JavaFX 动画在第一个周期后停止

Question

我想要一个计数到 3 的计数器，然后它应该从 0 重新开始并无限期地重复计数直到 3。 但是当我的计数器达到 3 时，我的程序所做的最后一件事就是设置文本 "0"。 我想我没有正确使用动画。 我希望有人知道我做错了什么。 请注意，这只是对我的实际问题的简化；可能有更简单的方法来数到 3...

import javafx.animation.Animation;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline; 
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.text.Font;
import javafx.scene.text.FontPosture;
import javafx.scene.text.FontWeight;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import javafx.util.Duration;

public class GeneralTesting extends Application{
    private Text text;
    private int counter = 1;
    public static void main(String[] args) {
        launch();
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        Pane pane = new Pane();

        text = new Text(500, 300, "0");

        text.setFont(Font.font("Comic Sans MS", FontWeight.BOLD, FontPosture.REGULAR, 100));

        Animation animation = new Timeline(new KeyFrame(Duration.millis(1000), e -> {changeText(counter++);}));
        animation.setCycleCount(Timeline.INDEFINITE);
        animation.play();

        pane.getChildren().addAll(text);

        Scene scene = new Scene(pane);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public void changeText(int counter){
        if (counter > 5){
            counter = 0;
        }
        text.setText(String.valueOf(counter));
    }

}

Answer 1

在

if (counter > 5) {
    counter = 0 ;
}

您正在将 local 变量 counter 重置为 0。实例字段保持其先前的值。因此，在时间线的下一次迭代中，它仍然大于 5，并且您再次将局部变量设置为零。

完全删除局部变量，只更新字段：

import javafx.animation.Animation;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline; 
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.text.Font;
import javafx.scene.text.FontPosture;
import javafx.scene.text.FontWeight;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import javafx.util.Duration;

public class GeneralTesting extends Application{
    private Text text;
    private int counter = 1;
    public static void main(String[] args) {
        launch();
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        Pane pane = new Pane();

        text = new Text(500, 300, "0");

        text.setFont(Font.font("Comic Sans MS", FontWeight.BOLD, FontPosture.REGULAR, 100));

        Animation animation = new Timeline(new KeyFrame(Duration.millis(1000), e -> {
            counter++; 
            changeText();
        }));

        animation.setCycleCount(Timeline.INDEFINITE);
        animation.play();

        pane.getChildren().addAll(text);

        Scene scene = new Scene(pane);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public void changeText(){
        if (counter > 5){
            counter = 0;
        }
        text.setText(String.valueOf(counter));
    }

}

更好的是，使用IntegerProperty 并将文本绑定到它的值：

import javafx.animation.Animation;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline; 
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.text.Font;
import javafx.scene.text.FontPosture;
import javafx.scene.text.FontWeight;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import javafx.util.Duration;

public class GeneralTesting extends Application{
    private Text text;
    public static void main(String[] args) {
        launch();
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        Pane pane = new Pane();

        text = new Text(500, 300, "0");

        text.setFont(Font.font("Comic Sans MS", FontWeight.BOLD, FontPosture.REGULAR, 100));

        IntegerProperty counter = new SimpleIntegerProperty(1);
        text.textProperty().bind(counter.asString());

        Animation animation = new Timeline(new KeyFrame(Duration.millis(1000), 
            e -> counter.set((counter.get()+1) % 5)));

        animation.setCycleCount(Timeline.INDEFINITE);
        animation.play();

        pane.getChildren().addAll(text);

        Scene scene = new Scene(pane);
        primaryStage.setScene(scene);
        primaryStage.show();
    }


}

Answer 2

一种方法是使用 mod 将范围保持在 0 到 3 之间。

    Pane pane = new Pane();

    Text text = new Text(500, 300, "0");
    int[] counter =
    {
        0
    };
    text.setFont(Font.font("Comic Sans MS", FontWeight.BOLD, FontPosture.REGULAR, 100));

    Animation animation = new Timeline(new KeyFrame(Duration.millis(1000), e
            ->
    {
        text.setText(Integer.toString(counter[0]++ % 4));
    }));
    animation.setCycleCount(Timeline.INDEFINITE);
    animation.play();

    pane.getChildren().addAll(text);

    Scene scene = new Scene(pane);
    primaryStage.setScene(scene);
    primaryStage.show();