Android: Passing values to another activity's function and then to Sqlite database

Question

It's been a month since I've kicked off with android studio, at this time I'm stuck at a point where I have to pass a set of <EditText/> values from MainActivity to UpdateActivity and then send those values to the Sqlite database for updating a table.

What I have accomplished:

Successfully sending values from MainActivity's <EditText/> to UpdateActivity's <EditText/>

How I have done that from MainActivity:

public class MainActivity extends AppCompatActivity {
    DatabaseHelper myDb;
    EditText editName, editSurname, editMarks;
    Button btnUpdate;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    myDb = new DatabaseHelper(this);

    editName = (EditText) findViewById(R.id.UpdName);
    editSurname = (EditText) findViewById(R.id.editTextSurname);
    editMarks = (EditText) findViewById(R.id.UpdMarks);
    btnUpdate = (Button)findViewById(R.id.btnUpdate);

    btnUpdate.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String MainName = editName.getText().toString();
            String MainSurname = editSurname.getText().toString();
            String MainMarks = editMarks.getText().toString();

            Intent UpdateAct = new Intent(MainActivity.this, UpdateActivity.class);
            UpdateAct.putExtra("Name", MainName);
            UpdateAct.putExtra("SurName",MainSurname );
            UpdateAct.putExtra("Marks", MainMarks);
            startActivity(UpdateAct);
        }
    });
}

Then inside the UpdateActivity:

public class UpdateActivity extends AppCompatActivity {
DatabaseHelper myDb;
Button btnUpd;
EditText editTextId, editUpdtName, editUpdSurname, editUpdMarks;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_update);

    Intent getData = getIntent();
    String Name = getData.getStringExtra("Name");
    String SurName = getData.getStringExtra("SurName");
    String Marks = getData.getStringExtra("Marks");

    editTextId = (EditText)findViewById(R.id.editTextID);
    editUpdtName = (EditText)findViewById(R.id.UpdName);
    editUpdSurname = (EditText)findViewById(R.id.UpdSurname);
    editUpdMarks = (EditText)findViewById(R.id.UpdMarks);
    btnUpd = (Button)findViewById(R.Id.btnUpd);

    editUpdtName.setText(Name);
    editUpdSurname.setText(SurName);
    editUpdMarks.setText(Marks);
}

What I'm stuck at is to send these values to a function named updateData(); For that I have tried to use the values from MainActivity directly to UpdateActivity but failed, then I tried to cast those <EditText/> and use it inside the function but failed again.

Inside my UpdateActivity:

..//    
        editUpdtName.setText(Name);
        editUpdSurname.setText(SurName);
        editUpdMarks.setText(Marks);
        //updateData(Name, SurName, Marks);
        updateData();
    }

//function definiton
//   public void updateData(final String Name, final String SurName, final String Marks)
    public void updateData()
    {
        btnUpd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
//             boolean isUpdated =   myDb.updateData(editTextId.getText().toString(), Name,SurName, Marks);
                boolean isUpdated =   myDb.updateData(editTextId.getText().toString(), editUpdtName.getText().toString(),
                        editUpdSurname.getText().toString(), editUpdMarks.getText().toString());
            if(isUpdated == true){
                Toast.makeText(UpdateActivity.this, "Data Updated Successfully!", Toast.LENGTH_SHORT).show();
            }
            else{
                    Toast.makeText(UpdateActivity.this, "Data NOT Updated!", Toast.LENGTH_SHORT).show();
        }

    }
        });
    }
}

The app crashes everytime the function updateData(); is called, to ensure that is the real cause I have even commented and also tried putting it in a handler to run it after 3000ms, as expcted it crashed after the time period.

Solved it by initializing the db.

myDb = new DatabaseHelper(this);

Answer 1

You forgot to initialize myDb. Initialize it in your onCreate() method:

myDb = new DatabaseHelper(this);