引言

因为之前没有相关经验，导致看视频理解写代码略有困难，

这将导致代码会很容易遗忘，毕竟不是自己写出来的，做个笔记加深印象

创建类及初始化

新建一个类，继承SQLiteOpenHelper，重写onCreate和onUpgrade方法

添加基本配置信息

private static final String DB_NAME = "user.db";//数据库文件名
private static final String TABLE_NAME = "user_info";//表单名
private static final int DB_VERSION = 1;//数据库版本号

使用单例模式，将构造方法用private修饰，调用父类构造方法

1	private static UserDBHelper mHelper = null;


private UserDBHelper(Context context)
{
    super(context,DB_NAME,null,DB_VERSION);
}

获取对象实例的方法


public static UserDBHelper getInstance(Context context)
{
    if (mHelper == null)
    {
        mHelper = new UserDBHelper(context);
        //为什么要传context
        //因为SQLiteOpenHelper要求传context，而UserDBHelper类调用了父类构造方法
    }
    return mHelper;

}

创建数据库后执行sql命令

@Override
public void onCreate(SQLiteDatabase db) {
    String sql = "CREATE TABLE IF NOT EXISTS "+TABLE_NAME+" (" +
            "_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," +
            " name VARCHAR NOT NULL," +
            " age INTEGER NOT NULL," +
            " height LONG NOT NULL," +
            " weight FLOAT NOT NULL," +
            " married INTEGER NOT NULL);";
    db.execSQL(sql);

}

这样初始化好了

创建读写连接

添加变量

1 2	private SQLiteDatabase mRDB = null; private SQLiteDatabase mWDB = null;

读写连接方法

public SQLiteDatabase openReadLink() {
    if (mRDB == null || !mRDB.isOpen()) {
        mRDB = mHelper.getReadableDatabase();

    }
    return mRDB;
}
public SQLiteDatabase openWriteLink() {
    if (mWDB == null || !mWDB.isOpen()) {
        mWDB = mHelper.getWritableDatabase();
    }
    return mWDB;
}

关闭读写连接

public void closeLink()
{
    if (mRDB != null && mRDB.isOpen())
    {
        mRDB.close();
        mRDB = null;
    }
    if (mWDB != null && mWDB.isOpen())
    {
        mWDB.close();
        mWDB = null;
    }

}

我感觉可以理解为关闭数据库，将数据库变量重置为null

写入的方法

自定义一个user类

public class User {

    public int id;

    public String name;
    public int age;
    public long height;
    public double weight;
    public boolean married;

    public User() {
    }

    public User(String name, int age, long height, double weight, boolean married) {
        this.name = name;
        this.age = age;
        this.height = height;
        this.weight = weight;
        this.married = married;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", height=" + height +
                ", weight=" + weight +
                ", married=" + married +
                '}';
    }
}

public long insert(User user)
{
    ContentValues values = new ContentValues();
    values.put("name",user.name);
    values.put("age",user.age);
    values.put("height",user.height);
    values.put("weight",user.weight);
    values.put("married",user.married);

   return mWDB.insert(TABLE_NAME,null,values);
   //返回的是序号，类似于...操作顺序？？？如果写入失败将返回-1
}

写入（`SqliteHelperActivity.java`）

初始化user

1	User user = null;

user = new User(name,
                Integer.parseInt(age),
                Long.parseLong(height),
                Double.parseDouble(weight),
                married);
if (mHelper.insert(user) > 0)
{
    ToastUtil.show(this,"添加成功");

}

结束语

没有jdbc基础感觉真的好难，希望坚持下去，背也得背下捏

2023-10-21 该篇文章被 QuietFall 打上标签: Android