鸿蒙需要的编程语言 零基础学鸿蒙编程-关系数据库

鸿蒙关系数据库是适合在移动设备上使用的轻量型关系型数据库,速度快,占用空间小.与轻量数据库适合存储少量简单类型数据相反,关系数据库适合存储大量复杂类型的数据.

1. 拷贝数据库相关依赖jar到工程目录下

• 文件：Orm_annotations_java.jar和orm_annotations_processor_java.jar存放目录样例：D:\Program Files\Huawei\sdk\java\3.0.0.0\build-tools\lib
• 拷贝到工程entry目录下libs里

2. 修改工程的build.gradle文件添加如下行：

annotationProcessor files("./libs/orm_annotations_java.jar", "./libs/orm_annotations_processor_java.jar")

3. 添加数据库对象定义:OrmUser.java

@Entity(tableName = "OrmUser") public class OrmUser extends OrmObject { @PrimaryKey(autoGenerate = true) private int id; private int userId; private String userName; public int getId() { return id; } public void setId(int id) { this.id = id; } public int getUserId() { return userId; } public void setUserId(int userId) { this.userId = userId; } public String getUserName() { return userName; } public void setUserName(String userName) { this.userName = userName; } }

4. 添加数据库操作对象定义:OrmDBDemo.java

@Database(entities = {OrmUser.class}, version = 1) public abstract class OrmDBDemo extends OrmDatabase { }

5. 修改Slice代码：MainAbilitySlice.java

public class MainAbilitySlice extends AbilitySlice { private OrmContext ormContext; @Override public void onStart(intent intent) { super.onStart(intent); super.setUIContent(ResourceTable.Layout_ability_main); findComponentById(ResourceTable.Id_writeText).setClickedListener(component -> write()); findComponentById(ResourceTable.Id_readText).setClickedListener(component -> read()); findComponentById(ResourceTable.Id_modifyText).setClickedListener(component -> modify()); findComponentById(ResourceTable.Id_delText).setClickedListener(component -> del()); initDb(); } private void initDb() { DatabaseHelper databaseHelper = new DatabaseHelper(this); ormContext = databaseHelper.getOrmContext("OrmDBTest", "OrmDBTest.db", OrmDBDemo.class); } private void write() { int userId = 1; OrmUser ormUser = new OrmUser(); ormUser.setUserId(userId); ormUser.setUserName("花生皮编程"); ormContext.insert(ormUser); ormContext.flush(); } private void read() { List<OrmUser> ormUsers = query(); new ToastDialog(getContext()).setText(ormUsers.get(0).getUserName()).show(); } private List<OrmUser> query() { //查询userId = 1的数据 int userId = 1; OrmPredicates ormPredicates = ormContext.where(OrmUser.class).equalTo("userId", userId); return ormContext.query(ormPredicates); } private void modify() { //将查询出来的数据值修改后更新到数据库 OrmUser ormUser = query().get(0); if (ormUser == null) { return; } ormUser.setUserName("花生皮編程2"); ormContext.update(ormUser); ormContext.flush(); } private void del() { //将查询出来的第一条数据从数据库中删除 OrmUser ormUser = query().get(0); if (ormUser == null) { return; } ormContext.delete(ormUser); ormContext.flush(); } }

6. 对应页面布局文件:

<?xml version="1.0" encoding="utf-8"?> <DirectionalLayout xmlns:ohos="http://schemas.huawei.com/res/ohos" ohos:height="match_parent" ohos:width="match_parent" ohos:alignment="center" ohos:orientation="vertical"> <Text ohos:id="$ id:writeText" ohos:height="match_content" ohos:width="match_content" ohos:text="写数据" ohos:text_size="20fp"/> <Text ohos:id="$ id:readText" ohos:height="match_content" ohos:width="match_content" ohos:text="读数据" ohos:text_size="20fp"/> <Text ohos:id="$ id:modifyText" ohos:height="match_content" ohos:width="match_content" ohos:text="修改数据" ohos:text_size="20fp"/> <Text ohos:id="$ id:delText" ohos:height="match_content" ohos:width="match_content" ohos:text="删除数据" ohos:text_size="20fp"/> </DirectionalLayout>

PS: 上述代码已包含数据库常见的增删改查功能，代码已优化至最简。

https://gitee.com/hspbc/harmonyos_demos/tree/master/dbDemo