使用C++；Windows桌面应用程序中的DLL 我有一些库与FTDI芯片进行交互，我把它封装到C++中的DLL中。 我想创建一个带有flatter的前端，并在windows桌面应用程序中使用该库。 这些功能在颤振中仍然是新的，并且文档非常浅薄，并且是特定于移动的
按照指南，我用FFI创建了一个插件：使用C++；Windows桌面应用程序中的DLL 我有一些库与FTDI芯片进行交互，我把它封装到C++中的DLL中。 我想创建一个带有flatter的前端，并在windows桌面应用程序中使用该库。 这些功能在颤振中仍然是新的，并且文档非常浅薄，并且是特定于移动的,c++,flutter,dart,ffi,flutter-desktop,C++,Flutter,Dart,Ffi,Flutter Desktop,按照指南，我用FFI创建了一个插件： import 'dart:ffi'; import 'dart:io'; import 'dart:async'; import 'package:flutter/services.dart'; final DynamicLibrary FT232H = DynamicLibrary.open(""); final int Function() initializeLibrary = FT232H .lookup<Na
import 'dart:ffi';
import 'dart:io';
import 'dart:async';
import 'package:flutter/services.dart';
final DynamicLibrary FT232H = DynamicLibrary.open("");
final int Function() initializeLibrary = FT232H
.lookup<NativeFunction<Uint8 Function()>>("initialize_library")
.asFunction();
final void Function() cleanupLibrary = FT232H
.lookup<NativeFunction<Void Function()>>("cleanup_library")
.asFunction();
final int Function() initializeI2C = FT232H
.lookup<NativeFunction<Uint8 Function()>>("Initialize_I2C")
.asFunction();
final int Function() closeI2C = FT232H
.lookup<NativeFunction<Uint8 Function()>>("Close_I2C")
.asFunction();
final int Function(
Uint8 slaveAddress, Uint8 registerAddress, Uint32 data, Uint32 numBytes)
i2cWriteBytes = FT232H
.lookup<NativeFunction<Uint8 Function(Uint8, Uint8, Uint32, Uint32)>>(
"I2C_write_bytes")
.asFunction();
final int Function(Uint8 slaveAddress, Uint8 registerAddress,
Uint8 bRegisterAddress, Pointer<Uint8> data, Uint32 numBytes)
i2cReadBytes = FT232H
.lookup<
NativeFunction<
Uint8 Function(Uint8, Uint8, Uint8, Pointer<Uint8>,
Uint32)>>("I2C_read_bytes")
.asFunction();
class DllImport {
static const MethodChannel _channel = const MethodChannel('dll_import');
static Future<String> get platformVersion async {
final String version = await _channel.invokeMethod('getPlatformVersion');
return version;
}
}
The type 'Uint8 Function(Uint8, Uint8, Uint8, Pointer<Uint8>, Uint32)' must be a subtype of 'int
Function(Uint8, Uint8, Uint8, Pointer<Uint8>, Uint32)' for 'asFunction'.
