public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//每个程序都有自己的数据库
//通过openOrCreateDatabase来打开或创建一个数据库,返回SQLiteDatabase对象
/**
* openOrCreateDatabase(String name,int mode,SQLiteDatabase.CursorFactory factory)
* name: 数据库名
* mode: 数据库权限，MODE_PRIVATE为本应用程序私有，MODE_WORLD_READABLE和MODE_WORLD_WRITEABLE分别为全局可读和可写。
* factory: 可以用来实例化一个cusor对象的工厂类
*/
SQLiteDatabase db = openOrCreateDatabase("user.db",MODE_PRIVATE,null);
//创建一个表
db.execSQL("create table if not exists userTb (" +
"_id integer primary key," +
"name text not null,age integer not null," +
"sex text not null)");
//向表中插入记录
db.execSQL("insert into userTb (name,age,sex) values ('张三',18,'女')");
db.execSQL("insert into userTb (name,age,sex) values ('李四',19,'男')");
db.execSQL("insert into userTb (name,age,sex) values ('王五',20,'女')");
//Cursor为查询结果对象，类似于JDBC中的ResultSet
Cursor queryResult = db.rawQuery("select * from userTb", null);
if (queryResult != null) {
while (queryResult.moveToNext()) {
Log.i("info", "id: " + queryResult.getInt(queryResult.getColumnIndex("_id"))
+ " 姓名: " + queryResult.getString(queryResult.getColumnIndex("name"))
+ " 年龄: " + queryResult.getInt(queryResult.getColumnIndex("age"))
+ " 性别: " + queryResult.getString(queryResult.getColumnIndex("sex")));
}
//关闭游标对象
queryResult.close();
}
//关闭数据库
db.close();
}
}

public class SQLiteHelper extends SQLiteOpenHelper {
/**
* context:上下文对象
* name:数据库名
*/
public SQLiteHelper(Context context, String name) {
super(context, name, null, 1);
}
//首次创建数据库的时候调用，一般进行建表或某些初始化的操作
@Override
public void onCreate(SQLiteDatabase db) {
//建表
db.execSQL("create table if not exists userTb (" +
"_id integer primary key," +
"name text not null,age integer not null," +
"sex text not null)");
}
//当数据库版本升级时自动调用
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}
}

public class MainActivity2 extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
//创建一个SQLiteHelper对象
SQLiteHelper helper = new SQLiteHelper(MainActivity2.this,"stu.db");
//使用getWritableDatabase()或getReadableDatabase()方法获得SQLiteDatabase对象
SQLiteDatabase db = helper.getWritableDatabase();
//插入记录
db.execSQL("insert into userTb (name,age,sex) values ('张三',18,'女')");
db.execSQL("insert into userTb (name,age,sex) values ('李四',19,'男')");
db.execSQL("insert into userTb (name,age,sex) values ('王五',20,'女')");
//获取游标对象
Cursor queryResult = db.rawQuery("select * from userTb", null);
if (queryResult != null) {
//打印所有记录
while (queryResult.moveToNext()) {
Log.i("info", "id: " + queryResult.getInt(queryResult.getColumnIndex("_id"))
+ " 姓名: " + queryResult.getString(queryResult.getColumnIndex("name"))
+ " 年龄: " + queryResult.getInt(queryResult.getColumnIndex("age"))
+ " 性别: " + queryResult.getString(queryResult.getColumnIndex("sex")));
}
//关闭游标对象
queryResult.close();
}
//关闭数据库
db.close();
}
}