JavaFX – QuadCurveTo Path Object


JavaFX – QuadCurveTo Path Object

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Quadratic Curve or QuadCurve is generally defined as the curve that is defined by a quadratic equation. In JavaFX, we make use of 6 different properties to create this QuadCurve node. And to create a complex shape using QuadCurve, we would have to specify these properties everytime it is required.

JavaFX makes this process simpler by providing a QuadCurve path object that takes lesser number of properties to draw it.

We will learn about the QuadCurve Path object in detail further in this chapter.

QuadCurve Path Object

The path element quadratic curve is used to draw a quadratic curve to a point in the specified coordinates from the current position.

It is represented by a class named QuadraticCurveTo. This class belongs to the package javafx.scene.shape.

This class has 4 properties of the double datatype namely −

  • setX − The x coordinate of the point to which a curve is to be drawn from the current position.

  • setY − The y coordinate of the point to which a curve is to be drawn from the current position.

  • controlX − The x coordinate of the control point of the curve.

  • controlY − The y coordinate of the control point of the curve.

To draw a quadratic curve, you need to pass values to these properties. This can be done either by passing them to the constructor of this class, in the same order, at the time of instantiation; Or, by using their respective setter methods.

Steps to draw PathElement Quadratic Curve

To draw a quadratic curve to a specified point from the current position in JavaFX, follow the steps given below.

Step 1: Creating a Path Object

Instantiate the Path class to create a Path object within the start() method of Application class as shown below −

public class ClassName extends Application { 
   @Override     
   public void start(Stage primaryStage) throws Exception {
      //Creating a Path object 
      Path path = new Path();   
   }
}

Step 2: Create a Path

Create the MoveTo path element and set the XY coordinates to the starting point of the line to the coordinates (100, 150). This can be done by using the methods setX() and setY() of the class MoveTo as shown below.

//Moving to the starting point 
MoveTo moveTo = new MoveTo(); 
moveTo.setX(100.0f); 
moveTo.setY(150.0f);

Step 3: Creating an Object of the Class QuadCurveTo

Create the path element Quadratic Curve by instantiating the class named QuadCurveTo which belongs to the package javafx.scene.shape as follows.

//Creating an object of the class QuadCurveTo 
QuadCurveTo quadCurveTo = new QuadCurveTo()

Step 4: Setting Properties to the Quadratic Curve Element

Specify the coordinates of the point to which a Quadratic Curve is to be drawn from the current position. Then you should set the properties x, y, controlx, controlY and the coordinates of the control point by their setter methods as shown below.

//Setting properties of the class QuadCurve            
quadCurveTo.setX(500.0f); 
quadCurveTo.setY(220.0f); 
quadCurveTo.setControlX(250.0f); 
quadCurveTo.setControlY(0.0f);

Step 5: Adding Elements to the Observable List of the Path Class

Add the path elements MoveTo and QuadraticCurveTo created in the previous steps to the observable list of the Path class as follows −

//Adding the path elements to Observable list of the Path class   
path.getElements().add(moveTo); 
path.getElements().add(quadCurveTo)

Step 6: Launching Application

Once the QuadCurveTo path object is created, follow the given steps below to launch the application properly −

  • 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.

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

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

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

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

Example 1

Following is a program which draws a quadratic curve from the current point to a specified position using the class named Path of JavaFX. Save this code in a file with the name QuadCurveToExample.java.

import javafx.application.Application; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.stage.Stage; 
import javafx.scene.shape.MoveTo; 
import javafx.scene.shape.Path;
import javafx.scene.shape.QuadCurveTo; 
         
public class QuadCurveToExample extends Application { 
   @Override 
   public void start(Stage stage) {      
      //Creating an object of the class named Path 
      Path path = new Path();  
      
      //Moving to the starting point 
      MoveTo moveTo = new MoveTo(); 
      moveTo.setX(100.0); 
      moveTo.setY(150.0); 
         
      //Instantiating the class QuadCurve 
      QuadCurveTo quadCurveTo = new QuadCurveTo(); 
       
