# BMI計算器0
[javafx.scene.layout.VBox](
https://docs.oracle.com/javase/10/docs/api/javafx/scene/layout/VBox.html)
[javafx.scene.layout.HBox](
https://docs.oracle.com/javase/10/docs/api/javafx/scene/layout/HBox.html)
[javafx.scene.control.Label](
https://docs.oracle.com/javase/10/docs/api/javafx/scene/control/Label.html)
[javafx.scene.control.TextField](
https://docs.oracle.com/javase/8/javafx/api/javafx/scene/control/TextField.html)
[javafx.scene.control.Button](
https://docs.oracle.com/javase/10/docs/api/javafx/scene/control/Button.html)

畫面設計:
Label 身高 TextField
Label 體重 TextField
Button 計算
Label BMI值
<hr>
VBOX{
HBOX: Label TextField
HBOX: Label TextField
Button
Label
}

import javafx.application.Application;

import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.Group;
import javafx.scene.layout.StackPane;
import javafx.scene.layout.VBox;
import javafx.scene.layout.HBox;
import javafx.scene.control.Label;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.shape.*; //Circle, Rectangle
import javafx.scene.paint.Color;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;

public class BMI0 extends Application {
    public static void main(String[] args) {
       System.out.println("main()"); 
       launch(args); //launch為Application中的靜態方法
        //Application.launch(args);
        
        System.out.println("after launch()");
    } 
    
    @Override
    public void start(Stage stage) {
        HBox hbox1=new HBox(10);// spacing = 10
    	TextField input_h=new TextField();
    	input_h.setPromptText("輸入身高"); //to set the hint text

    	hbox1.getChildren().addAll(new Label("身高"), input_h);
    	HBox hbox2=new HBox(10);// spacing = 10
    	TextField input_w=new TextField();
    	input_w.setPromptText("輸入體重"); //to set the hint text

    	hbox2.getChildren().addAll(new Label("體重"), input_w);    	
    	
    	Label lab_bmi=new Label("BMI值:");
    	
    	Button btn=new Button("計算");
        btn.setOnAction(new EventHandler<ActionEvent>() {
           @Override
           public void handle(ActionEvent event) {
                System.out.println("Hello World!");
                //計算bmi 程式碼.
                
           }
        });
        VBox vbox=new VBox();
        vbox.getChildren().addAll(hbox1, hbox2, btn, lab_bmi);
 		//VBox.setMargin(hbox1, new Insets(10, 10, 10, 10));
        //VBox.setMargin(hbox2, new Insets(10, 10, 10, 10));	
        Scene scene = new Scene(vbox, 400, 300);

        //stage.getIcons().add(new Image("file:resources/images/address_book_32.png"));
        stage.setTitle("My JavaFX Application");
        stage.setScene(scene);
        
        stage.show();
        
    }
     
    @Override
    public void stop(){
        System.out.println("stop");
    }
}

* 從TextField抓出身高體重值.
* 計算BMI
* 修改輸出格式
* 修改字體大小..

# 從TextField抓出身高體重值
TextField.getText();
TextField.getText();

# Double.parseDouble()
double h=...;
double w=...;
h=h/100.0;
double bmi=w/(h*h);

# Label.setText("bmi值:"+bmi)

# 修改輸出到小數第2位
DecimalFormat df = new DecimalFormat("###.##");
String str=df.format(bmi);
Label.setText(...);

# 修改字體大小(使用css設定)
https://motleybytes.com/w/JavaFxFonts

vbox.setStyle("-fx-font: 20pt 'verdana';");

verdana為 font-family

[JavaFX Fonts](https://jenkov.com/tutorials/javafx/fonts.html)
[JavaFxFonts](https://motleybytes.com/w/JavaFxFonts)

String      fontFamily  = "Arial";
double      fontSize    = 13;
FontWeight  fontWeight  = FontWeight.BOLD;
FontPosture fontPosture = FontPosture.ITALIC;

Font font1 = Font.font(fontFamily);
Font font2 = Font.font(fontSize);
Font font3 = Font.font(fontFamily, fontSize);
Font font4 = Font.font(fontFamily, fontWeight , fontSize);
Font font5 = Font.font(fontFamily, fontPosture, fontSize);
Font font6 = Font.font(fontFamily, fontWeight , fontPosture, fontSize);

Font font = Font.font("Arial");

Text text = new Text("This is the text");
text.setFont(font);

List<String> fontFamilies = Font.getFamilies();
List<String> fontNames    = Font.getFontNames();
for(String item : fontFamilies) {
    System.out.println(item);
}
for(String item : fontNames) {
    System.out.println(item);
}