JavaFX入门指南：打造动态用户界面 - CSDN文库

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"Pro JavaFX 是一本由James L.Weaver等人编著的JavaFX入门教程，适合初学者学习。本书涵盖了从基础到高级的各种JavaFX技术，包括用户界面创建、属性与绑定、动态布局、UI控件使用、集合与并发处理、图表创建、媒体类的运用、Web服务访问以及JavaFX语言和标记的深入探讨。" JavaFX是Java平台上的一个开源富客户端应用程序开发框架，用于构建具有丰富图形用户界面的应用程序。在"Getting a Jump Start in JavaFX"这一章节中，作者引导读者快速进入JavaFX的世界。他们鼓励开发者追求个人激情，并认为世界需要充满活力的创新者，这与JavaFX提供强大的工具和技术来激发开发者创造力的理念相吻合。在JavaFX中，Chapter 2介绍了如何使用JavaFX创建用户界面，包括布局管理器、组件和事件处理，这对于任何GUI应用都是至关重要的。Chapter 3深入讨论了属性和绑定，这是JavaFX中实现数据驱动UI的核心机制，允许UI元素动态响应数据变化。 Chapter 4讲解了如何构建动态的用户界面布局，使开发者能够创建适应不同屏幕尺寸和设备的灵活应用。Chapter 5则涉及JavaFX提供的各种内置UI控件，如按钮、文本框、菜单等，这些控件简化了界面设计的工作。 Chapter 6介绍了JavaFX中的集合和并发处理，这对于处理大量数据或优化多线程应用至关重要。Chapter 7展示了如何在JavaFX中创建各种图表，这对于数据可视化非常有用，可以制作出专业的报表和仪表盘。 Chapter 8讲解了如何利用JavaFX的媒体类播放音频和视频，使得开发者能够创建包含多媒体元素的应用。Chapter 9讨论了如何访问Web服务，结合JavaFX的图形能力，可以构建交互式的网络应用。Chapter 10则深入探讨了JavaFX支持的语言（如FXML）和标记，这些语言让界面设计变得更加声明式。最后，附录部分详细介绍了Visage语言，这是一种特定于JavaFX的编程语言，提供了更高级别的抽象，帮助开发者更高效地创建用户界面。通过这本教材，读者将全面了解JavaFX的各个方面，从基本概念到高级特性，从而能够开发出功能丰富、交互性强的桌面和移动应用。对于JavaFX的学习者来说，这本书无疑是一个宝贵的资源。

CHAPTER 1 ■ GETTING A JUMP START IN JAVAFX

13

javafx.scene.image package and the Group class in the javafx.scene package. In both cases, they inherit

from the Node class.

■ Tip We can’t emphasize enough the importance of having the JavaFX API documentation handy while

reading this book. As classes, variables, and functions are mentioned, it’s often a good idea to look at the

documentation to get more information. In addition, this habit helps you become more familiar with what is

available to you in the API.

Displaying Images

As shown in the following code, displaying an image entails using an ImageView instance in conjunction

with an Image instance.

ImageViewBuilder.create()

.image(new Image("http://projavafx.com/images/earthrise.jpg"))

.build(),

The Image instance identifies the image resource and loads it from the URL assigned to its URL

variable. Both of these classes are located in the javafx.scene.image package.

Working with Graphical Nodes as a Group

One powerful graphical feature of JavaFX is the ability to create scene graphs, which consist of a tree of

graphical nodes. You can then assign values to properties of a Group located in the hierarchy, and the

nodes contained in the Group will be affected. In our current example from Listing 1-1, we’re using a

Group to contain a Text node and to clip a specific rectangular region within the Group so that the text

doesn’t appear on the moon or the Earth as it animates upward. Here’s the relevant code snippet:

GroupBuilder.create()

.layoutX(50)

.layoutY(180)

.children(

textRef

)

.clip(

RectangleBuilder.create()

.width(430)

.height(85)

.build()

)

.build()

Notice that the Group is located 50 pixels to the right and 180 pixels down, from where it would have

been located by default. This is due to the values assigned to the layoutX and layoutY variables of the

Group instance. Because this Group is contained directly by the Scene, its upper-left corner’s location is

CHAPTER 1 ■ GETTING A JUMP START IN JAVAFX

15

The layoutX and layoutY properties of the Group just described are examples of our earlier

statement that nodes contained in a Group will be affected by values assigned to properties of the

Group. Another example is setting the opacity property of a Group instance to 0.5, which causes all of

the nodes contained in that Group to become translucent. If the JavaFX API documentation is handy,

look at the properties available in the javafx.scene.Group class. Then look at the properties available in

the javafx.scene.Node class properties, which is where you’ll find the layoutX, layoutY, and opacity

variables that are inherited by the Group class.

