User Interface (UI) trong Xamarin
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Style trong Xamarin Form là gì và cách sử dụng như thế nào?
Style trong Xamarin Form là gì ?
- class Style (Xamarin.Forms.Style )
- Nhóm các thành phần UI chung để sử dụng lại & thay đổi nhanh chóng như: các loại button, các loại text h1, h2 ...
- Style sử dụng : XAML Style hoặc Cascading Style Sheets ( CSS)
Sử dụng Style với XAML Style:
-
Explicit Styles: apply cho 1 đối tượng cụ thể
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="Styles.ExplicitStylesPage" Title="Explicit" IconImageSource="xaml.png"> <ContentPage.Content> <StackLayout Padding="0,20,0,0"> <StackLayout.Resources> <ResourceDictionary> <Style x:Key="labelRedStyle" TargetType="Label"> ... </Style> ... </ResourceDictionary> </StackLayout.Resources> <Label Text="These labels" Style="{StaticResource labelRedStyle}" /> ... </StackLayout> </ContentPage.Content> </ContentPage> -
Implicit Styles: Sử dụng để apply chung cho 1 TargetType vd: Button/ Label ...
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:Styles;assembly=Styles" x:Class="Styles.ImplicitStylesPage" Title="Implicit" IconImageSource="xaml.png"> <ContentPage.Resources> <ResourceDictionary> <Style TargetType="Entry"> <Setter Property="HorizontalOptions" Value="Fill" /> <Setter Property="VerticalOptions" Value="CenterAndExpand" /> <Setter Property="BackgroundColor" Value="Yellow" /> <Setter Property="FontAttributes" Value="Italic" /> <Setter Property="TextColor" Value="Blue" /> </Style> </ResourceDictionary> </ContentPage.Resources> <ContentPage.Content> <StackLayout Padding="0,20,0,0"> <Entry Text="These entries" /> <Entry Text="are demonstrating" /> <Entry Text="implicit styles," /> <Entry Text="and an implicit style override" BackgroundColor="Lime" TextColor="Red" /> <local:CustomEntry Text="Subclassed Entry is not receiving the style" /> </StackLayout> </ContentPage.Content> </ContentPage> -
Global Styles: Để sử dụng chung cho toàn pages (ResourceDictionary tại App.xaml ), tránh việc lặp đi lặp lại việc tạo style giữa các page , có thể override style tại resource page / resource của từng phần tử.
-
Style Inheritance: Để kế thừa lại từ style khác, mục đích tái sử dụng & ko duplicate. Sử dụng BaseOn:
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="Styles.StyleInheritancePage" Title="Inheritance" IconImageSource="xaml.png"> <ContentPage.Resources> <ResourceDictionary> <Style x:Key="baseStyle" TargetType="View"> <Setter Property="HorizontalOptions" Value="Center" /> <Setter Property="VerticalOptions" Value="CenterAndExpand" /> </Style> <Style x:Key="labelStyle" TargetType="Label" BasedOn="{StaticResource baseStyle}"> ... <Setter Property="TextColor" Value="Teal" /> </Style> <Style x:Key="buttonStyle" TargetType="Button" BasedOn="{StaticResource baseStyle}"> <Setter Property="BorderColor" Value="Lime" /> ... </Style> </ResourceDictionary> </ContentPage.Resources> <ContentPage.Content> <StackLayout Padding="0,20,0,0"> <Label Text="These labels" Style="{StaticResource labelStyle}" /> ... <Button Text="So is the button" Style="{StaticResource buttonStyle}" /> </StackLayout> </ContentPage.Content> </ContentPage> -
Dynamic Styles: Style sẽ ko thay đổi sau khi được assign. Sử dụng DynamicResource để giải quyết việc này. DynamicResource va StaticResource markup extension là giống nhau, chỉ khác StaticResource là : single dictionary lookup, và DynamicResource tồn lại liên kết đến Dictionary key -> khi dictionary entry đã liên kết với dictionary key bị thay đổi thì nó sẽ thay đổi theo -> UI sẽ được cập nhật. Tiến hành qua 2 bước:
-
Khai báo dynamic style XAML file:
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="Styles.DynamicStylesPage" Title="Dynamic" IconImageSource="xaml.png"> <ContentPage.Resources> <ResourceDictionary> <Style x:Key="baseStyle" TargetType="View"> ... </Style> <Style x:Key="blueSearchBarStyle" TargetType="SearchBar" BasedOn="{StaticResource baseStyle}"> ... </Style> <Style x:Key="greenSearchBarStyle" TargetType="SearchBar"> ... </Style> ... </ResourceDictionary> </ContentPage.Resources> <ContentPage.Content> <StackLayout Padding="0,20,0,0"> <SearchBar Placeholder="These SearchBar controls" Style="{DynamicResource searchBarStyle}" /> ... </StackLayout> </ContentPage.Content> </ContentPage> -
Xử lý ở code-behind:
public partial class DynamicStylesPage : ContentPage { bool originalStyle = true; public DynamicStylesPage () { InitializeComponent (); Resources ["searchBarStyle"] = Resources ["blueSearchBarStyle"]; } void OnButtonClicked (object sender, EventArgs e) { if (originalStyle) { Resources ["searchBarStyle"] = Resources ["greenSearchBarStyle"]; originalStyle = false; } else { Resources ["searchBarStyle"] = Resources ["blueSearchBarStyle"]; originalStyle = true; } } }
-
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Device Styles: X.F chứa 6 loại để hiển thị cho phần Label:
- BodyStyle
- CaptionStyle
- ListItemDetailTextStyle
- ListItemTextStyle
- SubtitleStyle
- TitleStyle
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="Styles.DeviceStylesPage" Title="Device" IconImageSource="xaml.png"> <ContentPage.Resources> <ResourceDictionary> <Style x:Key="myBodyStyle" TargetType="Label" BaseResourceKey="BodyStyle"> <Setter Property="TextColor" Value="Accent" /> </Style> </ResourceDictionary> </ContentPage.Resources> <ContentPage.Content> <StackLayout Padding="0,20,0,0"> <Label Text="Title style" Style="{DynamicResource TitleStyle}" /> <Label Text="Subtitle text style" Style="{DynamicResource SubtitleStyle}" /> <Label Text="Body style" Style="{DynamicResource BodyStyle}" /> <Label Text="Caption style" Style="{DynamicResource CaptionStyle}" /> <Label Text="List item detail text style" Style="{DynamicResource ListItemDetailTextStyle}" /> <Label Text="List item text style" Style="{DynamicResource ListItemTextStyle}" /> <Label Text="No style" /> <Label Text="My body style" Style="{StaticResource myBodyStyle}" /> </StackLayout> </ContentPage.Content> </ContentPage> -
Style Classes: để sử dụng nhiều style cho 1 TargetType: vd BoxView có nhiều Style :
<ContentPage ...> <ContentPage.Resources> <Style TargetType="BoxView" Class="Separator"> <Setter Property="BackgroundColor" Value="#CCCCCC" /> <Setter Property="HeightRequest" Value="1" /> </Style> <Style TargetType="BoxView" Class="Rounded"> <Setter Property="BackgroundColor" Value="#1FAECE" /> <Setter Property="HorizontalOptions" Value="Start" /> <Setter Property="CornerRadius" Value="10" /> </Style> <Style TargetType="BoxView" Class="Circle"> <Setter Property="BackgroundColor" Value="#1FAECE" /> <Setter Property="WidthRequest" Value="100" /> <Setter Property="HeightRequest" Value="100" /> <Setter Property="HorizontalOptions" Value="Start" /> <Setter Property="CornerRadius" Value="50" /> </Style> <Style TargetType="VisualElement" Class="Rotated" ApplyToDerivedTypes="true"> <Setter Property="Rotation" Value="45" /> </Style> </ContentPage.Resources> </ContentPage>
Sử dụng Style với CSS:
- Hiện tại vẫn chưa support full cho CSS.
- Xem Thêm
Theming và cách sử dụng:
Sử dụng để thay đổi toàn bộ visual ui của 1 ứng dụng, như theme dark / light.
Dùng DynamicResource để change theme:
Cách thực hiện:
- Define từng loại theme trong ResourceDictionary
- Sử dụng theme trong ứng dụng bằng DynamicResource
- Set default theme trong App.xaml file.
- Thêm code để thay đổi theme trong runtime.