Try changing one or both of the type arguments.dart(must_be_a_subtype)
类型“Uint8函数（Uint8，Uint8，Uint8，指针，Uint32）”必须是“int”的子类型
函数（Uint8、Uint8、Uint8、指针、Uint32）表示“asFunction”。
尝试更改一个或两个类型参数。dart（必须是子类型）
谢谢。我确实有一个解决方案，它与颤振桌面嵌入项目中提供的裸骨代码一起工作，我假设您将其用于您的桌面应用程序。你在正确的轨道上，但只需要一些定稿 为了进行测试，我使用这个简单的c代码和几个函数来测试传递指针、返回指针、填充内存、分配和释放。 这是我在dll中使用的C代码
#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
__declspec(dllexport) uint8_t* createarray(int32_t size) {
uint8_t* arr = malloc(size);
return arr;
}
__declspec(dllexport) void populatearray(uint8_t* arr,uint32_t size){
for (uint32_t index = 0; index < size; ++index) {
arr[index] = index & 0xff;
}
}
__declspec(dllexport) void destroyarray(uint8_t* arr) {
free(arr);
}
导入'dart:ffi'；//对于外国金融机构final DynamicLibrary nativePointerTestLib=DynamicLibrary.open（“dynamicloadtest.dll”）
我的句柄名为nativePointerTestLib
，dll的名称为“dynamicloadtest.dll”（是的，我可能应该使用更好的命名约定）
接下来，需要创建每个函数指针。我想调用dll中的三个函数：createarray、populatearray和destroyarray
第一个参数的大小为int->returns pointer to array（指针）
第二个将指针与size->void return一起使用
第三个只接受指针->void return
final Pointer<Uint8> Function(int size) nativeCreateArray =
nativePointerTestLib
.lookup<NativeFunction<Pointer<Uint8> Function(Int32)>>("createarray")
.asFunction();
final void Function(Pointer<Uint8> arr,int size) nativePopulateArray =
nativePointerTestLib
.lookup<NativeFunction<Void Function(Pointer<Uint8>, Int32)>>("populatearray")
.asFunction();
final void Function(Pointer<Uint8> arr) nativeDestroyArray =
nativePointerTestLib
.lookup<NativeFunction<Void Function(Pointer<Uint8>)>>("destroyarray")
.asFunction();
函数调用的新方法
void _setCounter(int value) {
setState(() {
Pointer<Uint8> parray = nativeCreateArray(5);
nativePopulateArray(parray,5);
//Now lets print
print(parray);
String str= "";
for(int i = 0 ; i < 5; ++i){
int val = parray.elementAt(i).value;
str+=val.toString() +" ";
}
print(str);
nativeDestroyArray(parray);
_counter = value;
});
}
void\u设置计数器（int值）{
设置状态（）{
指针阵列=nativeCreateArray（5）；
当地居民区（帕雷，5）；
//现在让我们打印
印刷品（鹦鹉学舌）；
字符串str=“”；
对于（int i=0；i<5；++i）{
int val=parray.elementAt（i）.值；
str+=val.toString（）+“”；
}
打印（str）；
nativeDestroyArray（帕雷）；
_计数器=值；
});
}
我打电话给5号的nativeCreate。dll将为数组分配5个字节
接下来我调用populate，它将在数组的每个元素中插入索引0到4
然后我在数组中循环，获取该数组索引处的每个元素，然后获取值。我将该值赋给一个字符串，最后打印并销毁该数组
最终代码将所有内容放在一起：
// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
import 'dart:io' show Platform;
import 'dart:math' as math;
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:menubar/menubar.dart';
import 'package:window_size/window_size.dart' as window_size;
import 'keyboard_test_page.dart';
import 'dart:ffi'; // For FFI
final DynamicLibrary nativePointerTestLib = DynamicLibrary.open("dynamicloadtest.dll");
final Pointer<Uint8> Function(int size) nativeCreateArray =
nativePointerTestLib
.lookup<NativeFunction<Pointer<Uint8> Function(Int32)>>("createarray")
.asFunction();
final void Function(Pointer<Uint8> arr,int size) nativePopulateArray =
nativePointerTestLib
.lookup<NativeFunction<Void Function(Pointer<Uint8>, Int32)>>("populatearray")
.asFunction();
final void Function(Pointer<Uint8> arr) nativeDestroyArray =
nativePointerTestLib
.lookup<NativeFunction<Void Function(Pointer<Uint8>)>>("destroyarray")
.asFunction();
void main() {
// Try to resize and reposition the window to be half the width and height
// of its screen, centered horizontally and shifted up from center.
WidgetsFlutterBinding.ensureInitialized();
window_size.getWindowInfo().then((window) {
final screen = window.screen;
if (screen != null) {
final screenFrame = screen.visibleFrame;
final width = math.max((screenFrame.width / 2).roundToDouble(), 800.0);
final height = math.max((screenFrame.height / 2).roundToDouble(), 600.0);
final left = ((screenFrame.width - width) / 2).roundToDouble();
final top = ((screenFrame.height - height) / 3).roundToDouble();
final frame = Rect.fromLTWH(left, top, width, height);
window_size.setWindowFrame(frame);
window_size.setWindowMinSize(Size(0.8 * width, 0.8 * height));
window_size.setWindowMaxSize(Size(1.5 * width, 1.5 * height));
window_size
.setWindowTitle('Flutter Testbed on ${Platform.operatingSystem}');
}
});
runApp(new MyApp());
}
/// Top level widget for the application.
