eclipse - android application crashes when EditText is empty

Question

Good day. I wrote application in eclipse for android and when EditText is empty application crashes. I try so much ways but it do not work. Every it crash when i enter it and EditText is emty. Sorry for my english. This is part of my code :

public class MainActivity extends Activity implements OnClickListener {

TextView mnozstvo;
TextView percento;
TextView hmotnost;
TextView vysledok1;
TextView vysledok2;
TextView text;
RadioButton muz1;
RadioButton zena1;
Button vysledok;
EditText coo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

text = (TextView)this.findViewById(R.id.text);

mnozstvo = (TextView)this.findViewById(R.id.dl);


percento = (TextView)this.findViewById(R.id.per);

hmotnost = (TextView)this.findViewById(R.id.kg);

vysledok1 = (TextView)this.findViewById(R.id.krv);

vysledok2 = (TextView)this.findViewById(R.id.dych);

muz1 = (RadioButton)this.findViewById(R.id.muz);

zena1 = (RadioButton)this.findViewById(R.id.zena);

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

vysledok.setOnClickListener(this);


}
.................
public void convertDollarsToEuros() {
double val = Double.parseDouble(mnozstvo.getText().toString());
double val1 = Double.parseDouble(percento.getText().toString());
double val2 = Double.parseDouble(hmotnost.getText().toString());

vysledok1.setText(Double.toString((val*val1*0.8)/(val2*0.68)));
vysledok2.setText(Double.toString(((val*val1*0.8)/(val2*0.68))/(2.1)));

text.setText(Double.toString(((val*val1*0.8)/(val2*0.68))*6.6164));



}

public void convertEurosToDollars() {

double val = Double.parseDouble(mnozstvo.getText().toString());
double val1 = Double.parseDouble(percento.getText().toString());
double val2 = Double.parseDouble(hmotnost.getText().toString());

vysledok1.setText(Double.toString((val*val1*0.8)/(val2*0.55)));
vysledok2.setText(Double.toString(((val*val1*0.8)/(val2*0.55))/(2.1)));
text.setText(Double.toString(((val*val1*0.8)/(val2*0.55))*6.6164));

Can someone help me?

Answer 1

http://docs.oracle.com/javase/6/docs/api/java/lang/Double.html#parseDouble(java.lang.String)

parseDouble will not be happy given null or ""

Answer 2

Double.parseDouble() will raise a NumberFormatException.

But instead of waiting for an Exception to happen and then handling it you can check for the length of the string before trying to parse it.

Your code should look something like this:

public void convertEurosToDollars() {
    double val = 0;
    double val1= 0;
    double val2= 0;
    if (mnozstvo.getText().length() > 0 ) {
        val = Double.parseDouble(mnozstvo.getText().toString());
    }
    if (percento.getText().length() > 0 ) {
        val2 = Double.parseDouble(percento.getText().toString());
    }
    if (hmotnost.getText().length() > 0 ) {
        val3 = Double.parseDouble(hmotnost.getText().toString());
    }       


    vysledok1.setText(Double.toString((val*val1*0.8)/(val2*0.55)));
    vysledok2.setText(Double.toString(((val*val1*0.8)/(val2*0.55))/(2.1)));
    text.setText(Double.toString(((val*val1*0.8)/(val2*0.55))*6.6164));
   }