[移动开发]学习用VS2019开发安卓app(二)

Xamarin跨平台移动开发

开发选择移动应用开发Xamarin.from

布局改为label和输入为一列和输入框占满屏幕

添加Orientation=“Horizontal”
WidthRequest=“200”

    <ContentPage.Content>
        <StackLayout >
            <StackLayout Orientation="Horizontal">
                <Image Source="user.png" />
                <Entry Placeholder="请输入用户名" 
                       ClearButtonVisibility="WhileEditing"
                       HorizontalOptions="Fill"
                       WidthRequest="200" />
            </StackLayout>

            <StackLayout Orientation="Horizontal">
                <Image Source="lock.png" />
                <Entry Placeholder="请输入密码"   
                       ClearButtonVisibility="WhileEditing"
                       HorizontalOptions="Fill"
                       WidthRequest="200"
                       MaxLength="15"
                       IsSpellCheckEnabled="false"
                       IsTextPredictionEnabled="false"
                       IsPassword="true"      />
            </StackLayout>
            <Button Text="登录" BackgroundColor="Blue" Clicked="BtnLogin" />
        </StackLayout>
    </ContentPage.Content>

添加导航标题

ContentPage中添加

Title="FIFO列印"

VS报错PushAsync is not supported globally on Android, please use a NavigationPage

在app.Xaml.cs中添加
MainPage = new NavigationPage(new MainPage());

显示清除按钮

XAML

<Entry Text="Xamarin.Forms"
      ClearButtonVisibility="WhileEditing" />

C#

var entry = new Entry { Text = "Xamarin.Forms", ClearButtonVisibility = ClearButtonVisibility.WhileEditing };

去掉导航栏

添加代码 NavigationPage.HasNavigationBar=“False”

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             NavigationPage.HasNavigationBar="False"
             x:Class="SeuicPrint.MainPage">

页面跳转

在.cs代码添加
ScanCodePages为页面名称

   private async void BtnUts(object sender, EventArgs e)
        {
            await Navigation.PushAsync(new ScanCodePages());
        }
private async void BtnShipping(object sender, EventArgs e)
        {
            await Navigation.PushAsync(new ScanCodePages());
        }

Label样式

整个居中
HorizontalOptions=“Center”
将文本内容居中如图

Orientation="Vertical"
HorizontalTextAlignment="Center"

显示在底部

加StackLayout 中加VerticalOptions=“FillAndExpand”
label中加
HorizontalOptions=“FillAndExpand”
VerticalOptions=“EndAndExpand”

     <StackLayout  Orientation="Vertical"  VerticalOptions="FillAndExpand"  >
                <Label Text="Message" 
                   FontSize ="30"
                   TextColor="White"
                   BackgroundColor="GreenYellow" 
                   HorizontalTextAlignment="Center"
                   HorizontalOptions="FillAndExpand"  
                   VerticalOptions="EndAndExpand"
                   FontAttributes="Bold"/>
            </StackLayout>

Editor实现输入自适应

 <Editor Placeholder="请输入二维码" 
                        AutoSize="TextChanges"
                        TextColor="Blue"/>

实现Entry修改事件和完成事件

TextChanged
Completed
.xam添加

    TextChanged="Entry_TextChangedPassword"
      Completed="EditorEnterCompleted"

.xam.cs添加

   public void Entry_TextChangedUser(object sender, TextChangedEventArgs e)
        {
            oldUserText = e.OldTextValue;
            newUserText = e.NewTextValue;
        }
        public void EditorEnterCompleted(object sender, TextChangedEventArgs e)
        {
            var Text = ((Editor)sender).Text;
        }

Label赋值修改

XMAL中加 x:Name=“code”

 <StackLayout  Orientation="Vertical"  VerticalOptions="FillAndExpand"  >
                <Label Text="Message" 
                        x:Name="code"
                   FontSize ="30"
                   TextColor="White"
                   BackgroundColor="GreenYellow" 
                   HorizontalTextAlignment="Center"
                   HorizontalOptions="FillAndExpand"  
                   VerticalOptions="EndAndExpand"
                   FontAttributes="Bold"/>
            </StackLayout>

XMAL.cs中加

code.Text = "所输入的二维码格式不正确,请确认!\n正确的格式：20210605141700254036@004.078.0050010@119414@@21231@20210605@9000";

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