首页 > 编程开发 > C类语言

WPF实现筛选下拉多选控件的示例代码

来自：网络
时间：2023-07-24
阅读：

修复 Issue WPF 实现筛选下拉多选控件

框架使用.NET4 至 .NET6；

Visual Studio 2022;

接着上一篇，MultiSelectionSearchComboBox 无法做到根据值选中选项，使用 Selecteditems 时会默认选中集合中的最后一个切选项选择功能会失效，这明显是不对的issue.

因为先前的 OnSelectedItemsChanged 逻辑处理错误，导致 Binding 多个选择值只保留了最后一次，因为之前为对 listBox.SelectionChanged 取消订阅。

WPF实现筛选下拉多选控件的示例代码

实现代码

1）修改 MultiSelectionSearchComboBox.cs 代码如下:

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Interop;
using WPFDevelopers.Helpers;
namespace WPFDevelopers.Controls
{
    [TemplatePart(Name = "PART_TextBox", Type = typeof(TextBox))]
    [TemplatePart(Name = "PART_Popup", Type = typeof(Popup))]
    [TemplatePart(Name = "PART_Selector", Type = typeof(ListBox))]
    [TemplatePart(Name = "PART_SelectAll", Type = typeof(CheckBox))]
    [TemplatePart(Name = "PART_SearchSelector", Type = typeof(ListBox))]
    public class MultiSelectionSearchComboBox : Control
    {
        private const string TextBoxTemplateName = "PART_TextBox";
        private const string PopupTemplateName = "PART_Popup";
        private const string ListBoxTemplateName = "PART_Selector";
        private const string CheckBoxTemplateName = "PART_SelectAll";
        private const string ListBoxTemplateNameSearch = "PART_SearchSelector";
        public static readonly RoutedEvent ClosedEvent =
            EventManager.RegisterRoutedEvent("Closed",
                RoutingStrategy.Bubble,
                typeof(RoutedEventHandler),
                typeof(MultiSelectionSearchComboBox));
        public static readonly DependencyProperty DisplayMemberPathProperty =
            DependencyProperty.Register("DisplayMemberPath",
                typeof(string),
                typeof(MultiSelectionSearchComboBox),
                new PropertyMetadata(string.Empty));
        public static readonly DependencyProperty SelectedValuePathProperty =
            DependencyProperty.Register("SelectedValuePath",
                typeof(string),
                typeof(MultiSelectionSearchComboBox),
                new PropertyMetadata(string.Empty));
        public static readonly DependencyProperty TextProperty =
            DependencyProperty.Register("Text",
                typeof(string),
                typeof(MultiSelectionSearchComboBox),
                new PropertyMetadata(string.Empty));
        public static readonly DependencyProperty ItemsSourceProperty =
            DependencyProperty.Register("ItemsSource", typeof(IEnumerable), typeof(MultiSelectionSearchComboBox),
                new PropertyMetadata());
        public static readonly DependencyProperty ItemsSourceSearchProperty =
            DependencyProperty.Register("ItemsSourceSearch", typeof(IEnumerable), typeof(MultiSelectionSearchComboBox),
                new PropertyMetadata());
        public static readonly DependencyProperty SelectAllContentProperty =
            DependencyProperty.Register("SelectAllContent", typeof(object), typeof(MultiSelectionSearchComboBox),
                new PropertyMetadata("全选"));
        public static readonly DependencyProperty IsSelectAllActiveProperty =
            DependencyProperty.Register("IsSelectAllActive", typeof(bool), typeof(MultiSelectionSearchComboBox),
                new PropertyMetadata(false));
        public static readonly DependencyProperty DelimiterProperty =
            DependencyProperty.Register("Delimiter", typeof(string), typeof(MultiSelectionSearchComboBox),
                new PropertyMetadata(";"));
        public static readonly DependencyProperty IsDropDownOpenProperty =
            DependencyProperty.Register("IsDropDownOpen", typeof(bool), typeof(MultiSelectionSearchComboBox),
                new PropertyMetadata(false, OnIsDropDownOpenChanged));
        public static readonly DependencyProperty MaxDropDownHeightProperty =
            DependencyProperty.Register("MaxDropDownHeight", typeof(double), typeof(MultiSelectionSearchComboBox),
                new UIPropertyMetadata(SystemParameters.PrimaryScreenHeight / 3.0, OnMaxDropDownHeightChanged));
        public static readonly DependencyProperty SelectedItemsProperty =
            DependencyProperty.Register("SelectedItems", typeof(IList), typeof(MultiSelectionSearchComboBox),
                new FrameworkPropertyMetadata(null,
                    FrameworkPropertyMetadataOptions.BindsTwoWayByDefault | FrameworkPropertyMetadataOptions.Journal,
                    OnSelectedItemsChanged));
        public static readonly DependencyProperty SearchWatermarkProperty =
            DependencyProperty.Register("SearchWatermark",
                typeof(string),
                typeof(MultiSelectionSearchComboBox),
                new PropertyMetadata(string.Empty));
        private CheckBox _checkBox;
        private ListBox _listBox;
        private ListBox _listBoxSearch;
        private Popup _popup;
        private TextBox _textBox;
        private List<object> selectedItems;
        private List<object> selectedList;
        private List<object> selectedSearchList;
        private string theLastText;
        static MultiSelectionSearchComboBox()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(MultiSelectionSearchComboBox),
                new FrameworkPropertyMetadata(typeof(MultiSelectionSearchComboBox)));
        }
