简短说明：运行一个简单的JavaFX程序，该程序 说明了AnimationTimer结果在我的PC中几乎处于锁定状态 起来该程序可以在其他PC和我的PC上正常运行时 与其他版本的Linux一起启动。详细说明
在校对在线Java教科书的新版本时 我在运行本书中的示例程序时遇到了问题 说明了JavaFX AnimationTimer。程序源 是SimpleAnimationTimer.java。见下文。这很简单 仅显示当前帧号的程序 经过的时间（以秒为单位）。预期的输出是看 “每秒60帧”；即显示的帧号 除以显示的经过时间应为60。
编译并在我的PC上运行时，它将淹没应用程序 窗口太大了，几乎无法将鼠标移到 另一个窗口，以便我可以杀死正在运行的程序。什么时候 我通知了该书的作者，他回答说该程序 在他的所有PC（Ubuntu，Linux Mint，Mac，Windows）上均可正常运行。 我的电脑正在运行Fedora27。
我通过实时USB下载并运行了最新的Linux Mint， 然后使用与所使用的相同的Java测试程序 适用于Fedora27。该程序在那里正确运行。
接下来，我重新启动了较旧的Fedora 24并测试了该程序 那里。它运行无误。
我从实时USB下载并运行Fedora 28。的 程序那里有问题。
我的测试环境和结果的摘要。
Java版本为1.8.0_181。它是来自Oracle的。
Linux Mint 19内核4.15.0-20（通用）。没问题。
Fedora 24内核4.11.12。没问题。
Fedora 27内核4.17.17。有问题。
Fedora 28内核4.16.3。有问题。
Linux内核之间似乎有所改变 导致此问题的版本4.15和4.16。
原始的SimpleAnimationStarter.java源已被修改 在60帧后停止。 Test02SimpleAnimationStarter.java 源，如下所示，就是这样做的。运行该程序时， 显示的帧号是60，如预期的那样，并且显示 经过时间为0.3秒，而不是预期的1秒。
目前，我不知所措。这是 JavaFX问题？这是Linux内核问题吗？东西 还有吗？
任何建议/评论将不胜感激。也， 运行两个程序时很高兴看到结果 在其他平台上-Windows，Mac，其他Linux版本。
警告：首先运行Test02版本！确保已过去 时间是一秒钟。
来源如下。首先，先输入SimpleAnimationStarter.java Test02SimpleAnimationStarter.java。
import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.scene.layout.BorderPane;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.paint.Color;
/**
* This file can be used to create very simple animations. Just fill in
* the definition of drawFrame with the code to draw one frame of the
* animation, and possibly change a few of the values in the rest of
* the program as noted below.
*/
public class SimpleAnimationStarter extends Application {
/**
* Draws one frame of an animation. This subroutine should be called
* about 60 times per second. It is responsible for redrawing the
* entire drawing area. The parameter g is used for drawing. The frameNumber
* starts at zero and increases by 1 each time this subroutine is called.
* The parameter elapsedSeconds gives the number of seconds since the animation
* was started. By using frameNumber and/or elapsedSeconds in the drawing
* code, you can make a picture that changes over time. That's an animation.
* The parameters width and height give the size of the drawing area, in pixels.
*/
public void drawFrame(GraphicsContext g, int frameNumber, double elapsedSeconds, int width, int height) {
/* NOTE: To get a different animation, just erase the contents of this
* subroutine and substitute your own.
*/
g.setFill(Color.WHITE);
g.fillRect(0, 0, width, height); // First, fill the entire image with a background color!
g.setFill(Color.BLACK);
g.fillText( "Frame number " + frameNumber, 40, 50 );
g.fillText( String.format("Elapsed Time: %1.1f seconds", elapsedSeconds), 40, 80);
}
//------ Implementation details: DO NOT EXPECT TO UNDERSTAND THIS ------
private int frameNum;
private long startTime;
public void start(Stage stage) {
int width = 800; // The width of the image. You can modify this value!
int height = 600; // The height of the image. You can modify this value!
