + "\n");
                }
                is.close();
                result = sb.toString();
            } catch (Exception e) {
                Log.e("log_tag", "Error converting result " + e.toString());
            }
            // paring data
            JSONArray jArray;
            try {
                jArray = new JSONArray(result);
                JSONObject json_data = null;
                ct_name = new String[jArray.length()];
                for (int i = 0; i < jArray.length(); i++) {
                    json_data = jArray.getJSONObject(i);
                    ct_id = json_data.getInt("A_ID");
                    ct_name[i] = json_data.getString("A_USERNAME");
                }
            } catch (JSONException e1) {
                Toast.makeText(getBaseContext(), "No output", Toast.LENGTH_LONG)
                        .show();
            } catch (ParseException e1) {
                e1.printStackTrace();
            }
            ausgabe.setText(ct_name[0]);
            return null;
        }
    }

我在 onCreate 中调用它:

new get_data().execute();

报告:

11-22 12:31:18.762: E/AndroidRuntime(376): FATAL EXCEPTION: AsyncTask #1
11-22 12:31:18.762: E/AndroidRuntime(376): Process: com.JewE.engoneengine, PID: 376
11-22 12:31:18.762: E/AndroidRuntime(376): java.lang.RuntimeException: An error occured while executing doInBackground()
11-22 12:31:18.762: E/AndroidRuntime(376):  at android.os.AsyncTask$3.done(AsyncTask.java:300)
11-22 12:31:18.762: E/AndroidRuntime(376):  at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
11-22 12:31:18.762: E/AndroidRuntime(376):  at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
11-22 12:31:18.762: E/AndroidRuntime(376):  at java.util.concurrent.FutureTask.run(FutureTask.java:242)
11-22 12:31:18.762: E/AndroidRuntime(376):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
11-22 12:31:18.762: E/AndroidRuntime(376):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
11-22 12:31:18.762: E/AndroidRuntime(376):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
11-22 12:31:18.762: E/AndroidRuntime(376):  at java.lang.Thread.run(Thread.java:841)
11-22 12:31:18.762: E/AndroidRuntime(376): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
11-22 12:31:18.762: E/AndroidRuntime(376):  at android.os.Handler.<init>(Handler.java:200)
11-22 12:31:18.762: E/AndroidRuntime(376):  at android.os.Handler.<init>(Handler.java:114)
11-22 12:31:18.762: E/AndroidRuntime(376):  at android.widget.Toast$TN.<init>(Toast.java:388)
11-22 12:31:18.762: E/AndroidRuntime(376):  at android.widget.Toast.<init>(Toast.java:114)
11-22 12:31:18.762: E/AndroidRuntime(376):  at android.widget.Toast.makeText(Toast.java:273)
11-22 12:31:18.762: E/AndroidRuntime(376):  at com.JewE.engoneengine.java_get_data$get_data.doInBackground(java_get_data.java:90)
11-22 12:31:18.762: E/AndroidRuntime(376):  at com.JewE.engoneengine.java_get_data$get_data.doInBackground(java_get_data.java:1)
11-22 12:31:18.762: E/AndroidRuntime(376):  at android.os.AsyncTask$2.call(AsyncTask.java:288)
11-22 12:31:18.762: E/AndroidRuntime(376):  at java.util.concurrent.FutureTask.run(FutureTask.java:237)
11-22 12:31:18.762: E/AndroidRuntime(376):  ... 4 more

PHP 是正确的，我正在获取我的 json 数据:

[{"A_ID":"1","A_USERNAME":"johann","A_PASSWORD":"joejoe"}]

Answer 1

使用下面所示的异步任务，并且不要忘记在 Android list 中包含权限

<uses-permission android:name="android.permission.INTERNET" />

将此用于 Android 中的异步任务:

要调用异步任务，请从任何方法使用此方法:

List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("key1", "value1"));
    params.add(new BasicNameValuePair("key1", "value2"));
    new WEBSERVICEREQUESTOR(URL, params).execute();

使其成为类(class)成员:

class WEBSERVICEREQUESTOR extends AsyncTask<String, Integer, String>
{

    String URL;
    List<NameValuePair> parameters;

    private ProgressDialog pDialog;

    public WEBSERVICEREQUESTOR(String url, List<NameValuePair> params)
    {
        this.URL = url;
        this.parameters = params;
    }

    @Override
    protected void onPreExecute()
    {
        pDialog = new ProgressDialog(LoginActivity.this);
        pDialog.setMessage("Processing Request...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params)
    {
        try
        {
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpEntity httpEntity = null;
            HttpResponse httpResponse = null;

            HttpPost httpPost = new HttpPost(URL);

            if (parameters != null)
            {
                httpPost.setEntity(new UrlEncodedFormEntity(parameters));
            }
            httpResponse = httpClient.execute(httpPost);

            httpEntity = httpResponse.getEntity();
            return EntityUtils.toString(httpEntity);

        }  catch (Exception e)
        {

        }
        return "";
    }

    @Override
    protected void onPostExecute(String result)
    {
        pDialog.dismiss();

        try
        {

        } catch (Exception e)
        {

        }
        super.onPostExecute(result);
    }

}