        public string Delimiter
        {
            get => (string) GetValue(DelimiterProperty);
            set => SetValue(DelimiterProperty, value);
        }
        public string SelectedValuePath
        {
            get => (string) GetValue(SelectedValuePathProperty);
            set => SetValue(SelectedValuePathProperty, value);
        }
        public string DisplayMemberPath
        {
            get => (string) GetValue(DisplayMemberPathProperty);
            set => SetValue(DisplayMemberPathProperty, value);
        }
        public string Text
        {
            get => (string) GetValue(TextProperty);
            set => SetValue(TextProperty, value);
        }
        public IEnumerable ItemsSource
        {
            get => (IEnumerable) GetValue(ItemsSourceProperty);
            set => SetValue(ItemsSourceProperty, value);
        }
        public IEnumerable ItemsSourceSearch
        {
            get => (IEnumerable) GetValue(ItemsSourceSearchProperty);
            set => SetValue(ItemsSourceSearchProperty, value);
        }
        public object SelectAllContent
        {
            get => GetValue(SelectAllContentProperty);
            set => SetValue(SelectAllContentProperty, value);
        }
        public bool IsSelectAllActive
        {
            get => (bool) GetValue(IsSelectAllActiveProperty);
            set => SetValue(IsSelectAllActiveProperty, value);
        }
        public bool IsDropDownOpen
        {
            get => (bool) GetValue(IsDropDownOpenProperty);
            set => SetValue(IsDropDownOpenProperty, value);
        }
        public double MaxDropDownHeight
        {
            get => (double) GetValue(MaxDropDownHeightProperty);
            set => SetValue(MaxDropDownHeightProperty, value);
        }
        public IList SelectedItems
        {
            get => (IList) GetValue(SelectedItemsProperty);
            set => SetValue(SelectedItemsProperty, value);
        }
        public string SearchWatermark
        {
            get => (string) GetValue(SearchWatermarkProperty);
            set => SetValue(SearchWatermarkProperty, value);
        }
        [DllImport(Win32.User32)]
        private static extern IntPtr SetFocus(IntPtr hWnd);
        public event RoutedEventHandler Closed
        {
            add => AddHandler(ClosedEvent, value);
            remove => RemoveHandler(ClosedEvent, value);
        }
        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            selectedList = new List<object>();
            selectedSearchList = new List<object>();
            selectedItems = new List<object>();
            _textBox = GetTemplateChild(TextBoxTemplateName) as TextBox;
            _popup = GetTemplateChild(PopupTemplateName) as Popup;
            if (_popup != null)
                _popup.GotFocus += _popup_GotFocus;
            _listBox = GetTemplateChild(ListBoxTemplateName) as ListBox;
            _checkBox = GetTemplateChild(CheckBoxTemplateName) as CheckBox;
            _listBoxSearch = GetTemplateChild(ListBoxTemplateNameSearch) as ListBox;
            if (_textBox != null)
            {
                _textBox.TextChanged -= _textbox_TextChanged;
                _textBox.TextChanged += _textbox_TextChanged;
            }
            if (_checkBox != null)
            {
                _checkBox.Checked -= _checkBox_Checked;
                _checkBox.Unchecked -= _checkBox_Unchecked;
                _checkBox.Checked += _checkBox_Checked;
                _checkBox.Unchecked += _checkBox_Unchecked;
            }
            if (_listBox != null)
            {
                _listBox.IsVisibleChanged -= _listBox_IsVisibleChanged;
                _listBox.IsVisibleChanged += _listBox_IsVisibleChanged;
                _listBox.SelectionChanged -= _listBox_SelectionChanged;
                _listBox.SelectionChanged += _listBox_SelectionChanged;
            }
            if (_listBoxSearch != null)
            {
                _listBoxSearch.IsVisibleChanged -= _listBoxSearch_IsVisibleChanged;
                _listBoxSearch.IsVisibleChanged += _listBoxSearch_IsVisibleChanged;
                _listBoxSearch.SelectionChanged -= _listBoxSearch_SelectionChanged;
                _listBoxSearch.SelectionChanged += _listBoxSearch_SelectionChanged;
            }
        }
        private void _listBoxSearch_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            if ((bool) e.NewValue)
                UpdateIsChecked(_listBoxSearch);
        }
        private void _listBox_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            if ((bool) e.NewValue)
            {
                foreach (var item in selectedSearchList)
                    if (!_listBox.SelectedItems.Contains(item))
                        _listBox.SelectedItems.Add(item);
                UpdateIsChecked(_listBox);
            }
        }
        private void UpdateIsChecked(ListBox listBox)
        {
            _checkBox.Checked -= _checkBox_Checked;
            if (listBox.Items.Count > 0 && listBox.Items.Count == listBox.SelectedItems.Count)
            {
                if (_checkBox.IsChecked != true)
                    _checkBox.IsChecked = true;
            }
            else
            {
                if (listBox.SelectedItems.Count == 0)
