Flutter 的屏幕适配

import 'package:flutter/material.dart';
import 'dart:ui' as ui;
//系统默认的appBar等高度
//位于Dart Packages/flutter/src/material/constans.dart

///默认设计稿尺寸（单位 dp or pt）
double _designW = 360.0;
double _designH = 640.0;
double _designD = 3.0;

/**

• 配置设计稿尺寸（单位 dp or pt）
• w 宽
• h 高
• density 像素密度
  */

/// 配置设计稿尺寸 屏幕 宽，高，密度。
/// Configuration design draft size screen width, height, density.
void setDesignWHD(double w, double h, {double density = 3.0}) {
_designW = w;
_designH = h;
_designD = density;
}

/// Screen Util.
class ScreenUtils {
double _screenWidth = 0.0;
double _screenHeight = 0.0;
double _screenDensity = 0.0;
double _statusBarHeight = 0.0;
double _bottomBarHeight = 0.0;
double _appBarHeight = 0.0;
MediaQueryData _mediaQueryData;

static final ScreenUtils _singleton = ScreenUtils();

static ScreenUtils getInstance() {
_singleton._init();
return _singleton;
}

_init() {
MediaQueryData mediaQuery = MediaQueryData.fromWindow(ui.window);
if (_mediaQueryData != mediaQuery) {
_mediaQueryData = mediaQuery;
_screenWidth = mediaQuery.size.width;
_screenHeight = mediaQuery.size.height;
_screenDensity = mediaQuery.devicePixelRatio;
_statusBarHeight = mediaQuery.padding.top;
_bottomBarHeight = mediaQuery.padding.bottom;
_appBarHeight = kToolbarHeight;
}
}

/// screen width
/// 屏幕 宽
double get screenWidth => _screenWidth;

/// screen height
/// 屏幕 高
double get screenHeight => _screenHeight;

/// appBar height
/// appBar 高
double get appBarHeight => _appBarHeight;

/// screen density
/// 屏幕 像素密度
double get screenDensity => _screenDensity;

/// status bar Height
/// 状态栏高度
double get statusBarHeight => _statusBarHeight;

/// bottom bar Height
double get bottomBarHeight => _bottomBarHeight;

/// media Query Data
MediaQueryData get mediaQueryData => _mediaQueryData;

/// screen width
/// 当前屏幕 宽
static double screenW(BuildContext context) {
MediaQueryData mediaQuery = MediaQuery.of(context);
return mediaQuery.size.width;
}

/// screen height
/// 当前屏幕 高
static double screenH(BuildContext context) {
MediaQueryData mediaQuery = MediaQuery.of(context);
return mediaQuery.size.height;
}

/// screen density
/// 当前屏幕 像素密度
static double getScreenDensity(BuildContext context) {
MediaQueryData mediaQuery = MediaQuery.of(context);
return mediaQuery.devicePixelRatio;
}

/// status bar Height
/// 当前状态栏高度
static double getStatusBarH(BuildContext context) {
MediaQueryData mediaQuery = MediaQuery.of(context);
return mediaQuery.padding.top;
}

/// status bar Height
/// 当前BottomBar高度
static double getBottomBarH(BuildContext context) {
MediaQueryData mediaQuery = MediaQuery.of(context);
return mediaQuery.padding.bottom;
}

/// 当前MediaQueryData
static MediaQueryData getMediaQueryData(BuildContext context) {
MediaQueryData mediaQuery = MediaQuery.of(context);
return mediaQuery;
}

/// returns the size after adaptation according to the screen width.(unit dp or pt)
/// 返回根据屏幕宽适配后尺寸（单位 dp or pt）
/// size 单位 dp or pt
static double getScaleW(BuildContext context, double size) {
if (context == null || screenW(context) == 0.0) return size;
return size * screenW(context) / _designW;
}

/// returns the size after adaptation according to the screen height.(unit dp or pt)
/// 返回根据屏幕高适配后尺寸 （单位 dp or pt）
/// size unit dp or pt
static double getScaleH(BuildContext context, double size) {
if (context == null || screenH(context) == 0.0) return size;
return size * screenH(context) / _designH;
}

/// returns the font size after adaptation according to the screen density.
/// 返回根据屏幕宽适配后字体尺寸
/// fontSize 字体尺寸
static double getScaleSp(BuildContext context, double fontSize) {
if (context == null || getScreenDensity(context) == 0.0) return fontSize;
return fontSize * screenW(context) / _designW;
}

/// Orientation
/// 设备方向(portrait, landscape)
static Orientation getOrientation(BuildContext context) {
MediaQueryData mediaQuery = MediaQuery.of(context);
return mediaQuery.orientation;
}

/// returns the size after adaptation according to the screen width.(unit dp or pt)
/// 返回根据屏幕宽适配后尺寸（单位 dp or pt）
/// size 单位 dp or pt
double getWidth(double size) {
return _screenWidth == 0.0 ? size : (size * _screenWidth / _designW);
}

/// returns the size after adaptation according to the screen height.(unit dp or pt)
/// 返回根据屏幕高适配后尺寸（单位 dp or pt）
/// size unit dp or pt
double getHeight(double size) {
return _screenHeight == 0.0 ? size : (size * _screenHeight / _designH);
}

/// returns the size after adaptation according to the screen width.(unit dp or pt)
/// 返回根据屏幕宽适配后尺寸（单位 dp or pt）
/// sizePx unit px
double getWidthPx(double sizePx) {
return _screenWidth == 0.0
? (sizePx / _designD)
: (sizePx * _screenWidth / (_designW * _designD));
}

/// returns the size after adaptation according to the screen height.(unit dp or pt)
/// 返回根据屏幕高适配后尺寸（单位 dp or pt）
/// sizePx unit px
double getHeightPx(double sizePx) {
return _screenHeight == 0.0
? (sizePx / _designD)
: (sizePx * _screenHeight / (_designH * _designD));
}

/// returns the font size after adaptation according to the screen density.
/// 返回根据屏幕宽适配后字体尺寸
/// fontSize 字体尺寸
double getSp(double fontSize) {
if (_screenDensity == 0.0) return fontSize;
return fontSize * _screenWidth / _designW;
}