Java语言程序设计基础篇_编程练习题**16.17（使用ScrollBar和Slider）

目录

**16.17（使用ScrollBar和Slider）

习题思路

示例代码

结果展示 

**16.17（使用ScrollBar和Slider）

  编写一个程序，使用滚动条或者滑动条选择文本的颜色，如图16-43所示。使用四个水平滚动条选择颜色（红色、绿色、和蓝色），以及透明度的百分比。

• 习题思路

1. 创建一个HBox，用于放置文本。
2. 创建一个GridPane，创建四个Label和四个水平滚动条，并依次添加到布局中。
3. 创建一个BorderPane，将HBox设置在顶部，将GridPane设置在中心。
4. 为四个水平滚动条注册事件监听器，当值滚动条的值改变时，分别获取四个滚动条的值(因为滚动条初始的值是0~100，需要除以100才能作为传入Color的参数)，再以new Color(r, g, b, a)设置到text文本的颜色上

• 示例代码

编程练习题16_17UseScrollBarAndSlider.java

package chapter_16;


import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.ContentDisplay;
import javafx.scene.control.Label;
import javafx.scene.control.ScrollBar;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.paint.Color;
import javafx.scene.text.Text;
import javafx.stage.Stage;

public class 编程练习题16_17UseScrollBarAndSlider extends Application{
	private ScrollBar sbRed = new ScrollBar();
	private ScrollBar sbGreen = new ScrollBar();
	private ScrollBar sbBlue = new ScrollBar();
	private ScrollBar sbAlpha = new ScrollBar();
	Text text = new Text("Show Colors");
	@Override
	public void start(Stage primaryStage) throws Exception {
		HBox hBox = new HBox(text);
		hBox.setAlignment(Pos.CENTER);
		hBox.setPadding(new Insets(15, 15, 10, 10));
		
		
		GridPane gridPane = new GridPane();
		gridPane.setHgap(10);
		gridPane.setAlignment(Pos.CENTER);
		
		Label lbRed = new Label("Red   ",sbRed);
		lbRed.setContentDisplay(ContentDisplay.RIGHT);
		lbRed.setGraphicTextGap(20);
		Label lbGreen = new Label("Green",sbGreen);
		lbGreen.setContentDisplay(ContentDisplay.RIGHT);
		lbGreen.setGraphicTextGap(20);
		Label lbBlue = new Label("Blue  ",sbBlue);
		lbBlue.setContentDisplay(ContentDisplay.RIGHT);
		lbBlue.setGraphicTextGap(20);
		Label lbAlpha = new Label("Alpha",sbAlpha);
		sbAlpha.setValue(100);
		lbAlpha.setContentDisplay(ContentDisplay.RIGHT);
		lbAlpha.setGraphicTextGap(20);
		
		gridPane.add(lbRed, 0, 0);
		gridPane.add(lbGreen, 0, 1);
		gridPane.add(lbBlue, 0, 2);
		gridPane.add(lbAlpha, 0, 3);
		gridPane.add(sbRed, 0, 0);
		gridPane.add(sbGreen, 1, 1);
		gridPane.add(sbBlue, 2, 2);
		gridPane.add(sbAlpha, 3, 3);
		
		BorderPane borderPane = new BorderPane();
		borderPane.setTop(hBox);
		borderPane.setCenter(gridPane);
		
		sbRed.valueProperty().addListener(ov ->{
			setColor();
		});
		sbGreen.valueProperty().addListener(ov ->{
			setColor();
		});
		sbBlue.valueProperty().addListener(ov ->{
			setColor();
		});
		sbAlpha.valueProperty().addListener(ov ->{
			setColor();
		});
		
		Scene scene = new Scene(borderPane,250, 150);
		primaryStage.setTitle("编程练习题16_17UseScrollBarAndSlider");
		primaryStage.setScene(scene);
		primaryStage.show();
	}
	public static void main(String[] args) {
		Application.launch(args);
	}
	public void setColor() {
		double r = Double.valueOf(sbRed.getValue())/100.0;
		double g = Double.valueOf(sbGreen.getValue())/100.0;
		double b = Double.valueOf(sbBlue.getValue())/100.0;
		double a = Double.valueOf(sbAlpha.getValue())/100.0;
		System.out.println("r:"+r);
		System.out.println("g:"+g);
		System.out.println("b:"+b);
		System.out.println("a:"+a);
		text.setFill(new Color(r, g, b, a));
	}
}

• 结果展示