                    _checkBox.IsChecked = false;
                else
                    _checkBox.IsChecked = null;
            }
            _checkBox.Checked += _checkBox_Checked;
        }
        private void _popup_GotFocus(object sender, RoutedEventArgs e)
        {
            var source = (HwndSource) PresentationSource.FromVisual(_popup.Child);
            if (source != null)
            {
                SetFocus(source.Handle);
                _textBox.Focus();
            }
        }
        private void _checkBox_Unchecked(object sender, RoutedEventArgs e)
        {
            if (_listBoxSearch.Visibility == Visibility.Visible)
                _listBoxSearch.UnselectAll();
            else
                _listBox.UnselectAll();
        }
        private void _checkBox_Checked(object sender, RoutedEventArgs e)
        {
            if (_listBoxSearch.Visibility == Visibility.Visible)
                _listBoxSearch.SelectAll();
            else
                _listBox.SelectAll();
        }
        private void Combination()
        {
            var seletedName = new List<string>();
            foreach (var item in _listBox.SelectedItems)
            {
                var name = GetDisplayText(item);
                if (!string.IsNullOrWhiteSpace(name))
                    seletedName.Add(name);
                else
                    seletedName.Add(item.ToString());
            }
            foreach (var item in _listBoxSearch.SelectedItems)
            {
                if (_listBox.SelectedItems.Contains(item))
                    continue;
                var name = GetDisplayText(item);
                if (!string.IsNullOrWhiteSpace(name))
                    seletedName.Add(name);
                else
                    seletedName.Add(item.ToString());
            }
            Text = string.Join(Delimiter, seletedName.ToArray());
        }
        private void _listBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if (e.RemovedItems.Count > 0)
            {
                foreach (var item in e.RemovedItems)
                {
                    if (_checkBox.IsChecked == true)
                    {
                        _checkBox.Unchecked -= _checkBox_Unchecked;
                        if (_listBox.Items.Count == 1)
                            _checkBox.IsChecked = false;
                        else
                            _checkBox.IsChecked = null;
                        _checkBox.Unchecked += _checkBox_Unchecked;
                    }
                    if (_listBoxSearch.SelectedItems.Contains(item))
                        _listBoxSearch.SelectedItems.Remove(item);
                    if (selectedSearchList.Contains(item))
                        selectedSearchList.Remove(item);
                }
                SelectionChecked(_listBox);
            }
            if (e.AddedItems.Count > 0)
                SelectionChecked(_listBox);
            Combination();
            SelectedItems = _listBox.SelectedItems;
        }
        private void _listBoxSearch_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if (!_listBoxSearch.IsVisible)
                return;
            if (e.RemovedItems.Count > 0)
            {
                foreach (var item in e.RemovedItems)
                {
                    if (selectedSearchList.Contains(item))
                        selectedSearchList.Remove(item);
                    if (_listBox.SelectedItems.Contains(item))
                        _listBox.SelectedItems.Remove(item);
                    if (selectedList.Contains(item))
                        selectedList.Remove(item);
                }
                Combination();
                SelectionChecked(_listBoxSearch);
            }
            if (e.AddedItems.Count > 0)
            {
                foreach (var item in e.AddedItems)
                    if (!selectedSearchList.Contains(item))
                        selectedSearchList.Add(item);
                Combination();
                SelectionChecked(_listBoxSearch);
            }
        }
        private void SelectionChecked(ListBox listbox)
        {
            if (listbox.SelectedItems.Count > 0
                &&
                listbox.Items.Count == listbox.SelectedItems.Count)
            {
                _checkBox.Checked -= _checkBox_Checked;
                _checkBox.IsChecked = true;
                _checkBox.Checked += _checkBox_Checked;
            }
            else
            {
                _checkBox.Checked -= _checkBox_Checked;
                if (listbox.SelectedItems.Count > 0
                    &&
                    listbox.Items.Count == listbox.SelectedItems.Count)
                {
                    if (_checkBox.IsChecked != true)
                        _checkBox.IsChecked = true;
                }
                else
                {
                    if (listbox.SelectedItems.Count == 0)
                        _checkBox.IsChecked = false;
                    else
                        _checkBox.IsChecked = null;
                }
                _checkBox.Checked += _checkBox_Checked;
            }
        }
        private string GetDisplayText(object dataItem, string path = null)
        {
            if (dataItem == null) return string.Empty;
