버튼을 누르면 숫자가 증가를 해야되는데 증가가 안되네요(앱을 종료했다 키면 1씩은 증가를 하지만 더 이상은 증가가 안됩니다) [closed]

Question

package com.example.abc.egg;


import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    int count = 0;
    TextView point;
    Button btn_point;
    String sfpoint = "0";
    private SharedPreferences pref;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        point = (TextView) findViewById(R.id.tv_point);
        btn_point = (Button) findViewById(R.id.btn_point);
        SharedPreferences sf = getSharedPreferences(sfpoint, 0);
        String str = sf.getString("0", "");
        point.setText("" + str);


        btn_point.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SharedPreferences sf = getSharedPreferences(sfpoint, 0);
                String str = sf.getString("0", "");
                count = Integer.parseInt(str);

                count++;

                point.setText("" + count);


            }
        });

    }


    protected void onStop() {
        super.onStop();
        SharedPreferences sf = getSharedPreferences(sfpoint, 0);
        SharedPreferences.Editor editor = sf.edit();//저장하려면 editor가 필요
        String str = point.getText().toString(); // 사용자가 입력한 값
        editor.putString("0", str); // 입력
        editor.commit(); // 파일에 최종 반영함


    }
}