Here is the username which is defined as Edittext I want to check when user entered the username and move to the next field ,but it generates Error
E/MessageQueue-JNI: java.lang.NullPointerException: Attempt to invoke interface method 'java.sql.Statement java.sql.Connection.createStatement()' on a null object reference
package com.example.software2.bloodbankmanagement;
import android.annotation.SuppressLint;
import android.content.Context;
import android.content.Intent;
import android.graphics.drawable.BitmapDrawable;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.StrictMode;
import android.os.VibrationEffect;
import android.os.Vibrator;
import android.provider.MediaStore;
import android.speech.tts.TextToSpeech;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.view.inputmethod.EditorInfo;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.io.ByteArrayOutputStream;
import java.io.FileNotFoundException;
import java.io.IOError;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.Random;
import android.annotation.SuppressLint;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.os.StrictMode;
import android.util.AndroidRuntimeException;
import android.util.Base64;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
public class RegisterActivity extends AppCompatActivity {
EditText name, email, password,
contactno, Address, city, Age, username, gender;
Button registerbtn;
public static final int REQUEST_LOAD_IMAGE = 1;
ImageView img;
Button btnupload;
TextView status1, uid,registration;
byte[] byteArray;
ProgressBar progressBar;
String encodedImage;
Spinner spinner;
Connection con;
String gender1 = "male";
CheckBox blood;
RadioGroup radioGroup;
private static String value;
private TextToSpeech textToSpeech;
public String getvalue() {
return value;
}
Statement stmt,stmt1;
static boolean isAllFieldsChecked = true;
private Context context;
@SuppressLint("SetTextI18n")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.register);
status1 = findViewById(R.id.status1);
username = (EditText) findViewById(R.id.username);
username.setOnFocusChangeListener(new View.OnFocusChangeListener() {
@Override
public void onFocusChange(View view, boolean b) {
if(!b){
switch (view.getId()){
case R.id.username:
try{
stmt1 = con.createStatement();
String sql1 = "select Username from register where Username = '" username.getText() "'";
ResultSet rs = stmt1.executeQuery(sql1);
if(rs.next()){
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(RegisterActivity.this, "Username already exists", Toast.LENGTH_LONG).show();
}
});
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
});
registerbtn.setOnClickListener(new View.OnClickListener() {
@RequiresApi(api = Build.VERSION_CODES.O)
@Override
public void onClick(View v) {
city.onEditorAction(EditorInfo.IME_ACTION_DONE);
new registeruser().execute("");
}
});
btnupload.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent galleryIntent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(galleryIntent, REQUEST_LOAD_IMAGE);
}
});
}
public class registeruser extends AsyncTask<String, String, String> {
String z = "";
Boolean isSuccess = false;
@Override
protected void onPreExecute() {
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(getApplicationContext(), "Please wait ", Toast.LENGTH_LONG).show();
}
});
}
@SuppressLint("SetTextI18n")
@Override
protected void onPostExecute(String s) {
// Toast.makeText(RegisterActivity.this, "Registration Successful", Toast.LENGTH_SHORT).show();
}
@Override
protected String doInBackground(String... strings) {
try {
con = connectionClass(MainActivity.ConnectionClass.un.toString(), MainActivity.ConnectionClass.pass.toString(), MainActivity.ConnectionClass.db.toString(), MainActivity.ConnectionClass.ip.toString());
if (con == null) {
z = "Check Your Internet Connection";
} else {
try {
final TextView textView = findViewById(R.id.status1);
stmt = con.createStatement();
String sql = "INSERT INTO register(Name,Age,gender,Email,Username,password,contactNo,Address,city,img,bloodgrp,Uid) VALUES ('" name.getText() "'," Age.getText() ",'" gender1.trim() "','" email.getText() "','" username.getText() "','" password.getText() "','" contactno.getText() "','" Address.getText() "','" city.getText() "','" encodedImage "','" textView.getText() "'," uid.getText() ");";
stmt.executeUpdate(sql);
if (blood.isChecked()) {
String sql1 = "insert into Donor (Name,contactNo,Address,city,donor,bloodgrp,img,Uid) values ('" name.getText() "','" contactno.getText() "','" Address.getText() "','" city.getText() "','yes','" textView.getText() "', '" encodedImage "'," uid.getText() ")";
stmt.executeUpdate(sql1);
} else {
String sql1 = "insert into Donor (Name,contactNo,Address,city,donor,bloodgrp,img,Uid) values ('" name.getText() "','" contactno.getText() "','" Address.getText() "','" city.getText() "','no','" textView.getText() "','" encodedImage "'," uid.getText() ")";
