Agfdhyk

I'm new to Android Studio and programming in general, but wanted to create a simple application that performs calculations based on the numbers inputted. The idea is to have 4 EditText fields that support decimal numerals where only 3 out of 4 fields require input for the calculation to work. After inputting 3 out of the 4 fields, my application will detect which of the 4 fields have an empty value and proceed with the other 3 inputs to output the correct number. When the "Calculate" Button is pressed, I want to have a TextView field display the final number.

Performing a simple calculation using just one EditText, TextView, and a Button is working, but can't seem to get the null field detection working when I add more code.

Appreciate any input you can give!

Edit:

To clarify, my simple calculation will be:

editText * editText2 = editText3 * editText4

Essentially, only 3 out of 4 values need to be supplied by the user and the null value will be calculated.

For example:

editText = 2

editText2 = 4

editText3 = null

editText4 = 1

The app will determine that editText3 was not supplied, and therefore, attempt to calculate its value using the above formula. In this example, the value of editText3 will be computed to 8 and displayed in the textView field after the user hits the Calculate button.

The code I'm using after Vero Gorena's suggestion is (although I'm still having problems compiling!):

public class MainActivity extends AppCompatActivity {

    EditText editText1;

    EditText editText2;

    EditText editText3;

    EditText editText4;

    TextView textView;

    Button button;





    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        textView=findViewById(R.id.textView);

        editText1=findViewById(R.id.editText);

        editText2=findViewById(R.id.editText2);

        editText3=findViewById(R.id.editText3);

        editText4=findViewById(R.id.editText4);

    }





    // Detects whether a field is null

    public String getTheNumber(View view){

        if(editText1.getText().length()>0){Toast.makeText(this,"1 Has data",Toast.LENGTH_LONG).show();}

        if(editText2.getText().length()>0){Toast.makeText(this,"2 Has data",Toast.LENGTH_LONG).show();}

        if(editText3.getText().length()>0){Toast.makeText(this,"3 Has data",Toast.LENGTH_LONG).show();}

        if(editText4.getText().length()>0){Toast.makeText(this,"4 Has data",Toast.LENGTH_LONG).show();}



        return null;

    }





    // Calculates and displays the result

    private void calculateResult() throws NumberFormatException {



        // Calculates the result

        int result = editText1 * editText2 = editText3 * editText4;



        // Displays the result

        textView.setText(result.toString());



        // Displays result to 2 decimal places

        textView.setText(String.format("%1.2f", result));

    }





}

Edit 2:

Just realized that my formula needs to be broken up into 4 cases:

If editText = null, then result = editText3 * editText4 / editText2

If editText2 = null, then result = editText3 * editText4 / editText

If editText3 = null, then result = editText * editText2 / editText4

If editText4 = null, then result = editText * editText2 / editText3

This code can help you, since it detects which EditText has or not a number and Instead of use Toast.makeText, there you can use your own code.
The function getTheNumber already consider to return a data, in this case a String.

   public class MainActivity extends AppCompatActivity {

        EditText editText1;

        EditText editText2; 

        EditText editText3; 

        EditText editText4;

        TextView textView;

        Button button;





    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        textView=findViewById(R.id.textView_atXML);

        editText1=findViewById(R.id.editText1_atXML);

        editText2=findViewById(R.id.editText2_atXML);

        editText3=findViewById(R.id.editText3_atXML);

        editText4=findViewById(R.id.editText4_atXML);







    }

    public String getTheNumber(View view){

        if(editText1.getText().length()>0){Toast.makeText(this,"1 Has data",Toast.LENGTH_LONG).show();}

        if(editText2.getText().length()>0){Toast.makeText(this,"2 Has data",Toast.LENGTH_LONG).show();}

        if(editText3.getText().length()>0){Toast.makeText(this,"3 Has data",Toast.LENGTH_LONG).show();}

        if(editText4.getText().length()>0){Toast.makeText(this,"4 Has data",Toast.LENGTH_LONG).show();}



        return null;

    }

}