php - 将 android 连接到队列应用程序的数据库
问题描述
我对android比较陌生，希望你们能提供任何帮助。在我的项目中，我正在尝试创建一个队列系统，以便登录到我的应用程序的任何人都必须输入会话名称。输入此会话名称会将他们移动到具有 2 个选项的新页面：问题和演示。单击其中一个选项，他们的信息将被发送到持有他们之前输入的会话的数据库。会话是该数据库中的表。基本上在我的项目中，我试图连接到一个名为 queue_lnsconnection 的数据库（phpmyadmin）。此数据库包含一个要使用的空会话。我试图指出会话。会话是该数据库中的一个表。我收到一条错误消息“com.android.volley.volleyerror java.lang.nullpointerexception:attempt to invoke virtual method 'int java.lang.string.
请注意，我创建了一个登录页面。
StudentActivity2.java
public class StudentActivity2 extends AppCompatActivity {
EditText joinSession;
// Creating button;
Button joinButton;
// Creating Volley RequestQueue.
RequestQueue requestQueue;
// Create string variable to hold the EditText Value.
String SessionHolder;
String DecisionHolder;
String FirstNameHolder;
String LastNameHolder;
// Creating Progress dialog.
ProgressDialog progressDialog;
String HttpUrl = "http://192.168.2.150:8080/decisionAndroid.php";
Boolean CheckEditText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_student2);
joinSession = (EditText) findViewById(R.id.sessName);
// Assigning ID's to Button.
joinButton = (Button) findViewById(R.id.session);
// Creating Volley newRequestQueue .
requestQueue = Volley.newRequestQueue(StudentActivity2.this);
// Assigning Activity this to progress dialog.
progressDialog = new ProgressDialog(StudentActivity2.this);
joinButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
CheckEditTextIsEmptyOrNot();
if (CheckEditText) {
PushedButton();
} else {
Toast.makeText(StudentActivity2.this, "Please fill all form fields.", Toast.LENGTH_LONG).show();
}
}
});
}
public void CheckEditTextIsEmptyOrNot() {
// Getting values from EditText.
SessionHolder = joinSession.getText().toString().trim();
// Checking whether EditText value is empty or not.
if (TextUtils.isEmpty(SessionHolder)) {
// If any of EditText is empty then set variable value as False.
CheckEditText = false;
} else {
// If any of EditText is filled then set variable value as True.
CheckEditText = true;
}
}
public void PushedButton() {
// Showing progress dialog at user registration time.
progressDialog.setMessage("Please Wait");
progressDialog.show();
// Creating string request with post method.
StringRequest stringRequest = new StringRequest(Request.Method.POST, HttpUrl,
new Response.Listener<String>() {
@Override
public void onResponse(String ServerResponse) {
// Hiding the progress dialog after all task complete.
progressDialog.dismiss();
// Matching server responce message to our text.
if(ServerResponse.equalsIgnoreCase("Data Matched")) {
// If response matched then show the toast.
Toast.makeText(StudentActivity2.this, "Logged In Successfully", Toast.LENGTH_LONG).show();
// Finish the current Login activity.
finish();
// Opening the user profile activity using intent.
Intent intent=new Intent(StudentActivity2.this,MainActivity.class);
// Sending User Email to another activity using intent.
intent.putExtra("SessionTAG", SessionHolder);
startActivity(intent);
}
else {
// Showing Echo Response Message Coming From Server.
Toast.makeText(StudentActivity2.this, ServerResponse, Toast.LENGTH_LONG).show();
}
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError volleyError) {
// Hiding the progress dialog after all task complete.
progressDialog.dismiss();
// Showing error message if something goes wrong.
Toast.makeText(StudentActivity2.this, volleyError.toString(), Toast.LENGTH_LONG).show();
}
}) {
@Override
protected Map<String, String> getParams() {
// Creating Map String Params.
Map<String, String> params = new HashMap<String, String>();
// Adding All values to Params.
