How to detect character key presses?

问题

I know how to listen for when the ENTER button is pressed in a TextView, as shown in the code below:

textView.setOnKeyListener(new View.OnKeyListener() {
    public boolean onKey(View v, int keyCode, KeyEvent event) {
            if((event.getAction() == KeyEvent.ACTION_DOWN) && (keyCode == KeyEvent.KEYCODE_ENTER)) {
                enterPressed();
                return true;
            }
            return false;
        }
});

However... how do I listen for when a character key (A-Z, 0-9, special characters, etc.), basically everything else other than ENTER, BACKSPACE, or SPACE, are pressed? I want to do this because I want a button to become enabled when the user has started typing text into a TextView. Strangely, the onKey() method isn't even called when these character keys are pressed, so is there another way I'm suppose to listen for them? Thanks in advance!

回答1:

Text watcher might help you

textView.addTextChangedListener(new TextWatcher(){

    @Override
    public void afterTextChanged(Editable arg0) {
        // TODO Auto-generated method stub

    }

    @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

    }

});

回答2:

"Key presses in software keyboards will generally NOT trigger this method, although some may elect to do so in some situations. Do not assume a software input method has to be key-based; even if it is, it may use key presses in a different way than you expect, so there is no way to reliably catch soft input key presses."

http://developer.android.com/reference/android/view/View.OnKeyListener.html

回答3:

you will have to write a function something like isCharacter(int), Pass the keyCode of the KeyEvent to this function check what is the range of the int - is in the character range which you want for the alphabets and numbers, if so returnTrue in you keypressed function hanlde the case of true or false returned from isCharacter...

来源：https://stackoverflow.com/questions/6515873/how-to-detect-character-key-presses

标签

android

textview

key

listener

keyevent