How to limit the scaling factor and shrink factor

[Karan Tripathi]

Hello, everyone

I made a container in which we scale, rotate, and shrink the widget but I want to limit the scale and shrink factor.

 How can I do this?

Here is my code.

import 'dart:io';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:image_picker/image_picker.dart';

File imageMock;

class StoryKaran extends StatefulWidget {
  @override
  _StoryKaranState createState() => _StoryKaranState();
}

class _StoryKaranState extends State<StoryKaran> {
  EditableItem _activeItem;
  Offset _initPos;
  Offset _currentPos;
  Size screenSize;
  double _currentScale;

  double _currentRotation;

  bool _inAction = false;
  File _image;
  final picker = ImagePicker();

  @override
  void initState() {
    super.initState();
    setState(() {
      imageMock = _image;
    });
  }

  Future getImage() async {
    final pickedFile = await picker.getImage(source: ImageSource.camera);

    setState(() {
      if (pickedFile != null) {
        _image = File(pickedFile.path);
      } else {
        print('No image selected.');
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    final screen = MediaQuery.of(context).size;
    setState(() {
      screenSize = screen;
    });
    return Scaffold(
      appBar: AppBar(
        title: Text('Image Picker Example'),
      ),
      body: GestureDetector(
        onScaleStart: (details) {
          if (_activeItem == null) return;

          _initPos = details.focalPoint;
          _currentPos = _activeItem.position;
          _currentScale = _activeItem.scale;
          _currentRotation = _activeItem.rotation;
        },
        onScaleUpdate: (details) {
          if (_activeItem == null) return;
          final delta = details.focalPoint - _initPos;
          final left = (delta.dx / screen.width) + _currentPos.dx;
          final top = (delta.dy / screen.height) + _currentPos.dy;

          setState(() {
            _activeItem.position = Offset(left, top);
            _activeItem.rotation = details.rotation + _currentRotation;
            _activeItem.scale = details.scale * _currentScale;
          });
        },
        child: Stack(
          children: [
            Container(color: Colors.black26),
            ...mockData.map(_buildItemWidget).toList(),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: getImage,
        tooltip: 'Pick Image',
        child: Icon(Icons.add_a_photo),
      ),
    );
  }

  Widget _buildItemWidget(EditableItem e) {
    var widget;
    switch (e.type) {
      case ItemType.Text:
        widget = Text(
          e.value.toString(),
          style: TextStyle(color: Colors.white),
        );
        break;
      case ItemType.Image:
        widget = Container(
          width: screenSize.width,
          height: screenSize.height,
          child: _image == null
              ? Center(
                  child: new Text('No image selected.'),
                )
              : Image.file(_image, fit: BoxFit.cover),
        );
    }

    return Positioned(
      top: e.position.dy * screenSize.height,
      left: e.position.dx * screenSize.width,
      child: Transform.scale(
        scale: e.scale,
        child: Transform.rotate(
          angle: e.rotation,
          child: Listener(
            onPointerDown: (details) {
              if (_inAction) return;
              _inAction = true;
              _activeItem = e;
              _initPos = details.position;
              _currentPos = e.position;
              _currentScale = e.scale;
              _currentRotation = e.rotation;
            },
            onPointerUp: (details) {
              _inAction = false;
            },
            child: widget,
          ),
        ),
      ),
    );
  }
}

enum ItemType { Image, Text }

class EditableItem {
  Offset position = Offset(0.0, 0.0);
  double scale = 1.0;
  double rotation = 0.0;
  ItemType type;
  File value;
}

final mockData = [
  EditableItem()
    ..type = ItemType.Image
    ..value = imageMock,
  // EditableItem()
  //   ..type = ItemType.Text
  //   ..value = 'Hello',
  // EditableItem()
  //   ..type = ItemType.Text
  //   ..value = 'World',
];

[Karan Tripathi]

[Karan Tripathi]

[Karan Tripathi]

[Karan Tripathi]