CODEWITHSUNDEEP
flutterdartflutter-layoutflutter-dependencies
xpetta
xpetta

Reputation: 718

Getting error when retrieving device screen info in Flutter

I have defined a class to retrieve the device info such as the width, height, orientation, and so on.

import 'package:flutter/material.dart';

class Device {
  static double? height;
  static double? width;
  static String? orientationType;
  static String? deviceType;

  void init(BuildContext context) {
    final mediaQueryData = MediaQuery.of(context);
    final appBar = AppBar();
    final appBarHeight = appBar.preferredSize.height;
    final statusBarHeight = mediaQueryData.padding.top;
    final bottomBarHeight = mediaQueryData.padding.bottom;

    height = mediaQueryData.size.height - appBarHeight - statusBarHeight - bottomBarHeight;
    width = mediaQueryData.size.width;

    orientationType = (mediaQueryData.orientation == Orientation.portrait) ? "Portrait" : "Landscape";
    deviceType = (orientationType == "Portrait" && width! < 600) ? "Mobile" : "Tablet";
  }
}

When I try to calculate the size then as shown below I'm getting an error.

return Container(
   width: Device.width! * 0.9,
);

Error message:

Null check operator used on a null value

But when I use it without multiplying width: Device.width it works fine and need not have to insert the null check operator as well.

Upvotes: 0

Views: 91

Answers (1)

p2kr
p2kr

Reputation: 604

Converting it to singleton class with parameters.

import 'package:flutter/material.dart';

class Device {
  late double height;
  late double width;
  late String orientationType;
  late String deviceType;

  static final Device _inst = Device._internal();
  Device._internal();

  factory Device({BuildContext context}) {
    final mediaQueryData = MediaQuery.of(context);
    final appBar = AppBar();
    final appBarHeight = appBar.preferredSize.height;
    final statusBarHeight = mediaQueryData.padding.top;
    final bottomBarHeight = mediaQueryData.padding.bottom;

    _inst.height = mediaQueryData.size.height - appBarHeight - statusBarHeight - bottomBarHeight;
    _inst.width = mediaQueryData.size.width;

    _inst.orientationType = (mediaQueryData.orientation == Orientation.portrait) ? "Portrait" : "Landscape";
    _inst.deviceType = (orientationType == "Portrait" && width! < 600) ? "Mobile" : "Tablet";

    return _inst;
  }
}

Use it like this:

Device(context: context).height

For more info on this topic visit:

Upvotes: 1

Related Questions