class MyApp extends StatefulWidget {
/// Constructs a new app with the given [key].
const MyApp({Key? key}) : super(key: key);
@override
_AppState createState() => new _AppState();
}
class _AppState extends State<MyApp> {
Color _primaryColor = Colors.blue;
int _counter = 0;
static _AppState? of(BuildContext context) =>
context.findAncestorStateOfType<_AppState>();
/// Sets the primary color of the app.
void setPrimaryColor(Color color) {
setState(() {
_primaryColor = color;
});
}
void incrementCounter() {
_setCounter(_counter + 1);
}
void _decrementCounter() {
_setCounter(_counter - 1);
}
void _setCounter(int value) {
setState(() {
Pointer<Uint8> parray = nativeCreateArray(5);
nativePopulateArray(parray,5);
//Now lets print
print(parray);
String str= "";
for(int i = 0 ; i < 5; ++i){
int val = parray.elementAt(i).value;
str+=val.toString() +" ";
}
print(str);
nativeDestroyArray(parray);
_counter = value;
});
}
/// Rebuilds the native menu bar based on the current state.
void updateMenubar() {
setApplicationMenu([
Submenu(label: 'Color', children: [
MenuItem(
label: 'Reset',
enabled: _primaryColor != Colors.blue,
shortcut: LogicalKeySet(
LogicalKeyboardKey.meta, LogicalKeyboardKey.backspace),
onClicked: () {
setPrimaryColor(Colors.blue);
}),
MenuDivider(),
Submenu(label: 'Presets', children: [
MenuItem(
label: 'Red',
enabled: _primaryColor != Colors.red,
shortcut: LogicalKeySet(LogicalKeyboardKey.meta,
LogicalKeyboardKey.shift, LogicalKeyboardKey.keyR),
onClicked: () {
setPrimaryColor(Colors.red);
}),
MenuItem(
label: 'Green',
enabled: _primaryColor != Colors.green,
shortcut: LogicalKeySet(LogicalKeyboardKey.meta,
LogicalKeyboardKey.alt, LogicalKeyboardKey.keyG),
onClicked: () {
setPrimaryColor(Colors.green);
}),
MenuItem(
label: 'Purple',
enabled: _primaryColor != Colors.deepPurple,
shortcut: LogicalKeySet(LogicalKeyboardKey.meta,
LogicalKeyboardKey.control, LogicalKeyboardKey.keyP),
onClicked: () {
setPrimaryColor(Colors.deepPurple);
}),
])
]),
Submenu(label: 'Counter', children: [
MenuItem(
label: 'Reset',
enabled: _counter != 0,
shortcut: LogicalKeySet(
LogicalKeyboardKey.meta, LogicalKeyboardKey.digit0),
onClicked: () {
_setCounter(0);
}),
MenuDivider(),
MenuItem(
label: 'Increment',
shortcut: LogicalKeySet(LogicalKeyboardKey.f2),
onClicked: incrementCounter),
MenuItem(
label: 'Decrement',
enabled: _counter > 0,
shortcut: LogicalKeySet(LogicalKeyboardKey.f1),
onClicked: _decrementCounter),
]),
]);
}
@override
Widget build(BuildContext context) {
// Any time the state changes, the menu needs to be rebuilt.
