我有一个 JavaFX 应用程序，它可以在屏幕上为机器人(黑点)设置动画，并在它们去过的任何地方在浅灰色背景上绘制一条小白线(想想 Tron)。为此，我保留了机器人和所有白色像素的所有坐标。机器人的行为由实现 Runnable 的不同线程控制，并且可以在模拟运行时更改。机器人坐标存储在 HashMap 中，坐标是扩展 Point 的类，并使用 double 来提高 x 和 y 值的内部计算精度。对于白点，我使用 HashMap，因为整数精度足以满足它们，因为它们不会移动并无限期地停留在屏幕上的 x 和 y 坐标处。
现在程序运行得很好，但是当存储白点点的 HashMap 增长时，应用程序的 JavaFX 线程崩溃的可能性越来越大(想想看，更具体地说，它只是机器人所在的 Canvas )绘制。)控件的 slider 保持响应，并且迭代的文本字段和 HashMap 的大小不断更新。但没有任何动画，几秒钟后 Canvas 变成白色。增加 Thread.sleep(ms) 的 ms 可以使程序更加稳定，但速度已经非常慢了。而且，这种情况在我的慢速学校上网本(运行 Win XP)上比在我的家用台式电脑(运行 Win7 64 位)上发生得更频繁、更快。异常(exception)也有不同的。对于台式电脑，如下:
java.lang.InternalError: Unrecognized PGCanvas token: 68
at com.sun.javafx.sg.prism.NGCanvas.renderStream(NGCanvas.java:651)
at com.sun.javafx.sg.prism.NGCanvas.renderContent(NGCanvas.java:320)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:187)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1145)
at com.sun.javafx.sg.prism.NGGroup.renderContent(NGGroup.java:204)
at com.sun.javafx.sg.prism.NGRegion.renderContent(NGRegion.java:420)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:187)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1145)
at com.sun.javafx.tk.quantum.ViewPainter.doPaint(ViewPainter.java:117)
at com.sun.javafx.tk.quantum.AbstractPainter.paintImpl(AbstractPainter.java:175)
at com.sun.javafx.tk.quantum.PresentingPainter.run(PresentingPainter.java:73)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)
at com.sun.prism.render.RenderJob.run(RenderJob.java:37)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:98)
at java.lang.Thread.run(Thread.java:724)
对于上网本来说:
java.lang.IllegalArgumentException: alpha value out of range
at java.awt.AlphaComposite.<init>(AlphaComposite.java:624)
at java.awt.AlphaComposite.getInstance(AlphaComposite.java:689)
at java.awt.AlphaComposite.derive(AlphaComposite.java:761)
at com.sun.prism.j2d.J2DPrismGraphics.setExtraAlpha(J2DPrismGraphics.java:569)
at com.sun.javafx.sg.prism.NGCanvas.renderStream(NGCanvas.java:739)
at com.sun.javafx.sg.prism.NGCanvas.renderContent(NGCanvas.java:389)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:201)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:40)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1145)
at com.sun.javafx.sg.prism.NGGroup.renderContent(NGGroup.java:204)
at com.sun.javafx.sg.prism.NGRegion.renderContent(NGRegion.java:420)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:201)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:40)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1145)
at com.sun.javafx.tk.quantum.ViewPainter.doPaint(ViewPainter.java:117)
at com.sun.javafx.tk.quantum.AbstractPainter.paintImpl(AbstractPainter.java:182)
at com.sun.javafx.tk.quantum.PresentingPainter.run(PresentingPainter.java:73)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)
at com.sun.prism.render.RenderJob.run(RenderJob.java:37)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:108)
at java.lang.Thread.run(Thread.java:722)
任何解决或缩小此问题范围的帮助将不胜感激。
编辑: 正如所建议的，我将添加一个仍然存在问题的代码的最小示例。主要方法位于类 Visualizer 中，用于绘制模拟区域
import java.awt.Point;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import javafx.application.Application;
import javafx.geometry.Rectangle2D;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.layout.BorderPane;
import javafx.scene.paint.Color;
import javafx.stage.Screen;
import javafx.stage.Stage;
public class Visualizer extends Application {
private static GraphicsContext gc;
private static Canvas canvas;
private static BorderPane pane;
