java JavaFX |画布类

JavaFX |画布类

原文:https://www.geeksforgeeks.org/javafx-canvas-class/

Canvas 类是 JavaFX 的一部分。Canvas 类基本上创建了一个图像，可以使用 GraphicsContext 提供的一组图形命令来绘制。画布具有指定的高度和宽度，所有的绘制操作都被裁剪到画布的边界。

类的构造函数:

画布():创建新的画布对象。
Canvas(双 w，双 h) :创建具有指定宽度和高度的新 Canvas 对象。

常用方法:

方法	说明
getgraphicstext 2d()	返回与画布关联的图形上下文。
getHeight（）	返回画布的高度。
getWidth（）	返回画布的宽度。
setHeight(双 v)	设置画布的高度。
setWidth(双 d)	设置画布的宽度。

下面的程序说明了 Canvas 类的使用:

Java Program to create a canvas with specified width and height(as arguments of constructor), add it to the stage and also add a circle and rectangle on it: In this program we will create a Canvas named canvas with specified width and height. We will extract the GraphicsContext using the getGraphicsContext2D() function and draw a rectangle and a oval of different color. Now we will create a Group named group and add the canvas to the group. Now create a scene and add the group to the scene and then attach the scene to the stage and call the show() function to display the results.

```java // Java Program to create a canvas with specified // width and height(as arguments of constructor), // add it to the stage and also add a circle and // rectangle on it import javafx.application.Application; import javafx.scene.Scene; import javafx.scene.control.; import javafx.scene.layout.; import javafx.stage.Stage; import javafx.event.ActionEvent; import javafx.event.EventHandler; import javafx.scene.canvas.*; import javafx.scene.paint.Color; import javafx.scene.Group;

public class canvas extends Application {

// launch the application     public void start(Stage stage)     {

// set title for the stage         stage.setTitle("creating canvas");

// create a canvas         Canvas canvas = new Canvas(100.0f, 100.0f);

// graphics context         GraphicsContext graphics_context =              canvas.getGraphicsContext2D();

// set fill for rectangle         graphics_context.setFill(Color.RED);         graphics_context.fillRect(20, 20, 70, 70);

// set fill for oval         graphics_context.setFill(Color.BLUE);         graphics_context.fillOval(30, 30, 70, 70);

// create a Group         Group group = new Group(canvas);

// create a scene         Scene scene = new Scene(group, 200, 200);

// set the scene         stage.setScene(scene);

stage.show();     }

// Main Method     public static void main(String args[])     {

// launch the application         launch(args);     } } ```

输出:
Java Program to create a canvas and use setHeight() and setWidth() function to set canvas size and add it to the stage and also add a circle and rectangle on it: In this program we will create a Canvas named canvas and set the width and height using the setWidth() and setHeight() function. We will extract the GraphicsContext using the getGraphicsContext2D() function and draw two rectangles and a oval of different color. We will create a Group named group and add the canvas to the group. We will create a scene and add the group to the scene and then attach the scene to the stage. Finally, call the show() function to display the results.

```java // Java Program to create a canvas and use // setHeight() and setWidth() function to // set canvas size and add it to the stage // and also add a circle and rectangle on it import javafx.application.Application; import javafx.scene.Scene; import javafx.scene.control.; import javafx.scene.layout.; import javafx.stage.Stage; import javafx.event.ActionEvent; import javafx.event.EventHandler; import javafx.scene.canvas.*; import javafx.scene.paint.Color; import javafx.scene.Group;

public class canvas1 extends Application {

// launch the application     public void start(Stage stage)     {

// set title for the stage         stage.setTitle("creating canvas");

// create a canvas         Canvas canvas = new Canvas();

// set height and width         canvas.setHeight(400);         canvas.setWidth(400);

// graphics context         GraphicsContext graphics_context =             canvas.getGraphicsContext2D();

// set fill for rectangle         graphics_context.setFill(Color.PINK);         graphics_context.fillRect(40, 40, 100, 100);

// set fill for rectangle         graphics_context.setFill(Color.RED);         graphics_context.fillRect(20, 20, 70, 70);

// set fill for oval         graphics_context.setFill(Color.BLUE);         graphics_context.fillOval(30, 30, 70, 70);

// create a Group         Group group = new Group(canvas);

// create a scene         Scene scene = new Scene(group, 400, 400);

// set the scene         stage.setScene(scene);

stage.show();     }

// Main Method     public static void main(String args[])     {

// launch the application         launch(args);     } } ```

输出:

注意:上述程序可能无法在在线 IDE 中运行。请使用离线编译器。

参考:https://docs . Oracle . com/javase/8/JavaFX/API/JavaFX/scene/canvas/canvas . html