在 SafeArea 中获取小部件高度的正确方法 [英] proper way to get widget height in SafeArea

问题描述

我正在尝试获取小部件的高度，但它打印的值相同

<块引用>

I/flutter (19253):全高:976.0I/flutter (19253):安全高度:976.0

我猜第二个值应该更小，因为 Container 放置在状态栏下方.我做错了什么?我需要高度，因为在这个容器中将是 Wrap 小部件(实际上是 ReorderableWrap https://pub.dartlang.org/packages/reorderables#-readme-tab-) 包含 36 张卡片，3 行 x 12 张卡片，卡片高度必须为其容器的 1/3.

我没有找到好的可重排网格.但无论如何，我的问题是为什么安全区域中的 Container 与填满整个屏幕的 Container 具有相同的高度?

import 'package:flutter/material.dart';无效的主要(){runApp(_MyApp());}类 _MyApp 扩展 StatelessWidget {@覆盖小部件构建(BuildContext 上下文){返回材料应用程序(debugShowCheckedModeBanner:假，家:脚手架(身体:_Body())，);}}类 _Body 扩展 StatelessWidget {@覆盖小部件构建(BuildContext 上下文){print('全高:${MediaQuery.of(context).size.height}');返回容器(约束:BoxConstraints.expand()，装饰:BoxDecoration(颜色:Colors.red)，孩子:安全区(孩子:_SafeHeightWidget()，),);}}类 _SafeHeightWidget 扩展 StatelessWidget {@覆盖小部件构建(BuildContext 上下文){print('安全高度:${MediaQuery.of(context).size.height}');返回容器(颜色:Colors.lightBlue，);}}

解决方案

在这种情况下，您始终可以使用 LayoutBuilder.

child: SafeArea(孩子:新的LayoutBuilder(构建器:(BuildContext 上下文，BoxConstraints 约束){//约束变量具有大小信息返回容器()；}),),

更多信息:https://www.youtube.com/watch?v=IYDVcriKjsw

I'm trying to get the height of widget but it prints the same values

I/flutter (19253): full height: 976.0
I/flutter (19253): safe height: 976.0

I guessed the second value should be smaller because the Container placed below the status bar. What I'm doing wrong? I need height because in this container will be Wrap widget (actually ReorderableWrap https://pub.dartlang.org/packages/reorderables#-readme-tab-) with 36 cards, 3 rows by 12 cards and cards height must be 1/3 of its container.

I didn't find good Reorderable Grid. But anyway my question why a Container in a safe area has the same height as Container that fills the entire screen?

import 'package:flutter/material.dart';

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

class _MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(body: _Body()),
    );
  }
}

class _Body extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    print('full height: ${MediaQuery.of(context).size.height}');
    return Container(
      constraints: BoxConstraints.expand(),
      decoration: BoxDecoration(color: Colors.red),
      child: SafeArea(
        child: _SafeHeightWidget(),
      ),
    );
  }
}

class _SafeHeightWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    print('safe height: ${MediaQuery.of(context).size.height}');
    return Container(
      color: Colors.lightBlue,
    );
  }
}

解决方案

You can always use LayoutBuilder for such cases.

child: SafeArea(
        child: new LayoutBuilder(
            builder: (BuildContext context, BoxConstraints constraints) {
              // constraints variable has the size info
              return Container();
            }
        ),
      ),

for more info: https://www.youtube.com/watch?v=IYDVcriKjsw

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