private static Scene scene;
private static Thread thread;
private static Simulator sim = new Simulator();
private static int optionsWidth = 200;
private static HashSet<Point> manganCollected = new HashSet<Point>();
private static HashMap<Integer, Coordinates> coordinates = new HashMap<Integer, Coordinates>();
private static final int zoom = 4;
private static Point cmpP;
/**
* Height in pixels that's available to draw the simulation on dependent on used monitor resolution
*/
public static double simHeight;
/**
* Width in pixels that's available to draw the simulation on dependent on used monitor resolution
*/
public static double simWidth;
/**
* Launches the JavaFX application
* @param args command line arguments if there are any
*/
public static void main(String[] args) {
launch(args);
}
/**
* Sets up the GUI with all options and the canvas to draw the robots on
*/
@Override
public void start(Stage stage) throws Exception {
// Determine screen width of the monitor
Screen screen = Screen.getPrimary();
Rectangle2D bounds = screen.getVisualBounds();
double screenHeight = bounds.getHeight();
double screenWidth = bounds.getWidth();
// set the stage
stage.setFullScreen(true);
stage.setHeight(screenHeight);
stage.setWidth(screenWidth);
stage.setTitle("Manganernte");
// Canvas to draw the simulation on
canvas = new Canvas();
simHeight = screenHeight;
simWidth = screenWidth - optionsWidth;
canvas.setHeight(simHeight);
canvas.setWidth(simWidth);
gc = canvas.getGraphicsContext2D();
gc = canvas.getGraphicsContext2D();
gc.setFill(Color.LIGHTGRAY);
gc.fillRect(0, 0, simWidth, simHeight);
gc.setStroke(Color.BLACK);
gc.setLineWidth(3);
gc.strokeRect(0, 0, simWidth, simHeight);
// BorderPane containing the buttons box and the Simulator canvas
pane = new BorderPane();
pane.setCenter(canvas);
// Scene containing the pane
scene = new Scene(pane);
// Show the whole stage
stage.setScene(scene);
stage.show();
thread = new Thread(sim);
thread.start();
}
/**
* Transforms double coordinates as used by the simulator (0/0 in the center) to monitor coordinates (0/0 top left corner)
* @param coordinates Floating point coordinates that should be transformed
* @return Coordinates Floating point coordinates that have been transformed
*/
private static Coordinates transform(Coordinates coordinates) {
return new Coordinates(Math.round((simWidth / 2) + (zoom * coordinates.getX())), Math.round((simHeight / 2) + (zoom * coordinates.getY())));
}
/**
* Transforms integer coordinates as used by the simulator (0/0 in the center) to monitor coordinates (0/0 top left corner)
* @param Point Integer coordinates that should be transformed
* @return Point Integer coordinates that have been transformed
*/
private static Point transform(Point point) {
return new Point((int)Math.round((simWidth / 2) + (zoom * point.getX())), (int)Math.round(((simHeight / 2) + (zoom * point.getY()))));
}
/**
* Clear the canvas by drawing a rectangle filled with light gray background
*/
private static void clear () {
gc.setFill(Color.LIGHTGRAY);
gc.fillRect(0, 0, simWidth, simHeight);
gc.setStroke(Color.BLACK);
gc.setLineWidth(3);
gc.strokeRect(0, 0, simWidth, simHeight);
}
/**
* Clears the canvas and then draws first the collected mangan as white rectangles followed by robots as black circles the given coordinates
* @param redraw boolean that's set to true if iteration hasn't changed but a redraw should be forced anyway (e.g. when simulation is paused and the zoom is used)
*/
