HarmonyOS NEXT Development Case: Light Intensity Meter

The following example demonstrates how to create a light intensity meter application using HarmonyOS NEXT's sensor capabilities. This application monitors ambient light levels through the device's light sensor and provides corresponding environmental descriptions and activity recommendations. Implementation Code import { sensor } from '@kit.SensorServiceKit'; // Import sensor service kit import { BusinessError } from '@kit.BasicServicesKit'; // Import business error classes // Class representing light intensity range information class LightIntensityItem { luxStart: number; // Starting lux value of the range luxEnd: number; // Ending lux value of the range type: string; // Intensity classification type description: string; // Environmental description recommendation: string; // Activity recommendation // Constructor to initialize object properties constructor(luxStart: number, luxEnd: number, type: string, description: string, recommendation: string) { this.luxStart = luxStart; this.luxEnd = luxEnd; this.type = type; this.description = description; this.recommendation = recommendation; } } // Light intensity meter component using decorators @Entry @Component struct LightIntensityMeter { @State currentType: string = ""; // Current light intensity type @State currentIntensity: number = 0; // Current light intensity value @State lightIntensityList: LightIntensityItem[] = [ // Light intensity range configuration new LightIntensityItem(0, 1, 'Extreme Dark', 'Outdoor night with minimal light', 'Avoid all activities, rest recommended'), new LightIntensityItem(1, 10, 'Very Dark', 'Indoor night with weak lighting', 'Suitable for sleep, avoid electronics'), new LightIntensityItem(10, 50, 'Dark', 'Dawn/dusk natural light', 'Casual relaxation, avoid prolonged reading'), new LightIntensityItem(50, 100, 'Dim', 'Cloudy day indoor light', 'Daily activities, short reading sessions'), new LightIntensityItem(100, 300, 'Moderate', 'Cloudy day indoor light', 'Work/study, moderate reading'), new LightIntensityItem(300, 500, 'Bright', 'Sunny day indoor light', 'Extended reading/work'), new LightIntensityItem(500, 1000, 'Very Bright', 'Outdoor cloudy light', 'Outdoor activities, sun protection'), new LightIntensityItem(1000, 100000, 'Overload', 'Direct noon sunlight', 'Avoid sun exposure, use sunglasses'), ]; // Component lifecycle method - before appearance aboutToAppear(): void { sensor.getSensorList((error: BusinessError) => { // Get sensor list if (error) { console.error('Sensor list fetch failed', error); return; } this.startLightIntensityUpdates(); // Start light sensor monitoring }); } // Start light sensor updates private startLightIntensityUpdates(): void { sensor.on(sensor.SensorId.AMBIENT_LIGHT, (data) => { // Ambient light sensor listener console.info(`Current intensity: ${data.intensity}`); this.currentIntensity = data.intensity; for (const item of this.lightIntensityList) { if (data.intensity >= item.luxStart && data.intensity 1000 ? 1000 : this.currentIntensity, min: 0, max: 1000 }) { Column() { Text(`${Math.floor(this.currentIntensity)}`) .fontSize(25) .fontWeight(FontWeight.Medium) .fontColor("#323232") .height('30%') .textAlign(TextAlign.Center) .margin({ top: '22.2%' }) .textOverflow({ overflow: TextOverflow.Ellipsis }) .maxLines(1); Text(`${this.currentType}`) .fontSize(16) .fontColor("#848484") .fontWeight(FontWeight.Regular) .width('47.4%') .height('15%') .textAlign(TextAlign.Center) .backgroundColor("#e4e4e4") .borderRadius(5); }.width('100%'); } .startAngle(225) .endAngle(135) .height(250) .strokeWidth(18) .description(null) .trackShadow({ radius: 7, offsetX: 7, offsetY: 7 }) .padding({ top: 30 }); }.width('100%').justifyContent(FlexAlign.Center); Column() { // Information list ForEach(this.lightIntensityList, (item: LightIntensityItem, index: number) => { Row() { Text(`${item.luxStart}~${item.luxEnd}Lux `) .fontSize('25lpx') .textAlign(TextAlign.Start) .fontColor("#3d3d3d") .width('220lpx') Text(`${item.description}\n${item.recommendation}`) .fontSize('23lpx') .textAlign(TextAlign.Start) .fontColor("#3d3d3d") .layoutWeight(1) }.width('660lpx') .padding({ bottom: 10, top: 10 }) .borderWidth({ bottom: 1 }) .borderColor("#737977"); }); }.width('100%');

May 11, 2025 - 02:46

HarmonyOS NEXT Development Case: Light Intensity Meter

The following example demonstrates how to create a light intensity meter application using HarmonyOS NEXT's sensor capabilities. This application monitors ambient light levels through the device's light sensor and provides corresponding environmental descriptions and activity recommendations.

