java 如何在 JavaFX 中移动形状？
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How to move shapes in JavaFX?
提问by dungo
I've been trying to make a program that displays a circle and lets you move it using buttons but I haven't been able to figure out how to tell Java what direction to move the Circle when you press a certain button. I've tried setX and setY but apparently they aren't native to Circle. Here's what I've got so far:
我一直在尝试制作一个程序来显示一个圆圈并让您使用按钮移动它，但是我一直无法弄清楚当您按下某个按钮时如何告诉 Java 移动圆圈的方向。我试过 setX 和 setY 但显然它们不是 Circle 原生的。这是我到目前为止所得到的：
import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
public class Ball extends Application {
private Circle circle = new Circle();
@Override
public void start(Stage primaryStage) {
HBox pane = new HBox();
pane.setSpacing(10);
pane.setAlignment(Pos.CENTER);
Button btUp = new Button("UP");
Button btDown = new Button("DOWN");
Button btLeft = new Button("LEFT");
Button btRight = new Button("RIGHT");
pane.getChildren().add(btUp);
pane.getChildren().add(btDown);
pane.getChildren().add(btRight);
pane.getChildren().add(btLeft);
btUp.setOnAction(e -> circle.setY(circle.getY() - 10));
btDown.setOnAction(e -> circle.setY(circle.getY() + 10));
btLeft.setOnAction(e -> circle.setX(circle.getX() - 10));
btRight.setOnAction(e -> circle.setX(circle.getX() + 10));
BorderPane borderPane = new BorderPane();
borderPane.setCenter(circle);
borderPane.setBottom(pane);
BorderPane.setAlignment(pane, Pos.CENTER);
Scene scene = new Scene(borderPane, 200, 200);
primaryStage.setTitle("Ball"); // Set the stage title
primaryStage.setScene(scene); // Place the scene in the stage
primaryStage.show();
circle.requestFocus();
}
public static void main(String[] args) {
launch(args);
}
}
回答by Jay Lin
The first problem with your code is the circle (or lack thereof).
您的代码的第一个问题是圆圈（或缺少圆圈）。
You shouldn't use the no-argument circle unless you plan to define it later. One solution is to define the radius and fill color in one line:
您不应该使用无参数圆，除非您打算稍后定义它。一种解决方案是在一行中定义半径和填充颜色：
private Circle circle = new Circle(50.0f, Color.RED);
As for moving the circle, you'll need to keep track of the changing circle position so add this with your instance variables:
至于移动圆圈，您需要跟踪不断变化的圆圈位置，因此将其添加到您的实例变量中：
private double newY, newX = 0;
I'll show you how to setup the down button (the code for Left, Right, and Up are very similar to down). Change your setOnAction method to:
我将向您展示如何设置向下按钮（Left、Right 和 Up 的代码与向下非常相似）。将您的 setOnAction 方法更改为：
btnDown.setOnAction(btnDownActionEvent);
Then define btnDownActionEvent after the main method (or wherever you want):
然后在 main 方法之后定义 btnDownActionEvent（或任何你想要的地方）：
EventHandler<ActionEvent> btnDownActionEvent = new EventHandler<ActionEvent>()
{
@Override
public void handle(ActionEvent event)
{
System.out.println("Pressed Down");
newY = circle.getCenterY() + 10 + newY;
circle.setTranslateX(newX);
circle.setTranslateY(newY);
}
};
Also, you can remove circle.requestFocus();
此外，您可以删除 circle.requestFocus();
回答by Maihan Nijat
Create two variables: One for X coordinates and one for Y coordinates.
创建两个变量：一个用于 X 坐标，一个用于 Y 坐标。
int newY, newX = 0;
int newY, newX = 0;
Now use setOnKeyPressedon Scene to move the circle when arrow keys are pressed, using IF Logic.
现在使用IF 逻辑在场景上使用setOnKeyPressed在按下箭头键时移动圆圈。
scene.setOnKeyPressed(e ->{
if(e.getCode() == KeyCode.RIGHT){
newX = newX + 10;
circle.setTranslateX(newX);
}
else if(e.getCode() == KeyCode.LEFT){
newX = newX - 10;
circle.setTranslateX(newX);
}
else if(e.getCode() == KeyCode.UP){
newY = newY - 10;
circle.setTranslateY(newY);
}
else if(e.getCode() == KeyCode.DOWN){
newY = newY + 10;
circle.setTranslateY(newY);
}
});
Make sure to create Scene before above code, else you will get undefined error.
确保在上面的代码之前创建场景，否则你会得到未定义的错误。
