Null exception error on dbString=" ";

Question

I often come across null exception errors and I always end up solving them, except this time I'm stuck with this error for days now.

Here it is:

In my mainActivity I need to print some data from the database through this method

  public void printDB(){

    String dbString= WinToDB.dbToString();
    wordDB.setText(dbString);
    word.setText("");

    meaningDB.setText(dbString);
    meaning.setText("");
}

dbString should carry what this this method from my database handler is returning

 public String dbToString(){
    dbString="";
    SQLiteDatabase db = getWritableDatabase();
    String query= "SELECT * FROM  " + TABLE_NAME +  " WHERE 1 ";  // * star means all 'columns' 1 means all 'row'

    Cursor c = db.rawQuery(query, null);
    //move to first location
    c.moveToFirst();

    while (!c.isAfterLast()){
        if(c.getString(c.getColumnIndex("wishe")) != null){
            dbString += c.getString(c.getColumnIndex("wishe"));
            dbString += "\n";

        }
    }
    db.close();
   // db.releaseReference();

    return dbString;
}

But it throws attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

here's the logcat:

.RuntimeException: Unable to start activity ComponentInfo{com.mirdox.myapplication/com.mirdox.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2362) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2424) at android.app.ActivityThread.access$900(ActivityThread.java:155) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1323) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:139) at android.app.ActivityThread.main(ActivityThread.java:5298) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:950) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:745) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at com.mirdox.myapplication.MainActivity.printDB(MainActivity.java:79) at com.mirdox.myapplication.MainActivity.onCreate(MainActivity.java:29) at android.app.Activity.performCreate(Activity.java:6072) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2315) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2424) at android.app.ActivityThread.access$900(ActivityThread.java:155) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1323) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:139) at android.app.ActivityThread.main(ActivityThread.java:5298) at java.lang.reflect.Method.invoke(Native Method)

What's wrong and what should I do? Thanks in advance!

EDIT Here's the onCreate of my mainActivity `public class MainActivity extends AppCompatActivity {

EditText word, meaning;
TextView wordDB, meaningDB;
DBhandler WinToDB;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    WinToDB= new DBhandler(this, null, null, 1);
    printDB();

    //_________input________________________
    word= (EditText)findViewById(R.id.word);
    meaning= (EditText)findViewById(R.id.meaning);

    //_________output_______________________
    wordDB= (TextView)findViewById(R.id.textView);
    meaningDB= (TextView)findViewById(R.id.textView2);

****EDIT 2 Here is my content_main.xml: I'had a problem adding the code to here; here's the link to code on evernotecontent_main.xml

ps: I have the printDb(); written in onCreate in the mainAcitvity.

The problem is not `dbString` it is the `TextView` you are trying to set that is null. Make sure you are using the proper res id and make sure the view is properly inflated before trying to set the text. — NoChinDeluxe, Apr 07 '16 at 22:29
@Gendarme Yes, I also added my mainAcitivity. Could you have a look please — Sruda, Apr 07 '16 at 22:43
@NoChinDeluxe I checked the xml id's and they're correct and I'm not inflating it. I've just added my mainAcitivity, could you have a look please. — Sruda, Apr 07 '16 at 22:44
@Shadab Ansari yes. I've just added my mainAcitivity, could you have a look please — Sruda, Apr 07 '16 at 22:48
Then the next thing to check is to make sure these are actually declared as TextViews and are actually located in `activity_main.xml`. If you want you can post `activity_main.xml` and we can have a look. — NoChinDeluxe, Apr 07 '16 at 22:50
@NoChinDeluxe I checked but they're correct :/ I added my content_main.xml as link above. — Sruda, Apr 07 '16 at 23:12
You are calling printDB(); before initializing your views. That's why you are getting excepttion. Call printDB(); after initializing your views. — Shadab Ansari, Apr 07 '16 at 23:15
@ShadabAnsari Damn I didn't I was this dumb! thanks a lot I can now launch it on my phone! :) — Sruda, Apr 07 '16 at 23:21

score 0 · Answer 1 · answered Apr 07 '16 at 22:33

0

wordDB, word, meaningDB or meaning is null, whichever is on line 79.

answered Apr 07 '16 at 22:33

Vampire

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Null exception error on dbString=" ";

1 Answers1