Android crash: nullpoint exception

Question

I am trying to make a login app for the android with PHP and MYSQL but it crashed whenever I start it. I have read similar problems but I still can't pinpoint the error

logcat report

09-25 15:34:07.722: E/AndroidRuntime(2515): FATAL EXCEPTION: main
09-25 15:34:07.722: E/AndroidRuntime(2515): Process: com.learn2crack.tab, PID: 2515
09-25 15:34:07.722: E/AndroidRuntime(2515): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.learn2crack.tab/com.learn2crack.tab.Login}: java.lang.NullPointerException
09-25 15:34:07.722: E/AndroidRuntime(2515):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at android.os.Handler.dispatchMessage(Handler.java:102)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at android.os.Looper.loop(Looper.java:136)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at android.app.ActivityThread.main(ActivityThread.java:5017)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at java.lang.reflect.Method.invokeNative(Native Method)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at java.lang.reflect.Method.invoke(Method.java:515)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at dalvik.system.NativeStart.main(Native Method)
09-25 15:34:07.722: E/AndroidRuntime(2515): Caused by: java.lang.NullPointerException
09-25 15:34:07.722: E/AndroidRuntime(2515):     at com.learn2crack.tab.Login.onCreate(Login.java:76)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at android.app.Activity.performCreate(Activity.java:5231)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
09-25 15:34:07.722: E/AndroidRuntime(2515):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)

My login.java package com.learn2crack.tab;

public class Login extends Activity implements OnClickListener {

    private EditText user, pass;
    private Button mSubmit, mRegister;

    // Progress Dialog
    private ProgressDialog pDialog;

    // JSON parser class
    JSONParser jsonParser = new JSONParser();

    // php login script location:


    private static final String LOGIN_URL = "http://10.0.2.2/webservice/login.php";


    private static final String TAG_SUCCESS = "success";
    private static final String TAG_MESSAGE = "message";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        // setup input fields
        user = (EditText) findViewById(R.id.username);
        pass = (EditText) findViewById(R.id.pword);

        // setup buttons
        mSubmit = (Button) findViewById(R.id.login);
        mRegister = (Button) findViewById(R.id.register);

        // register listeners
        mSubmit.setOnClickListener(this);
        mRegister.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch (v.getId()) {
        case R.id.login:
            new AttemptLogin().execute();
            break;
        case R.id.register:
            Intent i = new Intent(this, Register.class);
            startActivity(i);
            break;

        default:
            break;
        }
    }

    class AttemptLogin extends AsyncTask<String, String, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(Login.this);
            pDialog.setMessage("Attempting login...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();
        }

        @Override
        protected String doInBackground(String... args) {
            // TODO Auto-generated method stub
            // Check for success tag
            int success;
            String username = user.getText().toString();
            String password = pass.getText().toString();
            try {
                // Building Parameters
                List<NameValuePair> params = new ArrayList<NameValuePair>();
                params.add(new BasicNameValuePair("username", username));
                params.add(new BasicNameValuePair("password", password));

                Log.d("request!", "starting");
                // getting product details by making HTTP request
                JSONObject json = jsonParser.makeHttpRequest(LOGIN_URL, "POST",
                        params);

                // check your log for json response
                Log.d("Login attempt", json.toString());

                // json success tag
                success = json.getInt(TAG_SUCCESS);
                if (success == 1) {
                    Log.d("Login Successful!", json.toString());
                    // save user data
                    SharedPreferences sp = PreferenceManager
                            .getDefaultSharedPreferences(Login.this);
                    Editor edit = sp.edit();
                    edit.putString("username", username);
                    edit.commit();

                    Intent i = new Intent(Login.this, MainActivity.class);
                    finish();
                    startActivity(i);
                    return json.getString(TAG_MESSAGE);
                } else {
                    Log.d("Login Failure!", json.getString(TAG_MESSAGE));
                    return json.getString(TAG_MESSAGE);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

            return null;

        }

        protected void onPostExecute(String file_url) {
            // dismiss the dialog once product deleted
            pDialog.dismiss();
            if (file_url != null) {
                Toast.makeText(Login.this, file_url, Toast.LENGTH_LONG).show();
            }

        }

    }

}

PHP script

$_POST['username'] ); try { $stmt = $db->prepare($query); $result = $stmt->execute($query_params); } catch (PDOException $ex) { // For testing, you could use a die and message. //die("Failed to run query: " . $ex->getMessage()); //or just use this use this one to product JSON data: $response["success"] = 0; //$response["message"] = "Database Error1. Please Try Again!"; die(json_encode($response)); } //This will be the variable to determine whether or not the user's information is correct. //we initialize it as false. $validated_info = false; //fetching all the rows from the query $row = $stmt->fetch(); if ($row) { //if we encrypted the password, we would unencrypt it here, but in our case we just //compare the two passwords if ($_POST['password'] === $row['password']) { $login_ok = true; } } // If the user logged in successfully, then we send them to the private members-only page // Otherwise, we display a login failed message and show the login form again if ($login_ok) { $response["success"] = 1; //$response["message"] = "Login successful!"; die(json_encode($response)); } else { $response["success"] = 0; //$response["message"] = "Invalid Credentials!"; die(json_encode($response)); } } else { ?>

Login

Username:

Password:

Register

Looks like one of your Buttons are null. Check that they both are in activity_login.xml — codeMagic

user3439968 user3439968 · Accepted Answer · 2014-09-25T20:08:31

Use step-by-step execution, and check your resurces.

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

    // setup input fields
    user = (EditText) findViewById(R.id.username);
    pass = (EditText) findViewById(R.id.pword);

    // setup buttons
    mSubmit = (Button) findViewById(R.id.login);
    mRegister = (Button) findViewById(R.id.register);

    // register listeners
    mSubmit.setOnClickListener(this);
    mRegister.setOnClickListener(this);

}

Toggle breakpoint on OnCreate.

Check:

// setup buttons
    mSubmit = (Button) findViewById(R.id.login);
    mRegister = (Button) findViewById(R.id.register);

Android crash: nullpoint exception

Login

1 Answers