Android 数据库 sqlite 操作

测试类

package cn.mf.cts.utils;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;

/**
 * CopyRright (c)2018-2028: chanpinxue.cn
 * Project: cts
 * Module Name: SQLiteDBUtil
 * Comments: SQLite测试类
 * JDK version used: JDK1.8
 * Author: jzh
 * Create Date: 2018-11-23
 * Modified By: jzh
 * Modified Date: 2018-11-23
 * Why & What is modified:
 * Version: <1.0>
 */
public class SQLiteDBUtil {

    private static SQLiteDBUtil dbUtil;
    private SQLiteDatabase db;

    /**
     * 单例模式
     * @return
     */
    public static SQLiteDBUtil getInstance() {
        if (dbUtil == null) {
            dbUtil = new SQLiteDBUtil();
            return dbUtil;
        }
        return dbUtil;
    }

    /**
     * 初始化/建表
     * @param context 上下文对象
     */
    public void init(Context context) {
        String path = context.getCacheDir().getPath() + "/cts.db";
        db = SQLiteDatabase.openOrCreateDatabase(path, null);
        String sql = " create table if not exists app_users "
                   + "(user_id integer primary key autoincrement, "
                   + " user_code text(50), user_name text(50) ) ";
        db.execSQL(sql);
    }

    /**
     * 新增
     */
    public long insert(String usercode, String username) {
        ContentValues cv = new ContentValues();
        cv.put("user_code", usercode);
        cv.put("user_name", username);
        long flag = db.insert("app_users", null, cv);
        return flag;
    }

    /**
     * 修改
     */
    public int update(String usercode, String username) {
        ContentValues cv = new ContentValues();
        cv.put("user_name", username);
        int flag = db.update("app_users", cv, "user_code = ?", new String[]{usercode});
        return flag;
    }

    /**
     * 删除
     */
    public int delete(String usercode) {
        int flag = db.delete("app_users", "user_code = ?", new String[]{usercode});
        return flag;
    }

    /**
     * 查询数据
     */
    public String select(String user_code) {
        String username = "";
        Cursor cursor = db.query("app_users", null, "user_code = ?",  new String[]{user_code}, null, null, null);
        while (cursor.moveToNext()) {
            int userid = cursor.getInt(cursor.getColumnIndex("user_id"));
            username = cursor.getString(cursor.getColumnIndex("user_name"));
            Log.e("sqlite", String.valueOf(userid) + " " + username);
        }
        if (cursor != null) {
            cursor.close();
        }
        return username;
    }

}

调用

// sqlite调用测试
SQLiteDBUtil db = SQLiteDBUtil.getInstance();
db.init(this);
db.insert("9001", "蒋智昊1");
db.insert("9002", "蒋智昊2");
db.insert("9003", "蒋智昊3");
db.insert("9004", "蒋智昊4");
db.update("9004", "蒋智昊5");
db.delete("9003");
String username = db.select("9004");