      //Setting properties of the class QuadCurve            
      quadCurveTo.setX(500.0f); 
      quadCurveTo.setY(220.0f); 
      quadCurveTo.setControlX(250.0f);  
      quadCurveTo.setControlY(0.0f);      
       
      //Adding the path elements to Observable list of the Path class 
      path.getElements().add(moveTo); 
      path.getElements().add(quadCurveTo);         
      
      //Creating a Group object  
      Group root = new Group(path); 
         
      //Creating a scene object 
      Scene scene = new Scene(root, 600, 300);  
      
      //Setting title to the Stage 
      stage.setTitle("Drawing a QuadCurve through a specified path");
      
      //Adding scene to the stage 
      stage.setScene(scene); 
         
      //Displaying the contents of the stage 
      stage.show(); 
   }      
   public static void main(String args[]){ 
      launch(args); 
   } 
}

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 QuadCurveToExample.java 
java --module-path %PATH_TO_FX% --add-modules javafx.controls QuadCurveToExample

Output

On executing, the above program generates a JavaFX window displaying a quadratic curve. This is drawn from the current position to the specified point as shown below.

Drawing Quadratic Curve

Example 2

In this example, let us try to apply some animation to this QuadCurve Path. Here, we are drawing a sample QuadCurve and applying the Fade Transition to it. Save this code in a file with the name QuadCurveToAnimation.java.

import javafx.application.Application;
import javafx.animation.FadeTransition; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.stage.Stage; 
import javafx.scene.shape.MoveTo; 
import javafx.scene.shape.Path;
import javafx.scene.shape.QuadCurveTo;
import javafx.util.Duration;
         
public class QuadCurveToAnimation extends Application { 
   @Override 
   public void start(Stage stage) {      
      //Creating an object of the class named Path 
      Path path = new Path();  
      
      //Moving to the starting point 
      MoveTo moveTo = new MoveTo(); 
      moveTo.setX(100.0); 
      moveTo.setY(150.0); 
         
      //Instantiating the class QuadCurve 
      QuadCurveTo quadCurveTo = new QuadCurveTo(); 
       
      //Setting properties of the class QuadCurve            
      quadCurveTo.setX(500.0f); 
      quadCurveTo.setY(220.0f); 
      quadCurveTo.setControlX(250.0f);  
      quadCurveTo.setControlY(0.0f);      
       
      //Adding the path elements to Observable list of the Path class 
      path.getElements().add(moveTo); 
      path.getElements().add(quadCurveTo);

      //Creating the fade Transition 
      FadeTransition fadeTransition = new FadeTransition(); 
	  fadeTransition.setDuration(Duration.millis(1000));
	  
	  //Setting the node for Transition 
      fadeTransition.setNode(path);
      
      //Setting the property fromValue of the transition (opacity) 
      fadeTransition.setFromValue(1.0); 
      
      //Setting the property toValue of the transition (opacity) 
      fadeTransition.setToValue(0.3); 
      
      //Setting the cycle count for the transition 
      fadeTransition.setCycleCount(50); 
      
      //Setting auto reverse value to false 
      fadeTransition.setAutoReverse(false); 
  
      //Playing the animation 
      fadeTransition.play(); 	  
      
      //Creating a Group object  
      Group root = new Group(path); 
         
      //Creating a scene object 
      Scene scene = new Scene(root, 600, 300);  
      
      //Setting title to the Stage 
      stage.setTitle("Drawing a QuadCurve through a specified path");
      
      //Adding scene to the stage 
      stage.setScene(scene); 
         
      //Displaying the contents of the stage 
      stage.show(); 
   }      
   public static void main(String args[]){ 
      launch(args); 
   } 
}

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 QuadCurveToAnimation.java 
java --module-path %PATH_TO_FX% --add-modules javafx.controls QuadCurveToAnimation

Output

On executing, the above program generates a JavaFX window displaying a quadratic curve that is fading out. This is drawn from the current position to the specified point as shown below.

Drawing Quadratic Curve



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