App crashing during onTextChanged()

Question

I am making a simple notes app with SQLite. It has two activities and a helper class for SQLite. However when I click on the example note(Akhilesh Chobey) in MainActivity.java, and try to edit it in Main2Activity.java the application crashes.

Main Activity:

    public class MainActivity extends AppCompatActivity {



    ListView notesListView;
    static ArrayList<String> notesArrayList;
    ArrayAdapter<String> adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        notesListView = (ListView) findViewById(R.id.notesListView);
        notesArrayList = new ArrayList<String>();
        notesArrayList.add("Akhilesh Chobey");
        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, notesArrayList);
        notesListView.setAdapter(adapter);

        notesListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                Intent intent = new Intent(getApplicationContext(), Main2Activity.class);
                intent.putExtra("notePosition", i);
                startActivity(intent);
            }
        });



    }
}

Main2Activity:

public class Main2Activity extends AppCompatActivity implements TextWatcher {

DatabaseOperations myDB;
EditText editNote;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);
    editNote = (EditText) findViewById(R.id.noteEditText);

    myDb = new DatabaseOperations(Main2Activity.this);

    Intent intent = getIntent();
    int position = intent.getIntExtra("notePosition", -1);
    if(position != -1){

        editNote.setText(MainActivity.notesArrayList.get(position));

    }
    editNote.addTextChangedListener(this);
}
@Override
public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
    if (myDB == null){ 
    boolean isInserted = myDB.insertData(editNote.getText().toString());
        if(isInserted){
            Toast.makeText(getApplicationContext(), "Inserted", Toast.LENGTH_SHORT).show();
        }else {
            Toast.makeText(getApplicationContext(), "Error", Toast.LENGTH_SHORT).show();
    }
}
}

Helper Class:

public class DatabaseOperations extends SQLiteOpenHelper {

public static final String DatabaseName = "notes.db";
public static final String TableName = "notes";
public static final String Col1 = "text";

public DatabaseOperations(Context context) {
    super(context, DatabaseName, null, 1);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("create table " + TableName + " (text TEXT PRIMARY KEY AUTOINCREMENT) ");
}

@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1) {

    db.execSQL("DROP TABLE IF EXISTS " + TableName);
    onCreate(db);

}

public boolean insertData(String note){

    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(Col1, note);

    long result = db.insert(TableName, null, contentValues);
    if(result == -1){
        return false;
    }else {
        return true;
    }

}

}

Log:

06-29 17:23:34.996 2231-2231/com.akhileshchobey.mynotes E/AndroidRuntime: FATAL EXCEPTION: main
                                                                      Process: com.akhileshchobey.mynotes, PID: 2231
                                                                      java.lang.NullPointerException: Attempt to invoke virtual method 'boolean com.akhileshchobey.mynotes.DatabaseOperations.insertData(java.lang.String)' on a null object reference
                                                                          at com.akhileshchobey.mynotes.Main2Activity.onTextChanged(Main2Activity.java:39)
                                                                          at android.widget.TextView.sendOnTextChanged(TextView.java:7746)
                                                                          at android.widget.TextView.handleTextChanged(TextView.java:7806)
                                                                          at android.widget.TextView$ChangeWatcher.onTextChanged(TextView.java:9724)
                                                                          at android.text.SpannableStringBuilder.sendTextChanged(SpannableStringBuilder.java:964)
                                                                          at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:515)
                                                                          at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:454)
                                                                          at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:33)
                                                                          at android.view.inputmethod.BaseInputConnection.replaceText(BaseInputConnection.java:685)
                                                                          at android.view.inputmethod.BaseInputConnection.setComposingText(BaseInputConnection.java:445)
                                                                          at com.android.internal.view.IInputConnectionWrapper.executeMessage(IInputConnectionWrapper.java:340)
                                                                          at com.android.internal.view.IInputConnectionWrapper$MyHandler.handleMessage(IInputConnectionWrapper.java:78)
                                                                          at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                          at android.os.Looper.loop(Looper.java:135)
                                                                          at android.app.ActivityThread.main(ActivityThread.java:5264)
                                                                          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:900)
                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:695)

maybe you're not initializing `myDb` in your `Main2Activity` class. So it will be **NULL** — SripadRaj, Jun 29 '16 at 10:42
post your logcat here . without logcat how can someone know the error occurred. ? at which line your app crashed ? what was the stack trace ? — Sagar Nayak, Jun 29 '16 at 11:01

