Question

Ok,so I”m trying to make a Currency Converter between dollars and euros based on a tutorial I found on the web.The problem is that the tutorial is relying on 2 radio buttons to switch between the conversion, a reference for order stating to the program which method to call first.I want the program to make that conversion independetly from the two radio buttons and instantaneously,for instance if I write a number in the euro or dollar editText view…then clicking on the convert button will make the appropriate conversion.But I cannot because there are 2 methods and unless a have a way to display their input simultaneously it won’t work.So my question is how ca I update the two editText views simultaneously when I press the convert button?Thank you

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class ConvertorActivity extends Activity {
    TextView dollars;
    TextView euros;

    Button convert;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(R.layout.main);

        dollars = (TextView)this.findViewById(R.id.dollars);
        euros = (TextView)this.findViewById(R.id.euros);



        convert = (Button)this.findViewById(R.id.convert);

        convert.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                convertBoth();

            }
        });
    }

    public void convertBoth(){
        convertDollarsToEuros();
        convertEurosToDollars();
    }
    protected void convertDollarsToEuros() {
        double val = Double.parseDouble(dollars.getText().toString());
        // in a real app, we'd get this off the 'net
        euros.setText(Double.toString(val*0.67));
    }

    protected void convertEurosToDollars() {
        double val = Double.parseDouble(euros.getText().toString());
        // in a real app, we'd get this off the 'net
        dollars.setText(Double.toString(val/0.67));
    }
}

Answer 1

I think what you want is this:

• If the user changed the dollar amount, convert it to euro
• If the user changed the euro amount, convert it to dollar

If that’s the case, you can add a member variable mLastEditedViewId and use a TextWatcher to track which field was last changed. Then, onClick, call convertDollarsToEuros() or convertEurosToDollars accordingly.

In onCreate:

  dollars.addTextChangedListener(new MyTextWatcher(dollars));
  euros.addTextChangedListener(new MyTextWatcher(euros));

  convert.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
      switch (mLastEditedViewId) {
      case R.id.dollars:
        convertDollarsToEuros();
        break;
      case R.id.euros:
        convertEurosToDollars();
        break;
      }
    }
  });

Define an inner class for the TextWatcher:

private class MyTextWatcher implements TextWatcher {
  private int mTextViewId;
  public MyTextWatcher(TextView view) {
    mTextViewId = view.getId();
  }
  public void beforeTextChanged(CharSequence s, int start, int count, int after) {
  }
  public void onTextChanged(CharSequence s, int start, int before, int count) {
    mLastEditedViewId = mTextViewId;
  }
  public void afterTextChanged(Editable s) {
  }
}