如果edittext留为空白，则强制为“ 0”

Question

so I have tried some of the methods in prior posts re this problem yet none of them seem to work for me (user error no doubt).

Basically my calculation button will crash if a edittext is left blank. What I need to happen is that if it is left blank, the edittext is given a value of 0.

Here is my java:

public class kCals extends AppCompatActivity {
EditText firstNumber;
EditText secondNumber;
EditText thirdNumber;
TextView addResult;
Button btnAdd;
double num1,num2,num3,sum;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_k_cals);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    this.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);

    {
    firstNumber = (EditText)findViewById(R.id.txtNumber1);
    secondNumber = (EditText)findViewById(R.id.txtNumber2);
    thirdNumber = (EditText) findViewById(R.id.txtNumber3);
    addResult = (TextView)findViewById(R.id.txtResult);
    btnAdd = (Button)findViewById(R.id.btnAdd);
    btnAdd.setOnClickListener(new View.OnClickListener()

    {public void onClick(View v) {
            num1 = Double.parseDouble(firstNumber.getText().toString());
            num2 = Double.parseDouble(secondNumber.getText().toString());
            num3 = Double.parseDouble(thirdNumber.getText().toString());
            sum = (num1 * 4) + (num2 * 4) + (num3 * 9);
            addResult.setText(String.format("%.2f", sum));}
        });

   }}}

If anyone can help with this that would be great. Cheers, Jess.

Answer 1

It would be best to have a method do this for you like the following.

public double parseDouble(String doubleText) {
    if(TextUtils.isEmpty(doubleText)) {
        return 0;
    }

    try {
        return Double.parseDouble(doubleText);
    } catch(NumberFormatException e) {
        // do something if invalid number maybe also return 0?
        return 0;
    }
}

Then your code becomes

num1 = parseDouble(firstNumber.getText().toString());
num2 = parseDouble(secondNumber.getText().toString());
num3 = parseDouble(thirdNumber.getText().toString());

You could also update the method to pass the EditText objects themselves to avoid all the getText().toString() calls if you wanted to.

Answer 2

How about making a check before u parse.

if(firstNumber.getText().toString() != ""){
    num1 = Double.parseDouble(firstNumber.getText().toString());
}
else{
    num1 = 0;
}

Note that this will still output exceptions if you allow entries other than numbers in the EditText.

Answer 3

You should try using a function to check for the text. For example :

double getValue(Editable text){
   if (text == null || text.length() == 0){
     return 0;
} else {
   return Double.parseDouble(text.toString());
}
}

and call it :

num1 = getValue(firstNumber.getText());

Answer 4

It is really basic. Parsing a String to a Double may occur some unexpected, so the try-catch is the best choice for you to solve this question.

Answer 5

Check with your edittext value length something like String s = edittext.gettext().toString(); If(s.length()!=0) Your stuff