javascript - 函数未在 React native 中定义

Question

我在 React Native 中创建了一个循环进度条，错误是 get is rotateByStyle' is not defined。

这是我在一篇文章的帮助下设计的代码。这必须根据某些参数绘制带有进度的圆圈。我正在使用 ES6 定义函数

import React,{Component} from 'react';
import {Text, View, StyleSheet} from 'react-native';  

rotateByStyle = (percent, base_degrees, clockwise) => {
  let rotateBy = base_degrees;

  if(clockwise) {
    rotateBy = base_degrees + (percent * 3.6);
  } else {
    //anti clockwise progress
    rotateBy = base_degrees - (percent * 3.6);
  }

  return {
    transform:[{rotateZ: `${rotateBy}deg`}]
  };
}

renderThirdLayer = (percent, commonStyles, ringColorStyle, ringBgColorStyle, clockwise, bgRingWidth, progressRingWidth, innerRingStyle, startDegrees) => {
  let rotation = 45 + startDegrees;
  let offsetLayerRotation = -135 + startDegrees;

  if(!clockwise) {
    rotation += 180;
    offsetLayerRotation += 180;
  }

  if(percent > 50) {
    return <View style=    {[styles.secondProgressLayer,this.rotateByStyle((percent - 50), rotation, clockwise),
    commonStyles, ringColorStyle, {borderWidth: progressRingWidth}    ]}></View>
  } else {
    return <View 
             style={[styles.offsetLayer, innerRingStyle, ringBgColorStyle, {transform:[{rotateZ: `${offsetLayerRotation}deg`}], borderWidth: bgRingWidth}]}>
           </View>
    }
}

const CircularProgress = ({percent, radius, bgRingWidth, progressRingWidth, ringColor, ringBgColor, textFontSize, textFontWeight, clockwise, bgColor, startDegrees}) => {
  const commonStyles = {
    width: radius * 2,
    height: radius * 2,
    borderRadius: radius
  };
}

let firstProgressLayerStyle;
let displayThickOffsetLayer = false;

if(percent > 50){
  firstProgressLayerStyle = this.rotateByStyle(50, rotation, clockwise);
} else {
  firstProgressLayerStyle = this.rotateByStyle(percent, rotation, clockwise);
  if( progressRingWidth > bgRingWidth ) {
    displayThickOffsetLayer = true;
  }
}

let offsetLayerRotation = -135 + startDegrees;
if(!clockwise) {
  offsetLayerRotation += 180;
}


export default CircularProgress;   

我希望有一个带进度条的圆圈

Answer 1

解决方案

this.rotateByStyle

=>

rotateByStyle

为什么

rotateByStyle 不包含在 this 中。

In a method, this refers to the owner object. Alone, this refers to the global object. In a function, this refers to the global object. In a function, in strict mode, this is undefined. In an event, this refers to the element that received the event. Methods like call(), and apply() can refer this to any object.

官方:JS This