javafx事件处理机制 JavaFX事件过滤器

JavaFX教程 - JavaFX事件过滤器

事件过滤器允许我们在事件捕获阶段处理事件。

节点可以具有用于处理事件的一个或多个过滤器。

我们可以为多个节点使用一个过滤器来处理多个事件类型。

来自父节点的事件过滤器负责处理其子节点，并可拦截事件并防止子节点对事件执行操作。

注册事件过滤器

事件过滤器是EventHandler接口的实现。要注册过滤器，请使用addEventFilter()方法。

// Register an event filter for a single node and a specific event type
scene.addEventFilter(MouseEvent.MOUSE_CLICKED,
        new EventHandler<MouseEvent>() {
          public void handle(MouseEvent e) {
            System.out.println("mouse clicked");
          };
});

完整的源代码

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.scene.input.MouseEvent;
import javafx.stage.Stage;
//from   w  ww  .  ja  va 2 s  .  c o  m
public class Main extends Application {
  public static void main(String[] args) {
    Application.launch(args);
  }

  @Override
  public void start(Stage primaryStage) {
    Group root = new Group();
    Scene scene = new Scene(root, 300, 250);

    TextField textBox = new TextField();
    textBox.setPromptText("Write here");

    // Register an event filter for a single node and a specific event type
    scene.addEventFilter(MouseEvent.MOUSE_CLICKED,
        new EventHandler<MouseEvent>() {
          public void handle(MouseEvent e) {
            System.out.println("mouse clicked");
          };
        });

    root.getChildren().add(textBox);
    primaryStage.setScene(scene);
    primaryStage.show();
  }
}

上面的代码生成以下结果。

过滤器对象

以下代码定义了过滤器对象，并将其用于不同的事件过滤器。

// Define an event filter
EventHandler filter = new EventHandler<InputEvent>() {
  public void handle(InputEvent event) {
    System.out.println("Filtering out event " + event.getEventType());
    event.consume();
  }
};
// Register the same filter for two different nodes
scene.addEventFilter(MouseEvent.MOUSE_PRESSED, filter);

// Register the filter for another event type
scene.addEventFilter(KeyEvent.KEY_PRESSED, filter);

完整的源代码

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.scene.input.InputEvent;
import javafx.scene.input.KeyEvent;
import javafx.scene.input.MouseEvent;
import javafx.stage.Stage;

public class Main extends Application {
  public static void main(String[] args) {
    Application.launch(args);
  }

  @Override
  public void start(Stage primaryStage) {
    Group root = new Group();
    Scene scene = new Scene(root, 300, 250);

    TextField textBox = new TextField();
    textBox.setPromptText("Write here");
    // Define an event filter
    EventHandler filter = new EventHandler<InputEvent>() {
      public void handle(InputEvent event) {
        System.out.println("Filtering out event " + event.getEventType());
        event.consume();
      }
    };
    // Register the same filter for two different nodes
    scene.addEventFilter(MouseEvent.MOUSE_PRESSED, filter);

    // Register the filter for another event type
    scene.addEventFilter(KeyEvent.KEY_PRESSED, filter);

    root.getChildren().add(textBox);
    primaryStage.setScene(scene);
    primaryStage.show();
  }
}

上面的代码生成以下结果。

删除事件过滤器

要删除事件过滤器，请使用removeEventFilter()方法。此方法将事件类型和过滤器作为参数。

以下代码删除MouseEvent.MOUSEPRESSED事件的过滤器。

// Remove an event filter
myNode1.removeEventFilter(MouseEvent.MOUSE_PRESSED, filter);

完整的源代码

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.scene.input.InputEvent;
import javafx.scene.input.KeyEvent;
import javafx.scene.input.MouseEvent;
import javafx.stage.Stage;
// ww w.  ja  v a 2 s.co m
public class Main extends Application {
  public static void main(String[] args) {
    Application.launch(args);
  }

  @Override
  public void start(Stage primaryStage) {
    Group root = new Group();
    Scene scene = new Scene(root, 300, 250);

    TextField textBox = new TextField();
    textBox.setPromptText("Write here");
    // Define an event filter
    EventHandler filter = new EventHandler<InputEvent>() {
      public void handle(InputEvent event) {
        System.out.println("Filtering out event " + event.getEventType());
        event.consume();
      }
    };
    // Register the same filter for two different nodes
    scene.addEventFilter(MouseEvent.MOUSE_PRESSED, filter);

    // Register the filter for another event type
    scene.addEventFilter(KeyEvent.KEY_PRESSED, filter);

    scene.removeEventFilter(MouseEvent.MOUSE_PRESSED, filter);
    
    
    root.getChildren().add(textBox);
    primaryStage.setScene(scene);
    primaryStage.show();
  }
}

上面的代码生成以下结果。