How to Apply the Textchange event on EditText

问题:

I developed one simple app, like subtraction, addition. In this app I use three EditTexts, one for answer and other two for question. I want to calculate the answer of question on text change event. But when I apply the text change event on both of this the event occur but not properly work. Because when I enter in the text in first EditText of question the event occur but it throws this exception:

07-03 16:39:48.844: E/EduApp Log :=>(12537): Error In Text change Event java.lang.NumberFormatException: unable to parse '' as integer

What do I do? I use the TextWatcher for text change event.

txtOne.addTextChangedListener(this);
txtTwo.addTextChangedListener(this);

public void afterTextChanged(Editable s) {}

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

public void onTextChanged(CharSequence s, int start, int before, int count) {}  

回答1:

I think you are receiving empty String " " which is causing this problem. Make sure you get a non-empty String from your EditText.

Consider your EditText doesn't have any value typed in, and you are trying to get its value and convert into int you will run into this kind of problem.

edittext.addTextChangedListener(new TextWatcher() {

    public void onTextChanged(CharSequence s, int start, int before,
            int count) {
            if(!s.equals("") ) { 
                //do your work here 
            }
    }



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

    }

    public void afterTextChanged(Editable s) {

    }
});

Also check this link for more idea,

https://stackoverflow.com/a/3377648/603744

回答2:

i think the best in case the edittext type is number... use the (length function) of parameter instead of (equle() function) ex:

edittext.addTextChangedListener(new TextWatcher() {

    public void onTextChanged(CharSequence s, int start, int before,
            int count) {
        if (s.length() > 0)
                { //do your work here }
        }

    }

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

    }

    public void afterTextChanged(Editable s) {

    }
});

回答3:

I used this and it's correct:

public void afterTextChanged(Editable arg0) {
    String inputs = input.getText().toString();
    Integer index=0;
    if(!inputs.equals("")) 
        index=Integer.valueOf(inputs);

}

回答4:

I think you need to check your editText value is empty or not first. Something like this:

String textValue;
textValue = edittext().getText().toString());
Log.v("","Value is " + textValue);
if(textValue != ""){
   // Call Text Change Listener Here
}else{
   // Throw error message or something
}

Hope it's help.