How to get the text value of a button from another layout?

First of all, I have searched in forum for "How to get text from edittext in other layout", and try many other way then I decide to I use LayoutInflater but it does not help.

The implementation of LayoutInflater (I follow this guide)

LayoutInflater factory = getLayoutInflater();
View regisText = factory.inflate(R.layout.regis, null);
EditText user = (EditText) regisText.findViewById(R.id.edt1); 
String usr = user.getText().toString(); 

My parent layout is named activity_input.xml having 3 buttons (I do not set text button). I put only button Id for easy view.

<Button
    android:id="@+id/btn1"
</Button>

<Button
    android:id="@+id/btn2"
</Button>

<Button
    android:id="@+id/btn3"
</Button>

After I click a button, one dialog appears to select value (1, 2 or 3) to set the button display text (1, 2 or 3) in activity_input.xml.

final Dialog dialog1 = new Dialog(user_input.this);
            dialog1.setTitle("Select a Number");
            dialog1.setContentView(R.layout.game_dialog);
            dialog1.show();

            button1 = (Button) dialog1.findViewById(R.id.btn1);
            button1.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Button p1_btn = (Button) findViewById(x);
                    p1_btn.setText("1");
                    dialog1.dismiss();
                }
            });

The onClick works perfect.

But my prolem is that I want to get the text of the button in parent layout again, I try to implement Layoutinflater but it does not work, here is the code.

LayoutInflater f1 = getLayoutInflater();
    View v1 = f1.inflate(R.layout.activity_input, null);
    Button btn1 = (Button) v1.findViewById(R.id.b1);
    String t1 = btn1.getText().toString();

I check to make sure that the String t1 is retrieve successfully by print the string but it shows nothing

Hope you guide help me as soon as possible!

Thanks you very much.