Android App Crashes When Nothing Is Entered And Button Is Pressed

Hi I am working on an Android App and would like to ask for some help: The user enters a numbers on a editText and presses/clicks the button to get a conversion displayed in answer

Solution 1:

You are trying to convert an empty string to a number. What you should do is a check if the string is not empty:

Change these lines:

EditTexteditText= (EditText) findViewById(R.id.editText);
Doublenum1= Double.parseDouble(editText.getText().toString());

to

EditText editText = (EditText)findViewById(R.id.editText);
Double num1 = 0.0;
finalString myStr = editText.getText().toString();
if (!myStr.isEmpty())
{
    num1 = Double.parseDouble(myStr);
}
else
{
    Toast.makeText(getApplicationContext(), getResources().getString(R.string.noinput),
        Toast.LENGTH_LONG).show();
}

You might replace getResources().getString(R.string.noinput) (set it in your /values/strings.xml folder) by a hardcoded string (but that's not a good practice), like "You didn't enter any value"

And this:

answer.setText(ans.toString());

should be:

answer.setText("" + ans);

Solution 2:

If i understood you weel, what you are trying to achieve is this:

String input = editText.getText().toString();
    if (input.isEmpty())
        textView.setText("0.00");
    else{
    // do whatever conversions
        textView.setText(result);
   }

Solution 3:

I think this is because you are calling the toString() method on a primitive. Try this:

Replace:

answer.setText(ans.toString());

With:

answer.setText(String.valueOf(ans));