updateMenubar();
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
primaryColor: _primaryColor,
accentColor: _primaryColor,
),
darkTheme: ThemeData.dark(),
home: _MyHomePage(title: 'Flutter Demo Home Page', counter: _counter),
);
}
}
class _MyHomePage extends StatelessWidget {
const _MyHomePage({required this.title, this.counter = 0});
final String title;
final int counter;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(title),
),
body: LayoutBuilder(
builder: (context, viewportConstraints) {
return SingleChildScrollView(
child: ConstrainedBox(
constraints:
BoxConstraints(minHeight: viewportConstraints.maxHeight),
child: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text(
'You have pushed the button this many times:',
),
new Text(
'$counter',
style: Theme.of(context).textTheme.headline4,
),
TextInputTestWidget(),
new ElevatedButton(
child: new Text('Test raw keyboard events'),
onPressed: () {
Navigator.of(context).push(new MaterialPageRoute(
builder: (context) => KeyboardTestPage()));
},
),
Padding(
padding: const EdgeInsets.all(8.0),
child: Container(
width: 380.0,
height: 100.0,
decoration: BoxDecoration(
border: Border.all(color: Colors.grey, width: 1.0)),
child: Scrollbar(
child: ListView.builder(
padding: EdgeInsets.all(8.0),
itemExtent: 20.0,
itemCount: 50,
itemBuilder: (context, index) {
return Text('entry $index');
},
),
),
),
),
],
),
),
),
);
},
),
floatingActionButton: FloatingActionButton(
onPressed: _AppState.of(context)!.incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
/// A widget containing controls to test text input.
class TextInputTestWidget extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Row(
mainAxisAlignment: MainAxisAlignment.center,
children: const <Widget>[
SampleTextField(),
SampleTextField(),
],
);
}
}
/// A text field with styling suitable for including in a TextInputTestWidget.
class SampleTextField extends StatelessWidget {
/// Creates a new sample text field.
const SampleTextField();
@override
Widget build(BuildContext context) {
return Container(
width: 200.0,
padding: const EdgeInsets.all(10.0),
child: TextField(
decoration: InputDecoration(border: OutlineInputBorder()),
),
);
}
}
//版权所有2018谷歌有限责任公司
//
//根据Apache许可证2.0版（以下简称“许可证”）获得许可；
//除非遵守许可证，否则不得使用此文件。
//您可以通过以下方式获得许可证副本：
//
// http://www.apache.org/licenses/LICENSE-2.0
//
//除非适用法律要求或书面同意，软件
//根据许可证进行的分发是按“原样”进行分发的，
//无任何明示或暗示的保证或条件。
//请参阅许可证以了解管理权限和权限的特定语言
//许可证下的限制。
导入“dart:io”展示平台；
导入'dart:math'作为数学；
进口“包装：颤振/材料.省道”；
导入“包：flifter/services.dart”；
导入“package:menubar/menubar.dart”；
导入“包：窗口大小/窗口大小.省道”作为窗口大小；
导入“键盘测试页面.dart”；
导入“dart:ffi”；//外国金融机构
final DynamicLibrary nativePointerTestLib=DynamicLibrary.open（“dynamicloadtest.dll”）；
最终指针函数（int size）nativeCreateArray=
nativePointerTestLib
.lookup（“创建数组”）
.asFunction（）；
最终空函数（指针arr，int size）nativePopulateArray=
nativePointerTestLib
.lookup（“populatearray”）
.asFunction（）；
最终空洞函数（指针arr）nativeDestroyArray=
nativePointerTestLib
.lookup（“销毁数组”）
.asFunction（）；
void main（）{
//尝试调整窗口大小并将其重新定位为宽度和高度的一半
//它的屏幕，水平居中，从中心向上移动。
WidgetsFlutterBinding.ensureInitialized（）；
窗口大小。getWindowInfo（）。然后（（窗口）{
最终屏幕=window.screen；
如果（屏幕！=null）{
最终屏幕框=screen.visibleFrame；
最终宽度=math.max（（screenFrame.width/2）.roundToDouble（），800.0）；
最终高度=数学最大值（（screenFrame.height/2）.roundToDouble（），600.0）；
最后左=（（screenFrame.width-width）/2.roundToDouble（）；
最终顶部=（（screenFrame.height-height）/3.roundToDouble（）；
最终帧=垂直于LTWH（左、上、宽、高）；
窗口大小。设置窗口框架（框架）；
窗口大小。设置窗口大小（大小（0.8*宽度，0.8*高度））；
