参考: 基本的なSharedPreferencesの使い方 SharedPreferencesの使い方(基礎編)
サンプルコード
public class MainActivity extends AppCompatActivity{ private SharedPreferences data; private SharedPreferences.Editor editor; private Button btn_up, btn_show; private TextView txt; private Integer cnt; protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); data = getSharedPreferences("DataSave", Context.MODE_PRIVATE); editor = data.edit(); cnt = getCount(); txt = (TextView)findViewById(R.id.txt_count); showCount(); btn_up = (Button)findViewById(R.id.btn_up); btn_up.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { cnt += 1; saveCount(); } }); btn_show = (Button)findViewById(R.id.btn_show); btn_show.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { showCount(); } }); } private void saveCount() { editor.putInt("count", cnt); editor.apply(); } private Integer getCount() { return data.getInt("count", 0); } private void showCount() { txt.setText(String.valueOf(cnt)); } }