The Art of Data Synchronization in HarmonyOS Next: Creation and Management of Distributed Data Objects2

This article aims to deeply explore the technical details of the Huawei HarmonyOS Next system (up to API 12 as of now), and is summarized based on actual development practices. It mainly serves as a carrier for technical sharing and communication. Mistakes and omissions are inevitable. Colleagues are welcome to put forward valuable opinions and questions so that we can make progress together. This article is original content, and any form of reprint must indicate the source and the original author.

Introduction

In the intelligent ecosystem of multi-device collaboration, the distributed data object technology of Huawei HarmonyOS Next provides developers with a brand-new way of data management. It enables data to flow seamlessly between multiple devices, ensuring that users can obtain a consistent data experience on any device. This article will conduct an in-depth exploration of the lifecycle and management methods of distributed data objects, as well as how to create, synchronize, and listen for cross-device data changes through code examples.

Creation of Distributed Data Objects

The creation of distributed data objects is the first step in their application in HarmonyOS Next, involving the following key steps:

1. Define the Data Model: First, it is necessary to define the data model of the distributed data object, including its attributes and structure.
2. Initialize the Distributed Data Object: Initialize the object through APIs and set its attributes.

import distributedObject from '@ohos.data.distributedDataObject';
// Define the class of the distributed data object
class MyDistributedObject extends distributedObject.DistributedObject {
    constructor() {
        super();
        this.textData = '';
        this.numberData = 0;
    }
}
// Create an instance of the distributed data object
let myDistributedObject = new MyDistributedObject();

Synchronization of Distributed Data Objects

The synchronization of distributed data objects is the core of ensuring data consistency, including the following steps:

1. Join the Distributed Network: Ensure that the device has joined the distributed network, which is a prerequisite for data synchronization.
2. Configure the Synchronization Policy: According to the application requirements, configure the policy for data synchronization, such as automatic synchronization or manual synchronization.
3. Handle Synchronization Conflicts: Define how to resolve data conflicts, for example, taking the latest data as the standard or retaining local data.

// Join the distributed network
myDistributedObject.joinNetwork();
// Configure the synchronization policy
myDistributedObject.setSyncPolicy({
    strategy: distributedObject.SyncPolicy.AUTO_SYNC,
    conflictResolution: (local, remote) => {
        // Customize the conflict resolution logic
        return remote; // Take the remote data as the standard
    }
});

Status Monitoring and Event Handling

Monitoring the status of distributed data objects is crucial for promptly responding to data changes. The following is how to set up listeners to handle different events:

1. Data Change Monitoring: When the attributes of a distributed data object change, these changes can be monitored.
2. Network Status Monitoring: Monitor the connection status of the device in the distributed network.

// Monitor data changes
myDistributedObject.on('dataChange', (changes) => {
    changes.forEach((change) => {
        console.log(`Property ${change.field} changed to ${change.value}`);
    });
});
// Monitor network status changes
myDistributedObject.on('networkChange', (state) => {
    if (state === distributedObject.NetworkState.CONNECTED) {
        console.log('Device is now connected to the distributed network.');
    } else if (state === distributedObject.NetworkState.DISCONNECTED) {
        console.log('Device has been disconnected from the distributed network.');
    }
});

Example: Cross-Device Data Synchronization and Monitoring

The following is a complete example showing how to create a distributed data object in HarmonyOS Next and implement cross-device data synchronization and monitoring.

// Define the class of the distributed data object
class MyDistributedObject extends distributedObject.DistributedObject {
    constructor() {
        super();
        this.sharedText = 'Initial text';
    }
}
// Create an instance of the distributed data object
let myDistributedObject = new MyDistributedObject();
// Join the distributed network
myDistributedObject.joinNetwork();
// Set the data synchronization policy
myDistributedObject.setSyncPolicy({
    strategy: distributedObject.SyncPolicy.AUTO_SYNC,
    conflictResolution: (local, remote) => remote // Take the remote data as the standard
});
// Monitor data changes
myDistributedObject.on('dataChange', (changes) => {
    changes.forEach((change) => {
        if (change.field === 'sharedText') {
            console.log(`The shared text has been updated to: ${myDistributedObject.sharedText}`);
        }
    });
});
// Monitor network status changes
myDistributedObject.on('networkChange', (state) => {
    console.log(`Network state changed to: ${state}`);
});
// Update the data, triggering synchronization
myDistributedObject.sharedText = 'Updated text from Device A';

Summary

Distributed data objects are an advanced technology in Huawei HarmonyOS Next, making cross-device data synchronization simple and efficient. Through the detailed analysis and code examples in this article, we can master how to create and manage distributed data objects in HarmonyOS Next, as well as how to monitor and respond to data changes and network state changes.