my.setScreenBrightness

    <!-- API-DEMO page/API/screen/screen.axml-->
    <view class="page">
      <view class="page-description">Screen brightness API</view>
      <view class="page-section">
        <view class="page-section-title">Set whether to keep screen on</view>
        <view class="page-section-demo">
          <switch checked="{{status}}" onChange="switchKeepScreenOn"/>
        </view>
      </view>
      <view class="page-section">
        <view class="page-section-title">Set screen brightness</view>
        <view class="page-section-demo">
          <slider value="{{brightness}}" max="1" min="0" onChange="sliderChange" step="0.02"/>
        </view>
      </view>
      <view class="page-section">
        <view class="page-section-title">Get screen brightness</view>
        <view class="page-section-demo">
          <button type="primary" onTap="getBrightness">Get screen brightness</button>
        </view>
      </view>
    </view>

    // API-DEMO page/API/screen/screen.js
    Page({
      data: {
        status: false,
        brightness: 1,
      },
      onLoad() {
        my.getScreenBrightness({
          success: res => {
            this.setData({
              brightness: res.brightness
            })
          },
        })
      },
      sliderChange(e) {
        my.setScreenBrightness({
          brightness: e.detail.value,
          success: (res) => {
            this.setData({
              brightness: e.detail.value,
            })
          }
        })
      },
      switchKeepScreenOn(e) {
        my.setKeepScreenOn({
          keepScreenOn: e.detail.value,
          success: (res) => {
            this.setData({
              status: e.detail.value,
            })
          }
        })
      },
      getBrightness() {
        my.getScreenBrightness({
          success: res => {
            my.alert({
              content: `Current screen brightness: ${res.brightness}`
            });
          }
        })
      }
    });