为什么数学方程总是导致 0？

Question

我目前正在尝试第一次在 Visual Studio 中练习使用 Xamarin，我决定尝试制作一个计算器应用程序。我尝试了不同的方法来制作这个应用程序，只是发现使用属性可以让它更有效地运行。但是，在尝试从另一个来源实现某种格式之后，不知何故，结果总是为零。

XAML：

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="CalculatorApp.Calculator2">
    <ContentPage.Resources>
        <ResourceDictionary>
            <Style x:Key="display" TargetType="Label">
                <Setter Property="BackgroundColor" Value="Black"/>
                <Setter Property="TextColor" Value="White"/>
                <Setter Property="FontSize" Value="60"/>
                <Setter Property="FontAttributes" Value="None"/>
                <Setter Property="VerticalTextAlignment" Value="End"/>
                <Setter Property="HorizontalTextAlignment" Value="End"/>
            </Style>
            <Style x:Key="buttonYellow" TargetType="Button">
                <Setter Property="BackgroundColor" Value="#FF9F2A"/>
                <Setter Property="TextColor" Value="White"/>
                <Setter Property="FontSize" Value="16"/>
            </Style>
            <Style x:Key="buttonGrey" TargetType="Button">
                <Setter Property="BackgroundColor" Value="#AAAAAA"/>
                <Setter Property="TextColor" Value="#424242"/>
                <Setter Property="FontSize" Value="16"/>
            </Style>
            <Style x:Key="buttonDarker" TargetType="Button">
                <Setter Property="BackgroundColor" Value="#333333"/>
                <Setter Property="TextColor" Value="White"/>
                <Setter Property="FontSize" Value="16"/>
            </Style>
        </ResourceDictionary>
    </ContentPage.Resources>

    <!--Content Starts here-->

    <ContentPage.Content>
        <Grid BackgroundColor="Black">
            <!-- Place new controls here -->
            <!--Row and Column Definitions-->
            <Grid.RowDefinitions>
                <RowDefinition Height="2.5*"/>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="1*"/>
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="1*"/>
                <ColumnDefinition Width="1*"/>
                <ColumnDefinition Width="1*"/>
                <ColumnDefinition Width="1*"/>
            </Grid.ColumnDefinitions>

            <!--First Row-->
            <Label x:Name="displayLbl" Text="{Binding LblText}" Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="4" Style="{StaticResource display}"/>

            <!--AC and Divide-->
            <Button Text="AC" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="3" Style="{StaticResource buttonGrey}" Clicked="ClearButton"/>
            <Button Text="÷" Grid.Row="1" Grid.Column="3" Style="{StaticResource buttonYellow}" Clicked="DivideButton"/>

            <!--Third Row-->
            <Button Text="7" Grid.Row="2" Grid.Column="0" Style="{StaticResource buttonDarker}" Clicked="CalculatorButtons"/>
            <Button Text="8" Grid.Row="2" Grid.Column="1" Style="{StaticResource buttonDarker}" Clicked="CalculatorButtons"/>
            <Button Text="9" Grid.Row="2" Grid.Column="2" Style="{StaticResource buttonDarker}" Clicked="CalculatorButtons"/>
            <Button Text="×" Grid.Row="2" Grid.Column="3" Style="{StaticResource buttonYellow}" Clicked="MultiplyButton"/>

            <!--Fourth Row-->
            <Button Text="4" Grid.Row="3" Grid.Column="0" Style="{StaticResource buttonDarker}" Clicked="CalculatorButtons"/>
            <Button Text="5" Grid.Row="3" Grid.Column="1" Style="{StaticResource buttonDarker}" Clicked="CalculatorButtons"/>
            <Button Text="6" Grid.Row="3" Grid.Column="2" Style="{StaticResource buttonDarker}" Clicked="CalculatorButtons"/>
            <Button Text="-" Grid.Row="3" Grid.Column="3" Style="{StaticResource buttonYellow}" Clicked="MinusButton"/>

            <!--Fifth Row-->
            <Button Text="1" Grid.Row="4" Grid.Column="0" Style="{StaticResource buttonDarker}" Clicked="CalculatorButtons"/>
            <Button Text="2" Grid.Row="4" Grid.Column="1" Style="{StaticResource buttonDarker}" Clicked="CalculatorButtons"/>
            <Button Text="3" Grid.Row="4" Grid.Column="2" Style="{StaticResource buttonDarker}" Clicked="CalculatorButtons"/>
            <Button Text="+" Grid.Row="4" Grid.Column="3" Style="{StaticResource buttonYellow}" Clicked="PlusButton"/>

            <!--Sixth Row-->
            <Button Text="0" Grid.Row="5" Grid.Column="0" Grid.ColumnSpan="3" Style="{StaticResource buttonDarker}" Clicked="CalculatorButtons"/>
            <Button Text="=" Grid.Row="5" Grid.Column="3" Style="{StaticResource buttonYellow}" Clicked="EqualButton"/>
        </Grid>
    </ContentPage.Content>

</ContentPage>

代码隐藏：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace CalculatorApp
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class Calculator2 : ContentPage
    {
        private double _Number = 0;
        public double Number
        {
            get
            {
                return _Number;
            }
            set
            {
                _Number = value;
                displayLbl.Text = _Number.ToString();
            }
        }

        private double _Result;
        public double Result
        {
            get
            {
                return _Result;
            }

            set
            {
                _Result = value;
                displayLbl.Text = _Result.ToString();
            }
        }

        public Calculator2 ()
        {
            InitializeComponent ();
        }

        private void CalculatorButtons(object sender, EventArgs e)
        {
            displayLbl.Text += ((Button)sender).Text;
        }


        #region Operation Buttons
        private void PlusButton(object sender, EventArgs e)
        {
            Result += Number;
            Number = 0.0;
        }

        private void MinusButton(object sender, EventArgs e)
        {
            Result -= Number;
            Number = 0.0;
        }

        private void MultiplyButton(object sender, EventArgs e)
        {
            Result *= Number;
            Number = 0.0;
        }

        private void DivideButton(object sender, EventArgs e)
        {
            Result /= Number;
            Number = 0.0;
        }

        private void EqualButton(object sender, EventArgs e)
        {
            Result = Number;
        }

        private void ClearButton(object sender, EventArgs e)
        {
            ClearCommand();
        }
        #endregion

        public void ClearCommand() {
            displayLbl.Text = null;
        }
    }
}

任何帮助将不胜感激。

Answer 1

1.) 您的清除命令还应将结果重置为 0，因为通过查看此代码，无论您清除多少次，结果似乎仍会累积。

2.) Number 始终为零，因为除了在每次操作员函数调用后将其重置回 0 之外，您没有在任何地方设置它（它没有绑定到任何按钮）。根据您当前的设计，您可以在 CalculatorButtons 函数内部执行的操作是根据 ((Button)sender).Text 继续附加数字字符串，一旦调用 +-* 函数，将其转换为数字并执行您的计算.

这种方法是否是最有效的方法（不是）完全是一个不同的问题。