本节以一个“账本”为例，使用关系型数据库的相关接口实现了对账单的增、删、改、查操作。
为了演示该功能，创建一个名为“ArkTSRdb”的应用，源码见文末。
操作RdbStore
首先要获取一个RdbStore来操作关系型数据库。
在src/main/ets目录下创建名为“common/database”目录，用于存放常用的数据库相关的类。在该common/database目录创建工具类Rdb，代码如下：
import { relationalStore } from '@kit.ArkData';
import CommonConstants from '../constants/CommonConstants';
export default class Rdb {
private rdbStore: relationalStore.RdbStore | null = null;
private tableName: string;
private sqlCreateTable: string;
private columns: Array<string>;
constructor(tableName: string, sqlCreateTable: string, columns: Array<string>) {
this.tableName = tableName;
this.sqlCreateTable = sqlCreateTable;
this.columns = columns;
}
getRdbStore(callback: Function = () => {
}) {
if (!callback || typeof callback === 'undefined' || callback === undefined) {
console.info('getRdbStore() has no callback!');
return;
}
if (this.rdbStore !== null) {
console.info('The rdbStore exists.');
callback();
return
}
let context: Context = getContext(this) as Context;
relationalStore.getRdbStore(context, CommonConstants.STORE_CONFIG, (err, rdb) => {
if (err) {
console.error(`gerRdbStore() failed, err: ${err}`);
return;
}
this.rdbStore = rdb;
this.rdbStore.executeSql(this.sqlCreateTable);
console.info('getRdbStore() finished.');
callback();
});
}
// ...
}
数据库所需要的配置存在以下common/constants/CommonConstants.ets文件中：
import { relationalStore } from '@kit.ArkData';
export default class CommonConstants {
/**
* Rdb database config.
*/
static readonly STORE_CONFIG: relationalStore.StoreConfig = {
name: 'database.db',
securityLevel: relationalStore.SecurityLevel.S1
};
}
为了对数据进行增、删、改、查操作，我们要封装对应接口。关系型数据库接口提供的增、删、改、查方法均有callback和Promise两种异步回调方式，本例子使用了callback异步回调。代码如下：
insertData(data: relationalStore.ValuesBucket, callback: Function = () => {
}) {
if (!callback || typeof callback === 'undefined' || callback === undefined) {
console.info('insertData() has no callback!');
return;
}
let resFlag: boolean = false;
const valueBucket: relationalStore.ValuesBucket = data;
if (this.rdbStore) {
this.rdbStore.insert(this.tableName, valueBucket, (err, ret) => {
if (err) {
console.error(`insertData() failed, err: ${err}`);
callback(resFlag);
return;
}
console.info(`insertData() finished: ${ret}`);
callback(ret);
});
}
}
deleteData(predicates: relationalStore.RdbPredicates, callback: Function = () => {
}) {
if (!callback || typeof callback === 'undefined' || callback === undefined) {
console.info('deleteData() has no callback!');
return;
}
let resFlag: boolean = false;
if (this.rdbStore) {
this.rdbStore.delete(predicates, (err, ret) => {
if (err) {
console.error(`deleteData() failed, err: ${err}`);
callback(resFlag);
return;
}
console.info(`deleteData() finished: ${ret}`);
callback(!resFlag);
});
}
}
updateData(predicates: relationalStore.RdbPredicates, data: relationalStore.ValuesBucket, callback: Function = () => {
}) {
if (!callback || typeof callback === 'undefined' || callback === undefined) {
console.info('updateDate() has no callback!');
return;
}
let resFlag: boolean = false;
const valueBucket: relationalStore.ValuesBucket = data;
if (this.rdbStore) {
this.rdbStore.update(valueBucket, predicates, (err, ret) => {
if (err) {
console.error(`updateData() failed, err: ${err}`);
callback(resFlag);
return;
}
console.info(`updateData() finished: ${ret}`);
callback(!resFlag);
});
}
}
query(predicates: relationalStore.RdbPredicates, callback: Function = () => {
}) {
if (!callback || typeof callback === 'undefined' || callback === undefined) {
console.info('query() has no callback!');
return;
}
if (this.rdbStore) {
this.rdbStore.query(predicates, this.columns, (err, resultSet) => {
if (err) {
console.error(`query() failed, err: ${err}`);
return;
}
console.info('query() finished.');
callback(resultSet);
resultSet.close();
});
}
}
账目信息的表示
由于需要记录账目的类型（收入/支出）、具体类别和金额，因此我们需要创建一张存储账目信息的表，SQL脚本下：
export default class CommonConstants {
// ...
