多线程Java FX画布在完成之前不会显示

Question

我想创建一个JavaFX应用程序，它一步一步地在画布上绘制线条，线段之间有一个明显的时间间隔。在下面的应用程序中，我会画一条对角线，暂停一秒钟，然后画下一条对角线。相反，FX窗口弹出空白，等待2秒钟，然后同时显示两条对角线。我如何达到我想要的效果？javafx.scene.canvas.Canvas不是要使用的正确对象吗

import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;

import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.paint.Color;

public class FrameCanvas extends Application{
  public static void main(String[] args){
    launch(args);
  }
  @Override
  public void start(Stage primaryStage)throws Exception{
    ////////////////////Basic FX stuff
    Canvas theCanvas = new Canvas(900,900);
    StackPane theLayout = new StackPane();
    theLayout.getChildren().add(theCanvas);
    Scene theScene = new Scene(theLayout,900,900);
    primaryStage.setScene(theScene);
    primaryStage.show();
    ///////////////////////
    /////Drawing an X
    ///////////////////////
    GraphicsContext gc = theCanvas.getGraphicsContext2D();
    Thread.sleep(1000);
    gc.strokeLine(0,0,200,200);
    Thread.sleep(1000);
    gc.strokeLine(200,0,0,200);
    /////////////////////////////
  }
}

Answer 1

不要阻止（例如Thread.sleep(...)）FX应用程序线程。该线程负责渲染场景，因此您将阻止渲染任何更新

相反，使用动画实现类似的功能（毕竟，动画就是您在此处创建的）：

public void start(Stage primaryStage)throws Exception{
    ////////////////////Basic FX stuff
    Canvas theCanvas = new Canvas(900,900);
    StackPane theLayout = new StackPane();
    theLayout.getChildren().add(theCanvas);
    Scene theScene = new Scene(theLayout,900,900);
    primaryStage.setScene(theScene);
    primaryStage.show();
    ///////////////////////
    /////Drawing an X
    ///////////////////////
    GraphicsContext gc = theCanvas.getGraphicsContext2D();

    Timeline timeline = new Timeline(
        new KeyFrame(Duration.seconds(1), e -> gc.strokeLine(0,0,200,200)),
        new KeyFrame(Duration.seconds(2), e -> gc.strokeLine(200,0,0,200))
    );
    timeline.play();
    /////////////////////////////
}