將兩個edittext值加在一起並在另一個edittext中顯示結果

Question

我試圖將兩個EditText值的值加在一起。我使用了另一個例子，其中我可以得到從另一個EditText值中減去一個EditText值並將結果顯示在EditText中的結果。但是，我似乎無法弄清楚如何將兩者加在一起並得到結果。當前兩個EditText字段中有值時，應自動計算結果。

我的代碼如下：

public void afterTextChanged(Editable s) 
{ 
    eAmountReceived = (EditText) findViewById(R.id.amountReceived); 
    eTotalCost = (EditText) findViewById(R.id.orderTotal); 
    eTip = (EditText) findViewById(R.id.tip); 
    eMileage = (EditText) findViewById(R.id.mileage); 
    eGrandTotal = (EditText) findViewById(R.id.grandTotal); 

    sAmountReceived = eAmountReceived.getText().toString(); 
    sTotalCost = eTotalCost.getText().toString(); 
    sMileage = eMileage.getText().toString(); 
    sTip = eTip.getText().toString(); 

    try 
    { 
     dAmountReceived = Double.parseDouble(sAmountReceived); 
     dTotalCost = Double.parseDouble(sTotalCost); 
     dSubtract = dAmountReceived - dTotalCost; 
     dMileage = Double.parseDouble(sMileage); 
     dGrandTotal = dSubtract + dMileage; 


     dAdd = dTotalCost + dSubtract; 


    } catch (NumberFormatException e){} 

    sTip = String.valueOf(dSubtract); 

    DecimalFormat df = new DecimalFormat("0.00"); 
    sTip = df.format(dSubtract); 

    eTip.setText(sTip); 

    sGrandTotal = String.valueOf(dGrandTotal); 

    sGrandTotal = df.format(dGrandTotal); 

    eGrandTotal.setText(sGrandTotal); 
} 

「STIP」 是從AmountReceived減去TOTALCOST的結果。因此，當用戶輸入交易的總成本，然後鍵入他們從客戶那裏收到的金額時，它會自動從客戶計算他們的提示。

我試圖做到這一點的反面，但我試過的一切都會導致錯誤，或者只是不起作用。我希望它是如果用戶鍵入totalCost和提示，它顯示AmountReceived。提前感謝任何能指引我朝着正確方向的人！

編輯：更新後的代碼

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    eAmountReceived = (EditText) findViewById(R.id.amountReceived); 
    eTotalCost = (EditText) findViewById(R.id.orderTotal); 
    eTip = (EditText) findViewById(R.id.tip); 
    eMileage = (EditText) findViewById(R.id.mileage); 
    eGrandTotal = (EditText) findViewById(R.id.grandTotal); 

    eAmountReceived.addTextChangedListener(this); 
    //eTotalCost.addTextChangedListener(this); 
    eTip.addTextChangedListener(this); 
    //eMileage.addTextChangedListener(this); 
    //eGrandTotal.addTextChangedListener(this); 

    eTip.addTextChangedListener(new TextWatcher() 
    { 
     @Override 
     public void beforeTextChanged(CharSequence s, int start, 
             int count, int after){} 

     @Override 
     public void onTextChanged(CharSequence s, int start, 
            int before, int count) 
     { 
      if(eTip.isFocused() && isSet(eAmountReceived) && isSet(eTotalCost)) 
      { 
       updateSubtract(); 
      } 
     } 

     @Override 
     public void afterTextChanged(Editable s){} 
    }); 

    eAmountReceived.addTextChangedListener(new TextWatcher() 
    { 
     @Override 
     public void beforeTextChanged(CharSequence s, int start, 
             int count, int after){} 

     @Override 
     public void onTextChanged(CharSequence s, int start, 
            int before, int count) 
     { 
      if(eAmountReceived.isFocused() && isSet(eTotalCost) && isSet(eTip)) 
      { 
       updateAdd(); 
      } 
     } 

     @Override 
     public void afterTextChanged(Editable s){} 
    }); 
} 

private void updateAdd() 
{ 
    double dTotalCost = Double.valueOf(eTotalCost.getText().toString()); 
    double dTip = Double.valueOf(eTip.getText().toString()); 
    eAmountReceived.setText(String.valueOf(dTotalCost + dTip)); 
} 

private void updateSubtract() 
{ 
    double dAmountReceived = Double.valueOf(eAmountReceived.getText().toString()); 
    double dTotalCost = Double.valueOf(eTotalCost.getText().toString()); 
    eTip.setText(String.valueOf(dAmountReceived - dTotalCost)); 
} 

private boolean isSet(EditText editText) 
{ 
    return !editText.getText().toString().matches(""); 
} 

@Override 
public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) { 

} 

@Override 
public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) { 
    updateAdd(); 
    updateSubtract(); 
} 

@Override 
public void afterTextChanged(Editable editable) { 

} 

Answer 1

對於每一個EditText上添加文字更改偵聽器。例如，偵聽dTotalCost或dSubtract應該是這樣的：

dTotalCost.addTextChangedListener(new TextWatcher() { 

@Override 
public void afterTextChanged(Editable s) {} 

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

@Override  
public void onTextChanged(CharSequence s, int start, 
int before, int count) { 
    if(s.length() != 0) 
    dAdd = dTotalCost + dSubtract; 
    } 
}); 

編輯：添加接口TextWatcherand它添加到editexts

public class YourActivity extends Activity implements TextWatcher { 
/* initializations 
********** 
*/ 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

eAmountReceived = (EditText) findViewById(R.id.amountReceived); 
eTotalCost = (EditText) findViewById(R.id.orderTotal); 
eTip = (EditText) findViewById(R.id.tip); 
eMileage = (EditText) findViewById(R.id.mileage); 
eGrandTotal = (EditText) findViewById(R.id.grandTotal); 

eAmountReceived.addTextChangedListener(this); 
eTotalCost.addTextChangedListener(this); 
eTip.addTextChangedListener(this); 
eMileage.addTextChangedListener(this); 
eGrandTotal.addTextChangedListener(this); 

// put listener only to the fields you need 

} 

// implement interface methods 

@Override 
public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) { 

} 

@Override 
public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) { 

// THIS IS CALLED EVERY TIME CHARACTER IS WRITTEN 
// HERE YOU CAN CALL YOUR METHODS FOR CALCULATIONS i.e. afterTextChanged 

afterTextChangedCalculations(); 

} 

@Override 
public void afterTextChanged(Editable editable) { 

// This method is called to notify you that, somewhere within s, the text has been changed. 

}