eclipse - 當EditText爲空時android應用程序崩潰

Question

美好的一天。我在eclipse中爲android編寫應用程序，當EditText爲空時，應用程序崩潰。我嘗試了很多方法，但不起作用。當我輸入它並且EditText是emty時，它每當它崩潰。對不起我的英語不好。 這是我的部分代碼：

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)); 

有人可以幫助我嗎？

Answer 1

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

parseDouble不會幸福給空或「」

Answer 2

Double.parseDouble()將引發一個NumberFormatException異常。

但不是等待異常發生，然後處理它，您可以在嘗試解析它之前檢查字符串的長度。

您的代碼應該是這個樣子：

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)); 
    }