Offline ECharts In ThingsBoard Custom Widget: A Comprehensive Guide

by Alex Johnson 68 views

So, you're looking to jazz up your ThingsBoard dashboards with some slick Apache ECharts visualizations, but you're working in an environment without internet access? No worries, you're not alone! Many folks need to run ThingsBoard in offline or on-premise setups, and getting those custom widgets working with ECharts offline is a common challenge. Let's dive into how you can make this happen.

Understanding the Challenge

First off, it's great that you've already experimented with uploading echarts.min.js as a Resource, Extension, and Module. That shows you're on the right track! The core issue here is how ThingsBoard handles these different types of resources and how they're made available to your custom widgets. When you see that "Unable to load module from URL" error, it means ThingsBoard isn't finding the ECharts library where it expects to. This usually boils down to the way the resource is configured or how your widget is trying to access it.

Why the CDN Works (and Why We Need to Ditch It for Offline)

Using the CDN (like https://cdn.jsdelivr.net/...) is the simplest way to include ECharts because it fetches the library directly from the internet. However, since you're aiming for a fully offline solution, we need to ensure that all dependencies are stored locally within your ThingsBoard instance. This involves a few key steps: uploading the ECharts library correctly, configuring your widget to find it, and verifying that everything plays nicely together.

Step-by-Step Guide to Using ECharts Offline

Here’s a detailed breakdown of how to get ECharts running offline in your custom ThingsBoard widget:

1. Download ECharts

  • First things first, you'll need the ECharts library. Download the echarts.min.js file from the official Apache ECharts website or a trusted mirror. Make sure you have the version you need, and keep it handy.

2. Upload ECharts as a Resource

  • Log into your ThingsBoard instance as a tenant administrator. Navigate to Resources in the left-hand menu.
  • Click the + button to add a new resource. Give it a descriptive name (e.g., "echarts.min.js") and choose JS Module as the resource type.
  • Upload the echarts.min.js file you downloaded earlier. Ensure the resource is marked as Public if you want it to be accessible across different dashboards and widgets.

3. Configure Your Custom Widget

  • Now, let's set up your custom widget. Go to Widget Bundles and either create a new widget bundle or edit an existing one.
  • Create a new widget (or edit the one you're working on). In the widget editor, you'll need to modify the widget's JavaScript code to load ECharts from the resource you just uploaded.

4. Referencing the Resource in Your Widget Code

  • This is where the magic happens. Instead of relying on a CDN, you'll reference the ECharts library directly from ThingsBoard's resource storage. Here’s how you can do it:
 ```javascript
 // Assuming you named your resource "echarts.min.js"
 var echarts = require('load:static/r/echarts.min.js');
 
 // Now you can use echarts in your widget
 var chart = echarts.init(element);
 
 // Your chart options
 var option = {
     // ... your chart configuration here ...
 };
 
 chart.setOption(option);
 ```

 -   **Important**: The `load:static/r/echarts.min.js` path is crucial. It tells ThingsBoard to load the resource from the static resource storage. Adjust the path if you named your resource differently.

5. Testing Your Widget

  • Save your widget and add it to a dashboard. If everything is configured correctly, your ECharts visualization should appear without needing an internet connection.
  • If you encounter any issues, open your browser's developer console to check for errors. Common problems include incorrect resource paths or issues with the ECharts configuration itself.

Troubleshooting Common Issues

Even with a detailed guide, things can sometimes go sideways. Here are a few common issues and how to tackle them:

1. Resource Path Errors

  • Problem: The most frequent issue is an incorrect resource path. Double-check that the path in your require statement matches the actual name of your resource.
  • Solution: Go back to your widget code and verify that the path is exactly as you named the resource in ThingsBoard. Remember, it’s case-sensitive!

2. Resource Not Public

  • Problem: If the resource isn't marked as public, your widget might not have the necessary permissions to access it.
  • Solution: Ensure that the resource is set to Public in the resource settings. This makes it accessible to all widgets within your tenant.

3. JavaScript Errors in the Console

  • Problem: JavaScript errors can prevent ECharts from rendering correctly. These errors might be related to the ECharts configuration or conflicts with other libraries.
  • Solution: Open your browser's developer console (usually by pressing F12) and look for any error messages. Address these errors one by one. Common issues include missing dependencies or incorrect syntax in your ECharts options.

4. Caching Issues

  • Problem: Sometimes, your browser or ThingsBoard might cache older versions of your widget or resource files.
  • Solution: Try clearing your browser's cache and restarting your ThingsBoard instance. This ensures that you're loading the latest version of your code and resources.

Advanced Tips and Tricks

Once you've got the basics down, here are some advanced tips to enhance your offline ECharts experience:

1. Bundling ECharts with Your Widget

  • For a more self-contained solution, you can bundle the ECharts library directly into your widget's JavaScript code. This involves using a tool like Webpack or Browserify to create a single JavaScript file that includes all dependencies.
  • This approach eliminates the need to upload ECharts as a separate resource, making your widget more portable and easier to deploy.

2. Using Local Storage for Resources

  • If you have multiple widgets that rely on the same resources, you can store these resources in the browser's local storage. This reduces the number of requests to the ThingsBoard server and improves performance.
  • However, be mindful of the storage limits imposed by browsers and ensure that your resources are not too large.

3. Dynamic Loading of Resources

  • For more complex scenarios, you can dynamically load resources based on certain conditions. This allows you to load only the resources that are needed for a particular widget or dashboard, optimizing performance and reducing load times.

Alternative Approaches

While uploading ECharts as a JS Module resource is the most straightforward method, here are a couple of alternative approaches you might consider:

1. Using an IFrame

  • You can create an HTML file that includes ECharts and your chart configuration, then load this HTML file within an IFrame in your custom widget.
  • This approach provides a high degree of isolation and can be useful for complex visualizations that require more control over the rendering environment.

2. Creating a Custom Widget Extension

  • For more advanced users, you can create a custom widget extension that includes the ECharts library and provides a set of reusable components for creating visualizations.
  • This approach requires more development effort but can result in a more maintainable and scalable solution.

Conclusion

Getting ECharts to work offline in a custom ThingsBoard widget might seem daunting at first, but by following these steps and troubleshooting tips, you can achieve a fully functional offline visualization solution. Remember to double-check your resource paths, ensure that your resources are public, and use the browser's developer console to diagnose any issues. With a bit of patience and persistence, you'll be able to create stunning dashboards that work seamlessly in any environment.

If you're looking for more information on Apache ECharts, be sure to visit the official Apache ECharts website. Good luck, and happy visualizing!