// The firs argument should be same sa your MySQL database table columns.
params.put("id", SessionHolder);
params.put("decision", DecisionHolder);
return params;
}
};
// Creating RequestQueue.
RequestQueue requestQueue = Volley.newRequestQueue(StudentActivity2.this);
// Adding the StringRequest object into requestQueue.
requestQueue.add(stringRequest);
}
}
检查会话.php
<?php
//Define your host here.
$HostName = "localhost";
//Define your database username here.
$HostUser = "root";
//Define your database password here.
$HostPass = "";
//Define your database name here.
$DatabaseName = "queue_lnsconnection";
?>
决定Android.php
<?php
if($_SERVER['REQUEST_METHOD']=='POST'){
include 'CheckSession.php';
$con = mysqli_connect($HostName,$HostUser,$HostPass,$DatabaseName);
$First_Name = $_POST['firstname'];
$Last_Name = $_POST['lastname'];
$Bench = $_POST['bench'];
$Decision = $_POST['decision'];
$CheckSQL = "SELECT * FROM queue_template";
$check = mysqli_fetch_array(mysqli_query($con,$CheckSQL));
$result = mysqli_query($con,$CheckSQL);
$row = mysql_num_rows($result);
//if(isset($check))
if($row>0){
echo "Data Matched";
}
else{
echo "Bench not valid";
}
}else{
echo "Check Again";
}
mysqli_close($con);
?>
我试图尽可能减少代码，但我不确定问题是什么。提前致谢！
解决方案
Android 无法读取网页内容，尝试使用如下 JSON 响应
在你的PHP 文件中
<?php
// do Connection to DB if
(isset($_POST['bench'])) {
$bench = $_POST['bench'];
$sql = "SELECT COUNT(*) AS num FROM `queue_template ` WHERE bench = : bench";
// Prepare the SQL statement.
$stmt = $dbConn->prepare($sql);
// Bind our bench value to the : bench parameter.
$stmt->bindValue(': bench', $bench);
// Execute the statement.
$stmt->execute();
// Fetch the row / result.
$row = $stmt->fetch(PDO::FETCH_ASSOC);
// If num is bigger than 0, the bench already exists.
if($row['num'] > 0){
// Do your code Here like inserting in SQL or some Functions...
...
// required field is missing
$response["success"] = 1;
$response["message"] = "Bench not exist.";
// echoing JSON response
echo json_encode($response);
}else{
// bench already exist.
// required field is missing
$response["success"] = 0;
$response["message"] = "Bench already exist.";
// echoing JSON response
echo json_encode($response);
}
} //Closing if statement
?>
并在您的 Android Studio 中将此类添加到您的 Activity 类中并在 Gradle 中导入 Json
implementation 'com.googlecode.json-simple:json-simple:1.1'
这是课程
private class CheckBench extends AsyncTask<String, String, String> {
String bench = // get Value from EditText or whatever
// You can add more Strings Ints or anything here
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(PostShow.this);
pDialog.setMessage("Checking...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
/**
* Creating product
* */
@Override
protected String doInBackground(String... params) {
List<NameValuePair> param = new ArrayList<NameValuePair>();
//add your Strings Ints... as params here
param.add(new BasicNameValuePair("bench", bench));
JSONObject json = jsonParser.makeHttpRequest(HttpUrl, "POST", param);
try {
int success = json.getInt("success");
String messages = json.getString("message");
if (success == 1) {
}else{
Toast.makeText(getApplicationContext(), messages,
Toast.LENGTH_LONG).show();
}
} catch (Exception e) {
try {
String messager = json.getString("message");
Toast.makeText(getApplicationContext(), messager,
Toast.LENGTH_LONG).show();
} catch (JSONException ex) {
ex.printStackTrace();
}
// Toast.makeText(getApplicationContext(), "Error", Toast.LENGTH_LONG).show();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String url_link) {
// dismiss the dialog once done
COMMENTAIRE.setText("");
pDialog.dismiss();
Toast.makeText(getApplicationContext(), "Bench CHecked",
Toast.LENGTH_LONG).show();
}
}
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