SharedPreferences

参考：
https://blog.youkuaiyun.com/wxyyxc1992/article/details/17222841
https://www.jianshu.com/p/13f26d68b02e
https://blog.youkuaiyun.com/mountain_hua/article/details/81431096

SharedPreferences：小偷头仓库里的东西
存取简单，，以key-Value的形式存放，可用来存放软件配置信息，如登录用户名、密码。
只能用来存放简单的数据类型，如int, String, boolean, long。
只能在同一个包内使用。

存储：管理员把东西搬进去

取出：偷东西，所以不需要管理员，直接从仓库里偷

public class MainActivity extends Activity implements View.OnClickListener{
    private Button bt;
    private TextView tv;
    private int count=0;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity);
        bt=(Button)findViewById(R.id.button);
        tv=(TextView)findViewById(R.id.textview);

        SharedPreferences settings = (SharedPreferences)getSharedPreferences("shared", MODE_PRIVATE);
        settings.getInt("mycount", 0);
        bt.setOnClickListener(this);
        int a = settings.getInt("mycount", 0);
        tv.setText(a+"");
    }
	@Override
	public void onClick(View v) {
    if(v.getId()==R.id.button) {
        SharedPreferences settings = (SharedPreferences)getSharedPreferences("shared", MODE_PRIVATE);
        count = settings.getInt("mycount", 0);
        count++;
        tv.setText(count+"");
        
        SharedPreferences.Editor editor = settings.edit();
        editor.putInt("mycount", count);
        editor.commit();

    }
}`