edittext上的无效双转换错误

Question

我是编程新手，我无法弄清楚为什么下面的代码会导致错误。是什么导致v1 java.lang.NumberFormatException：无效的double：？

    public void onItemSelected (AdapterView < ? > parent, View view,int                  position  , long id){

           double answer;

           TextView mTextView = (TextView) findViewById(R.id.textView9);

           EditText value;

            value = (EditText)findViewById(R.id.editText);

            if(position == 0){

            v1 = Double.parseDouble(value.getText().toString());

                mTextView.setText(Double.toString(answer));
            }

Answer 1

您需要检查您尝试解析的值是否为空

String dv = null;
if (value.getText() != null) {
    dv = value.getText().toString ();
}
if(position == 0 && dv != null){

        v1 = Double.parseDouble(dv);
        mTextView.setText(Double.toString(answer));
}