/**
* Account table config.
*/
static readonly ACCOUNT_TABLE: TableConfig = {
tableName: 'accountTable',
sqlCreate: 'CREATE TABLE IF NOT EXISTS accountTable(id INTEGER PRIMARY KEY AUTOINCREMENT, accountType INTEGER, ' +
'typeText TEXT, amount INTEGER)',
columns: ['id', 'accountType', 'typeText', 'amount']
};
}
interface TableConfig {
tableName: string;
sqlCreate: string;
columns: Array<string>;
}
accountTable表的各字段含义如下：
- id：主键。
- accountType：账目类型。0表示支出；1表示收入。
- typeText：账目的具体类别。
- amount：账目金额。
在src/main/ets目录下创建名为“viewmodel”目录，并在该目录下创建与上述脚本对应的类AccountData，代码如下：
export default class AccountData {
id: number = -1;
accountType: number = 0;
typeText: string = '';
amount: number = 0;
}
操作账目信息表
创建针对账目信息表的操作类common/database/tables/AccountTable.ets。AccountTable类封装了增、删、改、查接口。代码如下：
import { relationalStore } from '@kit.ArkData';
import AccountData from '../../../viewmodel/AccountData';
import CommonConstants from '../../constants/CommonConstants';
import Rdb from '../Rdb';
export default class AccountTable {
private accountTable = new Rdb(CommonConstants.ACCOUNT_TABLE.tableName, CommonConstants.ACCOUNT_TABLE.sqlCreate,
CommonConstants.ACCOUNT_TABLE.columns);
constructor(callback: Function = () => {
}) {
this.accountTable.getRdbStore(callback);
}
getRdbStore(callback: Function = () => {
}) {
this.accountTable.getRdbStore(callback);
}
insertData(account: AccountData, callback: Function) {
const valueBucket: relationalStore.ValuesBucket = generateBucket(account);
this.accountTable.insertData(valueBucket, callback);
}
deleteData(account: AccountData, callback: Function) {
let predicates = new relationalStore.RdbPredicates(CommonConstants.ACCOUNT_TABLE.tableName);
predicates.equalTo('id', account.id);
this.accountTable.deleteData(predicates, callback);
}
updateData(account: AccountData, callback: Function) {
const valueBucket: relationalStore.ValuesBucket = generateBucket(account);
let predicates = new relationalStore.RdbPredicates(CommonConstants.ACCOUNT_TABLE.tableName);
predicates.equalTo('id', account.id);
this.accountTable.updateData(predicates, valueBucket, callback);
}
query(amount: number, callback: Function, isAll: boolean = true) {
let predicates = new relationalStore.RdbPredicates(CommonConstants.ACCOUNT_TABLE.tableName);
if (!isAll) {
predicates.equalTo('amount', amount);
}
this.accountTable.query(predicates, (resultSet: relationalStore.ResultSet) => {
let count: number = resultSet.rowCount;
if (count === 0 || typeof count === 'string') {
console.log('Query no results!');
callback([]);
} else {
resultSet.goToFirstRow();
const result: AccountData[] = [];
for (let i = 0; i < count; i++) {
let tmp: AccountData = {
id: 0, accountType: 0, typeText: '', amount: 0
};
tmp.id = resultSet.getDouble(resultSet.getColumnIndex('id'));