stmt.executeUpdate(sql1);
}
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(getApplicationContext(), "Registration successful", Toast.LENGTH_SHORT).show();
}
});
} catch (Exception e) {
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_SHORT).show();
}
});
}
}
} catch (Exception e) {
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_SHORT).show();
}
});
}
return z;
}
}
@SuppressLint("NewApi")
public Connection connectionClass(String user, String password, String database, String server) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
Connection connection = null;
String connectionURL;
try {
Class.forName("net.sourceforge.jtds.jdbc.Driver");
connectionURL = "jdbc:jtds:sqlserver://" server "/" database ";user=" user ";password=" password ";";
connection = DriverManager.getConnection(connectionURL);
} catch (Exception e) {
Log.e("SQL Connection Error : ", e.getMessage());
}
return connection;
}
}
E/InputEventReceiver: Exception dispatching input event.
E/MessageQueue-JNI: Exception in MessageQueue callback: handleReceiveCallback
E/MessageQueue-JNI: java.lang.NullPointerException: Attempt to invoke interface method 'java.sql.Statement java.sql.Connection.createStatement()' on a null object reference
at com.example.software2.bloodbankmanagement.RegisterActivity$19.onFocusChange(RegisterActivity.java:362)
at android.view.View.onFocusChanged(View.java:7084)
at android.widget.TextView.onFocusChanged(TextView.java:9754)
at android.view.View.clearFocusInternal(View.java:6916)
at android.view.View.unFocus(View.java:6949)
at android.view.ViewGroup.requestChildFocus(ViewGroup.java:757)
at android.view.View.handleFocusGainInternal(View.java:6743)
at android.view.View.requestFocusNoSearch(View.java:11029)
at android.view.View.requestFocus(View.java:11008)
at android.view.View.requestFocus(View.java:10975)
at android.view.View.requestFocus(View.java:10917)
at android.view.View.onTouchEvent(View.java:13236)
at android.widget.TextView.onTouchEvent(TextView.java:9813)
at android.view.View.dispatchTouchEvent(View.java:11969)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3052)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2703)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3052)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2703)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3052)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2703)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3052)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2703)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3052)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2703)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3052)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2703)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3052)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2703)
at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:516)
at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1874)
at android.app.Activity.dispatchTouchEvent(Activity.java:3453)
at androidx.appcompat.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
at com.android.internal.policy.DecorView.dispatchTouchEvent(DecorView.java:470)
at android.view.View.dispatchPointerEvent(View.java:12213)
at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:5510)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:5253)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4735)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4795)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4754)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4903)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4762)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4960)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4735)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4795)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4754)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4762)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4735)
at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:7493)
at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:7467)
at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:7424)
at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:7611)
at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:186)
at android.os.MessageQueue.nativePollOnce(Native Method)
at android.os.MessageQueue.next(MessageQueue.java:325)
at android.os.Looper.loop(Looper.java:180)
`
CodePudding user response：
stmt1 = con.createStatement();
Here con is not defined. Try initializing con first and then do this.
CodePudding user response：
From the error message, I can see you are trying to execute creteStatement() on the con variable but that is null at that point. Can't see any other code to give any other advice.