12

我想从 JavaFX(8) 中的 WebView 创建快照/屏幕截图/图像。
此 WebView 不需要可见（在我的情况下）。

我的问题：当 WebView不可见（或未添加到任何可见容器）
时 ，是否可以（以任何方式）从 WebView 创建屏幕截图/图像？

请参阅我的示例代码，当 WebView（或其父 ScrollPane）为visible=false时，
屏幕截图将不起作用（分别为 emtpy/blank）。

示例代码：

package test;

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.concurrent.Worker;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.SnapshotResult;
import javafx.scene.control.Label;
import javafx.scene.control.ScrollPane;
import javafx.scene.image.ImageView;
import javafx.scene.layout.VBox;
import javafx.scene.web.WebView;
import javafx.stage.Stage;
import javafx.util.Duration;

public class JavaFXApplication extends Application
{
   @Override
   public void start(Stage primaryStage)
   {
      ImageView webviewPreviewImage = new ImageView();
      Label waitLabel = new Label("Please wait...");
      WebView webView = new WebView();
      webView.setMaxHeight(480d);
      webView.setMinHeight(480d);
      webView.setMaxWidth(640d);
      webView.setMinWidth(640d);
      webView.setZoom(0.4);

      ScrollPane scrollpane = new ScrollPane(webView);
      scrollpane.setHbarPolicy(ScrollPane.ScrollBarPolicy.NEVER);
      scrollpane.setVbarPolicy(ScrollPane.ScrollBarPolicy.NEVER);
      scrollpane.setMaxWidth(0); //WORKAROUND: hide the WebView/ScrollPane
      scrollpane.setMaxHeight(0); //WORKAROUND: hide the WebView/ScrollPane
      scrollpane.setMinWidth(0); //WORKAROUND: hide the WebView/ScrollPane
      scrollpane.setMinHeight(0); //WORKAROUND: hide the WebView/ScrollPane

      //scrollpane.setVisible(false); //when WebView is invisible,  SnapShot doesn't work!

       webView.getEngine().getLoadWorker().stateProperty().addListener(new ChangeListener<Worker.State>() 
       {
          @Override
          public void changed(ObservableValue ov, Worker.State oldState, Worker.State newState) 
          {
              if (newState == Worker.State.SUCCEEDED) 
              {
                 //When SUCCEEDED is called, the WebPage may not has fully finished rendering!
                 //so, wait for few seceonds before making the screenshot...
                 Timeline timeline = new Timeline(new KeyFrame(
                         Duration.millis(1500),
                         ae -> takeSnapshot()));
                 timeline.play();
              }
           }

           private KeyFrame takeSnapshot()
           {
              webView.snapshot((SnapshotResult param) ->
              {
                 webviewPreviewImage.setImage(param.getImage());
                 webviewPreviewImage.setFitHeight(240d);
                 webviewPreviewImage.setFitWidth(320d);
                 webviewPreviewImage.setPreserveRatio(true);
                 waitLabel.setVisible(false);
                 return null;
              }, null, null);
              return null;
          }
      });
      webView.getEngine().load("http://www.bing.com");

      VBox root = new VBox();
      root.setAlignment(Pos.CENTER);
      root.setSpacing(10d);
      root.getChildren().add(waitLabel);
      root.getChildren().add(scrollpane);
      root.getChildren().add(webviewPreviewImage);

      Scene scene = new Scene(root, 800, 600);
      primaryStage.setScene(scene);
      primaryStage.show();
  }

  public static void main(String[] args)
  {
     launch(args);
  }
}
4

3 回答 3

2

WebView 类包含以下功能：

private boolean isTreeReallyVisible() {
    if (getScene() == null) {
        return false;
    }

    final Window window = getScene().getWindow();

    if (window == null) {
        return false;
    }

    boolean iconified = (window instanceof Stage) ? ((Stage)window).isIconified() : false;

    return impl_isTreeVisible()
           && window.isShowing()
           && window.getWidth() > 0
           && window.getHeight() > 0
           && !iconified;
}

只要函数返回false，渲染就会被阻塞。所以让它渲染可能非常棘手。通常，对于快照，您根本不必将节点放在场景中。

于 2018-10-24T20:34:43.517 回答
1

经过大量搜索和拼凑几块后，我发现了一个示例 SO-poster 在 oracle 论坛上发布，只有 webview 的大小是固定的，并且我的css 用于 html（不是 JavaFX）需要：

overflow-x: hidden;
overflow-y: hidden;

