Part 4: Mobile app development

In the previous episode, we looked at how to save Raspberry Pi's temperature and humidity sensor data to the Watap Project. This time, we'll look at how to query stored data using Watap's Open API and visualize it in a mobile app using Flutter. We plan to use an Android simulator as a development environment.

What to bring

1) Open API

To use the Wtab Open API, you need the following three pieces of information:

• Account API token
• Project API token
• project code

Detailed settings Watap official documentationPlease refer to

2) MXQL

MXQL is Watap's dedicated query language for querying Watap's performance data (metrics). As we saw in Part 3, MXQL can be used to visualize collected data as charts.

As shown in the example above, you can simply query the stored data.

3) MXQL Open API

MXQL can be called and results can be received via Open API. (MXQL Open API User Guide)

MXQL Open API testing

We will conduct a test to search the data based on the prepared information.

• x-whatap-token: Project API Key
• x-whatap-pcode: project id
• stime: query start time (UNIX epoch time, millisecond)
• etime: query end time (UNIX epoch time, millisecond)

View data for the last 7 days with a limit of 3.

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The results are the same as above.

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Mobile app development

Flutter

Flutter is a cross-platform framework developed by Google. It's efficient because you can develop both iOS and Android apps with a single codebase. The features are as follows:

• Using the Dart programming language
• Rich built-in widgets enable fast UI development
• Hot reload function enables real-time code modification and verification
• Provides native-level high performance

tools

The following tools must be installed for Flutter development:

1. Flutter SDK: Install the right version for the development PC's operating system

2. Android Studio: The official Android IDE

3. Android Studio plugins:

• Dart Plugins
• Flutter plugins

Detailed installation instructions Flutter official websitePlease refer to the guide at

project creation

Build and run an empty project

When you create a new Flutter project in Android Studio, a counter app example is included by default. This example code can be found in the lib/main.dart file.

Installing the library

The main libraries required for the project include:

• Dio: A powerful library for HTTP communication
• fl_chart: chart library for data visualization

Using these two libraries, we'll call WTAP's API and display the temperature and humidity data as a chart.

Main.dart screen cleanup

‍Organize lib/main.dart in a concise manner.

This is a blank screen after cleaning up unnecessary code that is automatically generated.

Writing Open API test code

Write Wtab Open API communication code.

WhaTap Open API test code

Confirm that the received data is correctly output to the AndroidStudio console.

Correct the actual operation code

Create a data model class.

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Modify the UI screen where the chart is displayed.

finishing

In this project, we looked at the entire process of storing IoT device data in Watap and visualizing it as a mobile app. The current configuration is for basic demonstration purposes, and the following additional features can be considered for actual use:

• Select a time/date range
• data filtering
• Detailed analysis tools

The full source code for this project GitHub repositoryYou can check it out at

WTAP provides various functions such as saving user data, setting notifications, and querying data through Open API. By utilizing these functions, it is possible to build a more comprehensive monitoring system by linking with existing server monitoring and APM solutions.