java - 生成5分钟的随机数

Question

我想创建一个数据库，基本上生成一个随机的 6 位数字 5 分钟(它可能会过期)，并且用户能够将该数字“发送”到数据库(如果它在用户获得的时间限制内)他发送邮件时的姓名、电子邮件和日期。我很困惑我该怎么做？ 在我当前的代码中，我获取了所有注册用户的列表。 我应该创建一个存储该数字的新数据库，而用户应该将该数字添加到当前数据库中吗？最好的方法是什么？

package com.example.prologue.activities;

import android.os.AsyncTask;
import android.os.Bundle;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.AppCompatTextView;
import androidx.recyclerview.widget.DefaultItemAnimator;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import com.example.prologue.R;
import com.example.prologue.adapters.UsersRecyclerAdapter;
import com.example.prologue.model.User;
import com.example.prologue.sql.DatabaseHelper;

import java.util.ArrayList;
import java.util.List;

public class UsersListActivity extends AppCompatActivity {

    private AppCompatActivity activity = UsersListActivity.this;
    private AppCompatTextView textViewName;
    private RecyclerView recyclerViewUsers;
    private List<User> listUsers;
    private UsersRecyclerAdapter usersRecyclerAdapter;
    private DatabaseHelper databaseHelper;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_users_list);
        getSupportActionBar().setTitle("");
        initViews();
        initObjects();

    }

    /**
     * This method is to initialize views
     */
    private void initViews() {
        textViewName = (AppCompatTextView) findViewById(R.id.textViewName);
        recyclerViewUsers = (RecyclerView) findViewById(R.id.recyclerViewUsers);
    }

    /**
     * This method is to initialize objects to be used
     */
    private void initObjects() {
        listUsers = new ArrayList<>();
        usersRecyclerAdapter = new UsersRecyclerAdapter(listUsers);

        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerViewUsers.setLayoutManager(mLayoutManager);
        recyclerViewUsers.setItemAnimator(new DefaultItemAnimator());
        recyclerViewUsers.setHasFixedSize(true);
        recyclerViewUsers.setAdapter(usersRecyclerAdapter);
        databaseHelper = new DatabaseHelper(activity);

        String emailFromIntent = getIntent().getStringExtra("EMAIL");
        textViewName.setText(emailFromIntent);

        getDataFromSQLite();
    }

    /**
     * This method is to fetch all user records from SQLite
     */
    private void getDataFromSQLite() {
        // AsyncTask is used that SQLite operation not blocks the UI Thread.
        new AsyncTask<Void, Void, Void>() {
            @Override
            protected Void doInBackground(Void... params) {
                listUsers.clear();
                listUsers.addAll(databaseHelper.getAllUser());

                return null;
            }

            @Override
            protected void onPostExecute(Void aVoid) {
                super.onPostExecute(aVoid);
                usersRecyclerAdapter.notifyDataSetChanged();
            }
        }.execute();
    }
}

Answer 1

用户处理程序以延迟重复任务

private int counter = 0; // global var
private int random = 0; // global var

final Handler handler = new Handler();

handler.post(r);

final Runnable r = new Runnable() {
    public void run() {
        //generate random number and do you work
        random = (int)(Math.random() * 50 + 1);
        counter++;
        // call Runnable again after 1 sec if counter <= 3000 (50 min)
        if (counter <= 3000){ // 3000 = 50min
            handler.postDelayed(this, 1000); // 1000 = 1 sec
        }
    }
};

希望这会有所帮助!