NullPointerException even though variables aren't null

Question

I have written a method to update a user's password in SQLite.

The method is updatePassword()

public class changePassword extends Activity {  
    SQLiteDatabase checkDB;     

    //Load session name 
    String sessionName;
    String sessionPassword;
    String currentPasswordString;
    String newPassword1String;
    String newPassword2String;
    //Load text fields
    EditText currentPassword;
    EditText newPassword1;
    EditText newPassword2;      

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.changepassword);
        Button changePassword = (Button)findViewById(R.id.changePasswordButton);
        //Load session name
        SharedPreferences preferences = getSharedPreferences("temp", getApplicationContext().MODE_PRIVATE);
        sessionName = preferences.getString("sessionName", ""); 
        sessionPassword = preferences.getString("sessionPassword", ""); 
        currentPassword = (EditText)findViewById(R.id.currentPassword);
        newPassword1 = (EditText)findViewById(R.id.newpassword1);

        newPassword2 = (EditText)findViewById(R.id.newpassword2);


    }

    //Mismatched password checking
    public void updatePassword(View v)
    {

        currentPasswordString = currentPassword.getText().toString();
        newPassword1String = newPassword1.getText().toString();
        newPassword2String = newPassword2.getText().toString();
        Toast.makeText(changePassword.this, sessionName.toString(), Toast.LENGTH_LONG).show();
        Toast.makeText(changePassword.this, newPassword2String.toString(), Toast.LENGTH_LONG).show();
        if (currentPasswordString.equals(sessionPassword))
        {
            if (newPassword1String.equals(newPassword2String))
            {

            checkDB.execSQL("UPDATE Students SET Student_Password=" + newPassword2String + "WHERE CNumber=" + sessionName);
            Log.d("Password", "Changed");
            }
        }
    }

}

When this method runs, if I comment out the SQL statement it will display the Log, so that suggests it is running through the if statement without a problem?

I also have toasts to display the variables used in the if's and in the SQL statement however they show the desired values and are not null!

As soon as I comment execSQL back in, this LogCat error shows:

04-08 16:22:55.973: E/AndroidRuntime(4150): FATAL EXCEPTION: main
04-08 16:22:55.973: E/AndroidRuntime(4150): Process: com.example.project, PID: 4150
04-08 16:22:55.973: E/AndroidRuntime(4150): java.lang.IllegalStateException: Could not execute method of the activity
04-08 16:22:55.973: E/AndroidRuntime(4150):     at android.view.View$1.onClick(View.java:3823)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at android.view.View.performClick(View.java:4438)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at android.view.View$PerformClick.run(View.java:18422)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at android.os.Handler.handleCallback(Handler.java:733)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at android.os.Handler.dispatchMessage(Handler.java:95)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at android.os.Looper.loop(Looper.java:136)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at android.app.ActivityThread.main(ActivityThread.java:5001)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at java.lang.reflect.Method.invokeNative(Native Method)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at java.lang.reflect.Method.invoke(Method.java:515)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at dalvik.system.NativeStart.main(Native Method)
04-08 16:22:55.973: E/AndroidRuntime(4150): Caused by: java.lang.reflect.InvocationTargetException
04-08 16:22:55.973: E/AndroidRuntime(4150):     at java.lang.reflect.Method.invokeNative(Native Method)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at java.lang.reflect.Method.invoke(Method.java:515)
04-08 16:22:55.973: E/AndroidRuntime(4150):     at android.view.View$1.onClick(View.java:3818)
04-08 16:22:55.973: E/AndroidRuntime(4150):     ... 11 more
04-08 16:22:55.973: E/AndroidRuntime(4150): Caused by: java.lang.NullPointerException
04-08 16:22:55.973: E/AndroidRuntime(4150):     at com.example.project.changePassword.updatePassword(changePassword.java:69)
04-08 16:22:55.973: E/AndroidRuntime(4150):     ... 14 more

score 1 · Accepted Answer · answered Apr 08 '16 at 20:27

1

If you comment out the

checkDB.execSQL("UPDATE Students SET Student_Password=" + newPassword2String + "WHERE CNumber=" + sessionName);

line and it runs to the log statement, then checkDB is null.

Where do you open/initialize your database?

answered Apr 08 '16 at 20:27

Darth Android

3,437
18
19

I initialize it at the top as a Global variable just below public class { – Matt Murphy Apr 08 '16 at 20:28
Post the code please. – Darth Android Apr 08 '16 at 20:29
Will post the entire class now - 1 sec – Matt Murphy Apr 08 '16 at 20:30
2

You do not open/initialize the database, you just define a variable to hold it. You need to open the database and assign it to `checkDB`. (Probably inside `onCreate`) – Darth Android Apr 08 '16 at 20:32
Initializing my DB.java as a global variable and adding checkDB = db.getWritableDatabase(); should do the trick then? – Matt Murphy Apr 08 '16 at 20:37
Those variables are not global - they are instance variables, fyi. And while I don't know for sure if that will do the trick, that does sound mostly correct. – Darth Android Apr 08 '16 at 20:39

NullPointerException even though variables aren't null

1 Answers1