问验证只允许在android中编辑文本中的数字和字符

EN

edittext.addTextChangedListener(new TextWatcher() {
                                        
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        // 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 afterTextChanged(Editable s) {
        // validation codes here
                                
        location_name=s.toString();
        Toast.makeText(getApplicationContext(),location_name, Toast.LENGTH_SHORT).show();                
        
        if (location_name.matches(".*[^a-z^0-9].*")) {
            location_name = location_name.replaceAll("[^a-z^0-9]", "");
            s.append(location_name);
            s.clear();
            Toast.makeText(getApplicationContext(),"Only lowercase letters and numbers are allowed!",Toast.LENGTH_SHORT).show();
        }                                   
    }

});     
                                    
location.add(location_name);