我正在开发一个 Android 应用程序，它将用户名和密码发送到 MySQL 数据库并在登录 Activity 中接收响应(“成功”或“错误”)。但返回的 JSONObject 为 null。下面是代码
userauth.php
<?php
//Connecting to mysql db
include("db.php");
//Check for POST request
//if(isset($_POST['tag']) && $_POST['tag'] !=''){
//Get tag
// $tag = $_POST['tag'];
//}
//Getting username and password from android via JSON
$username = $_POST['username'];
$password = $_POST['password'];
//Creating respose array
$respose = array("tag" => $tag, "success" => 1, "error" =>0);
//Getting data from json
//$username='asanka102';
//$password='asanka102';
//Querying mysql database against userauth table for user auth
$sql = "SELECT * FROM userauth WHERE username='$username' AND password='$password'";
$qry = mysql_query($sql);
$fin_result = mysql_num_rows($qry);
//Returning true when user exists & return false when user doen's exist
//if$fin_result > 0(){
// return true;
//}else{
// return false;
//}
if($fin_result > 0){
//User found, login should be granted
$response["success"] = 1;
echo json_encode($response);
}else{
//User not found, login shold be prohibited
$response["error"] = 0;
$response["error_msg"] = 'Invalid login';
echo json_encode($response);
}
?>
MainActivity.java
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
etUsername = (EditText) findViewById(R.id.et_username);
etPass = (EditText) findViewById(R.id.et_password);
errorTxt = (TextView) findViewById(R.id.text_invalid_input);
loginButton = (Button) findViewById(R.id.button_login);
loginButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
new GetPassword().execute();
}
});
}
private class GetPassword extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... arg0) {
String username = etUsername.getText().toString();
String password = etPass.getText().toString();
UserFunctions userFunctions = new UserFunctions();
JSONObject json = userFunctions.loginUser(username, password);
//Do other things
return null;
}
@Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
if (pDialog.isShowing())
pDialog.dismiss();
}
}
UserFunctions.java
public class UserFunctions {
private JSONParser jsonParser;
private static String login_url = "http://192.168.100.172/android/userauth.php";
public UserFunctions(){
jsonParser = new JSONParser();
}
/**
* function make Login Request
* @param username
* @param password
* */
public JSONObject loginUser(String username, String password){
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("username", username));
params.add(new BasicNameValuePair("password", password));
JSONObject json = jsonParser.getJSONFromUrl(login_url, params);
// return json
// Log.e("JSON", json.toString());
return json;
}
}
JSONParser.java
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
// Empty constructor
}
// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject getJSONFromUrl(String url, List<NameValuePair> params) {
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "n");
}
is.close();
json = sb.toString();
Log.e("JSON", json);
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
logcat 给出了这个
02-11 12:29:10.457: E/Buffer Error(13927): Error converting result java.lang.NullPointerException: lock == null
02-11 12:29:10.457: E/JSON Parser(13927): Error parsing data org.json.JSONException: End of input at character 0 of
02-11 12:29:10.457: W/dalvikvm(13927): threadid=11: thread exiting with uncaught exception (group=0x41ba5ba8)
02-11 12:29:10.467: D/dalvikvm(13927): GC_FOR_ALLOC freed 280K, 2% free 17142K/17456K, paused 10ms, total 11ms
02-11 12:29:10.477: E/AndroidRuntime(13927): FATAL EXCEPTION: AsyncTask #1
02-11 12:29:10.477: E/AndroidRuntime(13927): Process: collector.lbfinance, PID: 13927
02-11 12:29:10.477: E/AndroidRuntime(13927): java.lang.RuntimeException: An error occured while executing doInBackground()
02-11 12:29:10.477: E/AndroidRuntime(13927): at android.os.AsyncTask$3.done(AsyncTask.java:300)
02-11 12:29:10.477: E/AndroidRuntime(13927): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
02-11 12:29:10.477: E/AndroidRuntime(13927): at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
02-11 12:29:10.477: E/AndroidRuntime(13927): at java.util.concurrent.FutureTask.run(FutureTask.java:242)
02-11 12:29:10.477: E/AndroidRuntime(13927): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
02-11 12:29:10.477: E/AndroidRuntime(13927): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
02-11 12:29:10.477: E/AndroidRuntime(13927): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
02-11 12:29:10.477: E/AndroidRuntime(13927): at java.lang.Thread.run(Thread.java:841)
02-11 12:29:10.477: E/AndroidRuntime(13927): Caused by: java.lang.NullPointerException
02-11 12:29:10.477: E/AndroidRuntime(13927): at collector.lbfinance.MainActivity$GetPassword.doInBackground(MainActivity.java:102)
02-11 12:29:10.477: E/AndroidRuntime(13927): at collector.lbfinance.MainActivity$GetPassword.doInBackground(MainActivity.java:1)
02-11 12:29:10.477: E/AndroidRuntime(13927): at android.os.AsyncTask$2.call(AsyncTask.java:288)
02-11 12:29:10.477: E/AndroidRuntime(13927): at java.util.concurrent.FutureTask.run(FutureTask.java:237)
02-11 12:29:10.477: E/AndroidRuntime(13927): ... 4 more
最佳答案
$fin_result 是否返回行？
尝试以下操作
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();
json = sb.toString();
Log.e("JSON", json);
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
关于java - 返回的 JSONObject 始终为 null，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21694627/