图22-1使用菜单栏和三个菜单类别的应用程序

示例22-1菜单示例应用程序

import java.util.AbstractMap.SimpleEntry;
import java.util.Map.Entry;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.effect.DropShadow;
import javafx.scene.effect.Effect;
import javafx.scene.effect.Glow;
import javafx.scene.effect.SepiaTone;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.stage.Stage;public class MenuSample extends Application {final PageData[] pages = new PageData[] {new PageData("Apple","The apple is the pomaceous fruit of the apple tree, species Malus "+ "domestica in the rose family (Rosaceae). It is one of the most "+ "widely cultivated tree fruits, and the most widely known of "+ "the many members of genus Malus that are used by humans. "+ "The tree originated in Western Asia, where its wild ancestor, "+ "the Alma, is still found today.","Malus domestica"),new PageData("Hawthorn","The hawthorn is a large genus of shrubs and trees in the rose "+ "family, Rosaceae, native to temperate regions of the Northern "+ "Hemisphere in Europe, Asia and North America. "+ The name hawthorn was "+ "originally applied to the species native to northern Europe, "+ "especially the Common Hawthorn C. monogyna, and the unmodified "+ "name is often so used in Britain and Ireland.","Crataegus monogyna"),new PageData("Ivy","The ivy is a flowering plant in the grape family (Vitaceae) native to+ " eastern Asia in Japan, Korea, and northern and eastern China. "+ "It is a deciduous woody vine growing to 30 m tall or more given "+ "suitable support,  attaching itself by means of numerous small "+ "branched tendrils tipped with sticky disks.","Parthenocissus tricuspidata"),new PageData("Quince","The quince is the sole member of the genus Cydonia and is native to "+ "warm-temperate southwest Asia in the Caucasus region. The "+ "immature fruit is green with dense grey-white pubescence, most "+ "of which rubs off before maturity in late autumn when the fruit "+ "changes color to yellow with hard, strongly perfumed flesh.","Cydonia oblonga")};final String[] viewOptions = new String[] {"Title", "Binomial name", "Picture", "Description"};final Entry<String, Effect>[] effects = new Entry[] {new SimpleEntry<String, Effect>("Sepia Tone", new SepiaTone()),new SimpleEntry<String, Effect>("Glow", new Glow()),new SimpleEntry<String, Effect>("Shadow", new DropShadow())};final ImageView pic = new ImageView();final Label name = new Label();final Label binName = new Label();final Label description = new Label();public static void main(String[] args) {launch(args);}@Overridepublic void start(Stage stage) {stage.setTitle("Menu Sample");Scene scene = new Scene(new VBox(), 400, 350);scene.setFill(Color.OLDLACE);MenuBar menuBar = new MenuBar();// --- Menu FileMenu menuFile = new Menu("File");// --- Menu EditMenu menuEdit = new Menu("Edit");// --- Menu ViewMenu menuView = new Menu("View");menuBar.getMenus().addAll(menuFile, menuEdit, menuView);((VBox) scene.getRoot()).getChildren().addAll(menuBar);stage.setScene(scene);stage.show();}private class PageData {public String name;public String description;public String binNames;public Image image;public PageData(String name, String description, String binNames) {this.name = name;this.description = description;this.binNames = binNames;image = new Image(getClass().getResourceAsStream(name + ".jpg"));}}
}

与其他UI控件不同，Menu类的类和其他扩展MenuItem不会扩展Node类。它们无法直接添加到应用程序场景中，并且在通过该getMenus方法添加到菜单栏之前保持不可见。

