public void onClick(View v) {
        if (v.getId()==R.id.loadDataId){

            try {
                FileInputStream fileInputStream = openFileInput("Mydata.txt");
                StringBuffer buffer = new StringBuffer();
                int read = -1;
                while ((read =fileInputStream.read())!=-1){
                    buffer.append((char) read);
                }
                //get user name by indet of string
                String userName =buffer.substring(0,buffer.indexOf(" "));
                String userPass = buffer.substring(buffer.indexOf(" ")+1);

                unamrTextView.setText(userName);
                passTextView.setText(userPass);

            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }


            Toast.makeText(this, "Data retrive successfully", Toast.LENGTH_SHORT).show();
            }else if (v.getId()==R.id.gotoBackId){

            Intent intent = new Intent(SecondActivity.this,MainActivity.class);
            startActivity(intent);
            Toast.makeText(this, "Go to Main Activity", Toast.LENGTH_SHORT).show();
        }

        }