java - 在 JavaFX 中同时按下按键

Question

package javafx_pressing_simultaneous_keys;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.input.KeyCode;
import javafx.scene.input.KeyEvent;
import javafx.scene.paint.Color;
import javafx.scene.control.Label;
import javafx.scene.layout.BorderPane;
import javafx.scene.text.Font;
import javafx.stage.Stage;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.binding.BooleanBinding;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.EventHandler;

public class JavaFX_Pressing_Simultaneous_Keys extends Application
{
  final BooleanProperty ZPressed = new SimpleBooleanProperty(false);
  final BooleanProperty XPressed = new SimpleBooleanProperty(false);
  final BooleanBinding ZAndXPressed = ZPressed.and(XPressed);
  int i = 0;

  @Override
  public void start(Stage stage)
  {
    BorderPane bp = new BorderPane();
    bp.setStyle("-fx-background-color: linear-gradient(from 25% 25% to 100% 100%, #DC143C, #661A33)");
    Scene s = new Scene(bp, 340, 300);

    Label l1 = new Label();
    l1.setFont(new Font("Arial", 56));
    l1.setTextFill(Color.CADETBLUE);
    bp.setCenter(l1);
    l1.setText(Integer.toString(i));

    // How to Respond to both Keys ("Z" and "X") pressed together.
    ZAndXPressed.addListener(new ChangeListener<Boolean>()
    {
      @Override
      public void changed(ObservableValue<? extends Boolean> obs, Boolean werePressed, Boolean arePressed)
      {
        i++;
        l1.setText(Integer.toString(i));
      }
    });

    s.setOnKeyPressed(new EventHandler<KeyEvent>()
    {
      @Override
      public void handle(KeyEvent ke)
      {
        if (ke.getCode() == KeyCode.Z)
          ZPressed.set(true);
        else
          if (ke.getCode() == KeyCode.X)
            XPressed.set(true);
      }
    });

    s.setOnKeyReleased(new EventHandler<KeyEvent>()
    {
      @Override
      public void handle(KeyEvent ke)
      {
        if (ke.getCode() == KeyCode.Z)
          ZPressed.set(false);
        else
          if (ke.getCode() == KeyCode.X)
            XPressed.set(false);
      }
    });

    stage.setScene(s);
    stage.setTitle("JavaFX (Pressing Simultaneous Keys)");
    stage.setResizable(false);
    stage.show();
  }


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

我试图编写一段代码，允许我同时按下 2 个键(例如 Z 和 X 键)，然后计算我按下该组合键的次数。但我注意到每次我按 Z 和 X 键时程序都会计数两次。谁能告诉我这是正常的还是某些事件处理程序有问题？非常感谢。

Answer 1

ChangeListener 只知道其对象的状态已更改。它不知道它的对象如何或发生了什么。您现在的逻辑是每次 ZAndXPressed 更改时增加 i，无论是从 true 到 false，还是从 false 到 true。

试试这个:

// How to Respond to both Keys ("Z" and "X") pressed together.
ZAndXPressed.addListener(new ChangeListener<Boolean>()
{
  @Override
  public void changed(ObservableValue<? extends Boolean> observable, Boolean oldValue, Boolean newValue)
  {
    if (newValue == true)
    {
        i++;
        l1.setText(Integer.toString(i));
    }
  }
});