            return GetPropertyValue(dataItem);
        }
        private void _textbox_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (string.IsNullOrWhiteSpace(theLastText)) theLastText = _textBox.Text;
            SearchText(_textBox.Text);
        }
        private void SearchText(string _text)
        {
            var text = _text;
            if (string.IsNullOrWhiteSpace(text))
            {
                if (_listBoxSearch.Visibility != Visibility.Collapsed)
                    _listBoxSearch.Visibility = Visibility.Collapsed;
                if (_listBox.Visibility != Visibility.Visible)
                    _listBox.Visibility = Visibility.Visible;
            }
            else
            {
                if (_listBoxSearch.Visibility != Visibility.Visible)
                    _listBoxSearch.Visibility = Visibility.Visible;
                if (_listBox.Visibility != Visibility.Collapsed)
                    _listBox.Visibility = Visibility.Collapsed;
                var listSearch = new List<object>();
                foreach (var item in _listBox.Items)
                {
                    var str = GetPropertyValue(item);
                    if (string.IsNullOrWhiteSpace(str))
                        str = item.ToString();
                    if (!string.IsNullOrWhiteSpace(str))
                        if (str.Contains(text.ToUpperInvariant()))
                            listSearch.Add(item);
                }
                foreach (var item in selectedList)
                    if (!listSearch.Contains(item))
                        listSearch.Add(item);
                var lastItem = ItemsSourceSearch;
                ItemsSourceSearch = listSearch;
                SelectionChecked(_listBoxSearch);
                selectedItems.Clear();
                foreach (var item in _listBoxSearch.Items)
                    if (_listBox.SelectedItems.Contains(item))
                        if (!_listBoxSearch.SelectedItems.Contains(item))
                            _listBoxSearch.SelectedItems.Add(item);
            }
        }
        private string GetPropertyValue(object item)
        {
            var result = string.Empty;
            var nameParts = DisplayMemberPath.Split('.');
            if (nameParts.Length == 1)
            {
                var property = item.GetType().GetProperty(DisplayMemberPath);
                if (property != null)
                    return (property.GetValue(item, null) ?? string.Empty).ToString();
            }
            return result.ToUpperInvariant();
        }
        private static void OnIsDropDownOpenChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
        {
            var multiSelectionSearchComboBox = o as MultiSelectionSearchComboBox;
            if (multiSelectionSearchComboBox != null)
                multiSelectionSearchComboBox.OnIsOpenChanged((bool) e.OldValue, (bool) e.NewValue);
        }
        protected virtual void OnIsOpenChanged(bool oldValue, bool newValue)
        {
            if (!newValue)
                RaiseRoutedEvent(ClosedEvent);
        }
        private void RaiseRoutedEvent(RoutedEvent routedEvent)
        {
            var args = new RoutedEventArgs(routedEvent, this);
            RaiseEvent(args);
        }
        private static void OnMaxDropDownHeightChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
        {
            var comboBox = o as MultiSelectionSearchComboBox;
            if (comboBox != null)
                comboBox.OnMaxDropDownHeightChanged((double) e.OldValue, (double) e.NewValue);
        }
        protected virtual void OnMaxDropDownHeightChanged(double oldValue, double newValue)
        {
        }
        private static void OnSelectedItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var mltiSelectionSearchComboBox = d as MultiSelectionSearchComboBox;
            if (e.NewValue != null)
            {
                var collection = e.NewValue as IList;
                if (collection.Count <= 0) return;
                mltiSelectionSearchComboBox._listBox.SelectionChanged -=
                    mltiSelectionSearchComboBox._listBox_SelectionChanged;
                foreach (var item in collection)
                {
                    var name = mltiSelectionSearchComboBox.GetPropertyValue(item);
                    object model = null;
                    if (!string.IsNullOrWhiteSpace(name))
                        model = mltiSelectionSearchComboBox._listBox.ItemsSource.OfType<object>().FirstOrDefault(h =>
                            mltiSelectionSearchComboBox.GetPropertyValue(h).ToUpperInvariant()
                                .Equals(name));
                    else
                        model = mltiSelectionSearchComboBox._listBox.ItemsSource.OfType<object>()
                            .FirstOrDefault(h => h == item);
                    if (model != null && !mltiSelectionSearchComboBox._listBox.SelectedItems.Contains(item))
                        mltiSelectionSearchComboBox._listBox.SelectedItems.Add(model);
                }
                mltiSelectionSearchComboBox._listBox.SelectionChanged +=
                    mltiSelectionSearchComboBox._listBox_SelectionChanged;
                mltiSelectionSearchComboBox.Combination();
            }
        }
    }
}

