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我对android开发的新东西，我不知道我错过了什么让代码工作。尝试创建登录应用程序。使用dataoutputstream接收数据或发送数据的方式会有问题吗？有没有更好的方式，不被弃用和复杂。寻找最简约易懂的解决方案。Android发送数据到php并接收问题nullpointerexception
不要在后台代码
@Override
protected Boolean doInBackground(String... params) {
DataOutputStream printout;
HttpURLConnection urlConn;
BufferedReader reader;
URL url;
String json;
JSONObject jObj;
//send POST login details to server
try {
url = new URL(SERVER_ADDRESS + "login.php");
urlConn = (HttpURLConnection) url.openConnection();
urlConn.setRequestMethod("POST");
urlConn.setDoOutput(true);
urlConn.setRequestProperty("Accept-Charset", "UTF-8");
urlConn.setReadTimeout(10000);
urlConn.setConnectTimeout(15000);
HashMap<String, String> map = new HashMap<String, String>();
map.put("username", params[0]);
map.put("password", params[1]);
StringBuilder sb = new StringBuilder();
for(HashMap.Entry<String, String> e : map.entrySet()){
if(sb.length() > 0){
sb.append("&");
}
sb.append(URLEncoder.encode(e.getKey(), "UTF-8")).append("=").append(URLEncoder.encode(e.getValue(), "UTF-8"));
}
String loginDetails = sb.toString();
printout = new DataOutputStream(urlConn.getOutputStream());
printout.writeBytes(loginDetails);
printout.flush();
printout.close();
reader = new BufferedReader(new InputStreamReader(urlConn.getInputStream()));
StringBuilder sb2 = new StringBuilder();
String result = null;
while((result=reader.readLine())!=null) {
sb2.append(result + '\n');
Log.d("Results", sb2.toString());
};
json = result.toString();
jObj = new JSONObject(json);
JSONLogin = jObj.getBoolean(TAG_LOGINSTATUS);
Log.d("LoginStatus!!!!", JSONLogin.toString());
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (ProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
Log.d("JsonConvertion", "FAILED TO CONVERT JSON");
}
return JSONLogin;
}
堆栈错误
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: Process: com.httpkhronolog.khronolog, PID: 2459
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: java.lang.RuntimeException: An error occurred while executing doInBackground()
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at android.os.AsyncTask$3.done(AsyncTask.java:309)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at java.util.concurrent.FutureTask.run(FutureTask.java:242)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at java.lang.Thread.run(Thread.java:818)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.toString()' on a null object reference
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at com.httpkhronolog.khronolog.Login_Activity$checkUserDetails.doInBackground(Login_Activity.java:137)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at com.httpkhronolog.khronolog.Login_Activity$checkUserDetails.doInBackground(Login_Activity.java:79)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at android.os.AsyncTask$2.call(AsyncTask.java:295)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at java.util.concurrent.FutureTask.run(FutureTask.java:237)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
10-18 22:43:34.169 2459-2523/? E/AndroidRuntime: at java.lang.Thread.run(Thread.java:818)
的login.php
<?php
if($_SERVER["REQUEST_METHOD"] == "POST"){
// Establishing Connection with Server by passing server_name, user_id and password as a parameter
$connection = mysql_connect("localhost", "someusername", "Password");
// Selecting Database
$db = mysql_select_db("khronolo_systemdb", $connection);
$username = $_POST["username"];
$password = $_POST["password"];
$query = "SELECT * FROM user_table WHERE password='$password' AND email='$username';";
$result = mysql_query($query, $connection) or die (mysql_error($connection));
$rows = mysql_num_rows($result);
if ($rows == 1) {
$returnValue[] = array("loginStatus"=> "true");
echo json_encode($returnValue);
}
else {
$returnValue[] = array("loginStatus"=> "false");
echo json_encode($returnValue);
}
mysql_close($connection);
}
?>
还有什么对你行没有137
json = sb2.toString();取代json = result.toString();？ –json = result.toString（）; –
你的结果为空 –