In react-navigation, how do I get the dimensions of the visible area between the header and TabBar?

Solution 1

If you want to calculate viewable window height directly, then you can use the onLayout callback, for eg, on tab navigation each page,

 render() {
      return (
     <View style={{ flex: 1}} onLayout={(event) => {
              var {x, y, width, height} = event.nativeEvent.layout;
              this.viewableWindowHeight=height;
              // use height as viewableWindowHeight
       }} />

    <ScollView>
     //Your scrollable contant
    </ScrollView>
  </View>
);

Solution 2

According to an issue in react navigation, you can't directly calculate the height of the bottom tab Bar. But if you wrap bottom tab bar into a view and then you can calculate that views height as bottom tab bar. Consider the example below

    import React, { Component } from 'react';
import { connect } from 'react-redux';
import { View } from 'react-native';
import { BottomTabBar } from 'react-navigation';

class TabBarComponent extends Component {
  measure = () => {
    if (this.tabBar) {
      this.tabBar.measureInWindow(this.props.setTabMeasurement);
    }
  }

  render() {
    return (
      <View
        ref={(el) => { this.tabBar = el; }}
        onLayout={this.measure}
      >
        <BottomTabBar {...this.props} />
      </View>
    );
  }
}

function mapDispatchToProps(dispatch) {
  return {
    setTabMeasurement: (x, y, width, height) => dispatch({
      type: 'SET_TAB_MEASUREMENT',
      measurement: {
        x, y, width, height,
      },
    }),
  };
}

export default connect(null, mapDispatchToProps)(TabBarComponent);

Try this:

import { Dimensions, Platform } from 'react-native';
import {
  getStatusBarHeight,
  getBottomSpace,
} from 'react-native-iphone-x-helper';
import { Header } from 'react-navigation';

const { height } = Dimensions.get('window');
  const stackHeaderHeight = Header.HEIGHT;

  /* Taken from source code of react-navigation-tabs*/
  const TAB_BAR_DEFAULT_HEIGHT = 49;
  const TAB_BAR_COMPACT_HEIGHT = 29;

  const TAB_BAR_HEIGHT = this.bottomTabBarRef._shouldUseHorizontalLabels() && !Platform.isPad
    ? TAB_BAR_COMPACT_HEIGHT
    : TAB_BAR_DEFAULT_HEIGHT;

  const marginTop = getStatusBarHeight() + stackHeaderHeight;
  const marginBottom = getBottomSpace() + TAB_BAR_HEIGHT;

  // < What you're after 
  const viewableWindowHight = height - marginTop - marginBottom; 

FOR TBBAR

Height is changing between these two values >> TAB_BAR_COMPACT_HEIGHT, and TAB_BAR_DEFAULT_HEIGHT, according to a condition determined by this method:

According to react-navigation-tabs source code.

OR

You could set initialLayout to your TabNavigatorConfig as mentioned in the documentation:

initialLayout - Optional object containing the initial height and width, can be passed to prevent the one frame delay in react-native-tab-view rendering.

FOR IPHONE-X

You can access statusBar height, bottomSpace in Iphone-X safely though react-native-iphone-x-helper npm module

You can simply use SafeAreaView which will automatically set topBarHeight mainly for iPhoneX phones.