Slider with minimumValue > 0 doesn't move

[iKettles]

Issue Description

Using the React Native Slider works fine with a minimum value of 0. With a minimum value above 0, the slider doesn't respect the value set and places the thumb to the beginning of the slider. This prevents the thumb from being moved.

Steps to Reproduce / Code Snippets

With a minimum value of 0, this works and allows the thumb to be moved. With a value higher than 0 the thumb will be locked to the start of the slider.

import React, { 
  Component
} from 'react'

import {
  Slider,
  View
} from 'react-native';

export default class RangeSlider extends React.Component {
  constructor (props) {
    super(props)
  }

  render () {
    return (
      <View>
        <Slider 
          maximumValue={10}
          minimumValue={1} 
          stepValue={0.1} 
          value={4}
          />
      </View>
    )
  }
}

Expected Results

The thumb should be able to move with a minimum value above 0

Additional Information

• React Native version: 0.34.1
• Platform(s) (iOS, Android, or both?): Android
• Operating System (macOS, Linux, or Windows?): macOS

[reneweb]

The problem is in ReactSlider.java when calculating the step value: https://github.com/facebook/react-native/blob/master/ReactAndroid/src/main/java/com/facebook/react/views/slider/ReactSlider.java#L94

What happens is that before the maxValue property gets set, the minValue one will get set and causes the updateAll method to be called. If at the same time the step is zero and we therefore calculate it, the minValue will be greater zero and the maxValue will be zero resulting in a negative step value.

To work around this you need to provide the step value yourself, which you are trying to, but the name is just step not stepValue.
So, this should work:

import React, { 
  Component
} from 'react'

import {
  Slider,
  View
} from 'react-native';

export default class RangeSlider extends React.Component {
  constructor (props) {
    super(props)
  }

  render () {
    return (
      <View>
        <Slider 
          maximumValue={10}
          minimumValue={1} 
          step={0.1} 
          value={4}
          />
      </View>
    )
  }
}

I will also add a pr to fix the issue when the step is indeed 0.