收缩包裹特性在颤振中起什么作用? [英] What does the shrink wrap property do in flutter?

问题描述

我是Flutter的新手，非常渴望学习这项技术.我无法理解列表视图中的收缩包装属性的工作.我听不懂Flutter文档.有人可以帮忙吗?预先感谢.

I am new to Flutter and very eager to learn this technology. I cannot understand the work of shrink wrap property in list view. I couldn't understand the flutter documentation. Can somebody help? Thanks in advance.

推荐答案

通常ListView(以及GridView，PageView和CustomScrollView)尝试填充父元素给定的所有可用空间，即使列表项需要较少的空间.

Usually a ListView (as well as GridView, PageView and CustomScrollView) tries to fill all the available space given by the parent element, even when the list items would require less space.

使用shrinkWrap: true，您可以更改此行为，以使ListView仅占用其所需的空间(当有更多项目时，它仍会滚动).

With shrinkWrap: true, you can change this behavior so that the ListView only occupies the space it needs (it will still scroll when there more items).

看看这个例子:

import 'package:flutter/material.dart';

void main() => runApp(App());

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(),
        body: Center(
          child: Container(
            margin: EdgeInsets.all(32),
            decoration: BoxDecoration(border: Border.all(color: Colors.red)),
            child: ListView(
              shrinkWrap: false,
              children: <Widget>[
                ListTile(title: Text('Item 1')),
                ListTile(title: Text('Item 2')),
                ListTile(title: Text('Item 3')),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

使用shrinkWrap: false:

使用shrinkWrap: true:

您可以在AlertDialog s中使用它:当只有几个项目时，使对话框尽可能小.如果有很多项目，请填充屏幕高度并使列表可滚动:

You can use this in AlertDialogs: When there are only a few items, make the dialog as small as possible. When there are many items, fill the screen height and make the list scrollable:

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