SripadRaj · Accepted Answer · 2016-06-29T12:06:07.977

2

Don't initialize myDb = null;,

initialize myDb like this in your onCreate() of your Main2Activity

myDb = new DatabaseOperations(Main2Activity.this);

EDIT

you have now initialized your myDb, and it will not be null. So you have to change like below in your onTextChanged() method.

if (myDB == null)

to

if (myDB != null)

edited Jun 29 '16 at 12:06

answered Jun 29 '16 at 11:50

SripadRaj

1,687
2
22
33

Thanks. It works. Updated the code of Main2Activity. However the toast isn't being shown. Why is it so? – Akhilesh Chobey Jun 29 '16 at 12:01
@AkhileshChobey updated my answer – SripadRaj Jun 29 '16 at 12:07
1

Yup. Thanks. Had to delete the `AUTOINCREMENT` in `Helper Class` – Akhilesh Chobey Jun 29 '16 at 12:11
please accept my answer if it helped you :) – SripadRaj Jun 29 '16 at 12:11

Mani · Answer 2 · 2016-06-29T12:11:18.037

1

Change the line boolean isInserted = myDB.insertData(editNote.getText().toString()); with safety null check as below.

if (myDB == null)
   myDB = new DatabaseOperations(getApplicationContext() ); //Initialization
boolean isInserted = myDB.insertData(editNote.getText().toString());

edited Jun 29 '16 at 12:11

answered Jun 29 '16 at 11:33

Mani

17,549
13
79
100

but why do i need this extra if() condition what is the advantage.? – Abhijit Chakra Jun 29 '16 at 11:37
You may be initialized somewhere(myDB), but in this step, it gets crashed because of `myDB` is null. Add this check, it won't crash. – Mani Jun 29 '16 at 11:42
your right but he will never get a expected result it should first check why its not initialised in this function – Abhijit Chakra Jun 29 '16 at 11:46
@Mani I did as you said. Take a look at the code to verify it. However it still crashes. – Akhilesh Chobey Jun 29 '16 at 11:55
@AkhileshChobey No.. Your updated code is wrong. Checked as `null` instead of `not null`. Otherwise, If you check for null, initialize it as like in my code. – Mani Jun 29 '16 at 11:57
1

I made the initialization in the `onCreate` as suggested by @SripadRaj. If I change the condition to `!= null` it crashes again. But on keep it `== null` it doesn't show the toast. – Akhilesh Chobey Jun 29 '16 at 12:06
@AkhileshChobey So update the new crash log. It should not be previous one. – Mani Jun 29 '16 at 12:08
Otherwise create the db with applicationContext "myDb = new DatabaseOperations(getApplicationContext() );" – Mani Jun 29 '16 at 12:10
It worked. Thanks. The crash was due to `AUTOINCREMENT` in `Helper Class` – Akhilesh Chobey Jun 29 '16 at 12:12
1

@AkhileshChobey You're welcome. :) – Mani Jun 29 '16 at 12:14

score 0 · Answer 3 · answered Jun 29 '16 at 10:56

0

You have not initialize DatabaseOperations myDB = null;

The below line must be giving null pointer exception;

boolean isInserted = myDB.insertData(editNote.getText().toString());

because you have not initialized myDB

answered Jun 29 '16 at 10:56

Abhijit Chakra

3,201
37
66

I initialized it but it still shows the same. – Akhilesh Chobey Jun 29 '16 at 11:08
Where do you initialize myDB can you update your code – Mike Holtkamp Jun 29 '16 at 11:18
I can see still your myDB not initialised where is your updated code? – Abhijit Chakra Jun 29 '16 at 11:27
@AkhileshChobey show us your logcat, or else we wont be able to find what is going on – SripadRaj Jun 29 '16 at 11:29

score 0 · Answer 4 · answered Jun 29 '16 at 11:19

0

myDB is not initialised. You need to initialise it before using. Calling insertData on null object is the reason your app is crashing.

answered Jun 29 '16 at 11:19

am110787

316
1
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App crashing during onTextChanged()

4 Answers4