图22-2菜单栏已添加到应用程序中

您可以使用键盘的箭头键浏览菜单。但是，当您选择菜单时，不执行任何操作，因为尚未定义菜单的行为。

示例22-2使用Graphics添加Shuffle菜单项

import java.util.AbstractMap.SimpleEntry;
import java.util.Map.Entry;
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.*;
import javafx.scene.effect.DropShadow;
import javafx.scene.effect.Effect;
import javafx.scene.effect.Glow;
import javafx.scene.effect.SepiaTone;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.scene.text.TextAlignment;
import javafx.stage.Stage;public class MenuSample extends Application {final PageData[] pages = new PageData[] {new PageData("Apple","The apple is the pomaceous fruit of the apple tree, species Malus "+"domestica in the rose family (Rosaceae). It is one of the most "+"widely cultivated tree fruits, and the most widely known of "+"the many members of genus Malus that are used by humans. "+"The tree originated in Western Asia, where its wild ancestor, "+"the Alma, is still found today.","Malus domestica"),new PageData("Hawthorn","The hawthorn is a large genus of shrubs and trees in the rose "+ "family, Rosaceae, native to temperate regions of the Northern "+ "Hemisphere in Europe, Asia and North America. "+ "The name hawthorn was "+ "originally applied to the species native to northern Europe, "+ "especially the Common Hawthorn C. monogyna, and the unmodified "+ "name is often so used in Britain and Ireland.","Crataegus monogyna"),new PageData("Ivy","The ivy is a flowering plant in the grape family (Vitaceae) native"+" to eastern Asia in Japan, Korea, and northern and eastern China."+" It is a deciduous woody vine growing to 30 m tall or more given "+"suitable support,  attaching itself by means of numerous small "+"branched tendrils tipped with sticky disks.","Parthenocissus tricuspidata"),new PageData("Quince","The quince is the sole member of the genus Cydonia and is native"+" to warm-temperate southwest Asia in the Caucasus region. The "+"immature fruit is green with dense grey-white pubescence, most "+"of which rubs off before maturity in late autumn when the fruit "+"changes color to yellow with hard, strongly perfumed flesh.","Cydonia oblonga")};final String[] viewOptions = new String[] {"Title", "Binomial name", "Picture", "Description"};final Entry<String, Effect>[] effects = new Entry[] {new SimpleEntry<String, Effect>("Sepia Tone", new SepiaTone()),new SimpleEntry<String, Effect>("Glow", new Glow()),new SimpleEntry<String, Effect>("Shadow", new DropShadow())};final ImageView pic = new ImageView();final Label name = new Label();final Label binName = new Label();final Label description = new Label();private int currentIndex = -1;public static void main(String[] args) {launch(args);}@Overridepublic void start(Stage stage) {stage.setTitle("Menu Sample");Scene scene = new Scene(new VBox(), 400, 350);scene.setFill(Color.OLDLACE);name.setFont(new Font("Verdana Bold", 22));binName.setFont(new Font("Arial Italic", 10));pic.setFitHeight(150);pic.setPreserveRatio(true);description.setWrapText(true);description.setTextAlignment(TextAlignment.JUSTIFY);shuffle();MenuBar menuBar = new MenuBar();final VBox vbox = new VBox();vbox.setAlignment(Pos.CENTER);vbox.setSpacing(10);vbox.setPadding(new Insets(0, 10, 0, 10));vbox.getChildren().addAll(name, binName, pic, description);// --- Menu FileMenu menuFile = new Menu("File");MenuItem add = new MenuItem("Shuffle",new ImageView(new Image("menusample/new.png")));add.setOnAction(new EventHandler<ActionEvent>() {public void handle(ActionEvent t) {shuffle();vbox.setVisible(true);}});        menuFile.getItems().addAll(add);// --- Menu EditMenu menuEdit = new Menu("Edit");// --- Menu ViewMenu menuView = new Menu("View");menuBar.getMenus().addAll(menuFile, menuEdit, menuView);((VBox) scene.getRoot()).getChildren().addAll(menuBar, vbox);stage.setScene(scene);stage.show();}private void shuffle() {int i = currentIndex;while (i == currentIndex) {i = (int) (Math.random() * pages.length);}pic.setImage(pages[i].image);name.setText(pages[i].name);binName.setText("(" + pages[i].binNames + ")");description.setText(pages[i].description);currentIndex = i;}private class PageData {public String name;public String description;public String binNames;public Image image;public PageData(String name, String description, String binNames) {this.name = name;this.description = description;this.binNames = binNames;image = new Image(getClass().getResourceAsStream(name + ".jpg"));}}
} 

