Android programing :Display app

 

  public void main_function()
    {
        final TextView tv1 = (TextView) findViewById(R.id.textView2);
        final EditText et2 = (EditText) findViewById(R.id.editText2);
        Button btn =  (Button) findViewById(R.id.btn_Button1);

       btn.setOnClickListener(new View.OnClickListener() {

            String str = "" ;
           public void onClick(View v) {
               str = str + et2.getText() + System.getProperty("line.separator") ;
               tv1.setText(str);
               et2.setText("");

           }
       });

    }