tmp.accountType = resultSet.getDouble(resultSet.getColumnIndex('accountType'));
tmp.typeText = resultSet.getString(resultSet.getColumnIndex('typeText'));
tmp.amount = resultSet.getDouble(resultSet.getColumnIndex('amount'));
result[i] = tmp;
resultSet.goToNextRow();
}
callback(result);
}
});
}
}
function generateBucket(account: AccountData): relationalStore.ValuesBucket {
let obj: relationalStore.ValuesBucket = {};
obj.accountType = account.accountType;
obj.typeText = account.typeText;
obj.amount = account.amount;
return obj;
}
设计界面
为了简化程序，突出核心逻辑，我们的界面设计的非常简单，只是一个Text组件和四个Button组件。四个Button组件用于触发增、删、改、查操作，而Text组件用于展示每次操作后的结果。修改Index代码如下：
import AccountTable from '../common/database/tables/AccountTable';
import AccountData from '../viewmodel/AccountData';
@Entry
@Component
struct Index {
@State message: string = 'Hello World'
private accountTable = new AccountTable();
build() {
Row() {
Column() {
Text(this.message)
.fontSize(50)
.fontWeight(FontWeight.Bold)
// 增加
Button(('增加'), { type: ButtonType.Capsule })
.width(140)
.fontSize(40)
.fontWeight(FontWeight.Medium)
.margin({ top: 20, bottom: 20 })
.onClick(() => {
let newAccount: AccountData = { id: 1, accountType: 0, typeText: '苹果', amount: 0 };
this.accountTable.insertData(newAccount, () => {
})
})
// 查询
Button(('查询'), { type: ButtonType.Capsule })
.width(140)
.fontSize(40)
.fontWeight(FontWeight.Medium)
.margin({ top: 20, bottom: 20 })
.onClick(() => {
this.accountTable.query(0, (result: AccountData[]) => {
this.message = JSON.stringify(result);
}, true);
})
// 修改
Button(('修改'), { type: ButtonType.Capsule })
.width(140)
.fontSize(40)
.fontWeight(FontWeight.Medium)
.margin({ top: 20, bottom: 20 })
.onClick(() => {
let newAccount: AccountData = { id: 1, accountType: 1, typeText: '栗子', amount: 1 };
this.accountTable.updateData(newAccount, () => {
})
})
// 删除
Button(('删除'), { type: ButtonType.Capsule })
.width(140)
.fontSize(40)
.fontWeight(FontWeight.Medium)
.margin({ top: 20, bottom: 20 })
.onClick(() => {
let newAccount: AccountData = { id: 1, accountType: 1, typeText: '栗子', amount: 1 };
this.accountTable.deleteData(newAccount, () => {
})
})
}
.width('100%')
}
.height('100%')
}
}
上述代码，在aboutToAppear生命周期阶段，初始化了数据库。点击“新增”会将预设好的数据“{ id: 1, accountType: 0, typeText: '苹果', amount: 0 }”写入到数据库。点击“修改”会将预设好的“{ id: 1, accountType: 1, typeText: '栗子', amount: 1 }”的数据更新到数据库。点击“删除”则会将预设好的“{ id: 1, accountType: 1, typeText: '栗子', amount: 1 }”的数据从数据库删除。
运行
运行应用显示的界面效果如下图10-3所示。
当用户点击“增加”后再点击“查询”时，界面如下图10-4所示，证明数据已经成功写入数据库。
当用户点击“修改”后再点击“查询”时，界面如下图10-5所示，证明数据已经被修改并更新回数据库。
当用户点击“删除”后再点击“查询”时，界面如下图10-6所示，证明数据已经从数据库删除。
源码
- 《跟老卫学HarmonyOS开发》 开源免费教程，https://github.com/waylau/harmonyos-tutorial
點擊查看更多內容
為 TA 點贊
評論
評論
共同學習，寫下你的評論
評論加載中...
作者其他優質文章
正在加載中
感謝您的支持，我會繼續努力的～
掃碼打賞，你說多少就多少
贊賞金額會直接到老師賬戶
支付方式
打開微信掃一掃，即可進行掃碼打賞哦