窗口大小。设置窗口最大大小（大小（1.5*宽，1.5*高））；
窗口大小
.setWindowTitle（${Platform.operatingSystem}上的颤振试验台）；
}
});
runApp（新的MyApp（））；
}
///应用程序的顶级小部件。
类MyApp扩展了StatefulWidget{
///使用给定的[key]构造一个新应用程序。
常量MyApp（{Key？Key}）：超级
void _setCounter(int value) {
setState(() {
_counter = value;
});
}
void _setCounter(int value) {
setState(() {
Pointer<Uint8> parray = nativeCreateArray(5);
nativePopulateArray(parray,5);
//Now lets print
print(parray);
String str= "";
for(int i = 0 ; i < 5; ++i){
int val = parray.elementAt(i).value;
str+=val.toString() +" ";
}
print(str);
nativeDestroyArray(parray);
_counter = value;
});
}
// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
import 'dart:io' show Platform;
import 'dart:math' as math;
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:menubar/menubar.dart';
import 'package:window_size/window_size.dart' as window_size;
import 'keyboard_test_page.dart';
import 'dart:ffi'; // For FFI
final DynamicLibrary nativePointerTestLib = DynamicLibrary.open("dynamicloadtest.dll");
final Pointer<Uint8> Function(int size) nativeCreateArray =
nativePointerTestLib
.lookup<NativeFunction<Pointer<Uint8> Function(Int32)>>("createarray")
.asFunction();
final void Function(Pointer<Uint8> arr,int size) nativePopulateArray =
nativePointerTestLib
.lookup<NativeFunction<Void Function(Pointer<Uint8>, Int32)>>("populatearray")
.asFunction();
final void Function(Pointer<Uint8> arr) nativeDestroyArray =
nativePointerTestLib
.lookup<NativeFunction<Void Function(Pointer<Uint8>)>>("destroyarray")
.asFunction();
void main() {
// Try to resize and reposition the window to be half the width and height
// of its screen, centered horizontally and shifted up from center.
WidgetsFlutterBinding.ensureInitialized();
window_size.getWindowInfo().then((window) {
final screen = window.screen;
if (screen != null) {
final screenFrame = screen.visibleFrame;
final width = math.max((screenFrame.width / 2).roundToDouble(), 800.0);
final height = math.max((screenFrame.height / 2).roundToDouble(), 600.0);
final left = ((screenFrame.width - width) / 2).roundToDouble();
final top = ((screenFrame.height - height) / 3).roundToDouble();
final frame = Rect.fromLTWH(left, top, width, height);
window_size.setWindowFrame(frame);
window_size.setWindowMinSize(Size(0.8 * width, 0.8 * height));
window_size.setWindowMaxSize(Size(1.5 * width, 1.5 * height));
window_size
.setWindowTitle('Flutter Testbed on ${Platform.operatingSystem}');
}
});
runApp(new MyApp());
}
/// Top level widget for the application.
class MyApp extends StatefulWidget {
/// Constructs a new app with the given [key].
const MyApp({Key? key}) : super(key: key);
@override
_AppState createState() => new _AppState();
}
class _AppState extends State<MyApp> {
Color _primaryColor = Colors.blue;
int _counter = 0;
static _AppState? of(BuildContext context) =>
context.findAncestorStateOfType<_AppState>();
/// Sets the primary color of the app.
void setPrimaryColor(Color color) {
setState(() {
_primaryColor = color;
});
}
void incrementCounter() {
_setCounter(_counter + 1);
}
void _decrementCounter() {
_setCounter(_counter - 1);
}
void _setCounter(int value) {
setState(() {
Pointer<Uint8> parray = nativeCreateArray(5);
nativePopulateArray(parray,5);
//Now lets print
print(parray);
String str= "";
for(int i = 0 ; i < 5; ++i){
int val = parray.elementAt(i).value;
str+=val.toString() +" ";
}
print(str);
nativeDestroyArray(parray);
_counter = value;
});
}
/// Rebuilds the native menu bar based on the current state.
