How to know key presses in EditText

If you have an EditText, then you can use the TextWatcher interface. In my code, search_edit is an EditText.

search_edit.addTextChangedListener(new TextWatcher() {          
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {                                   
        //here is your code
        myadapter.getFilter().filter(s);
        listview.setAdapter(myadapter); 
    }                       
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        // TODO Auto-generated method stub                          
    }                       
    @Override
    public void afterTextChanged(Editable s) {
        // TODO Auto-generated method stub                  
    }
});