Javafx 简明教程

JavaFX - Drawing a Rectangle

一般来说，矩形是一种四边形，具有两对平行且同向的边，所有内角都是直角。

In general, a rectangle is a four-sided polygon that has two pairs of parallel and concurrent sides with all interior angles as right angles.

它由两个参数描述，即−

It is described by two parameters namely −

  1. height − The vertical length of the rectangle is known as height.

  2. width − The horizontal length of the rectangle is known as width.

rectangle

Rectangle in JavaFX

在 JavaFX 中，矩形由名为 Rectangle 的类表示。此类属于 javafx.scene.shape 包。

In JavaFX, a Rectangle is represented by a class named Rectangle. This class belongs to the package javafx.scene.shape.

通过实例化此类，您可以在 JavaFX 中创建一个矩形节点。

By instantiating this class, you can create a Rectangle node in JavaFX.

此类具有 4 个双数据类型的属性，即 −

This class has 4 properties of the double datatype namely −

  1. X − The x coordinate of the start point (upper left) of the rectangle.

  2. Y − The y coordinate of the start point (upper left) of the rectangle.

  3. Width − The width of the rectangle.

  4. height − The height of the rectangle.

要绘制一个矩形，需要将值传递给这些属性，方法是在实例化时将这些值传递给此类的构造函数，并且按照相同的顺序。

To draw a rectangle, you need to pass values to these properties, either by passing them to the constructor of this class, in the same order, at the time of instantiation.

Steps to Draw a Rectangle

需要按照下面给出的步骤在 JavaFX 中绘制一个矩形。

You need to follow the steps given below to draw a rectangle in JavaFX.

Step 1: Creating a Rectangle

要在 JavaFX 中创建一个矩形，将包 javafx.scene.shape 中名为 Rectangle 的类的实例化，如下所示 −

To create a rectangle in JavaFX, instantiate the class named Rectangle of the package javafx.scene.shape as shown below −

//Creating a rectangle object
Rectangle rectangle = new Rectangle();

由于整个代码都是写在 Application 类的 start() 方法中，所以 Rectangle 类也在其中实例化，如下所示 −

As the entire code is written within the start() method of Application class, the Rectangle class is also instantiated within it as shown below −

public class ClassName extends Application {
   public void start(Stage primaryStage) throws Exception {
      // Write code here
      Rectangle rectangle = new Rectangle();
   }
}

Step 2: Setting Properties to the Rectangle

指定要绘制的矩形的起点 (左上角) 的 x、y 坐标、高度和宽度。可以通过分别使用它们的setter方法设置 x、y、height 和 width 属性来执行此操作。

Specify the x, y coordinates of the starting point (upper left), height and the width of the rectangle, that is needed to be drawn. You can do this by setting the properties x, y, height and width, using their respective setter methods.

rectangle.setX(150.0f);
rectangle.setY(75.0f);
rectangle.setWidth(300.0f);
rectangle.setHeight(150.0f);

Step 3: Adding Rectangle Object to Group

在此步骤中，将包 javafx.scene 中的 Group 类通过将 Rectangle 对象作为其构造函数的参数值传递来实例化，如下所示 −

In this step, the Group class of package javafx.scene is instantiated by passing the Rectangle object as a parameter value to its constructor as follows −

Group root = new Group(rectangle);

Step 4: Launching Application

创建二维对象后，请按照下面给出的步骤正确启动应用程序：

Once the 2D object is created, follow the given steps below to launch the application properly −

  1. Firstly, instantiate the class named Scene by passing the Group object as a parameter value to its constructor. To this constructor, you can also pass dimensions of the application screen as optional parameters.

  2. Then, set the title to the stage using the setTitle() method of the Stage class.

  3. Now, a Scene object is added to the stage using the setScene() method of the class named Stage.

  4. Display the contents of the scene using the method named show().

  5. Lastly, the application is launched with the help of the launch() method.

Example

以下是生成一个矩形的 JavaFX 程序。将此代码保存在一个名为 RectangleExample.java 的文件中。

Following is the program which generates a rectangle JavaFX. Save this code in a file with the name RectangleExample.java.

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.scene.shape.Rectangle;

public class RectangleExample extends Application {
   @Override
   public void start(Stage stage) {
      //Drawing a Rectangle
      Rectangle rectangle = new Rectangle();

      //Setting the properties of the rectangle
      rectangle.setX(150.0f);
      rectangle.setY(75.0f);
      rectangle.setWidth(300.0f);
      rectangle.setHeight(150.0f);

      //Creating a Group object
      Group root = new Group(rectangle);

      //Creating a scene object
      Scene scene = new Scene(root, 600, 300);

      //Setting title to the Stage
      stage.setTitle("Drawing a Rectangle");

      //Adding scene to the stage
      stage.setScene(scene);

      //Displaying the contents of the stage
      stage.show();
   }
   public static void main(String args[]){
      launch(args);
   }
}

使用以下命令，从命令提示符编译并执行已保存的 java 文件。

Compile and execute the saved java file from the command prompt using the following commands.

javac --module-path %PATH_TO_FX% --add-modules javafx.controls RectangleExample.java
java --module-path %PATH_TO_FX% --add-modules javafx.controls RectangleExample

执行时，上述程序将生成一个 JavaFX 窗口，显示一个矩形，如下所示的屏幕截图。

On executing, the above program generates a JavaFX window displaying a rectangle as shown in the following screenshot.

drawing rectangle

Example - Drawing a House

让我们看另一个尝试使用矩形绘制房子的示例。在此，我们使用两个矩形和两条线完成卡通房屋的基本版本。我们将命名此文件为 RectangleHouse.java 。

Let us see another example where we try to draw a house using a rectangle. Here, we use two rectangles and two lines to finish a basic version of cartoon house. We will name this file RectangleHouse.java.

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.scene.shape.Rectangle;
import javafx.scene.shape.Line;
import javafx.scene.paint.Color;

public class RectangleHouse extends Application {
   @Override
   public void start(Stage stage) {
      //Drawing a Rectangle
      Rectangle rectangle1 = new Rectangle();
      Rectangle rectangle2 = new Rectangle(200.0f, 120.0f, 50.0f, 30.0f);
      rectangle2.setFill(Color.hsb(50, 1, 1));

      //Setting the properties of the rectangle
      rectangle1.setX(150.0f);
      rectangle1.setY(75.0f);
      rectangle1.setWidth(150.0f);
      rectangle1.setHeight(75.0f);

      // Setting the properties of Lines
      // without setter methods
	  Line line1 = new Line(150, 75, 225, 30);
	  Line line2 = new Line(225, 30, 300, 75);

      //Creating a Group object
      Group root = new Group();
      root.getChildren().addAll(rectangle1, rectangle2, line1, line2);

      //Creating a scene object
      Scene scene = new Scene(root, 600, 300);

      //Setting title to the Stage
      stage.setTitle("Drawing a House");

      //Adding scene to the stage
      stage.setScene(scene);

      //Displaying the contents of the stage
      stage.show();
   }
   public static void main(String args[]){
      launch(args);
   }
}

使用以下命令，从命令提示符编译并执行已保存的 java 文件。

Compile and execute the saved java file from the command prompt using the following commands.

javac --module-path %PATH_TO_FX% --add-modules javafx.controls RectangleHouse.java
java --module-path %PATH_TO_FX% --add-modules javafx.controls RectangleHouse

执行时，上述程序将生成一个 JavaFX 窗口，显示一个房子，如下所示的屏幕截图。

On executing, the above program generates a JavaFX window displaying a house as shown in the following screenshot.

drawing rectangle house