public static void DrawRobots() {
coordinates = Simulator.coordinates;
manganCollected = Simulator.manganCollected;
// clear the canvas with light gray background
clear();
// draw harvested mangan as white dots
gc.setFill(Color.WHITE);
Iterator<Point> it = manganCollected.iterator();
while(it.hasNext()) {
cmpP = it.next().getLocation();
double x = transform(cmpP).getX();
double y = transform(cmpP).getY();
gc.fillRect(x, y, zoom, zoom);
}
// draw robots
gc.setFill(Color.BLACK);
for(int i = 1; i <= coordinates.size(); i++) {
double x = transform(coordinates.get(i)).getX();
double y = transform(coordinates.get(i)).getY();
gc.fillOval(x, y, zoom, zoom);
}
}
}
模拟器类:
import java.awt.Point;
import java.util.HashMap;
import java.util.HashSet;
public class Simulator implements Runnable {
// start variable declarations
// HashMap of all robot objects the simulator controls
private static HashMap<Integer, Robot> robots = new HashMap<Integer, Robot>();
// HashMap of all coordinate objects the simulator controls
public static HashMap<Integer, Coordinates> coordinates = new HashMap<Integer, Coordinates>();
// HashMap of all point objects containing the coordinates of places where the mangan has already been collected
public static HashSet<Point> manganCollected = new HashSet<Point>();
/**
* communication radius of the robots according to the requirements
*/
public static int processSpeed = 100;
// end variable declarations
/**
* Create a robot with x and y
* @param x x-coordinate
* @param y y-coordinate
*/
public static void createRobot(int x, int y) {
coordinates.put(coordinates.size() + 1, new Coordinates(x, y));
robots.put(robots.size() + 1, new Robot());
}
/**
* Checks the status, changes it if necessary and acts accordingly
*/
@Override
public void run() {
for(int i = 0; i < 100; i++) createRobot(i - 50, 0);
Visualizer.DrawRobots();
while(true) {
for(int i = 1; i <= robots.size(); i++) robots.get(i).think();
for(int i = 1; i <= robots.size(); i++) {
coordinates.get(i).add(robots.get(i).move());
manganCollected.add(new Point((int)Math.round(coordinates.get(i).getX()), (int)Math.round(coordinates.get(i).getY())));
}
Visualizer.DrawRobots();
try {
Thread.sleep(processSpeed);
} catch(InterruptedException e) {
e.printStackTrace();
}
}
}
}
最后，在这个最小的示例中，机器人类不再做太多事情了:
public class Robot {
Coordinates future = new Coordinates(0, 0);
public void think () {
future.setY(1.0);
}
public Coordinates move() {
return future;
}
}
更新 刚刚安装了 JDK 8，现在的异常更能说明问题:
Exception in thread "Thread-4" java.lang.IllegalStateException: Not on FX application thread; currentThread = Thread-4
在网上搜索了一下，似乎我需要使用 Platform.runLater() 来避免这种情况发生。但我不知道该怎么做。 我将尝试再次解释我的项目现在的结构:
我有类Visualizer，它扩展了Application，它还包括main()方法，并在GraphicsContext Canvas上绘制UI，包括模拟区域作为灰色矩形。 UI 完成后，它会创建一个实现 Runnable 的 Simulator 类线程。 Simulator 类中的 run() 方法进入 while(true) 循环。只要没有单击任何按钮，循环除了 thread.sleep() 之外什么也不做。如果单击开始按钮，则会执行一些计算，并调用 Visualizer 上的一些方法来在模拟 Canvas 上绘制内容。据我了解，这些调用会导致异常，因为它们是从非 JavaFX 线程发出的。
我是否必须使用 runLater() 来避免此问题，如果是的话，我应该在哪里以及如何执行此操作？
更新2 最终通过将改变 UI/Canvas 任何内容的公共(public)方法的代码包装到 runLater block 中，使其稳定运行(据我现在所知)。
public static void drawStuff() {
Platform.runLater(new Runnable() {
@Override
public void run() {
// draw stuff
}
});
}
最佳答案
只是发布此内容，以便读者立即明显看出该问题实际上有答案/解决方案。
我遇到了同样的问题，正如作者最后指出的那样，他自己是“更新”。
如果您遇到此问题，您可能正在另一个线程中进行 ui Canvas 操作。您应该始终在应用程序线程上执行 ui 操作!使用
Platform.runLater(()->{
//your code
});
关于exception - JavaFX 线程崩溃，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21231557/