void updateMenubar() {
setApplicationMenu([
Submenu(label: 'Color', children: [
MenuItem(
label: 'Reset',
enabled: _primaryColor != Colors.blue,
shortcut: LogicalKeySet(
LogicalKeyboardKey.meta, LogicalKeyboardKey.backspace),
onClicked: () {
setPrimaryColor(Colors.blue);
}),
MenuDivider(),
Submenu(label: 'Presets', children: [
MenuItem(
label: 'Red',
enabled: _primaryColor != Colors.red,
shortcut: LogicalKeySet(LogicalKeyboardKey.meta,
LogicalKeyboardKey.shift, LogicalKeyboardKey.keyR),
onClicked: () {
setPrimaryColor(Colors.red);
}),
MenuItem(
label: 'Green',
enabled: _primaryColor != Colors.green,
shortcut: LogicalKeySet(LogicalKeyboardKey.meta,
LogicalKeyboardKey.alt, LogicalKeyboardKey.keyG),
onClicked: () {
setPrimaryColor(Colors.green);
}),
MenuItem(
label: 'Purple',
enabled: _primaryColor != Colors.deepPurple,
shortcut: LogicalKeySet(LogicalKeyboardKey.meta,
LogicalKeyboardKey.control, LogicalKeyboardKey.keyP),
onClicked: () {
setPrimaryColor(Colors.deepPurple);
}),
])
]),
Submenu(label: 'Counter', children: [
MenuItem(
label: 'Reset',
enabled: _counter != 0,
shortcut: LogicalKeySet(
LogicalKeyboardKey.meta, LogicalKeyboardKey.digit0),
onClicked: () {
_setCounter(0);
}),
MenuDivider(),
MenuItem(
label: 'Increment',
shortcut: LogicalKeySet(LogicalKeyboardKey.f2),
onClicked: incrementCounter),
MenuItem(
label: 'Decrement',
enabled: _counter > 0,
shortcut: LogicalKeySet(LogicalKeyboardKey.f1),
onClicked: _decrementCounter),
]),
]);
}
@override
Widget build(BuildContext context) {
// Any time the state changes, the menu needs to be rebuilt.
updateMenubar();
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
primaryColor: _primaryColor,
accentColor: _primaryColor,
),
darkTheme: ThemeData.dark(),
home: _MyHomePage(title: 'Flutter Demo Home Page', counter: _counter),
);
}
}
class _MyHomePage extends StatelessWidget {
const _MyHomePage({required this.title, this.counter = 0});
final String title;
final int counter;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(title),
),
body: LayoutBuilder(
builder: (context, viewportConstraints) {
return SingleChildScrollView(
child: ConstrainedBox(
constraints:
BoxConstraints(minHeight: viewportConstraints.maxHeight),
child: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text(
'You have pushed the button this many times:',
),
new Text(
'$counter',
style: Theme.of(context).textTheme.headline4,
),
TextInputTestWidget(),
new ElevatedButton(
child: new Text('Test raw keyboard events'),
onPressed: () {
Navigator.of(context).push(new MaterialPageRoute(
builder: (context) => KeyboardTestPage()));
},
),
Padding(
padding: const EdgeInsets.all(8.0),
child: Container(
width: 380.0,
height: 100.0,
decoration: BoxDecoration(
border: Border.all(color: Colors.grey, width: 1.0)),
child: Scrollbar(
child: ListView.builder(
padding: EdgeInsets.all(8.0),
itemExtent: 20.0,
itemCount: 50,
itemBuilder: (context, index) {
return Text('entry $index');
},
),
),
),
),
],
),
),
),
);
},
),
floatingActionButton: FloatingActionButton(
onPressed: _AppState.of(context)!.incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
/// A widget containing controls to test text input.
class TextInputTestWidget extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Row(
mainAxisAlignment: MainAxisAlignment.center,
children: const <Widget>[
SampleTextField(),
SampleTextField(),
],
);
}
}
/// A text field with styling suitable for including in a TextInputTestWidget.
class SampleTextField extends StatelessWidget {
/// Creates a new sample text field.
const SampleTextField();
@override
Widget build(BuildContext context) {
return Container(
width: 200.0,
padding: const EdgeInsets.all(10.0),
child: TextField(
decoration: InputDecoration(border: OutlineInputBorder()),
),
);
}
}