JavaFX：使用REST服务并在前端显示数据
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我正在开发一个JavaFX(在带有SceneBuilder的JDK8上)项目,该项目应该与基于Spring-MVC的服务器连接,我想从服务器访问一些对象并显示它.我已经编写了Spring服务器来根据请求回放所需的对象,但是我对UI编程和JavaFX的不熟悉使它变得有点困难.
在FXML文件中,我已经添加了一个网格窗格,我想在那里显示对象.我很感激你们的任何帮助,让我们开始.我只有基本代码,但我在下面粘贴它：
Canvas.fxml：
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<GridPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
</GridPane>
CanvasModel类：
public class Canvas {
private int canvasid;
private final StringProperty canvasName;
private final StringProperty canvasTitle;
private final StringProperty canvasImage;
private byte[] canvasImageInBytes;
public Canvas(String canvasName, String canvasTitle, String canvasImage){
this.canvasName = new SimpleStringProperty(canvasName);
this.canvasTitle = new SimpleStringProperty(canvasTitle);
this.canvasImage = new SimpleStringProperty(canvasImage);
}
//Getters and setters ommitted
}
主要课程：
public class Main extends Application {
private Stage primaryStage;
@Override
public void start(Stage primaryStage) throws Exception{
Parent root = FXMLLoader.load(getClass().getResource("../View/mainui.fxml"));
primaryStage.setTitle("CheckAPP");
primaryStage.setScene(new Scene(root, 300, 600));
primaryStage.setFullScreen(false);
primaryStage.setMaximized(false);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
public Stage getPrimaryStage() {
return this.primaryStage;
}
}
现在向下面发出请求：
http://localhost:8080/canvaslist
它将返回我想在GridPane中显示的java.util.List.图像采用String格式.我明白这不是一个常规问题,因为这不起作用,但我试图绕过我的头脑进行UI编程,我不知道还有什么要转向.非常感谢你的帮助.
解决方法:
只需加上我的几美分来帮助你.
>使用后台线程从服务中获取数据,因为可能需要一段时间才能获得响应.在JavaFX应用程序线程上执行它可能会导致不良用户体验.在这种情况下,Task将帮助您.
>一旦有了响应,就可以从中构造一个必要的对象/对象集合,您将使用它来更新场景图上的元素.
>由于JavaFX Application Thread是您可以访问实时场景图元素的唯一线程,因此您无法在后台线程中直接使用它们(使用它们将导致IllegalStateException).您可以使用Platform.runLater更新JavaFX场景图上的数据,或者调用保证在FX应用程序线程上更新状态的任务方法,如updateProgress(...),updateMessage(...),getValue(...)等.
>使用在步骤2中构建的对象/对象集合来创建(或更新)FX场景图元素.
>如果您有一个接受ObservableList作为其内容的控件(如TableView或ListView),您可以绑定内容和Task的属性之一,在执行期间/之后自动更新它们,具体取决于它们的用法.
>但是在你的情况下,由于你有GridPane,所以我们可能不得不更进一步,编写逻辑来创建控件并将它们添加到GridPane.
例
我创建了一个使用服务的示例,解析JSON数据并从中创建一个GridPane. JSON列出了StackOverflow上很少有人的名字,他们的名字,他们的喜欢(根据我)和SO上的个人资料.
它使用后台任务从服务加载JSON数据,使用任务的setOnSucceeded(...)处理程序将其传递给创建GridPane的createGridPane(onservableList).
GridPane的其中一列包含相应人员的个人资料图片.由于这些图像可能需要一段时间才能下载,因此我会生成多个线程来为每个用户加载图像.
你可以找到source code here.
它使用GSON作为库将JSON转换为POJO类.