当用户选择Shuffle菜单项时，shuffle调用的方法setOnAction通过计算相应数组中元素的索引来指定标题，二项式名称，工厂图片及其描述。

“清除”菜单项用于擦除应用程序场景。您可以通过使VBox具有GUI元素的容器不可见来实现此操作，如例22-3所示。

示例22-3使用加速器创建清除菜单项

MenuItem clear = new MenuItem("Clear");
clear.setAccelerator(KeyCombination.keyCombination("Ctrl+X"));
clear.setOnAction(new EventHandler<ActionEvent>() {public void handle(ActionEvent t) {vbox.setVisible(false);}
});

在实施MenuItem类别可让开发设置菜单加速器，执行相同的动作的菜单项的组合键。使用“清除”菜单，用户可以从“文件”菜单类别中选择操作，也可以同时按下“控制键”和“X”键。

Exit菜单关闭应用程序窗口。设置System.exit(0)为此菜单项的操作，如例22-4所示。

示例22-4创建退出菜单项

MenuItem exit = new MenuItem("Exit");
exit.setOnAction(new EventHandler<ActionEvent>() {public void handle(ActionEvent t) {System.exit(0);}
});

使用示例22-5中getItems显示的方法将新创建的菜单项添加到“文件”菜单。您可以创建一个分隔符菜单项并将其添加到方法中，以便可视地分离“退出”菜单项。getItems

示例22-5添加菜单项

menuFile.getItems().addAll(add, clear, new SeparatorMenuItem(), exit);

将示例22-2，示例22-3，示例22-4和示例22-5添加到Menu Sample应用程序，然后编译并运行它。选择Shuffle菜单项以加载有关不同植物的参考信息。然后清除场景（清除），并关闭应用程序（退出）。图22-3显示了Clear菜单项的选择。

图22-3包含三个菜单项的文件菜单

使用“视图”菜单，您可以隐藏和显示参考信息的元素。实现createMenuItem方法并在方法中调用它start以创建四个CheckMenuItem对象。然后将新创建的检查菜单项添加到“视图”菜单，以切换标题，二项式名称，工厂图片及其描述的可见性。例22-6显示了实现这些任务的两个代码片段。

示例22-6应用CheckMenuItem类创建切换选项

// --- Creating four check menu items within the start method
CheckMenuItem titleView = createMenuItem ("Title", name);                                                       
CheckMenuItem binNameView = createMenuItem ("Binomial name", binName);        
CheckMenuItem picView = createMenuItem ("Picture", pic);        
CheckMenuItem descriptionView = createMenuItem ("Description", description);     
menuView.getItems().addAll(titleView, binNameView, picView, descriptionView);...// The createMenuItem method
private static CheckMenuItem createMenuItem (String title, final Node node){CheckMenuItem cmi = new CheckMenuItem(title);cmi.setSelected(true);cmi.selectedProperty().addListener(new ChangeListener<Boolean>() {public void changed(ObservableValue ov,Boolean old_val, Boolean new_val) {node.setVisible(new_val);}});return cmi;
}

该CheckMenuItem班是的扩展MenuItem类。它可以在选定和取消选择的状态之间切换。选中后，检查菜单项会显示复选标记。

例22-6创建了四个CheckMenuItem对象并处理其selectedProperty属性的更改。例如，当用户取消选择该项时picView，该setVisible方法接收该false值，该工厂的图片变得不可见。将此代码片段添加到应用程序，编译并运行应用程序时，您可以尝试选择和取消选择菜单项。图22-4显示了显示工厂标题和图片时的应用程序，但隐藏了其二项式名称和描述。

图22-4使用检查菜单项

示例22-7使用单选菜单项创建子菜单

//Picture Effect menu
Menu menuEffect = new Menu("Picture Effect");
final ToggleGroup groupEffect = new ToggleGroup();
for (Entry<String, Effect> effect : effects) {RadioMenuItem itemEffect = new RadioMenuItem(effect.getKey());itemEffect.setUserData(effect.getValue());itemEffect.setToggleGroup(groupEffect);menuEffect.getItems().add(itemEffect);
}
//No Effects menu
final MenuItem noEffects = new MenuItem("No Effects");noEffects.setOnAction(new EventHandler<ActionEvent>() {public void handle(ActionEvent t) {pic.setEffect(null);groupEffect.getSelectedToggle().setSelected(false);}
});//Processing menu item selection
groupEffect.selectedToggleProperty().addListener(new ChangeListener<Toggle>() {public void changed(ObservableValue<? extends Toggle> ov,Toggle old_toggle, Toggle new_toggle) {if (groupEffect.getSelectedToggle() != null) {Effect effect = (Effect) groupEffect.getSelectedToggle().getUserData();pic.setEffect(effect);}}});
//Adding items to the Edit menu
menuEdit.getItems().addAll(menuEffect, noEffects);

