Android React-Native Realm 基础用法总结

最新推荐文章于 2024-05-04 18:26:26 发布

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本文介绍如何在React Native项目中配置并使用Realm数据库，包括环境搭建步骤、基本的增删改查操作示例。

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一、环境配置
1、创建一个ReactNative项目（RealmDemo）

react-native init RealmDemo

2、切换目录

cd RealmDemo

3、添加realm依赖库

npm install --save realm

4、关联realm库

rnpm link realm

注意：
如果关联失败，出现如下错误：

rnpm-link info Linking realm android dependency
rnpm-link info Android module realm has been successfully linked
rnpm-link info Linking realm ios dependency
rnpm-link info iOS module realm has been successfully linked
rnpm-link ERR! It seems something went wrong while linking. Error: spawn UNKNOWN
Please file an issue here: https://github.com/rnpm/rnpm/issues

则需要在 MainApplication 中添加

new RealmReactPackage()

不然会在运行时报错：

android Missing Realm constructor - please ensure RealmReact framework is included

还需要注意的是，添加过程中有可能出现很多奇怪的现象，有可能链接不上，也可能链接上了没有自动添加代码，需要手动处理：

settings.gradle中是否存在下面的代码，如不存在手动添加

include ':realm'
project(':realm').projectDir = new File(rootProject.projectDir, '../node_modules/realm/android')

app->build.gradle中是否存在如下代码

dependencies {
    compile project(':realm')//是否存在，不存在手动添加
    compile fileTree(dir: "libs", include: ["*.jar"])
    compile "com.android.support:appcompat-v7:23.0.1"
}

5、运行项目即可

react-native run-android

目前为止，Realm库就算配置成功了

二、Realm具体操作
作为一个数据库，最基本的增删改查是必须的，
1、建表
primaryKey属性，该属性的类型可以为string和int类型。声明主键之后，在更新和设置值的时候该值必须保持唯一。一旦一个使用主键的对象被添加到Realm之后，该主键值就无法被修改啦。

   const CarSchema = {
            name: 'Car',
            primaryKey: 'id',
            properties: {
                id: 'int',
                car_type: 'string',
                car_name: 'string',
                driver_name: 'string',
                 phone: {type: 'string', default: '10086'},//添加默认值的写法
            }
        };
  //初始化Realm
  let realm = new Realm({schema: [CarSchema]});

2、写数据
2.1 增

  realm.write(()=> {
                            realm.create('Car', {id: 1, car_type: 'QQ', car_name: 'SB001', driver_name: '张三'});
                            realm.create('Car', {id: 2, car_type: '宝马', car_name: 'SB002', driver_name: '李四'});
                            realm.create('Car', {id: 3, car_type: '奔驰', car_name: 'SB003', driver_name: '王五'});
                        })

2.2 删

 realm.write(()=> {
                            let cars = realm.objects('Car');
                            let car = cars.filtered('id==3');
                            realm.delete(car);
                        });

2.3 改

//更新id = 1的数据
                        realm.write(()=> {
                            realm.create('Car', {id: 2, driver_name: 'feiyang'}, true)
                            ToastAndroid.show("修改完成...", ToastAndroid.SHORT);
                        });

2.4 查

根据id=2 进行查询数据

  let cars = realm.objects('Car');
                        let car = cars.filtered('id==2');
                        if (car) {
                            ToastAndroid.show('Car的数据为，'
                                + '编号=' + car[0].id
                                + 'car_type=' + car[0].car_type
                                + 'car_name=' + car[0].car_name
                                + 'driver_name=' + car[0].driver_name, ToastAndroid.SHORT);
                        }

查询所有

 let cars = realm.objects('Car');
                        ToastAndroid.show('Car的数据为，'+cars.length, ToastAndroid.SHORT);

下边是完整代码

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 * @flow
 */

import React, {Component} from 'react';


import {
    AppRegistry,
    StyleSheet,
    Text,
    View,
    Image,
    TouchableHighlight,
    ToastAndroid,

} from 'react-native';

const Realm = require('realm');

class CustomButton extends Component {
    render() {
        return (
            <TouchableHighlight
                style={styles.button}
                underlayColor="#a5a5a5"
                onPress={this.props.onPress}>

                <Text style={styles.buttonText}>{this.props.text}</Text>
            </TouchableHighlight>
        );
    }
}

class Test extends Component {

    render() {
        const CarSchema = {
            name: 'Car',
            primaryKey: 'id',
            properties: {
                id: 'int',
                car_type: 'string',
                car_name: 'string',
                driver_name: 'string',
            }
        };

        //初始化Realm
        let realm = new Realm({schema: [CarSchema]});
        return (
            <View style={{marginTop: 20}}>
                <Text style={styles.welcome}>
                    Realm基础使用实例-增删改查
                </Text>
                <CustomButton
                    text="表新增"
                    onPress={()=>
                        realm.write(()=> {
                            realm.create('Car', {id: 1, car_type: 'QQ', car_name: 'SB001', driver_name: '张三'});
                            realm.create('Car', {id: 2, car_type: '宝马', car_name: 'SB002', driver_name: '李四'});
                            realm.create('Car', {id: 3, car_type: '奔驰', car_name: 'SB003', driver_name: '王五'});
                            realm.create('Car', {id: 4, car_type: '劳斯莱斯', car_name: 'SB004', driver_name: '张六'});
                            realm.create('Car', {id: 5, car_type: '比亚迪', car_name: 'SB005', driver_name: '理七'});
                            ToastAndroid.show('添加数据完成', ToastAndroid.SHORT);
                        })
                    }/>

                <CustomButton
                    text="表修改"
                    onPress={()=> {
                        //更新id = 1的数据
                        realm.write(()=> {
                            realm.create('Car', {id: 2, driver_name: 'feiyang'}, true)
                            ToastAndroid.show("修改完成...", ToastAndroid.SHORT);
                        });
                    }}
                />

                <CustomButton
                    text="表数据删除-删除id=3的数据"
                    onPress={()=> {
                        realm.write(()=> {
                            let cars = realm.objects('Car');
                            let car = cars.filtered('id==3');
                            realm.delete(car);
                        });
                    }}
                />

                <CustomButton
                    text="查询所有数据"
                    onPress={()=> {
                        let cars = realm.objects('Car');
                        ToastAndroid.show('Car的数据为，'+cars.length, ToastAndroid.SHORT);
                    }}
                />
                <CustomButton
                    text="根据id=2 进行查询数据"
                    onPress={()=> {
                        let cars = realm.objects('Car');
                        let car = cars.filtered('id==2');
                        if (car) {
                            ToastAndroid.show('Car的数据为，'
                                + '编号=' + car[0].id
                                + 'car_type=' + car[0].car_type
                                + 'car_name=' + car[0].car_name
                                + 'driver_name=' + car[0].driver_name, ToastAndroid.SHORT);
                        }
                    }}
                />
            </View>
        )
    }


}


const styles = StyleSheet.create({
    welcom: {
        fontSize: 20,
        textAlign: 'center',
        margin: 10,
    },
    button: {
        margin: 3,
        backgroundColor: 'white',
        padding: 10,
        borderBottomWidth: StyleSheet.hairlineWidth,
        borderBottomColor: '#cdcdcd'
    },
});
AppRegistry.registerComponent('RealmDemo', () => Test);