When the image is moved to the orange container, I want the image to grow to fit the size of the container. However, when moving the image now, the size does not change and remains the same. Please help the image to be changed I have tried several methods to resize the image, but the size of the image is not changing.

CodePudding user response：

I used

import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'dart:ui';
import 'package:flutter/cupertino.dart';
import 'package:flutter/rendering.dart';
import 'package:image/image.dart' as IMG;

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: drag_full(),
    );
  }
}

class drag_full extends StatefulWidget {
  @override
  _drag_fullState createState() => _drag_fullState();
}

class _drag_fullState extends State<drag_full> {
  GlobalKey _globalKey = GlobalKey();
  GlobalKey _widget2Key = GlobalKey();
  var _bytes;
  bool selected = false;
  Offset offset = Offset(200, 400);

  bool isLocatedInWidget2 = false;

  Uint8List resizeImage(Uint8List data, int targetWidth, int targetHeight) {
    Uint8List resizedData = data;
    IMG.Image img = IMG.decodeImage(data);
    IMG.Image resized =
        IMG.copyResize(img, width: targetWidth, height: targetHeight);
    resizedData = IMG.encodeJpg(resized);
    return resizedData;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("sample")),
      body: Container(
        child: Stack(
          children: <Widget>[
            Container(
              width: 300,
              height: 300,
              color: Colors.red,
              child: Text(
                "Widget1",
                textAlign: TextAlign.center,
                style: TextStyle(fontSize: 20),
              ),
            ),
            RepaintBoundary(
              key: _globalKey,
              child: Container(
                margin: EdgeInsets.all(100),
                width: 150,
                height: 150,
                color: Colors.black87,
              ),
            ),
            GestureDetector(
              onLongPress: () async {
                final render = (_globalKey.currentContext.findRenderObject()
                    as RenderRepaintBoundary);
                final imageBytes = (await (await render.toImage())
                        .toByteData(format: ImageByteFormat.png))
                    .buffer
                    .asUint8List();
                setState(() {
                  _bytes = imageBytes;
                });
              },
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: <Widget>[
                Stack(
                  clipBehavior: Clip.none,
                  children: [
                    Container(
                      key: _widget2Key,
                      width: 300,
                      height: 300,
                      color: Colors.orange,
                      child: Text(
                        "Widget2",
                        textAlign: TextAlign.center,
                        style: TextStyle(fontSize: 20),
                      ),
                    ),
                    if (_bytes != null)
                      if (isLocatedInWidget2)
                        Positioned.fill(
                          child: Container(
                            decoration: BoxDecoration(
                              color: Colors.yellow,
                              image: DecorationImage(
                                fit: BoxFit.fill,
                                image:
                                    MemoryImage(resizeImage(_bytes, 300, 300)),
                              ),
                            ),
                          ),
                        ),

                    //   Container(
                    //     decoration: BoxDecoration(
                    //       color: Colors.yellow,
                    //       image: DecorationImage(
                    //         fit: BoxFit.fill,
                    //         image: Image.memory(
                    //           _bytes,
                    //         ).image,
                    //         //MemoryImage(_bytes),
                    //       ),
                    //     ),
                    //   ),
                    // ),
                  ],
                ),
              ],
            ),
            if (_bytes != null)
              if (!isLocatedInWidget2)
                Positioned(
                  left: offset.dx,
                  top: offset.dy,
                  child: GestureDetector(
                    onPanUpdate: (details) {
                      print(details);
                      offset = Offset(offset.dx   details.delta.dx,
                          offset.dy   details.delta.dy);

                      print('Image posiiton: ${offset.dx}, ${offset.dy}');
                      print(
                          'Image posiiton: ${details.localPosition.dx}, ${details.localPosition.dy}');
                      print(
                          'Image posiiton: ${details.globalPosition.dx}, ${details.globalPosition.dy}');
                      final RenderBox renderBox = _widget2Key.currentContext
                          ?.findRenderObject() as RenderBox;

                      final Size widget2Size =
                          renderBox.size; // or _widgetKey.currentContext?.size
                      final Offset widget2Offset =
                          renderBox.localToGlobal(Offset.zero);

                      print('Offset: ${widget2Offset.dx}, ${widget2Offset.dy}');
                      print(
                          'Position: ${(widget2Offset.dx   widget2Size.width) / 2}, ${(widget2Offset.dy   widget2Size.height) / 2}');

                      if ((widget2Offset.dx < details.globalPosition.dx &&
                              details.globalPosition.dx <
                                  (widget2Offset.dx   widget2Size.width)) &&
                          (widget2Offset.dy < details.globalPosition.dy &&
                              details.globalPosition.dy <
                                  (widget2Offset.dy   widget2Size.height))) {
                        if (isLocatedInWidget2 != true) {
                          print('****** in ******');
                          isLocatedInWidget2 = true;
                          offset = Offset(widget2Offset.dx, 0);
                        }
                      } else {
                        if (isLocatedInWidget2 != false) {
                          print('****** out ******');
                          isLocatedInWidget2 = false;
                        }
                      }
                      setState(() {});
                    },
                    child: Image.memory(
                      _bytes,
                      width: 200,
                      color: Colors.yellow,
                    ),
                  ),
                ),
          ],
        ),
      ),
    );
  }
}