import com.google.common.reflect.TypeToken;
import com.google.gson.Gson;
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.concurrent.Task;
import javafx.concurrent.WorkerStateEvent;
import javafx.event.EventHandler;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.geometry.VPos;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ScrollPane;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.*;
import javafx.stage.Stage;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class ConsumeJSON extends Application {
private ObservableList<PeopleOnSO> listOfPeople;
private static final String JSON_URL = "https://api.myjson.com/bins/3jwmh";
private static final String IMAGE_URL = "http://www.fontspring.com/presentation_20150512/images/ajax_loader_blue_512.gif";
private final ExecutorService executorService = Executors.newCachedThreadPool();
private Image loadImage;
@Override
public void start(Stage stage) throws Exception {
loadImage = new Image(IMAGE_URL);
VBox root = new VBox();
root.setAlignment(Pos.TOP_CENTER);
root.setPadding(new Insets(20));
root.setSpacing(20);
Button button = new Button("Fill GridPane");
root.getChildren().addAll(button);
button.setOnAction(e -> {
// Display loading image
ImageView loading = new ImageView(loadImage);
loading.setFitWidth(60);
loading.setFitHeight(60);
root.getChildren().add(loading);
executorService.submit(fetchList);
});
fetchList.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
@Override
public void handle(WorkerStateEvent t) {
listOfPeople = FXCollections.observableArrayList(fetchList.getValue());
GridPane gridPane = createGridPane(listOfPeople);
//Remove Loading Image and add GridPane
root.getChildren().remove(1);
VBox.setVgrow(gridPane, Priority.ALWAYS);
root.getChildren().add(gridPane);
stage.sizeToScene();
}
});
ScrollPane scrollPane = new ScrollPane(root);
Scene scene = new Scene(scrollPane, 600, 500);
stage.setScene(scene);
stage.setTitle("Load Data from JSON");
stage.show();
stage.setOnCloseRequest(e -> {
executorService.shutdown();
});
}
public GridPane createGridPane(ObservableList<PeopleOnSO> listOfPeople){
GridPane gridPane = new GridPane();
gridPane.setAlignment(Pos.CENTER);
gridPane.setGridLinesVisible(true);
gridPane.setPadding(new Insets(20));
gridPane.setMinHeight(500);
gridPane.setMaxWidth(500);
//Create headings
Label nameHeading = new Label("Name");
nameHeading.setStyle("-fx-font-weight: bold");
Label likeHeading = new Label("Likes");
likeHeading.setStyle("-fx-font-weight: bold");
Label imageHeading = new Label("Image");
imageHeading.setStyle("-fx-font-weight: bold");
gridPane.add(nameHeading, 0, 0);
gridPane.add(likeHeading, 1, 0);
gridPane.add(imageHeading, 2, 0);
// Aligning at center
alignElements(nameHeading, likeHeading, imageHeading);
// Setting Constraints
for (int i = 0; i < 3; i++) {
ColumnConstraints column = new ColumnConstraints(150);
// column.setPercentWidth(80);
gridPane.getColumnConstraints().add(column);
}
for (int i = 0; i < listOfPeople.size(); i++) {
PeopleOnSO people = listOfPeople.get(i);
Label nameLabel = new Label(people.getName());
Label likeLabel = new Label(people.getLike());
ImageView imageView = new ImageView(loadImage);
imageView.setFitHeight(60);
imageView.setFitWidth(60);
//Thread for loading images later
FetchImage fetchImage = new FetchImage(people.getImageUrl());
fetchImage.setOnSucceeded(worker -> {
imageView.setImage((Image) fetchImage.getValue());
});
executorService.submit(fetchImage);
// Adding to GridPane and necessary configuration
gridPane.add(nameLabel, 0, i + 1);
gridPane.add(likeLabel, 1, i + 1);
gridPane.add(imageView, 2, i + 1);
//Aligning at center
alignElements(nameLabel, likeLabel, imageView);
gridPane.getRowConstraints().add(new RowConstraints(80));
}
return gridPane;
}
/**
* Align elements at the center
* @param nodes
*/
private void alignElements(Node ... nodes ) {
for(Node node : nodes) {
GridPane.setHalignment(node, HPos.CENTER);
GridPane.setValignment(node, VPos.CENTER);
}
}
/**
* Task to fetch details from JSONURL
* @param <V>
*/
private Task<List<PeopleOnSO>> fetchList = new Task() {
@Override
protected List<PeopleOnSO> call() throws Exception {
List<PeopleOnSO> list = null;
try {
Gson gson = new Gson();
list = new Gson().fromJson(readUrl(JSON_URL), new TypeToken<List<PeopleOnSO>>() {
}.getType());
} catch (Exception e) {
e.printStackTrace();
}
return list;
}
};
/**
* Task to fetch images for individual ImageViews
* @param <V>
*/
private class FetchImage<V> extends Task<Image> {
private String imageUrl;
public FetchImage(String imageUrl) {
this.imageUrl = imageUrl;
}
@Override
protected Image call() throws Exception {
Image image = new Image(imageUrl);
return image;
}
}
/**
* Read the URL and return the json data
* @param urlString
* @return
* @throws Exception
*/
private static String readUrl(String urlString) throws Exception {
BufferedReader reader = null;
try {
URL url = new URL(urlString);
reader = new BufferedReader(new InputStreamReader(url.openStream()));
StringBuffer buffer = new StringBuffer();
int read;
char[] chars = new char[1024];
while ((read = reader.read(chars)) != -1)
buffer.append(chars, 0, read);
return buffer.toString();
} finally {
if (reader != null)
reader.close();
}
}
private class PeopleOnSO {
private final String name;
private final String like;
private final String imageUrl;
public PeopleOnSO(String name, String like, String imageUrl){
this.name = new String(name);
this.like = new String(like);
this.imageUrl = new String(imageUrl);
}
public String getName() {
return name;
}
public String getLike() {
return like;
}
public String getImageUrl() {
return imageUrl;
}
}
public static void main(String[] args) {
launch(args);
}
}
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