flutter - 颤振 - 我希望图像离开该区域时消失

Question

Draggable 允许拖动图像。当图像离开橙色容器区域时，我希望它消失而不是隐藏。我使用了偏移量，但我不确定如何使图像消失在该区域之外。如果您能举一个代码示例，将不胜感激。

标签： flutterdraggable

Answer 1

这是我的试验。

• 更改了 Stack 小部件参数的 clipBehavior
  => 它允许上层堆栈项可以溢出。
• 如果位置更改为超出区域，则使用动画将不透明度更改为 0。
  
  

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      // Remove the debug banner
      debugShowCheckedModeBanner: false,
      title: 'Kindacode.com',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool _started = false;
  bool _isDisappeared = false;
  Offset _position = Offset(10, 220);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Stack(
          clipBehavior: Clip.none,
          children: <Widget>[
            Container(
              width: 300,
              height: 400,
              color: Colors.orange,
            ),
            Positioned(
              top: _position.dy - 30, // Size of widget to reposition correctly
              left: _position.dx,
              child: AnimatedOpacity(
                duration: const Duration(milliseconds: 500),
                opacity: _isDisappeared ? 0.0 : 1.0,
                child: Draggable(
                  child: Icon(Icons.home),
                  feedback: Icon(Icons.home),
                  onDragEnd: (details) {
                    print(details.offset);
                    setState(() {
                      if (!_started) _started = true;
                      _position = details.offset;

                      if (_position.dy - 30 > 400 || _position.dx > 300) {
                        setState(() {
                          _isDisappeared = true;
                        });
                      }
                    });
                  },
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}
[![enter image description here][1]][1]