1.创建一个类MyUserlogDBHelper去继承sqliteOpenHelper,在该类里面创建表。
package com.example.demo;
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.sqliteDatabase;
import android.database.sqlite.sqliteOpenHelper;
import androidx.annotation.Nullable;
public class MyUserlogDBHelper extends sqliteOpenHelper {
public MyUserlogDBHelper db;
//对外提供参数,单例模式
private static sqliteOpenHelper mHelper;
public static synchronized sqliteOpenHelper getInstance(Context context){
if (mHelper==null){
mHelper=new MyUserlogDBHelper(context,"user_log",null,1);
}
return mHelper;
}
private MyUserlogDBHelper(@Nullable Context context, @Nullable String name, @Nullable sqliteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(sqliteDatabase db) {
//创建表
String sql="create table user_log (_id integer primary key autoincrement,name text)";
//拿到db执行sql语句即可
db.execsql(sql);
}
@Override
public void onUpgrade(sqliteDatabase db, int oldVersion, int newVersion) {
}
}
2.在Activity中写查询,增加,修改,删除数据的操作。
package com.example.demo;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.sqliteDatabase;
import android.database.sqlite.sqliteOpenHelper;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void create(View view) {
sqliteOpenHelper helper = MyUserlogDBHelper.getInstance(this);
sqliteDatabase readableDatabase = helper.getReadableDatabase();
}
//查询语句
public void query(View view) {
sqliteOpenHelper instance = MyUserlogDBHelper.getInstance(this);
sqliteDatabase db = instance.getReadableDatabase();
if (db.isopen()){
//查询语句
String sql="select * from user_log";
//获取游标
Cursor cursor = db.rawQuery(sql, null);
while(cursor.movetoNext()){
//不规范的写法
/*int _id=cursor.getColumnIndex("0");
int name=cursor.getColumnIndex("1");
*/
//规范的写法
int _id=cursor.getInt(cursor.getColumnIndex("_id"));
String name=cursor.getString(cursor.getColumnIndex("name"));
Log.d("数据库", "_id: "+_id+",name:"+name);
}
//关闭游标
cursor.close();
//关闭数据库
db.close();
}
}
//插入语句
public void insert(View view) {
sqliteOpenHelper instance = MyUserlogDBHelper.getInstance(this);
sqliteDatabase db = instance.getWritableDatabase();
//判断数据库是否开启
if (db.isopen()){
String sql="insert into user_log(name) values('路宇')";
db.execsql(sql);
}
db.close();
}
//修改
public void update(View view) {
sqliteOpenHelper instance = MyUserlogDBHelper.getInstance(this);
sqliteDatabase db = instance.getWritableDatabase();
if (db.isopen()){
String sql="update user_log set name=? where _id=?";
db.execsql(sql,new Object[]{"成龙","5"});
}
//关闭数据库
db.close();
}
//删除数据
public void delete(View view) {
sqliteOpenHelper instance = MyUserlogDBHelper.getInstance(this);
sqliteDatabase db = instance.getWritableDatabase();
//判断数据是否是打开状态
if (db.isopen()){
String sql="delete from user_log where _id=?";
db.execsql(sql,new Object[]{6});
}
}
}
3.布局文件。
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:orientation="vertical"
>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="创建表"
android:onClick="create" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="查询"
android:onClick="query" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="插入"
android:onClick="insert" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="修改"
android:onClick="update" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="删除"
android:onClick="delete" />
</LinearLayout>
以上就是sqlite数据库中,最简单的增删改查操作,想深入学习sqlite在项目中的实际应用,请持续关注后面博文!
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