JavaFX - 2D Shapes Line


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In general, a line is a geometrical structure which joins two points on an XY plane.

Line

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

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

This class has 4 properties of the double datatype namely −

  • startX − The x coordinate of the start point of the line.

  • startY − The y coordinate of the start point of the line.

  • endX − The x coordinate of the end point of the line.

  • endY − The y coordinate of the end point of the line.

To draw a line, 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, as follows −

Line line = new Line(startX, startY, endX, endY);

Or, by using their respective setter methods as follows −

setStartX(value); 
setStartY(value); 
setEndX(value); 
setEndY(value); 

Steps to Draw a line

Follow the steps given below to Draw a Line in JavaFX.

Step 1: Creating a Class

Create a Java class and inherit the Application class of the package javafx.application and implement the start() method of this class as follows.

public class ClassName extends Application {  
   @Override     
   public void start(Stage primaryStage) throws Exception {
   }
}   

Step 2: Creating a line

You can create a line in JavaFX by instantiating the class named Line which belongs to a package javafx.scene.shape, instantiate this class as follows.

//Creating a line object         
Line line = new Line();

Step 3: Setting Properties to the Line

Specify the coordinates to draw the line on an XY plane by setting the properties startX, startY, endX and endY, using their respective setter methods as shown in the following code block.

line.setStartX(100.0); 
line.setStartY(150.0); 
line.setEndX(500.0); 
line.setEndY(150.0); 

Step 4: Creating a Group Object

Create a group object by instantiating the class named Group, which belongs to the package javafx.scene.

Pass the Line (node) object, created in the previous step, as a parameter to the constructor of the Group class, in order to add it to the group as follows −

Group root = new Group(line);

Step 5: Creating a Scene Object

Create a Scene by instantiating the class named Scene which belongs to the package javafx.scene. To this class pass the Group object (root), created in the previous step.

In addition to the root object, you can also pass two double parameters representing height and width of the screen along with the object of the Group class as follows.

Scene scene = new Scene(group ,600, 300);

Step 6: Setting the Title of the Stage

You can set the title to the stage using the setTitle() method of the Stage class. The primaryStage is a Stage object which is passed to the start method of the scene class, as a parameter.

Using the primaryStage object, set the title of the scene as Sample Application as follows.

primaryStage.setTitle("Sample Application");

Step 7: Adding Scene to the Stage

You can add a Scene object to the stage using the method setScene() of the class named Stage. Add the Scene Object prepared in the previous steps using this method as follows.

primaryStage.setScene(scene)

Step 8: Displaying the Contents of the Stage

Display the contents of the scene using the method named show() of the Stage class as follows.

primaryStage.show();

Step 9: Launching the Application

Launch the JavaFX application by calling the static method launch() of the Application class from the main method as follows.

public static void main(String args[]){   
   launch(args);      
} 

Example

Following is the program which generates a straight line using JavaFX. Save this code in a file with the name DrawingLine.java.

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

public class DrawingLine extends Application{ 
   @Override
   public void start(Stage stage) { 
      //Creating a line object
      Line line = new Line(); 
         
      //Setting the properties to a line 
      line.setStartX(100.0); 
      line.setStartY(150.0); 
      line.setEndX(500.0); 
      line.setEndY(150.0); 
         
      //Creating a Group 
      Group root = new Group(line); 
         
      //Creating a Scene 
      Scene scene = new Scene(root, 600, 300); 
         
      //Setting title to the scene 
      stage.setTitle("Sample application"); 
         
      //Adding the scene to the stage 
      stage.setScene(scene); 
         
      //Displaying the contents of a scene 
      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 DrawingLine.java 
java DrawingLine

On executing, the above program generates a JavaFX window displaying a straight line as shown below.

Drawing Line
javafx_2d_shapes.htm

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