隐藏最后一个滚动条。

所以我想出了以下快照方法（带有动画的应用程序作为您的应用程序的示例）：

package application;

import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import javafx.animation.Animation;
import javafx.animation.PauseTransition;
import javafx.animation.TranslateTransition;
import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.effect.GaussianBlur;
import javafx.scene.image.WritableImage;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.scene.web.WebView;
import javafx.stage.Modality;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
import javafx.util.Duration;

public class WebViewSnapshot extends Application {

    BorderPane rootPane;
    TranslateTransition animation;

    @Override
    public void start(Stage primaryStage) {

        Rectangle rect = new Rectangle(50, 50, 50, 50);
        rect.setFill(Color.CORAL);

        animation = createAnimation(rect);

        Button snapshotButton = new Button("Take snapshot");

        Pane pane = new Pane(rect);
        pane.setMinSize(600, 150);

        rootPane = new BorderPane(pane, null, null, snapshotButton, new Label("This is the main scene"));

        snapshotButton.setOnAction(e -> {
            // html file being shown in webview
            File htmlFile = new File ("generated/template.html");
            // the resulting snapshot png file
            File aboutFile = new File ("generated/about.png");
            generate(htmlFile, aboutFile, 1280, 720);
        });

        BorderPane.setAlignment(snapshotButton, Pos.CENTER);
        BorderPane.setMargin(snapshotButton, new Insets(5));
        Scene scene = new Scene(rootPane);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    private TranslateTransition createAnimation(Rectangle rect) {
        TranslateTransition animation = new TranslateTransition(Duration.seconds(1), rect);
        animation.setByX(400);
        animation.setCycleCount(Animation.INDEFINITE);
        animation.setAutoReverse(true);
        animation.play();
        return animation;
    }

    public void generate(File htmlFile, File outputFile, double width, double height) {
        animation.pause();
        // rootPane is the root of original scene in an FXML controller you get this when you assign it an id
        rootPane.setEffect(new GaussianBlur());
        Stage primaryStage = (Stage)rootPane.getScene().getWindow();
        // creating separate webview holding same html content as in original scene
        WebView webView = new WebView();
        // with the size I want the snapshot
        webView.setPrefSize(width, height);
        AnchorPane snapshotRoot = new AnchorPane(webView);
        webView.getEngine().load(htmlFile.toURI().toString());
        Stage popupStage = new Stage(StageStyle.TRANSPARENT);
        popupStage.initOwner(primaryStage);
        popupStage.initModality(Modality.APPLICATION_MODAL);
        // this popup doesn't really show anything size = 1x1, it just holds the snapshot-webview
        popupStage.setScene(new Scene(snapshotRoot, 1, 1));
        // pausing to make sure the webview/picture is completely rendered
        PauseTransition pt = new PauseTransition(Duration.seconds(2));
        pt.setOnFinished(new EventHandler<ActionEvent>() {
            @Override public void handle(ActionEvent event) {
                WritableImage image = webView.snapshot(null, null);
                // writing a png to outputFile
                // writing a JPG like this will result in a pink JPG, see other posts
                // if somebody can scrape me simple code to convert it ARGB to RGB or something
                String format = "png";
                try {
                    ImageIO.write(SwingFXUtils.fromFXImage(image, null), format, outputFile);
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } finally {
                    rootPane.setEffect(null);
                    popupStage.hide();
                    animation.play();
                }
            }
        });
        // pausing, after pause onFinished event will take + write snapshot
        pt.play();
        // GO!
        popupStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}
于 2019-09-22T08:51:59.313 回答
0

为什么不可见的 WebView 根本不呈现在这里得到解答：https ://stackoverflow.com/a/52977547/1534698 ，规避该问题的代码在这里https://stackoverflow.com/a/58047583/1534698。

但是这里提供了一个干净的解决方案来解决当 WebView 说“我准备好了”时可能还没有准备好拍摄快照的问题：https ://stackoverflow.com/a/60746994/1534698 。

这是一个总结，因为实际上有两个问题阻止了 WebView 的简单快照。我必须合并这两种解决方案才能获得一个有效的干净解决方案。

于 2021-11-09T19:29:56.693 回答