2）创建 MultiSelectSearchComboBoxExample.xaml 代码如下:

1.使用 SelectedItems 进行初始化选中

<UserControl
    x:Class="WPFDevelopers.Samples.ExampleViews.MultiSelectSearchComboBoxExample"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:WPFDevelopers.Samples.ExampleViews"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:model="clr-namespace:WPFDevelopers.Sample.Models"
    xmlns:vm="clr-namespace:WPFDevelopers.Samples.ViewModels"
    xmlns:wd="https://github.com/WPFDevelopersOrg/WPFDevelopers"
    d:DesignHeight="450"
    d:DesignWidth="800"
    mc:Ignorable="d">
    <UserControl.Resources>
        <model:HospitalList x:Key="myHospitalList" />
    </UserControl.Resources>
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition />
            </Grid.RowDefinitions>
            <Button
                Margin="0,20,0,0"
                HorizontalAlignment="Center"
                VerticalAlignment="Bottom"
                Click="Button_Click"
                Content="获取选中"
                Style="{StaticResource WD.SuccessPrimaryButton}" />
            <UniformGrid
                Grid.Row="1"
                Columns="2"
                Rows="2">
                <wd:MultiSelectionSearchComboBox
                    Width="200"
                    HorizontalAlignment="Center"
                    VerticalContentAlignment="Center"
                    Delimiter=","
                    DisplayMemberPath="Number"
                    IsSelectAllActive="True"
                    ItemsSource="{Binding Drawings}"
                    SelectedValuePath="Index">
                    <wd:MultiSelectionSearchComboBox.DataContext>
                        <vm:DrawingExampleVM />
                    </wd:MultiSelectionSearchComboBox.DataContext>
                </wd:MultiSelectionSearchComboBox>
                <wd:MultiSelectionSearchComboBox
                    Width="200"
                    HorizontalAlignment="Center"
                    VerticalContentAlignment="Center"
                    wd:ElementHelper.Watermark="MultiSelectionSearchComboBox"
                    Delimiter="^"
                    DisplayMemberPath="Number"
                    IsSelectAllActive="True"
                    ItemsSource="{Binding Drawings}"
                    SearchWatermark="请输入搜索内容"
                    SelectedValuePath="Index">
                    <wd:MultiSelectionSearchComboBox.DataContext>
                        <vm:DrawingExampleVM />
                    </wd:MultiSelectionSearchComboBox.DataContext>
                </wd:MultiSelectionSearchComboBox>
                <wd:MultiSelectionSearchComboBox
                    Name="MyMultiSelectionSearchComboBox2"
                    Width="200"
                    HorizontalAlignment="Center"
                    VerticalContentAlignment="Center"
                    wd:ElementHelper.Watermark="下拉多选搜索"
                    Delimiter="^"
                    IsSelectAllActive="True"
                    SearchWatermark="请输入搜索内容">
                    <wd:MultiSelectionSearchComboBox.DataContext>
                        <vm:DrawingExampleVM />
                    </wd:MultiSelectionSearchComboBox.DataContext>
                </wd:MultiSelectionSearchComboBox>
            </UniformGrid>
        </Grid>
</UserControl>

