Design and development practice of UniApp to realize chart display and data visualization

UniApp implements the design and development practice of chart display and data visualization

Introduction:
With the advent of the big data era, data visualization has become one of the necessary tools for enterprises and individuals to analyze data. In mobile application development, how to display rich data charts on a small screen has become one of the challenges faced by developers. This article will introduce how to use the UniApp framework to realize the design and development practice of chart display and data visualization.

1. Introduction to UniApp
UniApp is a multi-terminal development framework based on Vue.js, which can be published to multiple platforms at the same time, such as WeChat applet, Alipay applet, App, etc. It provides a rich set of components and APIs, allowing developers to quickly build feature-rich mobile applications.

2. Requirements Analysis for Chart Display and Data Visualization
In mobile applications, we usually need to display multiple types of charts, such as line charts, bar charts, pie charts, etc. In actual development, we need to select appropriate charts for display based on the different characteristics and needs of the data. In addition, we also need to consider the interactivity of the chart, whether the user can zoom, drag, select, etc. on the chart.

3. Selection and use of chart components
UniApp provides some commonly used chart components, such as u-charts, echarts, etc. Among them, u-charts is a lightweight chart library based on uni-app and uView packages. It supports multiple chart types and provides a wealth of configuration options that can flexibly meet different needs.

Taking the line chart as an example, we can develop according to the following steps:

1. Introduce the component library and style:
   In the page's <script>## In the # tag, introduce the u-charts component library through the </script>import statement, and introduce the u-charts style in the

<template>
  <view class="container">
    <u-charts :option="chartOption" :canvas-id="canvasId" ref="uCharts"></u-charts>
  </view>
</template>

<script>
  import uCharts from '@/components/u-charts/u-charts.vue'
  export default {
    components: {
      uCharts
    },
    data() {
      return {
        canvasId: 'lineChart',
        chartOption: {} // 图表配置项
      }
    },
    onLoad() {
      this.initChart()
    },
    methods: {
      initChart() {
        // 初始化图表配置项
        this.chartOption = {
          // 图表数据
          series: [
            {
              type: 'line',
              data: [10, 20, 30, 40, 50, 60]
            }
          ]
        }
      }
    }
  }
</script>

<style>
  .container {
    width: 100%;
    height: 300rpx;
  }
</style>

Write chart initialization code:
2. In the
   <script><code> tag of the page, write the chart initialization code. Through the this.$refs.uCharts.initChart<code> method, you can initialize the chart and pass in the corresponding configuration items. </script>

methods: {
  initChart() {
    // 初始化图表配置项
    this.chartOption = {
      // 图表数据
      series: [
        {
          type: 'line',
          data: [10, 20, 30, 40, 50, 60]
        }
      ]
    }
    
    // 初始化图表
    this.$refs.uCharts.initChart()
  }
}

Style adjustment:
3. Adjust the style of the chart component according to needs, such as setting the width and height of the chart, etc.
   

4. Chart interaction and data update

In actual applications, we usually need to support chart interactive operations, such as zooming, dragging, selecting, etc. And when the data changes, we also need to update the display of the chart.

Taking the bar chart as an example, we can develop it according to the following steps:

Introduce the component library and style:
1. Similar to the development of the above line chart, introduce it into the page u-charts library and introduce styles on demand.
   

<template>
  <view class="container">
    <u-charts :option="chartOption" :canvas-id="canvasId" ref="uCharts" @touch-start="onTouchStart" @touch-move="onTouchMove" @touch-end="onTouchEnd"></u-charts>
  </view>
</template>

<script>
  import uCharts from '@/components/u-charts/u-charts.vue'
  export default {
    components: {
      uCharts
    },
    data() {
      return {
        canvasId: 'barChart',
        chartOption: {} // 图表配置项
      }
    },
    onLoad() {
      this.initChart()
    },
    methods: {
      initChart() {
        // 初始化图表配置项
        this.chartOption = {
          // 图表数据
          series: [
            {
              type: 'bar',
              data: [10, 20, 30, 40, 50, 60]
            }
          ]
        }
        
        // 初始化图表
        this.$refs.uCharts.initChart()
      },
      onTouchStart(e) {
        // 触摸事件开始
      },
      onTouchMove(e) {
        // 触摸事件移动
      },
      onTouchEnd(e) {
        // 触摸事件结束
      }
    }
  }
</script>

<style>
  .container {
    width: 100%;
    height: 300rpx;
  }
</style>

Chart interactive operation:
2. By monitoring touch events, the interactive operation of the chart is realized in the corresponding event processing function.
   

methods: {
  onTouchStart(e) {
    // 触摸事件开始
    this.$refs.uCharts.touchEventHandler.start(e)
  },
  onTouchMove(e) {
    // 触摸事件移动
    this.$refs.uCharts.touchEventHandler.move(e)
  },
  onTouchEnd(e) {
    // 触摸事件结束
    this.$refs.uCharts.touchEventHandler.end(e)
  }
}

Update chart data:
3. When the data changes, update the chart data and configuration items according to requirements.
   

methods: {
  initChart() {
    // 初始化图表配置项
    this.chartOption = {
      // 图表数据
      series: [
        {
          type: 'bar',
          data: [10, 20, 30, 40, 50, 60]
        }
      ]
    }
    
    // 初始化图表
    this.$refs.uCharts.initChart()
  },
  updateChart() {
    // 更新图表数据
    this.chartOption.series[0].data = [30, 40, 50, 60, 70, 80]
    // 更新图表配置项
    this.$nextTick(() => {
      this.$refs.uCharts.updateData()
    })
  }
}

5. Summary

With the support of UniApp, we can easily realize the design and development of chart display and data visualization. This article takes u-charts as an example to introduce in detail how to select and use chart components, and implement chart interactive operations and data updates. In actual development, we can flexibly use chart components and related APIs according to specific needs to create rich data visualization applications.

6. References

[UniApp Documentation](https://uniapp.dcloud.io/)
• [u-charts Official Documentation](https ://github.com/16cheng/u-charts)

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