Implementation Code

import { sensor } from '@kit.SensorServiceKit'; // Import sensor service kit
import { BusinessError } from '@kit.BasicServicesKit'; // Import business error classes

// Class representing light intensity range information
class LightIntensityItem {
  luxStart: number; // Starting lux value of the range
  luxEnd: number; // Ending lux value of the range
  type: string; // Intensity classification type
  description: string; // Environmental description
  recommendation: string; // Activity recommendation

  // Constructor to initialize object properties
  constructor(luxStart: number, luxEnd: number, type: string, description: string, recommendation: string) {
    this.luxStart = luxStart;
    this.luxEnd = luxEnd;
    this.type = type;
    this.description = description;
    this.recommendation = recommendation;
  }
}

// Light intensity meter component using decorators
@Entry
@Component
struct LightIntensityMeter {
  @State currentType: string = ""; // Current light intensity type
  @State currentIntensity: number = 0; // Current light intensity value
  @State lightIntensityList: LightIntensityItem[] = [ // Light intensity range configuration
    new LightIntensityItem(0, 1, 'Extreme Dark', 'Outdoor night with minimal light', 'Avoid all activities, rest recommended'),
    new LightIntensityItem(1, 10, 'Very Dark', 'Indoor night with weak lighting', 'Suitable for sleep, avoid electronics'),
    new LightIntensityItem(10, 50, 'Dark', 'Dawn/dusk natural light', 'Casual relaxation, avoid prolonged reading'),
    new LightIntensityItem(50, 100, 'Dim', 'Cloudy day indoor light', 'Daily activities, short reading sessions'),
    new LightIntensityItem(100, 300, 'Moderate', 'Cloudy day indoor light', 'Work/study, moderate reading'),
    new LightIntensityItem(300, 500, 'Bright', 'Sunny day indoor light', 'Extended reading/work'),
    new LightIntensityItem(500, 1000, 'Very Bright', 'Outdoor cloudy light', 'Outdoor activities, sun protection'),
    new LightIntensityItem(1000, 100000, 'Overload', 'Direct noon sunlight', 
      'Avoid sun exposure, use sunglasses'),
  ];

  // Component lifecycle method - before appearance
  aboutToAppear(): void {
    sensor.getSensorList((error: BusinessError) => { // Get sensor list
      if (error) { 
        console.error('Sensor list fetch failed', error);
        return;
      }
      this.startLightIntensityUpdates(); // Start light sensor monitoring
    });
  }

  // Start light sensor updates
  private startLightIntensityUpdates(): void {
    sensor.on(sensor.SensorId.AMBIENT_LIGHT, (data) => { // Ambient light sensor listener
      console.info(`Current intensity: ${data.intensity}`);
      this.currentIntensity = data.intensity;
      for (const item of this.lightIntensityList) { 
        if (data.intensity >= item.luxStart && data.intensity <= item.luxEnd) {
          this.currentType = item.type;
          break;
        }
      }
    }, { interval: 10000000 }); // 1-second interval (nanoseconds)
  }

  // UI construction
  build() {
    Column() { // Main vertical layout
      Text("Light Intensity Meter")
        .width('100%')
        .height(44)
        .backgroundColor("#fe9900")
        .textAlign(TextAlign.Center)
        .fontColor(Color.White);

      Row() { // Gauge display area
        Gauge({
          value: this.currentIntensity > 1000 ? 1000 : this.currentIntensity,
          min: 0,
          max: 1000
        }) {
          Column() {
            Text(`${Math.floor(this.currentIntensity)}`)
              .fontSize(25)
              .fontWeight(FontWeight.Medium)
              .fontColor("#323232")
              .height('30%')
              .textAlign(TextAlign.Center)
              .margin({ top: '22.2%' })
              .textOverflow({ overflow: TextOverflow.Ellipsis })
              .maxLines(1);

            Text(`${this.currentType}`)
              .fontSize(16)
              .fontColor("#848484")
              .fontWeight(FontWeight.Regular)
              .width('47.4%')
              .height('15%')
              .textAlign(TextAlign.Center)
              .backgroundColor("#e4e4e4")
              .borderRadius(5);
          }.width('100%');
        }
        .startAngle(225)
        .endAngle(135)
        .height(250)
        .strokeWidth(18)
        .description(null)
        .trackShadow({ radius: 7, offsetX: 7, offsetY: 7 })
        .padding({ top: 30 });
      }.width('100%').justifyContent(FlexAlign.Center);

      Column() { // Information list
        ForEach(this.lightIntensityList, (item: LightIntensityItem, index: number) => {
          Row() {
            Text(`${item.luxStart}~${item.luxEnd}Lux `)
              .fontSize('25lpx')
              .textAlign(TextAlign.Start)
              .fontColor("#3d3d3d")
              .width('220lpx')

            Text(`${item.description}\n${item.recommendation}`)
              .fontSize('23lpx')
              .textAlign(TextAlign.Start)
              .fontColor("#3d3d3d")
              .layoutWeight(1)
          }.width('660lpx')
          .padding({ bottom: 10, top: 10 })
          .borderWidth({ bottom: 1 })
          .borderColor("#737977");
        });
      }.width('100%');
    }
    .height('100%')
    .width('100%');
  }
}

Key Features

Sensor Integration:
- Uses @kit.SensorServiceKit to access ambient light sensor data
- Implements 1-second update interval (10,000,000 nanoseconds)
Data Modeling:
- LightIntensityItem class defines light range characteristics
- Contains type, description, and activity recommendations
Reactive UI:
- @State decorators enable automatic UI updates
- Gauge component dynamically displays current intensity
- Real-time type classification updates
Information Display:
- Circular gauge with custom angle range (225°-135°)
- Scrollable list of light intensity parameters
- Adaptive text formatting and layout

Usage Scenarios

This solution is ideal for:

Environmental monitoring applications
Smart home automation systems
Health and wellness apps with light sensitivity features
IoT devices requiring ambient light adaptation

The implementation demonstrates HarmonyOS NEXT's capabilities in sensor integration and reactive UI development, providing a foundation for building context-aware applications.