我想显示 5 个随机定位的彩色圆圈。这是很容易的部分。现在我想将这段代码调整为动画。该应用程序应该无休止地生成随机圆圈,但条件是它应该只在屏幕上保留最后五个圆圈。这就是我被困住的地方。 JavaFx提供ListChangeListener。我认为这是我应该使用的。但如何呢?
以下是我未完成的代码:
import java.util.Random;
import javafx.application.Application;
import javafx.collections.ListChangeListener;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
public class RandomColorTest extends Application {
int radius = 20;
int sceneWidth = 300;
int sceneHeight = 300;
private void init(Stage primaryStage) {
Group root = new Group();
primaryStage.setResizable(false);
primaryStage.setScene(new Scene(root, sceneWidth,sceneHeight));
for (int i = root.getChildren().size(); i < 5; i++) {
root.getChildren().add(createCircle());
// the following should convey the idea:
// if the collection holds 5 elements then keep least recently generated element for 1 second and then delete it
// add one new element
// if the collection holds 5 elements then keep least recently generated element for 1 second and then delete it
// add one new element
// and so on
root.getChildren().addListener(new ListChangeListener<E>() {
@Override
public void onChanged(
javafx.collections.ListChangeListener.Change<? extends E> arg0) {
// TODO Auto-generated method stub
}
});
}
}
// Create randomly positioned and colored circle
private Circle createCircle() {
final Circle circle = new Circle();
circle.setRadius(radius);
Random r = new Random();
int rCol1 = r.nextInt(256);
int rCol2 = r.nextInt(256);
int rCol3 = r.nextInt(256);
int rX = radius+r.nextInt(sceneWidth);
if (rX>sceneWidth-radius) {
rX=rX-2*radius;
}
int rY = radius+r.nextInt(sceneHeight);
if (rY>sceneHeight-radius) {
rY=rY-2*radius;
}
circle.setLayoutX(rX);
circle.setLayoutY(rY);
circle.setStroke(Color.BLACK);
circle.setFill(Color.rgb(rCol1,rCol2,rCol3));
System.out.println(rCol1+"-"+rCol2+"-"+rCol3+"-"+rX+"-"+rY);
return circle;
}
@Override public void start(Stage primaryStage) throws Exception {
init(primaryStage);
primaryStage.show();
}
public static void main(String[] args) { launch(args); }
}
在设法使 ListChangeListener 编译没有错误后,它仍然无法按预期方式工作。对 for 循环所做的更改:
for (int i = root.getChildren().size();;i++) {
final ObservableList<Node> ol = root.getChildren();
// the following should convey the idea:
// if the collection holds 5 elements then keep least recently generated element for 1 second and then delete it
// add one new element
// if the collection holds 5 elements then keep least recently generated element for 1 second and then delete it
// add one new element
// and so on
ol.add(createCircle());
ol.addListener( new ListChangeListener<Node>(){
@Override
public void onChanged(
javafx.collections.ListChangeListener.Change<? extends Node> arg0) {
// TODO Auto-generated method stub
System.out.println("one new element added, size:"+ol.size());
if (ol.size()==5) {
ol.remove(0);
}
}
});
}
For 循环被定义为无限循环(可能也不是解决这个问题的正确方法),我可以从控制台看到圆圈在程序运行期间被删除和添加。唉,我再也看不到 GUI 了。
最佳答案
Oracle forums last year 上也有人提出类似的问题。 .
这是使用时间轴的示例解决方案,我更喜欢依赖工作线程的解决方案。虽然两者都可以完成工作,但我发现使用 JavaFX 动画 API 更优雅且更不易出错。
import javafx.animation.*;
import javafx.application.Application;
import javafx.event.*;
import javafx.scene.*;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
import javafx.util.Duration;
import java.util.Random;
public class FiveAutoCircleExample extends Application {
private static final Random r = new Random();
public static final int SCENE_SIZE = 800;
public static void main(String[] args) throws Exception { launch(args); }
public void start(final Stage stage) throws Exception {
final Group circles = new Group();
final Timeline animation = new Timeline(
new KeyFrame(Duration.seconds(.5),
new EventHandler<ActionEvent>() {
@Override public void handle(ActionEvent actionEvent) {
while (circles.getChildren().size() >= 5) circles.getChildren().remove(0);
int radius = 10 * r.nextInt(20);
circles.getChildren().add(
new Circle(
r.nextInt(SCENE_SIZE - radius * 2) + radius, r.nextInt(SCENE_SIZE - radius * 2) + radius,
radius,
new Color(r.nextDouble(), r.nextDouble(), r.nextDouble(), r.nextDouble())
)
);
}
})
);
animation.setCycleCount(Animation.INDEFINITE);
animation.play();
// display the scene.
stage.setScene(new Scene(circles, SCENE_SIZE, SCENE_SIZE, Color.CORNSILK));
stage.show();
}
}
关于javafx动画: displaying circles,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/10269017/