Question

I’m writing a simple app in Android.

I’ve encountered this problem: I’ve two EditText and a Button. The value of one EditText must be a multiple of the other one EditText.

When the user insert a value in the first EditText and then press the button, the other EditText should show the value calculated with the user input.
This should be possible in other verse, too.

Like a simple unit converter. When I insert value1 in EditText1 and press convert the app must show the converted value in EditText2, but if I insert a value2 in EditText2 and press convert button the app must show the converted value in EditText1.
My problem is: how can I recognize in which EditText there are last user-input?

public void convert(View view) {
    EditText textInEuro = (EditText) findViewById(R.id.euroNumber);
    EditText textInDollar = (EditText) findViewById(R.id.dollarNumber);
    if (toDollar) {
        String valueInEuro = textInEuro.getText().toString();
        float numberInEuro = Float.parseFloat(valueInEuro);
        // Here the conversione between the two currents
        float convertedToDollar = unit * numberInEuro;
        // set the relative value in dollars
        textInDollar.setText(Float.toString(convertedToDollar));
    }

    if (toEuro) {
        String valueInDollar = textInDollar.getText().toString();
        float numberInDollar = Float.parseFloat(valueInDollar);
        //Here the conversione between the two currents
        float convertedToEuro = numberInDollar / unit;
        //set the relative value in dollars
        textInEuro.setText(Float.toString(convertedToEuro));
    }
}

This is the code written. I’ve thinked to use OnClickListener..but it isn’t a good idea..

Answer 1

You can add a TextWatcher to your two EditText in order to know which one has been updated last.

public class MainActivity extends Activity {

EditText dollar;
EditText euro;

private static final int EURO = 0;
private static final int DOLLAR = 1;

private int lastUpdated = DOLLAR;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    dollar = findViewById(R.id.dollar);
    euro = findViewById(R.id.euro);

    dollar.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            lastUpdated = DOLLAR;

        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void afterTextChanged(Editable s) {

        }
    });

    euro.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            lastUpdated = EURO;

        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void afterTextChanged(Editable s) {

        }
    });

}

public void convert(View view) {
    switch (lastUpdated) {
    case EURO:
        //Do work for euro to dollar
        break;
    case DOLLAR:
        //Do work for dollar to euro
        break;
    default:
        break;
    }
}
}