Canvas canvas = new Canvas(width,height);
drawFrame(canvas.getGraphicsContext2D(), 0, 0, width, height);
BorderPane root = new BorderPane(canvas);
root.setStyle("-fx-border-width: 4px; -fx-border-color: #444");
Scene scene = new Scene(root);
stage.setScene(scene);
stage.setTitle("Simple Animation"); // STRING APPEARS IN WINDOW TITLEBAR!
stage.show();
stage.setResizable(false);
AnimationTimer anim = new AnimationTimer() {
public void handle(long now) {
if (startTime < 0)
startTime = now;
frameNum++;
drawFrame(canvas.getGraphicsContext2D(), frameNum, (now-startTime)/1e9, width, height);
}
};
startTime = -1;
anim.start();
}
public static void main(String[] args) {
launch();
}
} // end SimpleAnimationStarter
import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.scene.layout.BorderPane;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.paint.Color;
/**
* This file can be used to create very simple animations. Just fill in
* the definition of drawFrame with the code to draw one frame of the
* animation, and possibly change a few of the values in the rest of
* the program as noted below.
*/
public class Test02SimpleAnimationStarter extends Application {
/**
* Draws one frame of an animation. This subroutine should be called
* about 60 times per second. It is responsible for redrawing the
* entire drawing area. The parameter g is used for drawing. The frameNumber
* starts at zero and increases by 1 each time this subroutine is called.
* The parameter elapsedSeconds gives the number of seconds since the animation
* was started. By using frameNumber and/or elapsedSeconds in the drawing
* code, you can make a picture that changes over time. That's an animation.
* The parameters width and height give the size of the drawing area, in pixels.
*/
public void drawFrame(GraphicsContext g, int frameNumber, double elapsedSeconds, int width, int height) {
/* NOTE: To get a different animation, just erase the contents of this
* subroutine and substitute your own.
*/
g.setFill(Color.WHITE);
g.fillRect(0, 0, width, height); // First, fill the entire image with a background color!
g.setFill(Color.BLACK);
g.fillText( "Frame number " + frameNumber, 40, 50 );
g.fillText( String.format("Elapsed Time: %1.1f seconds", elapsedSeconds), 40, 80);
}
//------ Implementation details: DO NOT EXPECT TO UNDERSTAND THIS ------
private int frameNum;
private long startTime;
AnimationTimer anim = null; // Moved outside start() so handle() can call anim.stop()
public void start(Stage stage) {
int width = 800; // The width of the image. You can modify this value!
int height = 600; // The height of the image. You can modify this value!
Canvas canvas = new Canvas(width,height);
drawFrame(canvas.getGraphicsContext2D(), 0, 0, width, height);
BorderPane root = new BorderPane(canvas);
root.setStyle("-fx-border-width: 4px; -fx-border-color: #444");
Scene scene = new Scene(root);
stage.setScene(scene);
stage.setTitle("Simple Animation"); // STRING APPEARS IN WINDOW TITLEBAR!
stage.show();
stage.setResizable(false);
// AnimationTimer anim = new AnimationTimer() {
anim = new AnimationTimer() {
// Constants: change NUM_SECS and/or framesPerSec
private final int NUM_SECS = 1; // Desired number of seconds.
private final int framesPerSec = 60; // Expected frames per second.
private final int NUM_FRAMES = NUM_SECS*framesPerSec;
public void handle(long now) {
if (startTime < 0)
startTime = now;
frameNum++;
if (frameNum < NUM_FRAMES+1)
{
drawFrame(canvas.getGraphicsContext2D(),
frameNum,
(now-startTime)/1e9,
width, height);
}
else if (frameNum == NUM_FRAMES+1)
{
anim.stop();
System.out.println("Animation stopped");
}
else if (frameNum == NUM_FRAMES+2)
{
System.out.println("Animation kept going after stop ???");
}
}
};
startTime = -1;
anim.start();
}
public static void main(String[] args) {
launch();
}
} // end Test02SimpleAnimationStarter