Drawing Text

In the previous snippet, notice that several variables are available in the Text class. This particular

example is a little more complicated than the normal use of the Text class. Let’s first look at a typical

case, shown in the following snippet, in which you simply want to draw a string of text characters

somewhere in the scene.

TextBuilder.create()

.layoutX(65)

.layoutY(12)

.textOrigin(VPos.TOP)

.fill(Color.WHITE)

.text("Audio Configuration")

.font(Font.font("SansSerif", FontWeight.BOLD, 20))

.build(),

This snippet, borrowed from the Audio Configuration example in Figure 1-7 and Listing 1-3 later in

this chapter, draws the graphical Text string “Audio Configuration” in a bold Sans Serif font. The font

size is 20, and the color of the text is white.

Referring again to the JavaFX API documentation, notice that the VPos enum (in the javafx.geometry

package) has fields that serve as constants, for example, BASELINE, BOTTOM, and TOP. These control

the origin of the text with respect to vertical locations on the displayed Text:

• The TOP origin, as we’re using it in the previous code snippet, places the top of the

text (including ascenders) at the layoutY position, relative to the co-ordinate space

in which the Text is located.

• The BOTTOM origin would place the bottom of the text, including descenders

(located in a lowercase “g”, for example) at the layoutY position.

• The BASELINE origin would place the baseline of the text (excluding descenders)

at the layoutY position. This is the default value for the textOrigin property of a

Text instance.

While you’re looking at the javafx.scene.text package in the API documentation, take a look at the

font function of the Font class, which is used in the previous snippet to define the font family, weight,

and size of the Text.

CHAPTER 1 ■ GETTING A JUMP START IN JAVAFX

16

Turning back again to the Hello Earthrise example in Listing 1-1, we’re using some additional

properties of the Text class that enable it to flow from one line to the next:

• The wrappingWidth property enables you to specify at what number of pixels the

text will wrap.

• The textAlignment property enables you to control how the text will be justified. In

our example, TextAlignment.JUSTIFY aligns the text on both the left and right

sides, expanding the space between words to achieve that.

The text that we’re displaying is sufficiently long to wrap and be drawn on the Earth, so we need to

define a rectangular region outside of which that text can’t be seen.

Clipping Graphical Areas

To define a clipping area, we assign a Node subclass to the clip property that defines the clipping shape,

in this case a Rectangle that is 430 pixels wide and 85 pixels high. In addition to keeping the Text from

covering the moon, when the Text scrolls up as a result of animation the clipping area keeps the Text

from covering the earth.

Animating the Text to Make It Scroll Up

When the HelloEarthriseMain program is invoked, the Text begins scrolling up slowly. To achieve this

animation, we’re using the TranslateTransition class located in the javafx.animation package, as shown

in the following snippet from Listing 1-1.

TranslateTransition transTransition = TranslateTransitionBuilder.create()

.duration(new Duration(75000))

.node(textRef)

.toY(-820)

.interpolator(Interpolator.LINEAR)

.cycleCount(Timeline.INDEFINITE)

.build();

...code omitted...

// Start the text animation

transTransition.play();

The javafx.animation package contains convenience classes for animating nodes. This

TranslateTransition instance (created by the TranslateTransitionBuilder class) translates the Text node

referenced by the textRef variable from its original Y position of 100 pixels to a Y position of –820 pixels,

over a duration of 75 seconds. The Interpolator.LINEAR constant is assigned to the interpolator

property, which causes the animation to proceed in a linear fashion. A look at the API docs for the

Interpolator class in the javafx.animation package reveals that there are other forms of interpolation

available, one of which is EASE_OUT, which slows down the animation toward the end of the specified

duration.

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