3）创建 MultiSelectSearchComboBoxExample.xaml.cs 代码如下:

using ICSharpCode.AvalonEdit.Document;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
namespace WPFDevelopers.Samples.ExampleViews
{
    /// <summary>
    /// MultiSelectComboBoxExample.xaml 的交互逻辑
    /// </summary>
    public partial class MultiSelectSearchComboBoxExample : UserControl
    {
        public MultiSelectSearchComboBoxExample()
        {
            InitializeComponent();
            Loaded += MultiSelectSearchComboBoxExample_Loaded;
        }
        private void MultiSelectSearchComboBoxExample_Loaded(object sender, RoutedEventArgs e)
        {
            var list = new List<string>();
            for (int i = 0; i < 10; i++)
                list.Add(i.ToString());
            MyMultiSelectionSearchComboBox2.ItemsSource = list;
            MyMultiSelectionSearchComboBox2.SelectedItems = list.Skip(3).ToList();
        }
        private void Button_Click(object sender, System.Windows.RoutedEventArgs e)
        {
            WPFDevelopers.Controls.MessageBox.Show($"{MyMultiSelectionSearchComboBox2.Text} \r\n总共选中:{MyMultiSelectionSearchComboBox2.SelectedItems.Count} 条","选中内容",MessageBoxButton.OK,MessageBoxImage.Information);      
        }
    }
}

效果图

WPF实现筛选下拉多选控件的示例代码

最新文章 相关文章

使用C#判断文件是否为图片的多种方法

目录 0、常见的判断图片文件的方法 1. 根据文件扩展名判断 代码示例 优缺点 2. 通过文件头（Magic Number）判断 代码示例 优缺点 3. 使用 ImageSharp 判断文件是否为图

2024-10-18 23:26:39

QT 实现随机验证码功能

目录 1.界面实现效果 2.简介 3.使用1.界面实现效果以下是具体的项目需要用到的效果展示，用于验证字母。2.简介自定义CaptchaMovableLabel，继承自QLabel类：
中间的4个字母，就是Ca

2024-10-18 23:26:30

C# Winform截图指定控件范围内的图像的流程步骤

目录 一、函数输入 二、函数输出 三、使用示例一、函数输入输入有两个，参数一：需要截图的容器控件，参数二：保存截图的绝对路径路径<param name="control">控件名</param>
<param

2024-10-14 19:57:08

C++解决回调地狱问题的方法小结

目录1. 使用 Lambda 表达式和标准库 std::function2. 使用 std::future 和 std::promise3. 使用协程 (C++20)4. 使用异步框架总结“地狱回调”（Callback Hell）是指

2024-09-10 22:05:57

C语言报错：Buffer Overflow的原因和解决办法

目录简介什么是Buffer OverflowBuffer Overflow的常见原因如何检测和调试Buffer Overflow解决Buffer Overflow的最佳实践详细实例解析示例1：数组越界写入示例2：未检查输入长度

