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我有一些库可以与我用 C++ 打包到 DLL 中的 FTDI 芯片进行交互。
我想用 Flutter 创建一个前端并在 Windows 桌面应用程序中使用该库。
这些功能在 Flutter 中仍然是新的,并且文档非常浅薄且特定于移动设备。
遵循指南here ,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<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;
}
}
这是我在另一边的头文件:
#pragma once
/* Include D2XX header*/
#include "ftd2xx.h"
/* Include libMPSSE headers */
#include "libMPSSE_i2c.h"
#include "libMPSSE_spi.h"
#define FT232H_EXPORTS
#ifdef FT232H_EXPORTS
#define FT232H_API __declspec(dllexport)
#else
#define FT232H_API __declspec(dllimport)
#endif
extern "C" FT232H_API uint8 initialize_library();
extern "C" FT232H_API void cleanup_library();
extern "C" FT232H_API FT_STATUS Initialize_I2C();
extern "C" FT232H_API FT_STATUS Close_I2C();
extern "C" FT232H_API FT_STATUS I2C_write_bytes(uint8 slaveAddress, uint8 registerAddress,
const uint8 * data, uint32 numBytes);
extern "C" FT232H_API FT_STATUS I2C_read_bytes(uint8 slaveAddress, uint8 registerAddress,
uint8 bRegisterAddress, uint8 * data, uint32 numBytes);
在这里,我对 Uint8 指针有一些问题,因为我从我的 Dart 代码中得到了这个错误:
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)
任何有关如何在 flutter 中实现这一点的指示将不胜感激!
最佳答案
我确实有一个解决方案,它适用于 Flutter-Desktop-Embedding 项目中提供的准系统代码,我假设您将其用于您的桌面应用程序。你在正确的轨道上,但只需要一些最终确定。
为了测试,我使用这个带有几个函数的简单 c 代码来测试传递指针、返回指针、填充内存、分配和释放。
这是我在我的 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);
}
createarray
分配给定大小的 uint8_t 指针并将其返回给调用者。
populatearray
使用 uint8_t 指针参数和 size 并用 index 填充它
destroyarray
简单地释放分配的内存。
main.dart
提供的默认代码在我从这里克隆的 Flutter-Desktop-Embedding 项目中
https://github.com/google/flutter-desktop-embedding.git
(我假设你已经完成了这一步)
// 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';
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(() {
_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()),
),
);
}
}
现在对于我们的代码部分,我们必须为要在 dll 中调用的每个函数创建一个函数指针,我们需要正确的函数名称和正确/正确的参数数量。
import 'dart:ffi'; // For FFI
现在要创建需要加载的库的句柄,需要使用 dll 的名称调用 DynamicLibrary.open。 (dll需要放在dart应用的执行路径或者需要给出绝对路径,执行路径为build/windows/runner/Debug)
final DynamicLibrary nativePointerTestLib = DynamicLibrary.open("dynamicloadtest.dll");
我的句柄叫
nativePointerTestLib
并且 dll 的名称是“dynamicloadtest.dll”(是的,我可能应该使用更好的命名约定)
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();
我将函数指针命名为
nativeCreateArray
,
nativePopulateArray
,
nativeDestroyArray
最后,只需调用每个函数并测试它们是否有效。我刚刚在样板代码中选择了一个随机函数,
void _setCounter(int value)
它设置计数器值,然后显示。我只是要向该方法添加额外的代码来执行我们的函数调用以及打印结果以查看它是否有效。
void _setCounter(int value) {
setState(() {
_counter = value;
});
}
我们的函数调用的新方法
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;
});
}
我调用了大小为 5 的 nativeCreate。dll 将为数组分配 5 个字节。
// 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()),
),
);
}
}
运行示例应用程序后,点击增量按钮,然后将打印 0 1 2 3 4 以及指向控制台的指针地址。
关于c++ - 在 Flutter Windows 桌面应用程序中使用 C++ DLL,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/66877095/
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def char_check(x,y): if (str(x) in y or x.find(y) > -1) or (str(y) in x or y.find(x) > -1):
我有一种情况,我想将文本文件中的现有行包含到一个新 block 中。 line 1 line 2 line in block line 3 line 4 应该变成 line 1 line 2 line
我有一个新项目,我正在尝试设置 Django 调试工具栏。首先,我尝试了快速设置,它只涉及将 'debug_toolbar' 添加到我的已安装应用程序列表中。有了这个,当我转到我的根 URL 时,调试
在 Matlab 中,如果我有一个函数 f,例如签名是 f(a,b,c),我可以创建一个只有一个变量 b 的函数,它将使用固定的 a=a1 和 c=c1 调用 f: g = @(b) f(a1, b,
我不明白为什么 ForEach 中的元素之间有多余的垂直间距在 VStack 里面在 ScrollView 里面使用 GeometryReader 时渲染自定义水平分隔线。 Scrol
我想知道,是否有关于何时使用 session 和 cookie 的指南或最佳实践? 什么应该和什么不应该存储在其中?谢谢! 最佳答案 这些文档很好地了解了 session cookie 的安全问题以及
我在 scipy/numpy 中有一个 Nx3 矩阵,我想用它制作一个 3 维条形图,其中 X 轴和 Y 轴由矩阵的第一列和第二列的值、高度确定每个条形的 是矩阵中的第三列,条形的数量由 N 确定。
假设我用两种不同的方式初始化信号量 sem_init(&randomsem,0,1) sem_init(&randomsem,0,0) 现在, sem_wait(&randomsem) 在这两种情况下
我怀疑该值如何存储在“WORD”中,因为 PStr 包含实际输出。? 既然Pstr中存储的是小写到大写的字母,那么在printf中如何将其给出为“WORD”。有人可以吗?解释一下? #include
我有一个 3x3 数组: var my_array = [[0,1,2], [3,4,5], [6,7,8]]; 并想获得它的第一个 2
我意识到您可以使用如下方式轻松检查焦点: var hasFocus = true; $(window).blur(function(){ hasFocus = false; }); $(win
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