使用TextWatcher獲取輸入到兩個edittext的值並將這些值相乘而不用按鈕。自動計算。

Question

我希望應用程序在用戶將所請求的兩個值輸入到edittext中時自動計算，而不需要按鈕。

有沒有辦法做到這一點，而不使用TextWatcher？

這裏是我的嘗試。爲什麼不起作用？在edittext中輸入數字時，應用程序強制關閉。

' 

public class BodyMassIndex extends Activity 

{ 

double result; 
    EditText age, height, weight; 

TextView tvResult; 

int ageInt; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.bmi); 
    initialize(); 

    TextWatcher textWatcher = new TextWatcher() { 

     @Override 
     public void afterTextChanged(Editable s) { 
      // TODO Auto-generated method stub 
      calculate(); 

     } 



     @Override 
     public void beforeTextChanged(CharSequence s, int start, int count, 
       int after) { 
      // TODO Auto-generated method stub 

     } 

     @Override 
     public void onTextChanged(CharSequence s, int start, int before, 
       int count) { 
      // TODO Auto-generated method stub 

     } 

    }; 

    height.addTextChangedListener(textWatcher); 
    weight.addTextChangedListener(textWatcher); 

} 

private void initialize() { 
    // TODO Auto-generated method stub 

    age = (EditText) findViewById(R.id.etAge); 
    height = (EditText) findViewById(R.id.etHeight); 
    weight = (EditText) findViewById(R.id.etWeight); 

    tvResult = (TextView) findViewById(R.id.tvResult); 


} 

private void calculate() { 
    // TODO Auto-generated method stub 


    double heightInt = 1; 
    double weightInt = 0; 

    if (height != null) 
     heightInt = Double.parseDouble(height.getText().toString()); 

    if (weight != null) 
     weightInt = Double.parseDouble(weight.getText().toString()); 

    result = weightInt/(heightInt * heightInt); 
    String textResult = "Your BMI is " + result; 
    tvResult.setText(textResult); 




}} 
' 

Answer 1

你應該設置的EditText 0它可能強制關閉，因爲你正在試圖解析從具有什麼也沒有一個EditText一個空字符串的默認值;

編輯：使用一種情況，即無論什麼你會被解析時不會拋出異常