1. Define Theme:
** Theme Dark **
<ResourceDictionary xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="ThemingDemo.LightTheme">
<Color x:Key="PageBackgroundColor">White</Color>
<Color x:Key="NavigationBarColor">WhiteSmoke</Color>
<Color x:Key="PrimaryColor">WhiteSmoke</Color>
<Color x:Key="SecondaryColor">Black</Color>
<Color x:Key="PrimaryTextColor">Black</Color>
<Color x:Key="SecondaryTextColor">White</Color>
<Color x:Key="TertiaryTextColor">Gray</Color>
<Color x:Key="TransparentColor">Transparent</Color>
</ResourceDictionary>
Theme Light
<ResourceDictionary xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="ThemingDemo.DarkTheme">
<Color x:Key="PageBackgroundColor">Black</Color>
<Color x:Key="NavigationBarColor">Teal</Color>
<Color x:Key="PrimaryColor">Teal</Color>
<Color x:Key="SecondaryColor">White</Color>
<Color x:Key="PrimaryTextColor">White</Color>
<Color x:Key="SecondaryTextColor">White</Color>
<Color x:Key="TertiaryTextColor">WhiteSmoke</Color>
<Color x:Key="TransparentColor">Transparent</Color>
</ResourceDictionary>
2. Sử dụng DynamicResource cho các style:
Sử dụng trong App.xaml
<Application xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="ThemingDemo.App">
<Application.Resources>
<Style x:Key="LargeLabelStyle"
TargetType="Label">
<Setter Property="TextColor"
Value="{DynamicResource SecondaryTextColor}" />
<Setter Property="FontSize"
Value="30" />
</Style>
<Style x:Key="MediumLabelStyle"
TargetType="Label">
<Setter Property="TextColor"
Value="{DynamicResource PrimaryTextColor}" />
<Setter Property="FontSize"
Value="25" />
</Style>
<Style x:Key="SmallLabelStyle"
TargetType="Label">
<Setter Property="TextColor"
Value="{DynamicResource TertiaryTextColor}" />
<Setter Property="FontSize"
Value="15" />
</Style>
</Application.Resources>
</Application>
Sử dụng trong Content Page
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:ThemingDemo"
x:Class="ThemingDemo.UserSummaryPage"
Title="User Summary"
BackgroundColor="{DynamicResource PageBackgroundColor}">
...
<ScrollView>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="200" />
<RowDefinition Height="120" />
<RowDefinition Height="70" />
</Grid.RowDefinitions>
<Grid BackgroundColor="{DynamicResource PrimaryColor}">
<Label Text="Face-Palm Monkey"
VerticalOptions="Center"
Margin="15"
Style="{StaticResource MediumLabelStyle}" />
...
</Grid>
<StackLayout Grid.Row="1"
Margin="10">
<Label Text="This monkey reacts appropriately to ridiculous assertions and actions."
Style="{StaticResource SmallLabelStyle}" />
<Label Text=" • Cynical but not unfriendly."
Style="{StaticResource SmallLabelStyle}" />
<Label Text=" • Seven varieties of grimaces."
Style="{StaticResource SmallLabelStyle}" />
<Label Text=" • Doesn't laugh at your jokes."
Style="{StaticResource SmallLabelStyle}" />
</StackLayout>
...
</Grid>
</ScrollView>
</ContentPage>
3. Set theme mặc định : App.xml
<Application xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="ThemingDemo.App">
<Application.Resources>
<ResourceDictionary Source="Themes/LightTheme.xaml" />
</Application.Resources>
</Application>
4. Load theme runtime:
- Remove theme hiện tại (clear mergedictionary )
- Load theme đã chọn và thêm vào: MergedDictionaries
void OnPickerSelectionChanged(object sender, EventArgs e)
{
Picker picker = sender as Picker;
Theme theme = (Theme)picker.SelectedItem;
ICollection<ResourceDictionary> mergedDictionaries = Application.Current.Resources.MergedDictionaries;
if (mergedDictionaries != null)
{
mergedDictionaries.Clear();
switch (theme)
{
case Theme.Dark:
mergedDictionaries.Add(new DarkTheme());
break;
case Theme.Light:
default:
mergedDictionaries.Add(new LightTheme());
break;
}
}
}
Xem thêm: https://blog.quilv.com/blog/
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