我试图读取我的数据库中的数据,然后在我的应用程序中使用它,因为我使用 php 脚本作为 Web 服务来连接到我的 Mysql 数据库,但是我的程序在解析 Json 时抛出了一个异常我试图删除解析部分并在日志上打印结果值并显示为 null ,为什么结果值为 null ?错误是什么?
我已经在网上搜索并尝试了所有可能的解决方案,但问题仍然存在,请帮助我......我能做些什么来解决这个问题?
这是我打印结果值时的日志:
在 postExecute 方法中 sb.tostring之后为null
练习.php
<?php $Name=$_REQUEST['name']; mysql_connect("localhost","user","pass"); mysql_select_db("MYDB"); $sql=mysql_query("select burnedCalories from Exercise where name='$Name' "); while($row=mysql_fetch_assoc($sql)) $output=$row; print(json_encode($output)); mysql_close(); ?>
java类
public class ExercisesActivity extends Activity{
private String selected_ex_Name ="Walking";
private int calorie_factor;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.exercise_details);
new ConnectTask().execute();
}
private class ConnectTask extends AsyncTask<Void,Void,String>
{
private String result="";
private InputStream is=null;
protected String doInBackground(Void... params) {
try
{
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("name",selected_ex_Name));
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://10.0.2.2/Exercise.php");
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
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,"utf-8"),8);
StringBuilder sb = new StringBuilder();
String line = null;
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());
}
Log.e("log_tag", result+ "after sb.tostring ");
return result;
}
protected void onPostExecute(String result){
Log.e("log_tag", result+" in postExecute method ");
// try{
// JSONArray jArray = new JSONArray(result);
// JSONObject json_data=null;
// for(int i=0;i<jArray.length();i++)
// {
// json_data = jArray.getJSONObject(i);
// calorie_factor=json_data.getInt("burnedCalories");
// }
//
// }
// catch(JSONException e){
// Log.e("log_tag", "Error parsing data "+e.toString());
// }
}
}}