flutter通过 GlobalKey 获取界面任意元素坐标尺寸

Posted 2022-06-27 一叶飘舟

最初：

需求开发中遇到要获取屏幕任意元素坐标尺寸的功能，最终实现如下：

1. example：

//...
GlobalKey _globalKey = GlobalKey();

@override
Widget build(BuildContext context) 
    //...
    ElevatedButton.icon(
      icon: Icon(Icons.send),
      label: Text("发送"),
      // onPressed: () => ddlog('pressed'),
      key: _globalKey,
      onPressed: ()
        // _showCustomPopView();
        ddlog(_globalKey.position());// Offset(143.5, 117.0)
        ddlog(_globalKey.size);// Size(88.0, 48.0)
      ,
    ),
    //...

2. extension 封装：

import 'package:flutter/material.dart';

extension BuildContextExt on BuildContext 

  /// 获取当前组件的 RenderBox
  RenderBox? renderBox() 
    return this.findRenderObject() is RenderBox ? (this.findRenderObject() as RenderBox) : null;
  

  /// 获取当前组件的 position
  Offset? position(Offset offset = Offset.zero) 
    return this.renderBox()?.localToGlobal(offset);
  



extension GlobalKeyExt on GlobalKey

  /// 获取当前组件的 RenderBox
  RenderBox? renderBox() => this.currentContext?.renderBox();

  /// 获取当前组件的 position
  Offset? position(Offset offset = Offset.zero) => this.currentContext?.position(offset: offset);

  /// 获取当前组件的 Size
  Size? get size  => this.currentContext?.size;