通过CSS来给JavaFX程序换肤

Skinning JavaFX Applications with CSS

You can create a custom look, also called a skin, for your JavaFX application with cascading style sheets (CSS). CSS contain style definitions that control the look of user interface elements. Using CSS in JavaFX applications is similar to using CSS in HTML. JavaFX CSS are based on the W3C CSS version 2.1 specification (available at http://www.w3.org/TR/CSS21/) with some additions from current work on version 3 of the specification and some extensions that support specific JavaFX features.

Skinning your UI with JavaFX CSS enables you to change the UI shown in Figure 1 to the UI shown in Figure 2 just by changing the style sheet used.

Figure 1 Style 1

Description of "Figure 1 Style 1"

Figure 2 Style 2

Description of "Figure 2 Style 2"

Default Style Sheet

The default style sheet for JavaFX applications is caspian.css, which is found in the JavaFX runtime JAR file, jfxrt.jar. This style sheet defines styles for the root node and the UI controls. To view this file, go to the \rt\lib directory under the directory in which the JavaFX SDK is installed. Use the following command to extract the style sheet from the JAR file:

jar -xf jfxrt.jar com/sun/javafx/scene/control/skin/caspian/caspian.css

Figure 3 shows what the sample UI looks like with the default style sheet.

Figure 3 Default Style

Description of "Figure 3 Default Style"

Creating Style Sheets

You can create one or more of your own style sheets to override the default styles and to add your own styles. Typically style sheets that you create have an extension of .css and are located in the same directory as the main class for your JavaFX application.

The style sheet controlStyle1.css provides the skinning shown in Figure 1. The style sheetcontrolStyle2.css provides the skinning shown in Figure 2.

Style sheets are applied to Scene objects as shown in Example 1, where path is the directory structure that reflects the location of your style sheet, and stylesheet is the name of your style sheet. For example, the path and name of the style sheet for Figure 2 is uicontrolcss/controlStyle2.css.

Example 1 Adding a Style Sheet

Scene scene = new Scene(new Group(), 500, 400);
scene.getStylesheets().add("path/stylesheet.css");

Defining Styles

A style definition consists of the name of the style, also called the selector, and a series of rules that set the properties for the style. Rules for a definition are enclosed in braces ({}).Example 2 shows the definition for a style named .custom-button.

Example 2 Sample Style Definition

.custom-button {
    -fx-font: 16px "Serif";
    -fx-padding: 10;
    -fx-background-color: #CCFF99;
}

Note: The size of a font can be specified in either points (pt) or pixels (px). A resolution of 96 dots per inch (dpi) is assumed, so 1px = 0.75pt.

Selectors

Several types of styles can be defined. Each type of style has its own convention for selectors.

Style classes correspond to class names. By convention, style class names that consist of more than one word use a hyphen (-) between words. Style class selectors are preceded by a dot (.).

Examples of class selectors:

.button
.check-box
.scroll-bar

You can also define styles that are associated with a node through the node's ID. The ID is set using the node's setId() method. The style name is the ID preceded by a hash symbol (#). For example, a node with the ID my-button is skinned with the style #my-button.

Examples of ID style selectors:

#my-button
#shaded-hbox

Compound selectors are also possible. Some classes include elements that can have their own style definition, which are called descendant classes. For example, many UI controls have a descendant class for the label. These definitions are identified by the selector for the class and the selector for the descendant class separated by a space.

Examples of selectors for descendant classes:

.check-box .label
.check-box .box
.radio-button .dot

Pseudo-classes enable you to customize states of a node, such as when a node has focus. These definitions are identified by the selector for the class and the name for the state separated by a colon (:).

Examples of selectors for pseudo-classes:

.radio-button:focused
.radio-button:hover
.scroll-bar:vertical

Rules and Properties

The rules for a style definition assign values to properties associated with the class. Rule property names correspond to the names of the properties for a class. The convention for property names with multiple words is to separate the words with a hyphen (-). Property names for styles in JavaFX style sheets are preceded by -fx-. Property names and values are separated by a colon (:). Rules are terminated with a semicolon (;).

