假设您有一个显示用户图形(某种图像)的应用程序,那么您希望允许用户在此图像上绘制一些线条。关于这种情况我有以下问题:
你将如何实现这一目标? 您如何从用户拖动事件中获取图像的像素坐标? 你会如何实时更新图像?
答案 0 :(得分:2)
我将举例说明完全相反 [删除JavaFX上的图像] 我认为足以作为起点:
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.image.Image;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.paint.CycleMethod;
import javafx.scene.paint.LinearGradient;
import javafx.scene.paint.Stop;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;
public class EraseImageonCanvas extends Application {
private Pane root = new Pane();
private void setCanvas(Canvas canvas, Image img) {
GraphicsContext gc = canvas.getGraphicsContext2D();
gc.drawImage(img, 0, 0,canvas.getWidth(), canvas.getHeight());
}
@Override
public void start(Stage primaryStage) {
primaryStage.setTitle("Erasing the Image");
Rectangle rect = new Rectangle(400, 400);
drawBackground(rect);
root.getChildren().add(rect);
final Canvas canvas = new Canvas(200, 200);
canvas.setTranslateX(100);
canvas.setTranslateY(100);
//For local images use
//image = new Image(getClass().getResource(#Path#).openStream());
final Image image = new Image(
"http://kyllo.com.br/wp-content/uploads/2013/12/Faroeste-Cabloco.jpg"
);
setCanvas(canvas,image);
final GraphicsContext gc = canvas.getGraphicsContext2D();
// Clear away portions as the user drags the mouse
canvas.addEventHandler(MouseEvent.MOUSE_DRAGGED, new EventHandler<MouseEvent>() {
@Override
public void handle(MouseEvent e) {
gc.clearRect(e.getX() - 2, e.getY() - 2, 5, 5);
}
});
// Reset the Canvas when the user double-clicks
canvas.addEventHandler(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() {
@Override
public void handle(MouseEvent t) {
if (t.getClickCount() >1) {
setCanvas(canvas, image);
}
}
});
// Add the Canvas to the Scene, and show the Stage
root.getChildren().add(canvas);
primaryStage.setScene(new Scene(root, 400, 400));
primaryStage.show();
}
//Draws the background with a RadialGradient
private void drawBackground(Rectangle rect) {
rect.setFill(new LinearGradient(0, 0, 1, 1, true,
CycleMethod.REFLECT,
new Stop(0, Color.RED),
new Stop(1, Color.YELLOW)));
}
public static void main(String[] args) {
launch(args);
}
}
在gist
上下载答案 1 :(得分:1)
这个Canvas tutorial by Oracle在“与用户交互”部分中准确显示了您想要完成的任务。
它显示了如何向Canvas添加EventHandler以处理MouseEvent MouseEvent.MOUSE_DRAGGED
。然后使用GraphicsContext获取x和y坐标并在画布上绘制。
为了在主Application类之外使用Canvas,你可以在.fxml文件中声明Canvas:
<BorderPane fx:controller="controllers.MyController"
xmlns:fx="http://javafx.com/fxml">
<Canvas fx:id="drawArea" height="..." width="..."/>
</BorderPane>
然后,在你的MyController类上:
public class MyController implements Initializable {
@FXML
private Canvas drawArea;
private GraphicsContext gc;
@Override
public void initialize(URL location, ResourceBundle resources) {
gc = drawArea.getGraphicsContext2D();
// Java 8 syntax, beware!
drawArea.setOnMouseDragged(event -> gc.fillRect(event.getX(), event.getY(), 5, 5));
}
}