2024-09-10 22:05:55

C++报错：Segmentation Fault的解决方案

目录引言段错误的产生原因段错误的检测方法段错误的预防措施段错误的解决方案总结引言段错误（Segmentation Fault）是 C++ 编程中常见且令人头疼的错误之一。段错误通常发生在

2024-09-10 22:05:53

Qt中QPushButton组件的使用详解

QPushButton是Qt库中的一个重要组件，它是用户界面（UI）设计中常用的一个按钮控件。在Qt程序中，QPushButton用于创建可以在界面上点击响应操作的交互元素。它的主要作用包括：显示文

2024-09-10 22:05:51

Qt实现手动切换多种布局的完美方案

目录引言示例需求开发环境代码实现运行结果程序分析注意引言之前写了一个手动切换多个布局的程序，下面来记录一下。
程序运行效果如下：示例需求通过点击程序界面上不同的布局

2024-09-10 22:05:49

一篇文章详解Qt中如何访问数据库

目录前言1. 加载数据库驱动2. 创建数据库连接3. 执行SQL查询或命令4. 关闭数据库连接示例完整代码片段打开多个数据库使用建议总结 前言在Qt中访问数据库涉及到几个关键步骤

2024-09-10 22:05:47

Qt 编译配置 Protobuf 的详细步骤

目录步骤 1: 安装Protobuf步骤 2: 配置Qt项目步骤 3: 编译和运行项目 运行qmake以生成Makefile：注意事项在Qt项目中使用Protobuf（Protocol Buffers）可以有效地处理数据序列化和

2024-09-10 22:05:45

C++ STL iota 和 atoi 用法示例详解

目录一：功能二：用法一：功能 iota 是给定一个初始元素，然后依次对序列中每个元素进行递增++操作，详见代码一； atoi 是将字符串转换成整数；atol, atoll 将字符串转换成

2024-09-10 22:05:43

C语言中输出空格的五种方法

目录前言1. 直接在字符串中包含空格2. 使用 %s 和空格3. 使用 \t 输出制表符（Tab）4. 使用循环输出多个空格5. 使用格式控制符输出空格总结前言在C语言中，输出空格可以通过使用

2024-09-10 22:05:41

C语言文件操作入门指南

一、为什么使用文件在学习完结构体后，为了检验学习成果，我们写了一个通讯录的小程序，当通讯录运行起来的时候，可以给通讯录中增加、删除数据，此时数据是存放在内存中的，当程序退出

2024-09-10 22:05:39

Qt中暂停程序的几种方法小结

目录1. 使用 QThread::sleep示例代码：说明：优点：缺点：2. 使用 QTimer 和事件循环示例代码：说明：优点：缺点：3. 使用 QEventLoop 结合 QTimer示例代码：说明：优点：缺点：4. 使用 QPauseAnima

2024-09-10 22:05:35

C语言中实现自定义数据类型的输入输出的方法和技巧

目录C 语言中如何实现自定义数据类型的输入输出一、结构体数据类型的输入输出二、枚举数据类型的输入输出三、联合数据类型的输入输出四、使用指针实现复杂数据结构的输入输

2024-09-10 22:05:34

详解C/C++如何发送与接收Kafka消息

目录一、背景二、环境依赖安装三、编写kakfa生产者消费者3.1 生产者3.2 消费者3.3 编译运行3.3.1 编译生产者消费者3.3.2 运行验证3.4 SASL认证kakfa3.5 结束语一、背景在实

2024-09-10 22:05:32

C++传值、传址、传引用的区别和选择小结

目录传值传址传引用如何选择合适的参数传递方式在C++中，参数传递方式主要有三种：传值（pass by value）、传址（pass by address）、传引用（pass by reference）。每种方式都有其特定的使

2024-09-10 22:05:30

C++如何实现sha256算法

目录概述CHP_Sha256总结概述SHA-256，英文全称为Secure Hash Algorithm 256-bit，是一种广泛使用的密码散列函数，属于SHA-2家族。SHA-256算法由美国国家安全局（NSA）设计，并由美国国

2024-09-10 22:05:28

C语言中的断言函数assert详解

简介assert 是 C 语言中的一个宏，用于在程序运行时进行条件检查，主要用于调试目的。它在 <assert.h> 头文件中定义，用于验证程序中的假设条件是否成立，如果不成立，程序将打印错误

