Can't add setOnClickListener on function showInputDialog : I write a function to handle showing dialog but I can't use on click Listeriner to it what wrong with my code can any one tell me?

Here is my function 


     private void showInputDialog() {
    
            final Dialog dialog=new Dialog(MainDashboard.this);
            dialog.setContentView(R.layout.frg_dialog_change_pass);
            btn_save_password=(Button) findViewById(R.id.btn_save_password);
            btn_cancel_pass=(Button) findViewById(R.id.btn_cancel_pass);
            edtOldpass=(EditText) findViewById(R.id.edtOldpass);
            edtNewpass=(EditText) findViewById(R.id.edtNewpass);
            edtConfirmpass=(EditText)findViewById(R.id.edtConfirmpass);
            dialog.show();///Show the dialog.
            btn_save_password.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Toast.makeText(MainDashboard.this, "Success", Toast.LENGTH_SHORT).show();
                    dialog.cancel();
                }
            });