Examples of rules:

-fx-background-color: #333333;
-fx-text-fill: white;
-fx-alignment: CENTER;

The .root style class is applied to the root node of the Scene instance. Because all nodes in the scene graph are a descendant of the root node, styles in the .root style class can be applied to any node.

The .root style class includes properties that can be used by other styles to provide consistency in a UI. For example, the property -fx-focused-base is defined in the .root style. This property is used by styles for other UI controls as the color for the control when it has focus. The following definition shows how this property is used in the style for the classCheckBox:

.check-box:focused {
    -fx-color: -fx-focused-base;
}

Skinning the Scene

You can quickly change the look of your UI just by customizing the .root style class. Both of the sample style sheets set the font size and family, the base color from which other colors are derived, and the background color of the scene. Example 3 shows the .root style fromcontrolStyle2.css.

Example 3 Root Style from controlStyle2.css

.root{
    -fx-font-size: 16pt;
    -fx-font-family: "Courier New";
    -fx-base: rgb(132, 145, 47);
    -fx-background: rgb(225, 228, 203);
}

With just this style, you create the basic look of Figure 2. This is possible because the built-in UI controls use the properties set for the root node to derive their own colors and fonts.

Skinning Controls

You can further customize your UI by defining styles for the different controls that you are using. You can override the definitions in the default style sheet or create new class or ID styles. You can also define the style for a node within your code.

Overriding Default Styles

You can override the default style by including the style in your style sheet and assigning it different properties. Example 4 shows the style for the Button class from controlStyle2.css.

Example 4 Override a Style

.button{
    -fx-text-fill: rgb(49, 89, 23);
    -fx-border-color: rgb(49, 89, 23);
    -fx-border-radius: 5;
    -fx-padding: 3 6 6 6;
}

The font color, border color, border radius, and padding are picked up from this definition. The color of the button and the font style of the label are picked up from the .root definition fromExample 3. Buttons with this styling look as shown in the following image.

Description of the illustration button_style2.png

Creating Class Styles

You can create a class style by adding a definition for it to your style sheet. Example 5 defines a new style in controlStyle1.css called .button1.

Example 5 Define a New Style

.button1{
    -fx-text-fill: #006464;
    -fx-background-color: #DFB951;
    -fx-border-radius: 20;
    -fx-background-radius: 20;
    -fx-padding: 5;
}

Any button to which this style is added looks as shown in the following image. Note that the font of the label is picked up from the .root definition in controlStyle1.css.

Description of the illustration button_style1.png

To assign this class style to a node, use the getStyleClass().add() sequence of methods.Example 6 shows the .button1 style assigned to the Accept button.

Example 6 Assign a Class Style

Button buttonAccept = new Button("Accept");
buttonAccept.getStyleClass().add("button1");

Be aware that adding styles to a node is accumulative. After adding the .button1 style class to the buttonAccept node, the node is rendered using rules from both the .button and .button1styles.

Creating ID Styles

You can define a style for an individual node by creating a style and assigning the style to the node. The style name is the ID preceded by a hash symbol (#). Example 7 creates a definition for a style named #font-button.

Example 7 Define an ID Style

#font-button {
    -fx-font: bold italic 20pt "Arial";
    -fx-effect: dropshadow( one-pass-box , black , 8 , 0.0 , 2 , 0 );
}

The button that is assigned the ID font-button looks as shown in the following image.

Description of the illustration button_style_id.png

Example 8 shows how to assign the ID style to a node.

Example 8 Assign an ID Style

Button buttonFont = new Button("Font");
buttonFont.setId("font-button");

Setting Styles in the Code

You also have the option of setting style properties for a node within the code for your application. Rules set within the code take precedence over styles from a style sheet. Example 9 shows how to change the background color and font color for a button.

Example 9 Define a Style Inline

Button buttonColor = new Button("Color");
buttonColor.setStyle("-fx-background-color: slateblue; -fx-text-fill: white;");

The following image shows how the button appears.

Description of the illustration button_style_inline.png

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