该setUserData方法定义特定无线电菜单项的视觉效果。当选择切换组中的一个项目时，相应的效果将应用于图片。选择“无效果”菜单项时，该setEffect方法指定该null值，并且不对图片应用任何效果。

图22-5捕获用户选择Shadow菜单项的时刻。

图22-5带有三个单选菜单项的子菜单

当DropShadow效果被施加到图像，它看起来如图图22-6。

图22-6应用了DropShadow效果的Quince图片

在“图片效果”子菜单中未选择任何效果时，可以使用类的setDisable方法MenuItem禁用“无效果”菜单。修改例22-7，如例22-8所示。

示例22-8禁用菜单项

Menu menuEffect = new Menu("Picture Effect");
final ToggleGroup groupEffect = new ToggleGroup();
for (Entry<String, Effect> effect : effects) {RadioMenuItem itemEffect = new RadioMenuItem(effect.getKey());itemEffect.setUserData(effect.getValue());itemEffect.setToggleGroup(groupEffect);menuEffect.getItems().add(itemEffect);
}
final MenuItem noEffects = new MenuItem("No Effects");
noEffects.setDisable(true);      
noEffects.setOnAction(new EventHandler<ActionEvent>() {public void handle(ActionEvent t) {pic.setEffect(null);groupEffect.getSelectedToggle().setSelected(false);noEffects.setDisable(true);}
});groupEffect.selectedToggleProperty().addListener(new ChangeListener<Toggle>() {public void changed(ObservableValue<? extends Toggle> ov,Toggle old_toggle, Toggle new_toggle) {if (groupEffect.getSelectedToggle() != null) {Effect effect = (Effect) groupEffect.getSelectedToggle().getUserData();pic.setEffect(effect);noEffects.setDisable(false);} else {noEffects.setDisable(true);}}
});
menuEdit.getItems().addAll(menuEffect, noEffects);

如果未RadioMenuItem选择任何选项，则禁用“无效果”菜单项，如图22-7所示。当用户选择其中一个视觉效果时，将启用“无效果”菜单项。

图22-7效果菜单项被禁用

示例22-9定义上下文菜单

final ContextMenu cm = new ContextMenu();
MenuItem cmItem1 = new MenuItem("Copy Image");
cmItem1.setOnAction(new EventHandler<ActionEvent>() {public void handle(ActionEvent e) {Clipboard clipboard = Clipboard.getSystemClipboard();ClipboardContent content = new ClipboardContent();content.putImage(pic.getImage());clipboard.setContent(content);}
});cm.getItems().add(cmItem1);
pic.addEventHandler(MouseEvent.MOUSE_CLICKED,new EventHandler<MouseEvent>() {@Override public void handle(MouseEvent e) {if (e.getButton() == MouseButton.SECONDARY)  cm.show(pic, e.getScreenX(), e.getScreenY());}
});

当用户右键单击该ImageView对象时，将show调用该方法以使其显示上下文菜单。

setOnAction为上下文菜单的“复制图像”项定义的方法会创建一个Clipboard对象，并将图像添加为其内容。图22-8捕获用户选择“复制图像”上下文菜单项的时刻。

图22-8使用上下文菜单

您可以尝试复制图像并将其粘贴到图形编辑器中。

要进一步增强，可以向上下文菜单添加更多菜单项并指定不同的操作。您还可以使用CustomMenuItem该类创建自定义菜单。使用此类，您可以在菜单中嵌入任意节点，并指定例如按钮或滑块作为菜单项。

相关的API文档 

• Menu

• MenuItem

• RadioMenuItem

• CheckMenuItem

• ContextMenu

• SeparatorMenuItem

• CustomMenuItem