2024-09-10 22:05:26

C++之assert推荐用法及注意事项

目录1.引言2.简单示例3.推荐使用方法4.常见使用场景和注意事项4.1.检查参数的合法性4.2.assert不能使用改变环境的语句4.3.在未知的逻辑中添加assert(false)5.总结1.引言ass

2024-09-10 22:05:24

Qt中connect()函数及用法详解

目录一、基本概念二、用法1.旧版用法（Qt4和早期Qt5）2.新版用法（推荐）3.自动连接（无需使用connect()函数）4.Lambda表达式（Qt5.4）三、断开连接disconnect()1.为什么使用disconnect()2.

2024-09-10 22:05:23

深入解读C++ 内联函数inline|nullptr

目录一、inline关键字1.1 什么是内联函数？1.2 为什么会有内联函数？1.2.1 回顾宏1.2.2 宏的改进&ndash;内联函数1.3 内联函数的特性二、指针空值nullptr2.1 C和C++中NULL的含义

2024-09-10 22:05:21

vscode远程连接服务器(免密登录+远程开发)

目录1.获取服务器IP2.安装并且启用ssh服务3.在vscode中远程连接 4.实现免密登录vscode的远程连接功能十分方便，可以让我们在一个开发工具中实现完整的工作流，下面介绍如何在vs

2024-09-10 22:05:18

C++实现LRU缓存的操作方法

目录LRU的概念哈希表（unordered_map）主要特性常用操作双向链表（list）特性常用操作LRU缓存（C++）初始化状态LRU的概念LRU（Least Recently Used，最近最少使用）是一种常用的缓存淘汰策略，

2024-09-10 22:05:16

使用C语言生成图片的base64编码的代码实现

目录一、前言二、代码实操2.1 将二进制数据转为Base64编码2.2 实现图片的base64编码和解码一、前言Base64编码是一种广泛使用的编码方案，将任意二进制数据转换为可打印的ASCI

2024-09-10 22:05:14

C语言strcat函数详解：字符串追加的利器

目录一、strcat函数的简介二、strcat函数的使用三、strcat函数的注意事项四、strcat函数的模拟实现一、strcat函数的简介strcat函数用于将源字符串追加到目标字符串的末尾，并

2024-09-10 22:05:12

C++之thread_local变量的一些用法

目录1.C++ 的存储类型1.1.存储周期（Storage duration）1.2.存储类型说明符（Storage class specifiers）1.3.存储类型说明符与存储周期的关系2.thread_local简介3.thread_local 应

2024-09-10 22:05:10

c++栈内存和堆内存的基本使用小结

c++栈内存和堆内存的基本使用#include <iostream>// 定义一个简单的结构体struct Person { std::string name; int age;};int main() { // 栈内存分配 int a = 10; //

2024-09-10 22:05:08

C++11标准库 互斥锁 <mutex> 详解

目录<mutex>std::call_once函数例程:使用call_once实现的单例模式std::mutex类 -- 独占互斥锁成员函数std::recursive_mutex类 -- 递归互斥锁使用注意:描述:std::timed_mute

2024-09-10 22:05:06

C++实现字符串元音字母反转的两种方法

目录C++实现字符串元音字母反转的巧妙方法示例方法一：利用数据结构存储元音位置和字符并反转代码实现1. 如何在C++中存储数字和字符并支持翻转2. 判断字符是否在列表中3. 巧

2024-09-10 22:05:04

热点内容

c语言中fun用法详解
2020-05-31
C语言实现520表白代码 祝你表白成功!
2021-06-03
Qt图形图像开发之高性能曲线图模块QCustomplot库详细使用方法与实例(支持动、静曲线图
2020-05-26
C语言实战之浪漫烟花表白程序代码
2021-04-24
VS Code C/C++环境配置教程(无法打开源文件“xxxxxx.h”或者检测到 #include 错误,请
2020-11-01
VS2019如何添加头文件路径的方法步骤
2020-11-01
VS2019配置OpenCV时找不到Microsoft.Cpp.x64.user的解决方法
2020-05-26
C语言实现放烟花的程序
2021-02-22
c语言如何用if判断成绩等级？
2020-06-19
VSCode同时更改所有相同的变量名或类名的图文教程
2020-11-01
返回顶部
顶部